The document discusses membrane structure and transport of small molecules across membranes. It begins by introducing the roles and components of cell membranes, including defining compartments and regulating transport. The membrane is composed of lipids like phospholipids and cholesterol, as well as integral and peripheral proteins. Transport across membranes can occur through passive or active methods. Passive transport includes simple diffusion of small soluble molecules and facilitated diffusion using channel or carrier proteins to transport molecules down their concentration gradients without energy.
Structure and functions of cell, transport across cell membrane, cell
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the smallest unit that can live on its own and that makes up all living organisms and the tissues of the body
The basic tenets of the cell theory are as follows:
All living things are made up of one or more cells.
The cell is the structural and functional unit of all living things.
Cells come from pre-existing cells through the process of division.
All cells are the same in regard to chemical composition.
Cells also communicate with each other. Whether in plants, humans, or animals, they connect to create a solid, well formed organism. In humans, cells build tissues, tissues form organs, and organs work together to keep the body alive.
Experts estimate that there are around 200Trusted Source cell types in the human body.
Structure and functions of cell, transport across cell membrane, cell
division, cell junctions. General principles of cell communication,
the smallest unit that can live on its own and that makes up all living organisms and the tissues of the body
The basic tenets of the cell theory are as follows:
All living things are made up of one or more cells.
The cell is the structural and functional unit of all living things.
Cells come from pre-existing cells through the process of division.
All cells are the same in regard to chemical composition.
Cells also communicate with each other. Whether in plants, humans, or animals, they connect to create a solid, well formed organism. In humans, cells build tissues, tissues form organs, and organs work together to keep the body alive.
Experts estimate that there are around 200Trusted Source cell types in the human body.
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The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
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The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
2. Introduction
• Cell membranes define compartments of different
compositions.
• Membranes are composed of a large number of different
lipids and proteins that exhibit dynamic organisation and
behaviour.
• The lipid bilayer of biological membranes has a very low
permeability for most biological molecules and ions.
– Materials that are soluble in lipids can pass through the
cell membrane easily
3. Homeostasis
• Balanced internal condition of cells
• Also called equilibrium
• Maintained by plasma membrane controlling
what enters & leaves the cell
4. Introduction
• The plasma membrane plays several key roles in the cell:
– Seperates the interior of the cell from the extracellular
environment
– Regulates the materials in and out of the cell
– Communicates with other cells
• Cell membranes also form compartments within eukaryotic
cells where they participate in and serve as surfaces for the
reactions necessary for life.
7. Phospholipids
• Phospholipids make up the
cell membrane.
• Phospholipids contain
– two fatty acids (nonpolar,
hydrophobic): tail
– Head is polar containing the
glycerol and phosphate group.
This region is hydrophilic.
9. Phospholipids
• When exposed to an aqueous solution,
the heads are attracted to the water
phase, and the nonpolar tails are repelled
from the water phase.
• This property, which is also known as
amphipathicity, causes lipids to naturally
assume single layers (micelles) or double
layers (bilayers) which contribute to their
biological significance in membranes.
• Lipid micelle and bilayer formation is
exergonic (releases energy).
10. Other Membrane Lipids
• In addition to phospholipids, there are two other types of
lipids in the plasma membrane.
• Glycolipids have a structure similar to phospholipids except
that the hydrophilic head is a variety of sugars joined to form
a straight or branching carbohydrate chain.
• Cholesterol is a lipid that is found in animal plasma
membranes; related steroids are found in the plasma
membrane of plants.
• Altogether, lipids account for about half the mass of cell
membranes.
12. Membrane Fluidity
• The fatty acids of the phospholipids make the membrane
somewhat fluid.
• The fluid nature of the membrane allows individual lipid
molecules to move laterally within each layer.
• Membrane fluidity is affected by several factors, two of
which are particularly important: lipid composition and
temperature.
14. Membrane Fluidity
• Membrane fluidity is important for the cell
because it affects membrane functions, such
as
– catalysis ,
– signal transduction,
– membrane transport, and
– membrane trafficking.
15. Membrane Fluidity
• Cholesterol and long-chain, saturated fatty acids pack
tightly together, resulting in less fluid membranes.
• Unsaturated fatty acids or those with shorter chains tend to
increase membrane fluidity.
• Membrane fluidity decreases under cold conditions
because molecules move more slowly at lower
temperatures.
18. Membrane Proteins
• Phospholipids are 50 times more than the proteins in the
membrane.
– BUT the proteins are so large that they sometimes make
up half the mass of a membrane.
• Like lipids, some membrane proteins move relatively freely
within the phospholipid bilayer.
• The proteins in a membrane may be peripheral proteins or
integral proteins.
• Peripheral proteins:
– on outside or inside surface of the membrane
– held in place either by covalent bonding or noncovalent
interactions.
