1. Diseases caused by mutations in genes encoding tight junction and connexin proteins include various forms of deafness, skin diseases, cancer, and neurological disorders.
2. Dysfunctions of adherens junctions and desmosomes can result in colon cancer and autoimmune blistering diseases respectively.
3. Abnormalities in sodium-potassium pumps and ion channels can cause conditions like cardiac failure, hypertension, muscle spasms, deafness, and cystic fibrosis.
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.
This document discusses various mechanisms of transport across cell membranes, including:
1) Passive transport mechanisms like diffusion and facilitated diffusion of small molecules.
2) Active transport of ions and macromolecules against a concentration gradient using ATP.
3) Endocytosis and exocytosis for transport of large molecules and macromolecules across the membrane.
4) Specific transport proteins and ion channels that facilitate movement of substances in and out of cells.
Active transport requires energy from ATP to pump molecules against their concentration gradient through carrier proteins in the cell membrane. The sodium-potassium pump is a specific example which uses ATP to pump 3 sodium ions out of and 2 potassium ions into the cell, maintaining concentration gradients and cell volume. Bulk transport uses endocytosis to bring molecules into the cell through pinocytosis or phagocytosis, forming vesicles, and exocytosis to export molecules by vesicle fusion with the cell membrane.
prof . dr. ihsan edan alsaimary
department of microbiology - college of medicine - university of basrah - basrah -IRAQ
ihsanalsaimary@gmail.com
00964 7801410838
This document discusses the structure and functions of the cell membrane. It notes that the cell membrane is selectively permeable, allowing some substances to pass through freely while requiring assistance for others. The fluid mosaic model describes the structure of the membrane. Integral proteins assist in transporting larger molecules and ions across. The cytoskeleton provides structure and transport within the cell. Various modes of transport across the membrane are covered, including passive diffusion and facilitated transport which move down gradients, and active transport which moves against gradients and requires energy. Endocytosis and exocytosis involve transport of substances into and out of the cell.
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.
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.
This document discusses various mechanisms of transport across cell membranes, including:
1) Passive transport mechanisms like diffusion and facilitated diffusion of small molecules.
2) Active transport of ions and macromolecules against a concentration gradient using ATP.
3) Endocytosis and exocytosis for transport of large molecules and macromolecules across the membrane.
4) Specific transport proteins and ion channels that facilitate movement of substances in and out of cells.
Active transport requires energy from ATP to pump molecules against their concentration gradient through carrier proteins in the cell membrane. The sodium-potassium pump is a specific example which uses ATP to pump 3 sodium ions out of and 2 potassium ions into the cell, maintaining concentration gradients and cell volume. Bulk transport uses endocytosis to bring molecules into the cell through pinocytosis or phagocytosis, forming vesicles, and exocytosis to export molecules by vesicle fusion with the cell membrane.
prof . dr. ihsan edan alsaimary
department of microbiology - college of medicine - university of basrah - basrah -IRAQ
ihsanalsaimary@gmail.com
00964 7801410838
This document discusses the structure and functions of the cell membrane. It notes that the cell membrane is selectively permeable, allowing some substances to pass through freely while requiring assistance for others. The fluid mosaic model describes the structure of the membrane. Integral proteins assist in transporting larger molecules and ions across. The cytoskeleton provides structure and transport within the cell. Various modes of transport across the membrane are covered, including passive diffusion and facilitated transport which move down gradients, and active transport which moves against gradients and requires energy. Endocytosis and exocytosis involve transport of substances into and out of the cell.
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.
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.
Ionophores are molecules that transport ions across biological membranes. They contain both hydrophilic regions that bind ions and hydrophobic regions that interact with membrane lipids. Ionophores are classified based on their mechanism of action as either mobile carrier ionophores which transport ion complexes, or channel-forming ionophores which introduce pores for ion passage. Examples include valinomycin which transports potassium ions, gramicidin A which forms channels for cation transport, and ionomycin which carries calcium ions into cells. Ionophores have important applications as antibiotics, in research to manipulate cellular physiology, and as feed additives to improve livestock growth and productivity.
Calcium ions play an important role in cell signaling as a secondary messenger. When cells are stimulated, calcium is released from intracellular stores like the endoplasmic reticulum or enters the cell through ion channels in the cell membrane. This increase in intracellular calcium activates calcium-binding proteins to exert effects on various cellular processes. Calcium signaling is involved in muscle contraction, neuronal transmission, cell growth, and other key functions. It is regulated through calcium influx and efflux mechanisms to maintain appropriate calcium levels in cells. Dysregulation of calcium signaling has been implicated in cancer metastasis and cell damage.
