The document discusses various aspects of membrane transport in cells. It explains that the plasma membrane defines cell borders and is selectively permeable, allowing some materials to pass through freely while others require transport proteins. It describes the fluid mosaic model of the plasma membrane and its components. Various modes of transport are summarized, including passive diffusion and facilitated diffusion, as well as active transport mechanisms like pumps, channels, and endocytosis/exocytosis. Nerve impulse transmission is also covered, explaining the resting membrane potential and how action potentials propagate signals in neurons.
Dr. B. Victor presented on the biochemical principles of enzyme action. Some key points include: enzymes are proteins that act as catalysts to lower the activation energy of biochemical reactions; they have an active site that binds specifically to substrates; the lock and key and induced fit models describe how enzymes and substrates interact; factors like temperature, pH, and inhibitors can impact an enzyme's activity level; and coenzymes, isoenzymes, and allosteric enzymes are types of modified enzymes. Dr. Victor has over 30 years experience teaching biochemistry and guiding PhD students.
The red blood cell membrane consists of 50% protein, 20% phospholipid, 20% cholesterol, and 10% carbohydrate. It has three basic components: a lipid bilayer, integral membrane proteins, and a membrane cytoskeleton. The cytoskeleton is formed by structural proteins including spectrin, actin, ankyrin, and proteins 4.1 and 4.2. It interacts with the lipid bilayer and maintains the biconcave shape of red blood cells. Defects in membrane proteins can cause hereditary disorders like hereditary spherocytosis or elliptocytosis, which are inherited hemolytic anemias.
The document discusses the proteins found in human plasma. It describes how plasma proteins can be separated into fractions including albumin, globulins, fibrinogen, and others. Specific plasma proteins are then discussed in more detail, including their structure, function, concentration in plasma, and clinical significance. Albumin, the most abundant plasma protein, is highlighted for its roles in maintaining colloidal osmotic pressure and transporting various substances through the bloodstream.
This document discusses multiple blood group systems including ABO and Rh factor. It explains that the ABO system has three alleles (IA, IB, i) which determine four blood types (A, B, AB, O). The Rh system involves the D antigen, with Rh+ possessing the antigen and Rh- lacking it. Compatible blood transfusions require matching both systems to avoid hemolysis from antigen-antibody reactions. A kit test can determine blood type through agglutination reactions between cell antigens and serum antibodies.
This document summarizes key information about blood groups and blood typing:
- Blood is typed based on the presence or absence of antigens on red blood cells and the presence of corresponding antibodies in the plasma. The main blood group systems are ABO and Rh. Mismatched blood can cause agglutination and hemolysis.
- Erythroblastosis fetalis occurs when an Rh-negative mother is sensitized to Rh antigens from an Rh-positive fetus, leading to destruction of the fetus's red blood cells. Administration of Rh immunoglobulin prevents sensitization.
- Proper blood typing and cross-matching is important for safe blood transfusions to prevent transfusion reactions from antigen-antibody incompatibility
The document discusses enzyme-linked immunosorbent assays (ELISAs), which can qualitatively and quantitatively measure antigen-antibody binding. There are three main types of ELISAs - indirect ELISAs measure antibodies, sandwich ELISAs measure antigens, and competitive ELISAs also measure antigens but the extent of color development is inversely proportional to the amount of antigen. The document provides details on the basic procedures and components needed to perform each type of ELISA.
Blood group substances biochemistry presentation.
this presentation helps in the better understanding of the topic h substances which are the primitive substances that help in the formation of the ABO blood groups.
1. Karl Landsteiner discovered the main blood group systems (ABO and Rh) in 1900 and 1940 respectively. The ABO system categorizes blood into A, B, AB and O groups based on antigens on red blood cells.
2. Blood typing and cross-matching are important to ensure safe and compatible blood transfusions. Transfusing incompatible blood can cause hemolytic or allergic reactions in the recipient.
3. Other minor blood group systems have been discovered including MNS, Duffy, Kell and Lewis systems which are important for transfusion medicine and anthropological research. Understanding blood groups is crucial for blood banking and preventing diseases like hemolytic disease of the newborn.
Dr. B. Victor presented on the biochemical principles of enzyme action. Some key points include: enzymes are proteins that act as catalysts to lower the activation energy of biochemical reactions; they have an active site that binds specifically to substrates; the lock and key and induced fit models describe how enzymes and substrates interact; factors like temperature, pH, and inhibitors can impact an enzyme's activity level; and coenzymes, isoenzymes, and allosteric enzymes are types of modified enzymes. Dr. Victor has over 30 years experience teaching biochemistry and guiding PhD students.
The red blood cell membrane consists of 50% protein, 20% phospholipid, 20% cholesterol, and 10% carbohydrate. It has three basic components: a lipid bilayer, integral membrane proteins, and a membrane cytoskeleton. The cytoskeleton is formed by structural proteins including spectrin, actin, ankyrin, and proteins 4.1 and 4.2. It interacts with the lipid bilayer and maintains the biconcave shape of red blood cells. Defects in membrane proteins can cause hereditary disorders like hereditary spherocytosis or elliptocytosis, which are inherited hemolytic anemias.
The document discusses the proteins found in human plasma. It describes how plasma proteins can be separated into fractions including albumin, globulins, fibrinogen, and others. Specific plasma proteins are then discussed in more detail, including their structure, function, concentration in plasma, and clinical significance. Albumin, the most abundant plasma protein, is highlighted for its roles in maintaining colloidal osmotic pressure and transporting various substances through the bloodstream.
This document discusses multiple blood group systems including ABO and Rh factor. It explains that the ABO system has three alleles (IA, IB, i) which determine four blood types (A, B, AB, O). The Rh system involves the D antigen, with Rh+ possessing the antigen and Rh- lacking it. Compatible blood transfusions require matching both systems to avoid hemolysis from antigen-antibody reactions. A kit test can determine blood type through agglutination reactions between cell antigens and serum antibodies.
This document summarizes key information about blood groups and blood typing:
- Blood is typed based on the presence or absence of antigens on red blood cells and the presence of corresponding antibodies in the plasma. The main blood group systems are ABO and Rh. Mismatched blood can cause agglutination and hemolysis.
- Erythroblastosis fetalis occurs when an Rh-negative mother is sensitized to Rh antigens from an Rh-positive fetus, leading to destruction of the fetus's red blood cells. Administration of Rh immunoglobulin prevents sensitization.