19. Membrane Proteins
• Integral proteins
– within the membrane
– have hydrophobic regions embedded within the membrane and
hydrophilic regions that project from both surfaces of the bilayer
(transmembrane proteins).
• Many integral proteins are glycoproteins.
• As with glycolipids, the carbohydrate chain of sugars is on
the surface of the membrane called glycocalyx.
• Glycocalyx helps protect and lubricate the cell surface and
is involved in specific cell‒cell recognition.
21. Membrane Proteins
• Function of the membrane is mainly determined by integral
proteins.
• Functions of integral proteins:
– Passing on the molecules or ions through the membrane.
– Receptors that bring about cellular responses to signals
– Some are enzymes that carry out metabolic reactions directly.
• Peripheral proteins often have a structural role
– they help to stabilise and shape the plasma membrane
22. Membrane Proteins
Functional
class
Description Example
Carrier
proteins
Combine with a substance and help it to
move across the membrane
Na+‒K+ pump
Channel
proteins
Act as pores through which a substance can
simply move across the membrane
K+ leak channels
Recognition
proteins
Serve as identification tags that are
specifically recognised by membrane
proteins of other cells
Major histocompatibility
complex (MHC)
glycoproteins
Anchor
proteins
Are the bridges for cell‒cell and
cell‒extracellular matrix (ECM) interactions
Integrins
Receptor
proteins
Are shaped in such a way that a signalling
molecule can bind to it
Growth hormone
receptors
Enzymatic
proteins
Catalyse a specific reaction Adenylate cyclase
23.
24. Membrane Structure
• Membrane structure are mosaic.
– Proteins form different patterns
• The plasma membrane is fluid-mosaic model due to the
fluidity and the mosaic arrangement of the protein
molecules
25. FLUID- because individual phospholipids and proteins can move side-
to-side within the layer, like it’s a liquid.
MOSAIC- because of the pattern produced by the scattered protein
molecules when the membrane is viewed from above.
FLUID MOSAIC MODEL
26. Membrane Structure
• The plasma membrane is asymmetrical
– the two halves are not identical.
• Membrane asymmetry results from the following facts:
– The outer and inner lipid layers have different lipids.
– The proteins are differentially located in the outer, inner or middle
parts of the membrane.
– Glycolipids and glycoproteins are exposed only on the outer
surface and cytoskeletal filaments attach to proteins only on the
inner surface.
28. Membranes as Selective Barriers
• Membrane has selective permeability
– regulate which substances pass through them
• Macromolecules cannot cross the membrane because they
are too large.
• Ions and charged molecules cannot cross the membrane
because they are unable to enter the hydrophobic phase of
the lipid bilayer.
• Small, noncharged molecules such as oxygen and alcohols
are lipid-soluble and therefore can cross the membrane.
29. Small molecules and larger hydrophobic molecules
move through easily.
e.g. O2, CO2, H2O
Semipermeable Membrane
30. Ions, hydrophilic molecules larger than water, and large
molecules such as proteins do not move through the
membrane on their own.
Semipermeable Membrane
34. Membranes as Selective Barriers
• There are three methods for substances to cross membranes.
• Passive transport: diffusion of a substance across a
membrane with no energy.
– It involves simple diffusion and facilitated diffusion.
• Active transport uses energy to move solutes against their
gradients.
• Bulk transport is the packaging of macromolecules and
particles in vesicles and involves exocytosis and endocytosis.
– require energy.
36. Diffusion through a Membrane
Cell membrane
Solute moves DOWN concentration gradient (HIGH to LOW)
37. Passive Transport
• Simple diffusion is the random movement of simple atoms or
molecules from area of higher concentration to an area of
lower concentration until they are equally distributed
• No energy required.
38. Passive Transport
• Facilitated diffusion: Impermeable molecules like large,
polar or charged ones diffuse passively with the help of
tranport proteins that span the membrane.
• No energy required because the molecules are moving
down their concentration gradient.
• The two types of transport proteins are channel proteins
and carrier proteins.
• Particular channel or carrier proteins can operate in both
directions.
41. Facilitated Diffusion
• Some carrier proteins
do not extend
through the
membrane.
• They bond and drag
molecules through
the lipid bilayer and
release them on the
opposite side.
42. Passive Transport
• Channel proteins allow specific molecules or ions to cross
the membrane.
• Ion channels: channel proteins that transport ions
• Many ion channels function as gated channels
– They open or close in response to a stimulus (e.g., the binding of a
ligand or a change in the voltage).
• Water channels, or aquaporins: osmosis occur in plant cells
and in animal cells such as red blood cells.
43. • Can transport up to 100 million ions per second, a rate 105
times greater than that mediated by a carrier protein
• Among their many functions, ion channels:
• control the pace of the heart
• regulate the secretion of hormones into the bloodstream
• generate the electrical impulses underlying information
transfer in the nervous system.
