2. CHARACTERISTIC OF CELL
MEMBRANE
Composed of phospholipid,
cholesterol, proteins & chains of
oligosaccharides
Range of thickness : 7.5 nm – 10 nm
Visible only in the electron microscope
5. FUNCTIONS OF CELL MEMBRANE
Selective Permeability
• Size, charge, chemical properties of
atoms / molecules determine whether
the success in getting through the
membrane
Physical Barrier
• Separates substances inside and
outside of the cell
6. Act As Communicator
• Communication between cells & its
environment can occur because it contains
receptors that recognize & respond to
molecular signals
Allows Intercellular Connection
• Establish a flexible boundary, protects
cellular contents and also supports cell
structure
7. Transport Across
The Cell
Membrane
Passive Active Transport Vesicle Transport
Transport
Simple Facilitated Primary Secondary
Diffusion Osmosis Endocytosis Exocytosis
Diffusion
9. Passive transport
Goes down the concentration gradient
From high concentration to low concentration of
solute
Does not require energy (ATP)
10. SIMPLE DIFFUSION ACROSS A PLASMA
MEMBRANE
Movement of small molecule through phospholipid
bilayer.
Lipid soluble molecule due to hydrophobic
characteristic of the bilayer.
11.
12. FACILITATED DIFFUSION ACROSS A PLASMA
MEMBRANE
Diffusion of large molecules
Requires carrier protein
Each carrier protein is specific for one molecule
Example – Potassium diffusion.
18. The movement of substances across the plasma
membrane against the concentration gradient
Molecules or ions move from a region of lower
concentration to higher concentration
Requires the use of both carrier protein and
cellular energy to transport molecules
Carrier protein involved in active transport are
often called pumps
The most known pumps is Sodium-Potassium
pumps
19. Na-K
pumps
Primary
Proton
pumps
Active
Transport
Na-glucose
co-transport
Secondary
Na-Ca
exchange
20. PRIMARY ACTIVE
TRANSPORT
SODIUM-POTASSIUM PUMP
PROTON PUMP
26. VESICULAR TRANSPORT
A means for transport of large sized molecules
(e.g. proteins) across cell membrane.
It represents a specialized function of cell
membrane.
Requires energy.
2 types;
27. ENDOCYTOSIS
Divided into 3 parts:
1.Phagocytosis
-cell eating (uptake of large molecules)
2.Pinocytosis
-cell drinking (uptake of solutes)
3.Receptor-mediated
-cytoplasm membrane folds inwards
and form coated pits.
31. EXOCYTOSIS
The excretion of waste material from the cell to its
outer environment.
Large waste product which requires the formation of vesicles
Molecules excreted includes:
Cell Debris
Waste products
Membrane
proteins + lipids
which are bound to
become part of the
actual membrane
Vesicular transporti.e the transport of macromolecules involving vesicles.Most cells use endo and exo to ingest and secrete macromolecules because most of the important subs are large polar molecules and thus arent able to pass through the membrane by the previously discussed methods.
Why do cells need endocytosis mechanism? Because most substances are important to them are: polar consist of big moleculesPHAGOCYTOSISThe process by which cells ingest large objects, (such as cells which have undergone apoptosis, bacteria, or viruses). The membrane folds around the object, and the object is sealed off into a large vacuole; known as a phagosome.PINOCYTOSISThis process is concerned with the uptake of solutes and single molecules such as proteins.The membrane folds around the liquid, and the liquid is sealed off into a large vacuole; known as a pinocytic vesicles.RECEPTOR MEDIATED ENDOCYTOSISThe process by which cells internalize molecules (endocytosis) into a cell. by the inward budding of plasma membrane vesicles containing proteins.with receptor sites, specific to the molecules being internalized.The cytoplasm membrane folds inward to form clathrin-coated pits. These inward budding vesicles bud to form cytoplasmic vesicles.
In exo the contents of the vesicle are released out of the cell to the extracellular environmentLikewise to endocytosis it requires the formation of vesicles in order to excrete the macromolecules out of the cell.