This document discusses four main mechanisms of membrane transport: ion channels, transporters, cotransporters, and uniporters.
Ion channels form hydrophilic passageways for ions to pass through rapidly down electrochemical gradients. Transporters are integral membrane proteins that undergo conformational changes to transport substances across membranes against concentration gradients or down gradients with the help of ion gradients.
Cotransporters couple the transport of one substance with the favorable transport of another substance against its gradient. Uniporters transport a single molecule down its concentration gradient through facilitated diffusion. Common examples like glucose transporters are discussed in detail.
The document summarizes the structure and functions of a normal human cell. It describes the main components of a cell including the nucleus that contains DNA, cytosol, cytoskeleton, and various organelles such as mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, secretory vesicles, lysosomes, peroxisomes, and proteasomes. It also discusses cell membranes, transport through membranes, and transmission of messages across cell membranes through receptors and second messengers.
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.
This document provides information on the basic cell structure and organelles of eukaryotic cells. It discusses the plasma membrane and fluid mosaic model. It then describes the main organelles - nucleus, ribosomes, endoplasmic reticulum, Golgi complex, lysosomes, mitochondria - and their functions. It also discusses transport mechanisms, including active transport, passive transport, ion channels, and carrier proteins. Finally, it briefly mentions secretory vesicles, exocytosis, endocytosis, pinocytosis and phagocytosis.
This document summarizes membrane transport mechanisms, including passive transport processes like simple diffusion, facilitated diffusion, and osmosis as well as active transport processes like primary active transport, secondary active transport, and vesicular transport. Key transport proteins like carrier proteins, ion channels, and pumps are described. Specific examples of transport systems like sodium-potassium pumps, glucose transporters, and exocytosis/endocytosis are provided. The roles of these transport mechanisms in maintaining homeostasis and their implications for certain diseases are also mentioned.
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
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 cell membrane regulates the movement of materials in and out of cells. It is composed of a phospholipid bilayer with proteins, lipids, and carbohydrates embedded. The membrane maintains homeostasis by transporting nutrients into the cell and waste out, while preventing unwanted substances from entering or needed materials from leaving. Transport occurs through diffusion, osmosis, facilitated diffusion, active transport, and bulk transport like endocytosis and exocytosis.
Active transport moves molecules or ions against their concentration gradient using energy. There are two types: primary active transport which directly uses ATP as an energy source, and secondary active transport which uses the concentration gradient of another substance like sodium. Primary active transport examples include the sodium-potassium pump and calcium pumps. Secondary active transport occurs by co-transport or counter-transport using the sodium gradient. Passive diffusion requires no energy and occurs down a gradient, while active transport is an uphill process requiring a carrier protein and energy. Vesicular transport involves endocytosis which brings substances into cells through pinocytosis or phagocytosis, and exocytosis which releases substances from cells.
The plasma membrane, also called the cell membrane, is the membrane found in all cells that separates the interior of the cell from the outside environment. . The plasma membrane consists of a lipid bilayer that is semipermeable. The plasma membrane regulates the transport of materials entering and exiting the cell.
This document discusses the structure and functions of the cell. It divides the cell into three main parts - the plasma membrane, cytoplasm, and nucleus. The plasma membrane forms the outer boundary of the cell and is selectively permeable. The cytoplasm contains the cytosol and various organelles. Key organelles include the nucleus, which houses the cell's DNA, and mitochondria, which generate energy. Materials move across the plasma membrane through passive diffusion, facilitated diffusion, active transport, and osmosis. Transport proteins help move substances against concentration gradients using cellular energy.
The cell membrane regulates the movement of materials in and out of the cell through diffusion, osmosis, facilitated diffusion, and active transport. It is composed of a phospholipid bilayer with embedded proteins. Membrane proteins come in two types - integral proteins that span the membrane and peripheral proteins attached to the surface. Carbohydrates on membrane proteins and lipids aid in cell recognition. The fluid mosaic model describes membranes as fluid structures that allow lipids and proteins to move laterally.
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.