- Proper blood typing and cross-matching is important for safe blood transfusions to prevent transfusion reactions from antigen-antibody incompatibility
The document discusses enzyme-linked immunosorbent assays (ELISAs), which can qualitatively and quantitatively measure antigen-antibody binding. There are three main types of ELISAs - indirect ELISAs measure antibodies, sandwich ELISAs measure antigens, and competitive ELISAs also measure antigens but the extent of color development is inversely proportional to the amount of antigen. The document provides details on the basic procedures and components needed to perform each type of ELISA.
Blood group substances biochemistry presentation.
this presentation helps in the better understanding of the topic h substances which are the primitive substances that help in the formation of the ABO blood groups.
1. Karl Landsteiner discovered the main blood group systems (ABO and Rh) in 1900 and 1940 respectively. The ABO system categorizes blood into A, B, AB and O groups based on antigens on red blood cells.
2. Blood typing and cross-matching are important to ensure safe and compatible blood transfusions. Transfusing incompatible blood can cause hemolytic or allergic reactions in the recipient.
3. Other minor blood group systems have been discovered including MNS, Duffy, Kell and Lewis systems which are important for transfusion medicine and anthropological research. Understanding blood groups is crucial for blood banking and preventing diseases like hemolytic disease of the newborn.
The cell membrane has a fluid mosaic structure, comprising a phospholipid bilayer with embedded proteins. The phospholipid tails face each other at the center of the bilayer to be protected from the watery environments inside and outside the cell, while the phosphate heads face outwards. Transmembrane and peripheral proteins embedded in the bilayer form channels to regulate what passes in and out of the cell. Cholesterol maintains the fluidity and stability of the membrane. The membrane acts as a selectively permeable barrier and facilitates cell structure, communication, recognition, mobility, and chemical reactions.
A blood group also called a Blood Type
Classification of blood is based on the presence or absence of inherited antigenic substances on the surface of red blood cells (RBCs)
These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system.
The ABO blood group system is the most important blood type system (or blood group system) in human blood transfusion.
ABO blood types are also present in some other animals for example rodents and apes such as chimpanzees, bonobos and gorillas.
Immunoglobulins, also known as antibodies, are Y-shaped glycoproteins produced by plasma cells that function to identify and neutralize foreign objects like bacteria and viruses. Each arm of the Y contains a paratope that binds to a specific epitope on an antigen. There are five classes of immunoglobulins - IgG, IgM, IgA, IgD, and IgE - which differ in their structure and functions like complement fixation, binding to cells, and roles in allergic reactions and parasitic infections. Multiple myeloma is a plasma cell tumor characterized by overproduction of IgG and IgM antibodies and Bence Jones proteins in the serum and urine.
Protein is essential for growth, repair, and maintenance of the body. It is made up of amino acids and there are essential amino acids that must be obtained through diet. Animal sources of protein generally have higher biological value than plant sources as they contain all essential amino acids. Collagen is the most abundant protein in the body and forms connective tissues. It has a unique triple helical structure responsible for its mechanical properties.
This document discusses blood groups and blood transfusion. It explains that blood transfusions can be life-saving but require compatibility between donor and recipient blood types. The two major blood group systems are ABO and RhESUS. ABO includes types A, B, AB and O while RhESUS determines Rh positive or negative status. Compatibility testing and screening for antibodies is required before transfusion to avoid rejection reactions. Indications, alternatives, and hazards of transfusion are also outlined.
This document presents information about mitochondria. It discusses that mitochondria are organelles found in aerobic cells that were first discovered in 1880. Mitochondria have a double membrane structure that encloses the matrix. The inner membrane folds inward to form cristae which increase surface area. Mitochondria contain DNA, ribosomes, and particles involved in oxidation and phosphorylation. They perform important functions like biological oxidation of carbohydrates and fats to synthesize ATP, releasing energy in the process. As mitochondria produce ATP, they are considered the powerhouse of the cell.
Red blood cells, also known as erythrocytes, are produced through erythropoiesis in the red bone marrow. Their main function is to transport oxygen from the lungs to tissues via hemoglobin. Red blood cells are biconcave disks that are flexible enough to squeeze through small blood vessels. They have a lifespan of about 120 days before being broken down and recycled. Factors involved in red blood cell production include erythropoietin, iron, vitamins, and minerals. Abnormalities can result in anemias or polycythemia.
Blood clotting is a process called coagulation where blood changes from a liquid to a solid gel-like state. It occurs through a cascade of biochemical reactions involving multiple clotting factors. Initially fibrinogen is converted to fibrin, which forms a mesh that entangles blood cells. Then the clot undergoes further changes to strengthen it. Precise regulation of coagulation prevents clotting inside healthy blood vessels but allows it to occur when vessels are damaged.
lehninger(sixth edition) Ch 01: The foundations of biochemistrykrupal parmar
This document provides an overview of key topics in biochemistry including:
1) The structures and functions of prokaryotic and eukaryotic cells.
2) Organic chemical bonds and functional groups that make up biomolecules.
3) The evolution of cells through endosymbiosis and the evolution of proteins through gene duplication events.
4) Central concepts like the genetic code, DNA replication, transcription, translation and the flow of genetic information.
For More Medicine Free PPT - http://playnever.blogspot.com/
For Health benefits and medicine videos Subscribe youtube channel - https://www.youtube.com/playlist?list=PLKg-H-sMh9G01zEg4YpndngXODW2bq92w
The Rh blood group system is one of the most complex with over 50 antigens. The Rh factor refers to the presence (Rh positive) or absence (Rh negative) of the D antigen on red blood cells. The RHD gene encodes the D antigen, while the RHCE gene encodes the C, c, E, and e antigens. Rh proteins are integral membrane proteins that may function in ammonium or carbon dioxide transport. The Rh system was discovered in 1939 when a woman had an immune response after transfusion with her husband's Rh positive blood after delivering a stillborn infant. This led to the identification of the highly immunogenic Rh antigens which can cause hemolytic transfusion reactions or hemolytic disease of the newborn if a
The document provides instructions for drawing blood from donors. It states that donors must be healthy and comfortable, and the skin where blood will be drawn must be thoroughly cleaned. It also notes that blood is drawn into bottles or bags containing an anticoagulant solution to prevent clotting, and several safety and quality control procedures are followed before and after drawing blood.
This document discusses various mechanisms of enzyme regulation in living systems. It begins by explaining that hundreds of enzyme-catalyzed reactions must be precisely controlled for proper cellular functioning. It then describes several key mechanisms by which this regulation can be achieved, including allosteric regulation, isoenzyme expression, zymogen activation, and covalent modification via phosphorylation or glycosylation. Specific examples are provided for each type of regulation, such as feedback inhibition of threonine dehydratase and phosphorylation control of glycogen phosphorylase activity. The document concludes by emphasizing that multiple regulatory strategies acting together ensure survival of the cell and maintenance of homeostasis.