Passive Transport: Ion channels
44. • Ion channels are ion-selective (ion selectivity) and fluctuate between open
and closed states (gated)
• Ion channels, like enzymes, have their specific substrates: potassium, sodium,
calcium, and chloride channels permit only their namesake ions to diffuse
through their pores. The ability of channels to discriminate among ions is called
ion selectivity.
Passive Transport: Ion channels
45. Passive Transport
• Some substances, such as glucose and amino acids, can
bind to membrane proteins carrier proteins
• Carrier proteins speed up their diffusion through the
phospholipid bilayer.
47. Passive Transport
•There are a limited number of
carrier protein molecules per
unit of membrane area
•Therefore, the rate of
diffusion reaches a
maximum when all the
carrier molecules are fully
loaded with solute
molecules.
•At this point, the facilitated
diffusion system is said to be
saturated.
48. Passive Transport
• Gases (e.g., O2 and CO2) and alcohols (e.g., glycerol and
ethanol) can diffuse through the lipid bilayer.
• Examples: Glucose or amino acids moving from blood into a
cell.
• The diffusion of free water across a selectively permeable
membrane is called osmosis.
49. Osmosis
• Diffusion of water
across a membrane
• Moves from HIGH
water potential (low
solute) to LOW water
potential (high solute)
Diffusion across a membrane
Semipermeabl
e membrane
50. Diffusion of H2O Across a Membrane
High H2O potential
Low solute concentration
Low H2O potential
High solute concentration
52. Passive Transport
Water moves across the membrane into the area of lower water
(higher solute) content.
when cells are in a
hypertonic solution,
they lose water.
cells neither gain nor
lose water
when cells are in a
hypotonic solution,
they gain water
53. CELL
10% NaCL
90% H2O
10% NaCL
90% H2O
What is the direction of water movement?
ENVIRONMENT
NO NET
MOVEMENT
56. Active Transport
• Active transport requires the use of
chemical energy to move substances
across membranes against their
concentration gradients.
• Moves materials from LOW to
HIGH concentration
• AGAINST concentration gradient
58. Active Transport
• Sodium‒potassium (Na+‒K+) pump uses
energy released from the hydrolysis of ATP to
move ions against their concentration
gradients (Na+ out, K+ in)
• Sodium‒potassium (Na+‒K+) pump is
especially associated with nerve and muscle
cells.
67. •Capture of a
yeast cell
(yellow) by
membrane
extensions of an
Immune System
Cell (blue)
Phagocytosis
68. •The opposite of endocytosis
•Large molecules that are manufactured in the cell
are released through the cell membrane.
Inside Cell Cell environment
Exocytosis
69. Summary
Both membrane phospholipids and membrane proteins have hydrophilic
and hydrophobic regions, giving them dual solubility properties.
Hydrophobic regions of these membrane components are oriented inward
and hydrophilic regions oriented outward.
Biological membranes are based on a fluid phospholipid bilayer in which
phospholipids can diffuse laterally. Membrane fluidity is dependent on the
lipid composition of the membrane and on temperature.
Integral membrane proteins are embedded in the phospholipid bilayer;
peripheral proteins are attached to the membrane surface. Different
patterns of membrane proteins give the membrane the look of a mosaic.
Membrane proteins play essential roles in many biological processes, such
as molecular transport, signalling, biocatalysis, interaction and fusion
between cells.
70. Summary
Membranes also contain glycoproteins and glycolipids, oligosaccharide
groups of which form a viscous layer called glycocalyx on the surface of
the cell. Many of the molecular recognition events take place in this layer
of the cell membrane.
Diffusion is the kinetic movement of molecules or ions from an area of
high concentration to an area of low concentration (that is, down their
concentration gradients).
Osmosis is the diffusion of water. As all cells are composed of mostly
water, maintaining osmotic balance is essential to life.
71. Summary
Ions and large polar molecules cannot cross the phospholipid bilayer. This
is due to the selectively permeable nature of the cell membrane. Diffusion
can still occur with the help of proteins, hence this process is referred to
as facilitated diffusion.
Transport proteins can be either channels or carriers.
Ion channels (most gated) form aqueous pores in the membrane and allow
the diffusion of specific ions; carriers bind to the molecules they transport
so the rate of transport is limited by the number of carriers in the
membrane.
Cells employ active transport to move substances across the plasma
membrane against their concentration gradients, either accumulating
them within the cell or extruding them from the cell. Active transport uses
specialised carrier proteins (pumps) that require energy from ATP.
72. Two main classes of membrane transport proteins: Transporters and Channels
All these proteins are multi-pass transmembrane proteins
1. Transporters bind to a specific solute and undergo a series of conformational changes.
2. Channel proteins interact with the solute much more weakly; form aqueous pores; transport
at a much faster rate.