Ionophores are molecules that transport ions across biological membranes. They contain both hydrophilic regions that bind ions and hydrophobic regions that interact with membrane lipids. Ionophores are classified based on their mechanism of action as either mobile carrier ionophores which transport ion complexes, or channel-forming ionophores which introduce pores for ion passage. Examples include valinomycin which transports potassium ions, gramicidin A which forms channels for cation transport, and ionomycin which carries calcium ions into cells. Ionophores have important applications as antibiotics, in research to manipulate cellular physiology, and as feed additives to improve livestock growth and productivity.
Calcium ions play an important role in cell signaling as a secondary messenger. When cells are stimulated, calcium is released from intracellular stores like the endoplasmic reticulum or enters the cell through ion channels in the cell membrane. This increase in intracellular calcium activates calcium-binding proteins to exert effects on various cellular processes. Calcium signaling is involved in muscle contraction, neuronal transmission, cell growth, and other key functions. It is regulated through calcium influx and efflux mechanisms to maintain appropriate calcium levels in cells. Dysregulation of calcium signaling has been implicated in cancer metastasis and cell damage.
This document discusses four main mechanisms of membrane transport: ion channels, transporters, cotransporters, and uniporters.
Ion channels form hydrophilic passageways for ions to pass through rapidly down electrochemical gradients. Transporters are integral membrane proteins that undergo conformational changes to transport substances across membranes against concentration gradients or down gradients with the help of ion gradients.
Cotransporters couple the transport of one substance with the favorable transport of another substance against its gradient. Uniporters transport a single molecule down its concentration gradient through facilitated diffusion. Common examples like glucose transporters are discussed in detail.
The document summarizes the structure and functions of a normal human cell. It describes the main components of a cell including the nucleus that contains DNA, cytosol, cytoskeleton, and various organelles such as mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, secretory vesicles, lysosomes, peroxisomes, and proteasomes. It also discusses cell membranes, transport through membranes, and transmission of messages across cell membranes through receptors and second messengers.
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.
This document provides information on the basic cell structure and organelles of eukaryotic cells. It discusses the plasma membrane and fluid mosaic model. It then describes the main organelles - nucleus, ribosomes, endoplasmic reticulum, Golgi complex, lysosomes, mitochondria - and their functions. It also discusses transport mechanisms, including active transport, passive transport, ion channels, and carrier proteins. Finally, it briefly mentions secretory vesicles, exocytosis, endocytosis, pinocytosis and phagocytosis.
This document summarizes membrane transport mechanisms, including passive transport processes like simple diffusion, facilitated diffusion, and osmosis as well as active transport processes like primary active transport, secondary active transport, and vesicular transport. Key transport proteins like carrier proteins, ion channels, and pumps are described. Specific examples of transport systems like sodium-potassium pumps, glucose transporters, and exocytosis/endocytosis are provided. The roles of these transport mechanisms in maintaining homeostasis and their implications for certain diseases are also mentioned.
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
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 cell membrane regulates the movement of materials in and out of cells. It is composed of a phospholipid bilayer with proteins, lipids, and carbohydrates embedded. The membrane maintains homeostasis by transporting nutrients into the cell and waste out, while preventing unwanted substances from entering or needed materials from leaving. Transport occurs through diffusion, osmosis, facilitated diffusion, active transport, and bulk transport like endocytosis and exocytosis.
Active transport moves molecules or ions against their concentration gradient using energy. There are two types: primary active transport which directly uses ATP as an energy source, and secondary active transport which uses the concentration gradient of another substance like sodium. Primary active transport examples include the sodium-potassium pump and calcium pumps. Secondary active transport occurs by co-transport or counter-transport using the sodium gradient. Passive diffusion requires no energy and occurs down a gradient, while active transport is an uphill process requiring a carrier protein and energy. Vesicular transport involves endocytosis which brings substances into cells through pinocytosis or phagocytosis, and exocytosis which releases substances from cells.
The plasma membrane, also called the cell membrane, is the membrane found in all cells that separates the interior of the cell from the outside environment. . The plasma membrane consists of a lipid bilayer that is semipermeable. The plasma membrane regulates the transport of materials entering and exiting the cell.
This document discusses the structure and functions of the cell. It divides the cell into three main parts - the plasma membrane, cytoplasm, and nucleus. The plasma membrane forms the outer boundary of the cell and is selectively permeable. The cytoplasm contains the cytosol and various organelles. Key organelles include the nucleus, which houses the cell's DNA, and mitochondria, which generate energy. Materials move across the plasma membrane through passive diffusion, facilitated diffusion, active transport, and osmosis. Transport proteins help move substances against concentration gradients using cellular energy.