Hemoglobin is an iron-containing protein in red blood cells that transports oxygen from the lungs to tissues and carbon dioxide from tissues back to the lungs. It is a globular tetrameric protein composed of two alpha and two beta chains, with each chain containing a heme group that binds to oxygen. Hemoglobin undergoes a conformational change upon oxygen binding that makes the remaining binding sites have a higher affinity for oxygen in a cooperative binding process essential for oxygen transport.
The document discusses several key topics regarding the origin of life:
1. It outlines the aim of studying biomolecules and becoming acquainted with life processes.
2. It discusses early evidence for life on Earth from 3.45 billion year old fossils and poses two big questions about how the earliest life forms emerged and evolved into all extant organisms.
3. It notes that all living things share the same core biomolecules and principles of function, implying descent from a common ancestor.
Erythropoietin (EPO) secreted by kidney
Inhibitor: High concentration of O2 in kidney
Life span of RBC: 120 days
RBC metabolism: anaerobic glycolysis [reason for
Heinz body and G6PD deficiency anemia]
RBC destruction: spleen and macrophage in liver,
bone marrow [reason for spherocytosis and
elliptocytosis]
RBC regeneration: bone marrow
RBC reserve: about 25% of total RBC
RBC production: 2.4×1011/day
Plasma is the liquid component of blood that holds the blood cells in suspension. It makes up 55% of the blood's total volume and is mostly composed of water (92%) and dissolved proteins (8%). Plasma carries nutrients, hormones, carbon dioxide, and oxygen to tissues and transports waste products away from tissues. It plays a vital role in maintaining electrolyte balance and protects the body from infection. Plasma is separated from blood cells when a tube of blood is spun in a centrifuge.
White blood cells, or leukocytes, are nucleated blood cells that play an important role in the immune system. Compared to red blood cells, white blood cells are larger in size and fewer in number. The main types of white blood cells are neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Each type has a distinct shape and granule composition and serves different immune functions, such as phagocytosis of pathogens by neutrophils and antibody production by B lymphocytes. White blood cell counts can vary in different physiological and pathological conditions to help fight infection and disease.
Blood clotting is a process called coagulation where blood loses fluidity and forms a mesh of fibrin fibrils entangling blood cells. There are 12 coagulation factors involved in a sequential process to convert fibrinogen into fibrin. First, the extrinsic and intrinsic pathways form prothrombin activator which converts prothrombin to thrombin. Thrombin then converts fibrinogen to fibrin to form the clot. Anticoagulants like heparin and warfarin prevent clotting by interfering with parts of this coagulation cascade.
Dr. Aamir Ali Khan is the principal of Ghazali Institute of Medical Sciences in Peshawar. The document discusses various mechanisms of transport across the plasma membrane, including passive transport processes like simple diffusion, facilitated diffusion, and osmosis. It also discusses active transport processes, distinguishing between primary active transport which directly uses ATP and secondary active transport which relies on ion gradients established by primary transport. Specific transport examples covered include the sodium-potassium pump, glucose co-transport, and receptor-mediated endocytosis.
The cell membrane is selectively permeable due to its lipid bilayer structure. Integral proteins embedded in the membrane, including channels, carriers, and receptors, facilitate the passage of substances and relay signals from outside to inside the cell. Passive transport processes like simple diffusion and facilitated diffusion rely on concentration gradients and do not require energy, while active transport uses ATP to move substances against their gradients via pumps or coupled transporters. Key cellular functions powered by ATP include transport, synthesis, and mechanical work like muscle contraction. The sodium-potassium pump maintains ion gradients that generate the resting membrane potential and regulate cell volume.
The cell membrane has a fluid mosaic structure, comprising a phospholipid bilayer with embedded proteins. The phospholipid tails face each other at the center of the bilayer to be protected from the watery environments inside and outside the cell, while the phosphate heads face outwards. Transmembrane and peripheral proteins embedded in the bilayer form channels to regulate what passes in and out of the cell. Cholesterol maintains the fluidity and stability of the membrane. The membrane acts as a selectively permeable barrier and facilitates cell structure, communication, recognition, mobility, and chemical reactions.
A blood group also called a Blood Type
Classification of blood is based on the presence or absence of inherited antigenic substances on the surface of red blood cells (RBCs)
These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system.
The ABO blood group system is the most important blood type system (or blood group system) in human blood transfusion.
ABO blood types are also present in some other animals for example rodents and apes such as chimpanzees, bonobos and gorillas.
Immunoglobulins, also known as antibodies, are Y-shaped glycoproteins produced by plasma cells that function to identify and neutralize foreign objects like bacteria and viruses. Each arm of the Y contains a paratope that binds to a specific epitope on an antigen. There are five classes of immunoglobulins - IgG, IgM, IgA, IgD, and IgE - which differ in their structure and functions like complement fixation, binding to cells, and roles in allergic reactions and parasitic infections. Multiple myeloma is a plasma cell tumor characterized by overproduction of IgG and IgM antibodies and Bence Jones proteins in the serum and urine.
Protein is essential for growth, repair, and maintenance of the body. It is made up of amino acids and there are essential amino acids that must be obtained through diet. Animal sources of protein generally have higher biological value than plant sources as they contain all essential amino acids. Collagen is the most abundant protein in the body and forms connective tissues. It has a unique triple helical structure responsible for its mechanical properties.
This document discusses blood groups and blood transfusion. It explains that blood transfusions can be life-saving but require compatibility between donor and recipient blood types. The two major blood group systems are ABO and RhESUS. ABO includes types A, B, AB and O while RhESUS determines Rh positive or negative status. Compatibility testing and screening for antibodies is required before transfusion to avoid rejection reactions. Indications, alternatives, and hazards of transfusion are also outlined.
This document presents information about mitochondria. It discusses that mitochondria are organelles found in aerobic cells that were first discovered in 1880. Mitochondria have a double membrane structure that encloses the matrix. The inner membrane folds inward to form cristae which increase surface area. Mitochondria contain DNA, ribosomes, and particles involved in oxidation and phosphorylation. They perform important functions like biological oxidation of carbohydrates and fats to synthesize ATP, releasing energy in the process. As mitochondria produce ATP, they are considered the powerhouse of the cell.
Red blood cells, also known as erythrocytes, are produced through erythropoiesis in the red bone marrow. Their main function is to transport oxygen from the lungs to tissues via hemoglobin. Red blood cells are biconcave disks that are flexible enough to squeeze through small blood vessels. They have a lifespan of about 120 days before being broken down and recycled. Factors involved in red blood cell production include erythropoietin, iron, vitamins, and minerals. Abnormalities can result in anemias or polycythemia.
