Biochemistry Flashcards
what is width of plasma membrane
7-10 nm wide
what is the chemical composition of plasma membrane
43% lipids
49 % proteins
8 % carbohydrates
what are the types of lipids in cell membrane
Phospholipids (Lecithin & Cephalin)
Glycosphingolipids (Cerebrosides & Gangliosides)
Cholesterol
what is significance of lecithin in cell membrane
Lecithin is composed of units of choline, phosphoric acid, fatty acids and glycerol. … Without lecithin, the cell membranes would become less fluid, thus less permeable.
what is the significance of cephalin in cell membrane
Cephalin plays a role in membrane fusion. Fusion is the process by which two initially distinct lipid bilayers merge their hydrophobic cores, resulting in one interconnected structure.
what is the function of ganliosides in cell membrane
Gangliosides is a component of the plasma membrane that modulates cell signal transduction events.
The functions of gangliosides as specific determinants suggest its important role in the growth and differentiation of tissues as well a
s in carcinogenesis.
what is the significance of cholesterol in cell membrane
Cholesterol provides stability to the plasma membrane by limiting the movement of the phospholipids.
cholesterol in the cell membrane is to maintain stability, anchor other molecules.
Cholesterol acts as a bidirectional regulator of membrane fluidity because at high temperatures, it stabilizes the membrane and raises its melting point, whereas at low temperatures it intercalates between the phospholipids and prevents them from clustering together and stiffening.
write a short note on the fatty acids in cell membrane
They are also major component of cell membrane. 50% of fatty acid groups are saturated. The other half contains unsaturated and polyunsaturated fatty acids.
Oleic acid is the most abundant unsaturated fatty acids in animal membranes.
The degree of unsaturation determines the fluidity of the membranes.
which types of proteins form the cell membrane
Integral or intrinsic proteins
Peripheral or extrinsic proteins
Trans-membrane proteins
(span the whole width )
what is integral membrane protein and write about its signifiance
An integral membrane protein (IMP) is a type of membrane protein that is permanently attached to the biological membrane.
IMPs include transporters, linkers, channels, receptors, enzymes, structural membrane-anchoring domains, proteins involved in accumulation and transduction of energy, and proteins responsible for cell adhesion. Common examples are Insulin receptors, Glycophorin, Rhodopsins. Band-3 proteins etc
what is peripheral membrane protein and its significance in cell membrane
Peripheral membrane proteins are membrane proteins that adhere only temporarily to the biological membrane with which they are associated.
Peripheral enzymes participate in metabolism of different membrane components, such as lipids (phospholipases and cholesterol oxidases).
what is transmembrane protein and write about its significance
A trans membrane protein (TP) is a type of integral membrane protein that spans entirely the cell membrane to which it is permanently attached. Many trans membrane proteins function as gateways to permit the transport of specific substances across the membrane.
what are the major functions of membrane proteins
Transport Enzymatic activity Signal transduction Cell-cell recognition Intercellular joining Attachment to the cytoskeleton and extracellular matrix (ECM)
which carbohydrates are present in cell membrane
Glycoproteins
Glycolipids
what is glycosylation
The carbohydrate is attached to the protein in a posttranslational modification. This process is known as glycosylation.
what is the significance og glycoprotein and give a detailed example
Glycoproteins are also often important integral membrane proteins, where they play a role in cell–cell interactions. One example of glycoproteins found in the body is mucins, which are secreted in the mucus of the respiratory and digestive tracts. The sugars when attached to mucins give them considerable water-holding capacity and also make them resistant to proteolysis by digestive enzymes.
what are glycolipids and write about their significance
Glycolipids are lipids with a carbohydrate attached by a glyosidic (covalent) bond. Their role is to maintain the stability of the cell membrane and to facilitate cellular recognition, which is crucial to the immune response and in the connections that allow cells to connect to one another to form tissues. They include glyceroglycolipids and glycosphingolipids.
what is glycocalyx and write about its significance
The glycocalyx, is a glycoprotein and glycolipid covering that surrounds the cell membranes. This viscous coating consists of several carbohydrate moieties of membrane glycolipids and glycoproteins, which serve as backbone molecules for support. Generally, the carbohydrate portion of the glycolipids found on the surface of plasma membranes helps these molecules contribute to cell–cell recognition, communication, and intercellular adhesion.
how are caveolae formed
The caveolae are formed by the curving inward of the inner leaflet of the plasma membrane an integral protein named caveolin forces the formation of caveolae which are involved in the membrane transport and rigidity
how are rafts formed and write about their structure
The rafts are made by the clustering of sphingolipid with cholesterol in the outer monolayer of the plasma membrane. The rafts appear to have receptors and signaling proteins.
write about the clinical significance of cell membrane
ALZHEIMER’S DISEASE: Oxidative stress in brain results in alterations in phospholipids that comprise the cell membrane and disrupts the functions of effected brain cells.
CYSTIC FIBROSIS: Defect in calcium ion channels for the unclear reasons in excess production of fluid in lungs
what are ion channels and describe their types
Ion channels are transmembrane channels, pore like structures composed of proteins”.
All channels have gates & are controlled by opening
and closing.
TYPES:
Ligand gated channels:
In this a specific molecule binds to a receptor and opens the channel.
Voltage gated channels:
These channels open or close in response to changes in membrane potential.
write a short note on simple or passive diffusion
It depends on concentration gradient of a particular substance across the membrane
The solute passes from higher concentration to lower concentration till equilibrium is reached
The process neither requires any carrier protein nor energy
write a short note on facilitated diffuision
It is similar to passive diffusion in that the solutes move along the concentration gradient.
But it differs from passive diffusion in that it requires a carrier protein or transport protein.
Energy is not required.