The cell membrane regulates the movement of materials in and out of the cell through diffusion, osmosis, facilitated diffusion, and active transport. It is composed of a phospholipid bilayer with embedded proteins. Membrane proteins come in two types - integral proteins that span the membrane and peripheral proteins attached to the surface. Carbohydrates on membrane proteins and lipids aid in cell recognition. The fluid mosaic model describes membranes as fluid structures that allow lipids and proteins to move laterally.
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CELL JUNCTIONS AND MEMBRANE TRANSPORT 2.docx
1. CELL JUNCTIONS AND MEMBRANE
TRANSPORT 2
Diseasescaused by mutation of genes encoding proteins of
tight junction:
1. Hereditary deafness
2. Ichthyosis (scaly skin)
3. Sclerosing cholangitis (inflammation of bile duct causing
obstruction)
4. Hereditary hypomagnesemia(low level of magnesium in the
blood)
5. Synovial sarcoma(soft tissue cancer)
Functions of tight junction are affected by some bacteria and viruses
also.
Mutation in the genes encodingthe connexinscauses
diseasessuch as:
1.Deafness
2. Keratoderma(thickening of skin on palms and soles)
3. Cataract (opacity of lens in eye)
4. Peripheral neuropathy (damage to the nerves of peripheral
nervous system)
5. CharcotMarieToothdisease (a form of neuropathy)
6. Heterotaxia (abnormal arrangement of organs or parts of the
body in relation to leftrightsymmetry).
1. Dysfunction of adherens junction and focaljunction in colon due
to mutation of proteins results in colon cancer. It also leads to tumor
metastasis (spread of cancer cells from a primary tumor to other
parts of the body)
2. Dysfunction of desmosomecauses bullous pemphigoid
(autoimmune disease with tense blister ingeruptions of the skin).
The patients with this disease develop antibodies against cadherins
3. Dysfunction of hemidesmosome also causes bullous pemphigoid.
The patients develop antibodies against integrins.
TYPES OF GATED CHANNELS
i. Voltage-gated channel
Voltage-gated channels are the channels which openwhenever
there is a change in the electrical potential.
2. For example, in the neuromuscular junction, when action potential
reaches axon terminal, the calcium channels are opened and
calcium ions diffuse into the interior of the axon terminal from ECF
Similarly, in the muscle during the excitation-contraction coupling,
the action potential spreads through the transverse tubules of the
sarcotubular system.When the action potential reaches the
cisternae, large number of calcium ions diffuse from cisternae into
sarcoplasm.
ii. Ligand-gated channel
Ligand-gated channels are the type of channels which openin the
presence of some hormonal substances.
The hormonal substances are called ligands and the channels are
called ligand-gated channels. During the transmission of impulse
through the neuromuscular junction, acetylcholine is released from
the vesicles.
The acetylcholine moves through the presynaptic membrane
(membrane of the axon terminal) and reaches the synaptic cleft.
Then, the acetylcholine molecules cause opening of sodium
channels in the postsynaptic membrane and sodium ions diffuse
into the neuromuscular junction from ECF.
iii. Mechanically gated channel
Mechanically gated channels are the channels which are opened by
some mechanical factors.Examples are, channels present in the
pressure receptors (Pacinian corpuscles)and the receptorcells
(hair cells)of organ of Corti and vestibular apparatus. When a
Pacinian corpuscle is subjected to pressure,it is compressed
resulting in deformationof its core fiber. This deformation
causes opening of sodium channel and developmentof
receptorpotential
Potassium: Sodium-Potassium Pump
Sodium and potassium ions are transported across the cell membrane by
means of a common carrier proteincalled sodium-potassium (Na+-K+) pump. It
is also called Na+-K+ ATPase pump or Na+-K+ ATPase. This pump
transports sodium from inside to outside the cell and potassium from outside to
inside the cell. This pump is present in all the cells of the body.
Na+-K+ pump is responsible for the distribution of sodium and potassium ions
across the cell membrane and the development of resting membrane potential.
Structure of Na+-K+ pump
Carrier protein that constitutes Na+-K+ pump is made up of two protein subunit
molecules, an α-subunit with a molecular weight of 100,000 and a β-subunit
with a molecular weight of 55,000.