Blood clotting is a process called coagulation where blood changes from a liquid to a solid gel-like state. It occurs through a cascade of biochemical reactions involving multiple clotting factors. Initially fibrinogen is converted to fibrin, which forms a mesh that entangles blood cells. Then the clot undergoes further changes to strengthen it. Precise regulation of coagulation prevents clotting inside healthy blood vessels but allows it to occur when vessels are damaged.
lehninger(sixth edition) Ch 01: The foundations of biochemistrykrupal parmar
This document provides an overview of key topics in biochemistry including:
1) The structures and functions of prokaryotic and eukaryotic cells.
2) Organic chemical bonds and functional groups that make up biomolecules.
3) The evolution of cells through endosymbiosis and the evolution of proteins through gene duplication events.
4) Central concepts like the genetic code, DNA replication, transcription, translation and the flow of genetic information.
For More Medicine Free PPT - http://playnever.blogspot.com/
For Health benefits and medicine videos Subscribe youtube channel - https://www.youtube.com/playlist?list=PLKg-H-sMh9G01zEg4YpndngXODW2bq92w
The Rh blood group system is one of the most complex with over 50 antigens. The Rh factor refers to the presence (Rh positive) or absence (Rh negative) of the D antigen on red blood cells. The RHD gene encodes the D antigen, while the RHCE gene encodes the C, c, E, and e antigens. Rh proteins are integral membrane proteins that may function in ammonium or carbon dioxide transport. The Rh system was discovered in 1939 when a woman had an immune response after transfusion with her husband's Rh positive blood after delivering a stillborn infant. This led to the identification of the highly immunogenic Rh antigens which can cause hemolytic transfusion reactions or hemolytic disease of the newborn if a
The document provides instructions for drawing blood from donors. It states that donors must be healthy and comfortable, and the skin where blood will be drawn must be thoroughly cleaned. It also notes that blood is drawn into bottles or bags containing an anticoagulant solution to prevent clotting, and several safety and quality control procedures are followed before and after drawing blood.
This document discusses various mechanisms of enzyme regulation in living systems. It begins by explaining that hundreds of enzyme-catalyzed reactions must be precisely controlled for proper cellular functioning. It then describes several key mechanisms by which this regulation can be achieved, including allosteric regulation, isoenzyme expression, zymogen activation, and covalent modification via phosphorylation or glycosylation. Specific examples are provided for each type of regulation, such as feedback inhibition of threonine dehydratase and phosphorylation control of glycogen phosphorylase activity. The document concludes by emphasizing that multiple regulatory strategies acting together ensure survival of the cell and maintenance of homeostasis.
Hemoglobin is an iron-containing protein in red blood cells that transports oxygen from the lungs to tissues and carbon dioxide from tissues back to the lungs. It is a globular tetrameric protein composed of two alpha and two beta chains, with each chain containing a heme group that binds to oxygen. Hemoglobin undergoes a conformational change upon oxygen binding that makes the remaining binding sites have a higher affinity for oxygen in a cooperative binding process essential for oxygen transport.
The document discusses several key topics regarding the origin of life:
1. It outlines the aim of studying biomolecules and becoming acquainted with life processes.
2. It discusses early evidence for life on Earth from 3.45 billion year old fossils and poses two big questions about how the earliest life forms emerged and evolved into all extant organisms.
3. It notes that all living things share the same core biomolecules and principles of function, implying descent from a common ancestor.
Erythropoietin (EPO) secreted by kidney
Inhibitor: High concentration of O2 in kidney
Life span of RBC: 120 days
RBC metabolism: anaerobic glycolysis [reason for
Heinz body and G6PD deficiency anemia]
RBC destruction: spleen and macrophage in liver,
bone marrow [reason for spherocytosis and
elliptocytosis]
RBC regeneration: bone marrow
RBC reserve: about 25% of total RBC
RBC production: 2.4×1011/day
Plasma is the liquid component of blood that holds the blood cells in suspension. It makes up 55% of the blood's total volume and is mostly composed of water (92%) and dissolved proteins (8%). Plasma carries nutrients, hormones, carbon dioxide, and oxygen to tissues and transports waste products away from tissues. It plays a vital role in maintaining electrolyte balance and protects the body from infection. Plasma is separated from blood cells when a tube of blood is spun in a centrifuge.
White blood cells, or leukocytes, are nucleated blood cells that play an important role in the immune system. Compared to red blood cells, white blood cells are larger in size and fewer in number. The main types of white blood cells are neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Each type has a distinct shape and granule composition and serves different immune functions, such as phagocytosis of pathogens by neutrophils and antibody production by B lymphocytes. White blood cell counts can vary in different physiological and pathological conditions to help fight infection and disease.
Blood clotting is a process called coagulation where blood loses fluidity and forms a mesh of fibrin fibrils entangling blood cells. There are 12 coagulation factors involved in a sequential process to convert fibrinogen into fibrin. First, the extrinsic and intrinsic pathways form prothrombin activator which converts prothrombin to thrombin. Thrombin then converts fibrinogen to fibrin to form the clot. Anticoagulants like heparin and warfarin prevent clotting by interfering with parts of this coagulation cascade.
Dr. Aamir Ali Khan is the principal of Ghazali Institute of Medical Sciences in Peshawar. The document discusses various mechanisms of transport across the plasma membrane, including passive transport processes like simple diffusion, facilitated diffusion, and osmosis. It also discusses active transport processes, distinguishing between primary active transport which directly uses ATP and secondary active transport which relies on ion gradients established by primary transport. Specific transport examples covered include the sodium-potassium pump, glucose co-transport, and receptor-mediated endocytosis.
The cell membrane is selectively permeable due to its lipid bilayer structure. Integral proteins embedded in the membrane, including channels, carriers, and receptors, facilitate the passage of substances and relay signals from outside to inside the cell. Passive transport processes like simple diffusion and facilitated diffusion rely on concentration gradients and do not require energy, while active transport uses ATP to move substances against their gradients via pumps or coupled transporters. Key cellular functions powered by ATP include transport, synthesis, and mechanical work like muscle contraction. The sodium-potassium pump maintains ion gradients that generate the resting membrane potential and regulate cell volume.
Ion transport through cell membranes occurs through passive and active transport mechanisms. Passive transport includes simple diffusion, facilitated diffusion, and osmosis. Simple diffusion allows small, nonpolar molecules to freely pass through the phospholipid bilayer. Facilitated diffusion uses channel and carrier proteins to transport ions and larger molecules down their concentration gradients without expending energy. Osmosis allows for the diffusion of water through semipermeable membranes. Active transport moves solutes against their concentration gradients and requires energy in the form of ATP hydrolysis. Primary active transport uses ATP and carrier proteins like Na+/K+ ATPase to pump ions. Secondary active transport couples the uphill transport of one solute to the downhill flow of another.