Transport of Na+ and K+occurs only by α-subunit. The β-subunit is a
glycoprotein the function of which is not clear.
α-subunit of the Na+-K+ pump has got six sites:
3. i. Three receptor sites for sodium ions on the inner (towards cytoplasm) surface
of the protein molecule
ii. Two receptor sites for potassium ions on the outer (towards ECF) surface of
the protein molecule
iii. One site for enzyme adenosine triphosphatase (ATPase), which is near the
sites for sodium.
Mechanism of action of Na+-K+ pump
Three sodium ions from the cell get attached to the receptor sites of sodium
ions on the inner surface of the carrier protein. Two potassium ions outside the
cell bind to the receptor sites of potassium ions located on the outer surface of
the carrier protein
Binding of sodium and potassium ions to carrier protein activates the enzyme
ATPase. ATPase causes breakdown of ATP into adenosine diphosphate (ADP)
with the release of one high energy phosphate. Now, the energy liberated
causes some sort of conformational change in the molecule of the carrier
protein. Because of this, the outer surface of the molecule (with potassium
ions) now faces the inner side of the cell. And, the inner surface of the protein
molecule (with sodium ions) faces the outer side of the cell
Now, dissociationand release of the ions take place so that the sodium ions are
released outside the cell (ECF) and the potassium ions are released inside the
cell (ICF).
Exact mechanisms involved in the dissociation and release of ions are not yet
known.
Electrogenic activity of Na+-K+ pump
Na+-K+ pump moves three sodium ions outside the cell and two potassium
ions inside cell. Thus, when the pump works once, there is a net loss of one
positively charged ion from the cell. Continuous activity of the
sodium-potassium pumps causes reductionin the number of positively charged
ions inside the cell leading to increase in the negativity inside the cell. This is
called the electrogenic activity of Na+-K+ pump.
Hydrogen ion is actively transported across the cell membrane by
the carrier protein called hydrogen pump.
It also obtains energy from ATP by the activity of ATPase.
The hydrogen pumps that are present in two important organs have
some functional significance.
1. Stomach: Hydrogen pumps in parietal cells of the gastric glands
are involved in the formation of hydrochloric acid
2. Kidney: Hydrogen pumps in epithelial cells of distal convoluted
tubules and collecting ducts are involved in the secretionof
hydrogen ions from blood into urine
Is operated by a separate carrier protein. Energy is obtained from
ATP by the catalytic activity of ATPase.Calcium pumps are also
presentin some organelles of the cell such as sarcoplasmic
4. reticulum in the muscle and the mitochondria of all the cells.These
pumps move calcium into the organelles.
When sodium is transported by a carrier protein, another substance
is also transported by the same protein simultaneously, either in the
same direction (of sodium movement) or in the opposite direction.
Thus, the transport of sodium is coupled with transport of another
substance.
Substances carried by sodium cotransport are
glucose,amino acids, chloride, iodine, iron and urate.
BULK TRANSPORT
i.Macromolecules (in the form of droplets of fluid) bind to the outer
surface of the cell membrane
ii. Now, the cell membrane evaginates around the droplets
iii. Droplets are engulfed by the membrane
iv. Engulfed droplets are converted into vesicles and vacuoles,
which are called endosomes
v. Endosometravels into the interior of the cell
vi. Primary lysosome in the cytoplasm fuses with endosomeand
forms secondarylysosome
vii. Now, hydrolytic enzymes present in the secondary lysosome are
activated resulting in digestionand degradation of the endosomal
contents.
i. Receptor-mediated endocytosisis induced by substances like
ligands
ii. Ligand molecules approachthe cell and bind to receptors in the
clarithin-coated pits and form ligand-receptorcomplex
iii. Ligand-receptorcomplexgets aggregated in the coated pits.
Then, the pit is detached from cell membrane and becomesthe
coated vesicle. This coated vesicle forms the endosome
iv. Endosometravels into the interior of the cell.