Cell membrane and its functions, how it make effect on our cell surface. It can implies the structure along with the components of a cell. Which portion of membrane take part in an specific functioning of the body. It can be identified easily by this presentation. Huge opportunity to get a glimpse of cell membrane and activities.
The document summarizes key concepts about solute transport across membranes in plant and animal cells. It discusses passive diffusion of small molecules, facilitated diffusion mediated by carrier and channel proteins, and active transport driven by ATP hydrolysis including sodium-potassium pumps and co-transport. It also describes bulk transport mechanisms like phagocytosis, pinocytosis, and receptor-mediated endocytosis as well as exocytosis for exporting materials. The seminar was presented to discuss these transport mechanisms in detail.
cell membrane transport mechanisms and related disorders ppt..pptxNitinchaudharY351367
The document discusses cell membranes and transport mechanisms. It begins by describing the structure and function of the cell membrane, including that it is a lipid bilayer containing proteins. It then explains the different types of transport across membranes, including passive transport mechanisms like simple diffusion and facilitated diffusion, as well as active transport mechanisms like primary active transport using ATP and secondary active transport using ion gradients. Specific transport proteins and mechanisms discussed include sodium-potassium pumps, calcium pumps, hydrogen-potassium pumps, and sodium-glucose co-transporters. The document concludes by mentioning some applied aspects regarding transport mechanisms.
The document discusses the structure and functions of the cell membrane. It begins by defining the cell and cell membrane. The cell membrane, also called the plasma membrane, is a biological membrane separating the interior of a cell from the outside environment. It has a double layered structure of phospholipids and embedded proteins. The cell membrane serves protective, selective permeability, absorptive, excretory, gas exchange, and shape maintenance functions. It discusses various transport mechanisms like passive transport, active transport, ion channels, and vesicular transport that allow movement of substances across the membrane.
Membrane transport systems allow molecules to pass through cell membranes. There are two main types - passive transport, which moves molecules down concentration gradients without energy, and active transport, which moves molecules against gradients by using cellular energy. Passive transport includes diffusion, facilitated diffusion, and osmosis. Active transport involves transmembrane proteins that act as pumps powered by ATP.
The document discusses mechanisms of transport across the cell membrane. It explains that transport is necessary for cells to exchange materials and carry out life functions. The cell membrane is selectively permeable, allowing some substances to pass through freely via diffusion or with the assistance of transport proteins via facilitated diffusion. Active transport requires energy to move substances against their concentration gradient using pumps and carriers. The cell membrane is made up of a lipid bilayer with embedded and peripheral proteins that facilitate different types of transport.
Structure of a eukaryotic plasma membrane.pdfYosef251
The plasma membrane is a phospholipid bilayer with embedded proteins that separates the interior of the cell from the external environment. The bilayer is composed of phospholipids with hydrophilic heads and hydrophobic tails. There are two types of membrane proteins - integral proteins that are permanently attached, and peripheral proteins that temporarily attach. Transportation across the membrane occurs through four main mechanisms: simple diffusion of small non-polar molecules, facilitated diffusion of larger molecules through channels, primary active transport using ATP hydrolysis to pump molecules against gradients, and secondary active transport using the gradient of one molecule to power another molecule against its gradient. Endocytosis and exocytosis provide mechanisms for bulk transport, with endocytosis engulfing material and exocytosis releasing material out of
The plasma membrane is a selectively permeable membrane that surrounds the cell. It is composed of a phospholipid bilayer with embedded proteins. The fluid mosaic model describes the plasma membrane structure, with integral and peripheral proteins embedded within or attached to the fluid phospholipid bilayer. The plasma membrane regulates what enters and exits the cell through passive diffusion, facilitated diffusion, active transport, osmosis, and bulk transport mechanisms like endocytosis and exocytosis.
This document summarizes the three main types of transport across cell membranes: passive transport, active transport, and bulk transport. Passive transport includes diffusion, osmosis, and facilitated diffusion, which move molecules through membranes down concentration gradients without energy expenditure. Active transport moves molecules against concentration gradients using carrier proteins and energy from ATP hydrolysis. Bulk transport uses endocytosis and exocytosis to move large particles and vesicles across membranes.
This document discusses the mechanisms of transport across cell membranes. It describes two basic mechanisms - passive transport, which moves substances down concentration gradients without energy usage, and active transport, which moves substances against gradients by using cellular energy. Passive transport includes diffusion (simple, facilitated) and osmosis. Active transport includes primary transport using ion pumps and secondary transport coupling to ion gradients. Special transport mechanisms like endocytosis, exocytosis, and transcytosis are also covered.
Physiology at a glance 2013 keyrevisionpointsElsa von Licy
Homeostasis involves physiological systems maintaining equilibrium. The shape and binding of proteins is essential for their normal functioning and is maintained by homeostatic mechanisms. Small changes in the environment can modify protein shape. Negative feedback loops involving detectors, comparators and effectors regulate most physiological variables. [END SUMMARY]
The plasma membrane acts as a selectively permeable barrier that regulates what enters and exits the cell. It has a fluid mosaic structure consisting of a phospholipid bilayer with embedded proteins. This structure allows small hydrophobic molecules to pass through the membrane freely via diffusion, while hydrophilic molecules require transport proteins like channels and carriers. Transport proteins help move molecules across the membrane through active or passive transport.
There are two main types of membrane transport - passive and active. Passive transport includes diffusion, osmosis, and facilitated diffusion, which move molecules down concentration gradients without energy expenditure. Active transport moves molecules against concentration gradients and requires energy in the form of ATP. A key example of active transport is the sodium-potassium pump, which maintains ion gradients across cell membranes.
Transport across cell membrane, CELL MEMBRANERajshri Ghogare
Transport across cell membrane, Active transport, Active transport,
Types of passive transport-Diffusion, Filtration, Osmosis, Facilitated diffusion , Types of active transport antiport and symport
The document summarizes transport across the cell membrane. There are two main types of transport - passive transport (diffusion) and active transport. Passive transport involves the movement of substances down their concentration gradient without energy expenditure, and can occur through simple diffusion, facilitated diffusion via channel or carrier proteins. Active transport moves substances against their concentration gradient by expending cellular energy in the form of ATP. Key examples discussed are the sodium-potassium pump, which actively transports sodium out and potassium into cells.
This document summarizes the four main types of transport across cell membranes: diffusion, osmosis, active transport, and vesicular transport. It provides details on diffusion and facilitated diffusion, describing simple diffusion, facilitated diffusion via channel or carrier proteins. Active transport is outlined, distinguishing primary from secondary active transport. Secondary active transport can occur via symporters or antiporters. Key transport proteins like sodium-potassium pumps and proton pumps are described.
Similar to Biochemistry of Cell Membrane.pptx (20)
Lipid Profile test & Cardiac Markers for MBBS, Lab. Med. and Nursing.pptxRajendra Dev Bhatt
The lipid profile is a group of tests that have been shown to be good indicators of whether someone is likely to have a Coronary disease or heart attack or stroke caused by blockage of blood vessels or hardening of the arteries (atherosclerois).
Blood plasma contains 8% solids, which has 7% albumin. The different plasma proteins are albumins, globulins, and fibrinogen. Usually, total plasma proteins are 6 to 8 gms / 100 ml of blood.
The proteins present in human blood plasma are a mixture of simple proteins, glycoproteins, lipoproteins, and other conjugated proteins called “Plasma Protein”.
Hemoglobin is red color blood pigment, present in red blood cells (erythrocytes).
It is a chromoprotein, containing heme as the prosthetic group & globin as the protein part-apoprotein.
It is a tetrameric protein & molecular weight about 67,000 dalton.
Each gram of Hb contains 3.4 mg of iron.
The principal eicosanoids of biological significance to humans are a group of molecules derived from the 20:4 (20 carbons: 4 sites of unsaturation) fatty acid, arachidonic acid.
Parathyroid hormone (PTH) is one of three key hormones modulating calcium and phosphate homeostasis; the other two are calcitriol (1,25-dihydroxyvitamin D) and fibroblast growth factor 23 (FGF23).
Lipids are insoluble in water, the problem of transportation in the aqueous plasma is solved by associating nonpolar lipids (triacylglycerols and cholesteryl esters) with amphipathic lipids (phospholipids and cholesterol) and proteins to make water-miscible lipoproteins.
Cholesterol Biosynthesis and catabolism for MBBS, Lab. MEd. BDS.pptxRajendra Dev Bhatt
Cholesterol is found exclusively in animals, hence it is often called as animal sterol.
The total body content of cholesterol in an
adult man weighing 70 kg is about 140 g i.e., around 2 g/kg body weight.
The level of cholesterol in blood is related to the development of atherosclerosis & MI.
Thyroid function tests (TFTs) are the most frequently ordered endocrine investigations in children and adolescents.
Abnormalities in TFTs can help in diagnosis of primary thyroid disorders (i.e. disorders in which the defect is at the thyroid level) as well as secondary or central thyroid disorders (in which defect is at the pituitary level).
Amino Acid Metabolism for MBBS, Laboratory Medicine.pptxRajendra Dev Bhatt
All tissues have some capability for synthesis of the non-essential amino acids, amino acid remodeling, and conversion of non-amino acid carbon skeletons into amino acids and other derivatives that contain nitrogen.
However, the liver is the major site of nitrogen metabolism in the body.
In times of dietary surplus, the potentially toxic nitrogen of amino acids is eliminated via transaminations, deamination, and urea formation.
KETONE BODY METABOLISM. FOR MBBS, BDS, LABORATORY MEDICINE pptxRajendra Dev Bhatt
Ketone bodies are produced from acetyl-CoA, mainly in the mitochondrial matrix of liver cells when carbohydrates are so scarce that energy must be obtained from breaking down of fatty acids.
A fatty acid contains a long hydrocarbon chain and a terminal carboxylate group. The hydrocarbon chain may be saturated (with no double bond) or may be unsaturated (containing double bond).
1.FATTY ACID SYNTHESIS FOR MBBS, LABORATORY MEDICINEAND BDS.pptRajendra Dev Bhatt
Lipid metabolism is the processing of lipids for energy use, energy storage, and structural component (Cholesterol & lipoproteins) production. Lipids are digested by lipase enzymes in the GI tract (with the help of bile acids) and are absorbed directly through the cell membrane. Free fatty acids are then resynthesized into triacylglycerols (TAGs) in the enterocytes. Finally, lipid components are repackaged into chylomicrons and transported throughout the body for use or storage.
Cell :Structure & Functions for Medical and Health allied StudentsRajendra Dev Bhatt
The cell is the basic structural and functional unit of all known living organisms.
It is the smallest unit of life that is classified as a living thing, and is often called the building block of life.
Biochemistry of Carbohydrates for MBBS, BDS, Lab Med 2024.pptxRajendra Dev Bhatt
Carbohydrates are carbon compounds that contain large quantities of hydroxyl groups.
The simplest carbohydrates also contain either an aldehyde moiety (these are termed polyhydroxyaldehydes) or a ketone moiety (polyhydroxyketones).
All carbohydrates can be classified as either monosaccharides, oligosaccharides or polysaccharides.
The main function of the kidney is excretion of water soluble waste products from our body.
Derangement of any of these function would result in either decreased excretion of waste products and hence their accumulation in the body or loss of some vital nutrient from the body.
4. Renal Block-Acid Base Balance-for Medical students.pptxRajendra Dev Bhatt
Acid–Base balance (also known as pH HOMEOSTASIS ) : one of the essential functions of the body, it is concerned with the precise regulation of free (unbound) hydrogen ion concentration in body fluids.
3. Renal Block-Water and Electrolyte Balance-MBBS-2024.pptxRajendra Dev Bhatt
Water is the most ubiquitous substance in the chemical reactions of life.
The interactions of various aqueous solutions, solutions in which water is the solvent, are continuously monitored and adjusted by a large suite of interconnected feedback systems in our body.
Understanding the ways in which the body maintains these critical balances is key to understanding good health.
Clinical laboratories that use AI have both possibilities and obstacles. It is crucial to create rules that guarantee fairness, security, and dependability for AI systems. Guidelines for regulators and parties involved in creating medical products based on artificial intelligence have previously been released by numerous international organizations.
Basic Instruments-Equipment; Application and Management.pptxRajendra Dev Bhatt
Equipment management (Buying to Disposing) is one of the essential elements out of 12 quality management system.
Proper management of the equipment in the laboratory is necessary to ensure accurate, reliable, and timely testing.
Research is what I’m doing when I don’t know what I’m doing.
Wernher von Braun
Research is to see what everybody else has seen and think what nobody has thought.
Albert Szent Gyorgyi
Knee anatomy and clinical tests 2024.pdfvimalpl1234
This includes all relevant anatomy and clinical tests compiled from standard textbooks, Campbell,netter etc..It is comprehensive and best suited for orthopaedicians and orthopaedic residents.