Primary lysosome in the cytoplasm fuses with endosome and forms
secondarylysosome.
v. Now, the hydrolytic enzymes presentin secondarylysosome are
activated resulting in release of ligands into the cytoplasm
vi. Receptormay move to a new pit of the cell membrane
5. Receptor-mediated endocytosis play an important role in the
transport of several types of macromolecules into the cells, viz.
i. Hormones:Growth hormone, thyroid stimulating
hormone,luteinizing hormone, prolactin, insulin, glucagon,
calcitonin and catecholamines
ii. Lipids:Cholesteroland low-density lipoproteins (LDL)
platelet-derived GF, interferon
iv. Toxins and bacteria: Cholera toxin, diphtheria toxin,
pseudomonas toxin, recin and concanavalin
v. Viruses:Rous sarcoma virus, semliki forestvirus, vesicular
stomatitis virus and adenovirus
vi. Transport proteins: Transferrin and transcobalamine
vii. Antibodies:IgE,polymeric IgG and maternal IgG.
Some of the receptor-coated pits in cell membrane are coated with
another protein called of clathrin. Caveolin-coated pits are
cocaveolininstead are coated with another protein called caveolin
instead of clathrin. Caveolin-coated pits are concerned with the
transport of vitamins into the cell.
Calcium ions play an important role during the release of
some secretorysubstances such as neurotransmitters.
The calcium ions enter the cell and cause exocytosis.
Transcytosis is a transport mechanism in which an extracellular
macromolecule enters through one side of a cell, migrates across
cytoplasm of the cell and exits through the other side.
Cell encloses the extracellular substance by invagination
of the cell membrane to form a vesicle. Vesicle then
moves across the cell and thrown out through opposite cell
membrane by means of exocytosis.Transcytosis involves the
receptor-coated pits as in receptor-mediated endocytosis. Receptor
protein coating the pits in this process is caveolin and not clathrin.
Transcytosis is also called, vesicle traffickingor cytopempsis.
Transcytosis plays an important role in selectivelytransporting the
substances between two environments across the cells without any
distinct change in the compositionof these environments. Example
of this type of transport is the movementof proteins from capillary
blood into interstitial fluid across the endothelial cells of
the capillary. Many pathogenslike human immunodeficiencyvirus
(HIV) are also transported by this mechanism.
MOLECULAR MOTORS
6. Molecular motors are the protein-based molecularmachines that
perform intracellular movements in response to specific stimuli.
1. Transport of synaptic vesicles containing neurotransmitters from
the nerve cell body to synaptic terminal
2. Role in cell division (mitosis and meiosis)by pulling the
chromosomes
3. Transport of viruses and toxins to the interior of the cell for its own
detriment.
TYPES OF MOLECULAR MOTORS
Molecular motors are classified into three super families:
1. Kinesin
2. Dynein
3. Myosin.
1. Kinesin
Kinesin transports substances by moving over the microtubules.
Each kinesin molecule has two heads and a tail portion. One of the
heads hydrolyses ATP to obtain energy. By utilizing this energy, the
other head swings continuously causing movement of the whole
kinesin
Molecule. End portion of the tail carries the cargo (substances to be
transported). Kinesin is responsible for anterograde transport
(transport of substances towards the positive end of microtubule).
2. Dynein
Dynein is almost similar to kinesin and transports substances by
moving over the microtubules.But it is responsiblefor retrograde
transport (transport of substances towards the negative end of
microtubule).
3. Myosin
Myosin transports substances by moving over micro filaments.
Myosins are classified into 18 types according to the amino acid
sequence.However, myosin II and V are functionally significant.
Myosin II is involved in muscle contraction . Myosin V is involved
in transport of vesicles.
ABNORMALITIES OF SODIUMPOTASSIUM PUMP
Abnormalities in the number or function of Na+-K+ pump are
associated with several pathological conditions.
Important examples are:
7. 1. Reduction in either the number or concentration of Na+-K+ pump
in myocardium is associated with cardiac failure
2. Excess reabsorption of sodium in renal tubules is associated with
hypertension.
CHANNELOPATHIES / ION CHANNEL DISEASES
1.Sodium Channel Diseases
Dysfunction of sodium channels leads to muscle spasm and Liddle’
s syndrome (dysfunction of sodium channels in kidney resulting in
increased osmotic pressure in the blood and hypertension).
2. Potassium Channel Diseases
Potassium channel dysfunction causes disorders of heart, inherited
deafness and epileptic seizures in newborn.
3. Chloride Channel Diseases
Dysfunction of chloride channels results in formation of renal stones
and cystic fibrosis. Cystic fibrosis is a generalized disorder affecting
the functions of many organs such as lungs (due to excessive
mucus), exocrine glands like pancreas, biliary system and immune
system.