Basavarajeeyam is an important text for ayurvedic physician belonging to andhra pradehs. It is a popular compendium in various parts of our country as well as in andhra pradesh. The content of the text was presented in sanskrit and telugu language (Bilingual). One of the most famous book in ayurvedic pharmaceutics and therapeutics. This book contains 25 chapters called as prakaranas. Many rasaoushadis were explained, pioneer of dhatu druti, nadi pareeksha, mutra pareeksha etc. Belongs to the period of 15-16 century. New diseases like upadamsha, phiranga rogas are explained.
Rasamanikya is a excellent preparation in the field of Rasashastra, it is used in various Kushtha Roga, Shwasa, Vicharchika, Bhagandara, Vatarakta, and Phiranga Roga. In this article Preparation& Comparative analytical profile for both Formulationon i.e Rasamanikya prepared by Kushmanda swarasa & Churnodhaka Shodita Haratala. The study aims to provide insights into the comparative efficacy and analytical aspects of these formulations for enhanced therapeutic outcomes.
Basavarajeeyam is a Sreshta Sangraha grantha (Compiled book ), written by Neelkanta kotturu Basavaraja Virachita. It contains 25 Prakaranas, First 24 Chapters related to Rogas& 25th to Rasadravyas.
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
TEST BANK For Community Health Nursing A Canadian Perspective, 5th Edition by...Donc Test
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1. MEMBRANE TRANSPORT
Rajendra Dev Bhatt (PhD Scholar)
Asst. Professor
Clinical Biochemistry & Laboratory Medicine
Fellow: Translational Research (2018-2022) in CVD in
Nepal, NHLBI & NIH, USA
2. The plasma membrane, which is also called the cell
membrane, has many functions, but the most basic
one is to define the borders of the cell and keep the
cell functional.
The plasma membrane is selectively permeable.
This means that the membrane allows some
materials to freely enter or leave the cell, while
other materials cannot move freely, but require the
use of a specialized structure, and occasionally, even
energy investment for crossing.
Introduction
3. Membrane Components and
Structure
Among the most sophisticated functions of the
plasma membrane is the ability to transmit signals
by means of complex, integral proteins known as
receptors.
These proteins act both as receivers of extracellular
inputs and as activators of intracellular processes.
These membrane receptors provide extracellular
attachment sites for effectors like hormones and
growth factors, and they activate intracellular
response cascades when their effectors are bound.
4. Fluid Mosaic Model
The explanation proposed by Singer and Nicolson is
called the fluid mosaic model.
The model has evolved somewhat over time, but it
still best accounts for the structure and functions of
the plasma membrane as we now understand them.
The fluid mosaic model describes the structure of
the plasma membrane as a mosaic of components
including phospholipids, cholesterol, proteins, and
carbohydrates that gives the membrane a fluid
character.
Plasma membranes range from 5 to 10 nm in
thickness.
5. Components of a plasma
membrane
The principal components of a plasma membrane
are lipids, proteins, and carbohydrates.
The lipids include phospholipids and cholesterol
Proteins. Carbohydrate chains are attached to the
proteins and lipids on the outside surface of the
membrane.
Typical human cell, protein accounts for about 50%
of the composition by mass, lipids account for about
40% of the composition by mass, with the
remaining 10% of the com-position by mass being
carbohydrates.
7. Passive Transport
Passive transport is a naturally occurring
phenomenon and does not require the cell to exert
any of its energy to accomplish the movement.
In passive transport, substances move from an area
of higher concentration to an area of lower
concentration.
A physical space in which there is a range of
concentrations of a single substance is said to have
a concentration gradient.
8. Selective Permeability
Recall that plasma membranes are amphipathic:
They have hydrophilic and hydrophobic regions.
This characteristic helps the movement of some
materials through the membrane and hinders the
movement of others.
Lipid-soluble material with a low molecular weight
can easily slip through the hydrophobic lipid core
of the membrane. Substances such as the fat-
soluble vitamins A, D, E, and K readily pass
through the plasma membranes in the digestive
tract and other tissues.
Molecules of oxygen and carbon dioxide have no
charge and so pass through membranes by simple
diffusion.
9. Diffusion
• Diffusion is a passive process of transport. A
single substance tends to move from an area of
high concentration to an area of low
concentration until the concentration is equal
across a space.
10. Facilitated diffusion
In facilitated diffusion, materials diffuse across the
plasma membrane with the help of membrane proteins.
A concentration gradient exists that would allow these
materials to diffuse into the cell without expending
cellular energy.
However, these materials are ions or polar molecules that
are repelled by the hydrophobic parts of the cell
membrane. Facilitated diffusion proteins shield these
materials from the repulsive force of the membrane,
allowing them to diffuse into the cell.
These proteins are called transport-proteins and can be
channels or carrier proteins.
11. Channel proteins are trans-membrane
proteins that fold in such as way as to form a
channel or pore through the membrane. Each
channel is specific for one particular
substance.
12. Some channel proteins are always open but many
are “gated,” meaning that they can be opened and
closed.
If a channel is ligand-gated, the attachment of a
particular molecule to the channel protein may
cause it to open.
Other channels are voltage-gated, requiring a
change in voltage across the membrane to open
them.
Cells involved in the transmission of electrical
impulses, such as nerve and muscle cells, have
voltage-gated ion channels in their membranes.
13. Another type of trans-membrane transporter
protein is a carrier protein. Like channels, carrier
proteins are usually specific for particular
molecules. A carrier proteins binds a substance
and, in doing so, triggers a change of its own
shape, moving the bound molecule across the
membrane.
14. Osmosis
Osmosis is the diffusion of water across a
semipermeable membrane. Since it is diffusion,
it depends on the concentration gradient, or the
amount of water on each side of the membrane.
15. Active transport
Active transport mechanisms require the use of the cell’s
energy, usually in the form of adenosine triphosphate
(ATP).
If a substance must move into the cell against its
concentration gradient—that is, if the concentration of the
substance inside the cell is greater than its concentration
in the extracellular fluid (and vice versa)—the cell must
use energy to move the substance.
Some active transport mechanisms move small-molecular
weight materials, such as ions, through the membrane.
Other mechanisms transport much larger molecules.
16. Electrochemical gradient
The interior of living cells is electrically negative with
respect to the extracellular fluid surrounding them. At the
same time, cells have a lower concentration of (Na+) than
does the extracellular fluid. Therefore, both the
concentration gradient and the electrical gradient tend to
drive Na+ into the cell.
Conversely, cells have a higher concentration of K+ than
the extracellular fluid does. Therefore, the concentration
gradient tends to drive K+ out of the cell, while the
electrical gradient tends to drive it inside the cell. The
combined gradient of concentration and electrical charge
that affects an ion is called its electrochemical gradient.
17. Injection of a potassium solution into a
person’s blood is lethal; this is used in
capital punishment and euthanasia. Why do
you think a potassium solution injection is
lethal?
18. Proteins for Active Transport
The specific proteins that facilitate active transport
are called transporters. There are three types of
transporters.
A uniporter carries one specific ion or molecule.
A symporter carries two different ions or
molecules, both in the same direction.
An antiporter carries two different ions or
molecules in different directions.
All of these transporters can transport small,
uncharged organic molecules such as glucose.
20. Primary Active Transport
One of the most important
pumps in animals cells is
the sodium-potassium
pump (Na+-K+ ATPase),
which maintains the
electrochemical gradient
and the correct
concentrations of Na+ and
K+ in living cells. The
sodium-potassium pump
moves two K+ into the cell
while moving three Na+
out of the cell.
21. The sodium-potassium pump works in the following six steps:
– Three sodium ions bind to the protein.
– ATP is hydrolyzed by the protein carrier and a low-
energy phosphate group attaches to it.
– The carrier changes shape and opens towards the
exterior of the membrane. The three sodium ions are
released.
– Two potassium ions attach to the protein, causing the
low-energy phosphate group to detach.
– The carrier protein changes shape so that is open
towards the interior of the cell.
– The two potassium ions are released into the cytoplasm
and the process begins again.
22. Several things have happened as a result of this
process. First, there are now more sodium ions outside
of the cell than inside and more potassium ions inside
than out.
Second, since three sodium ions moved out for each
two potassium ions that moved in, the interior is
slightly more negative relative to the exterior.
This difference in charge is important in creating the
conditions necessary for secondary active transport.
The sodium-potassium pump is, therefore,
an electrogenic pump (a pump that creates a charge
imbalance), creating an electrical imbalance across the
membrane and contributing to the membrane potential.
24. Endocytosis
Endocytosis is a type of active transport that
moves particles, such as large molecules, parts of
cells, and even whole cells, into a cell. There are
different variations of endocytosis, but all share a
common characteristic.
The three types of endocytosis are phagocytosis,
pinocytosis, and receptor mediated
endocytosis.
25. Phagocytosis (“cell eating”) is the process by
which large particles, such as other cells or
relatively large particles, are taken in by a cell.
For example, when microorganisms invade the
human body, a type of white blood cell called a
neutrophil will “eat” the invaders through
phagocytosis, surrounding and engulfing the
microorganism, which is then destroyed by
lysosomes inside the neutrophil.
26. Through Pinocytosis (“cell drinking”), cells
take in molecules, including water, which the
cell needs from the extracellular fluid.
Pinocytosis results in a much smaller vesicle
than does phagocytosis, and the vesicle does
not need to merge with a lysosome.
Receptor-mediated endocytosis is a targeted
variation of endocytosis that employs receptor
proteins in the plasma membrane that have a
specific binding affinity for certain substances
27. Receptor-mediated
endocytosis, as in
phagocytosis, uses clathrin
protein attached to the
cytoplasmic side of the
plasma membrane. Some
human diseases are caused
by the failure of receptor-
mediated endocytosis.
28. Exocytosis
The reverse process of moving material into a cell is
the process of exocytosis. The purpose of exocytosis
is to expel material from the cell into the
extracellular fluid. Waste material is enveloped in
vesicle, which fuses with the interior of the plasma
membrane, expelling the waste material into the
extracellular space.
Cells also use exocytosis to secrete proteins such as
hormones, neurotransmitters, or parts of the extra
cellula rmatrix.
30. Nerve Impulse Transmission
For the nervous system to function, neurons must
be able to send and receive signals. These signals
are possible because each neuron has a charged
cellular membrane (a voltage difference between
the inside and the outside), and the charge of this
membrane can change in response to
neurotransmitter molecules released from other
neurons and environmental stimuli.
31. Resting Membrane Potential
A neuron at rest is negatively charged: the inside
of a cell is approximately 70 millivolts more
negative than the outside (40−80 mV, note that
this number varies by neuron type and by
species). This voltage is called the resting
membrane potential; it is caused by differences
in the concentrations of ions inside and outside
the cell.
32. The difference in the number of positively charged
potassium ions (K+) inside and outside the cell
dominates the resting membrane potential.
The negative charge within the cell is created by the
cell membrane being more permeable to potassium
ion movement than sodium ion movement.
In neurons, potassium ions are maintained at high
concentrations within the cell while sodium ions are
maintained at high concentrations outside of the
cell.
As more cations are expelled from the cell than
taken in, the inside of the cell remains negatively
charged relative to the extracellular fluid.
33. Action Potential
A neuron can receive input from other neurons and,
if this input is strong enough, send the signal to
downstream neurons.
Transmission of a signal between neurons is
generally carried by a chemical called a
neurotransmitter.
Transmission of a signal within a neuron (from
dendrite to axon terminal) is carried by a brief
reversal of the resting membrane potential called an
action potential.
34. When neurotransmitter molecules bind to
receptors located on a neuron’s dendrites, ion
channels open. At excitatory synapses, this
opening allows positive ions to enter the neuron
and results in depolarization of the membrane a
decrease in the difference in voltage between the
inside and outside of the neuron.
35. A stimulus from a sensory cell or another neuron
depolarizes the target neuron to its threshold
potential (-55 mV). Na channels in the axon
hillock open, allowing positive ions to enter the
cell. Once the sodium channels open, the neuron
completely depolarizes to a membrane potential of
about +40 mV.
Action potentials are considered an "all-or
nothing" event, in that, once the threshold
potential is reached, the neuron always completely
depolarizes. Once depolarization is complete, the
cell must now "reset" its membrane voltage back
to the resting potential
36. Summary
Neurons have charged membranes because there are different
concentrations of ions inside and outside of the cell. Voltage-gated
ion channels control the movement of ions into and out of a neuron.
When a neuronal membrane is depolarized to at least the threshold
of excitation, an action potential is fired.
The action potential is then propagated along a myelinated axon to
the axon terminals. In a chemical synapse, the action potential
causes release of neurotransmitter molecules into the synaptic cleft.
Through binding to postsynaptic receptors, the neurotransmitter can
cause excitatory or inhibitory postsynaptic potentials by
depolarizing or hyperpolarizing, respectively, the postsynaptic
membrane.
In electrical synapses, the action potential is directly communicated
to the postsynaptic cell through gap junctions—large channel
proteins that connect the pre-and postsynaptic membranes.