PHY MOD 5-STRUCTURAL ORGANISATION OF CELL MEMBRANE

Question 1

significance of cell membrane

Answer 1

• regulate cellular activities

- action site of many drugs

Question 2

function of cell membrane

Answer 2

• protects intracellular organelles
• regulate the passage of substances
• detects chemical messengers arriving at the cell surface
• stable site for binding and catalysis of enzymes

Question 3

3 major types of lipids

Answer 3

phospholipids,glycolipids and steroids

Question 4

phospholipid consist of

Answer 4

• 1 molecule glycerol
• 2 molecules fatty acid
• 1 phosphate group

Question 5

match the hydrophilic heads of the phosphatidate to their correct PO4?
choline-
ethanolamine-
inositol-
serine-

Answer 5

phosphatidylcholine
phosphatidylethanolamine
phosphatidylinositol
phosphatidylserine

Question 6

phosphatidylcholine function

Answer 6

vit B source
major component of cell membrane
critical for brain and liver function
precursor to acetylcholine

Question 7

phosphatidylethanolamine function

Answer 7

key building block of cell membrane bilayers

needed to orient enzymes correctly in the inner membrane

Question 8

phosphatidylinositol

Answer 8

primary source of arachidonic acid required for biosynthesis of eicasanoids including prostaglandins

Question 9

phosphatidylserine

Answer 9

promotes stability and integrity of the cellular membrane

Question 10

why are all membrane lipids amphipathic?

Answer 10

they have hydrophilic and hydrophobic properties

Question 11

how is sphingomyelin produced and what is the function?

Answer 11

ceramide+phosphocholine=sphingomyelin,found especially in myelin sheath of neural axons.

Question 12

how is ganglioside produced and what is the function?

Answer 12

ceramide+ oligosaccharide= ganglioside,present points of recognition for extracellular molecules or surface of neighboring cells

Question 13

what is cholesterol and its properties and function

Answer 13

• a member of steroids
• weakly amphipathic
• prevents crystallization of hydrocarbons and phase shifts in the membrane
• increases membrane packaging
• precursor for steroid hormones and vitamin D

Question 14

physical characteristics of lipid bilayer

Answer 14

• flexible
• width of bilayer is determined by lenth of fatty acids
• nature of head groups determines how densely packed adjacent phospholipids molecules are in the membrane
• depends on temperature

Question 15

is the lipid bilayer able to reseal when torn?

Answer 15

yes because of its fluidity

Question 16

what do we call carbohydrates attached to protein by a glycosidic bond

Answer 16

glycoprotein

Question 17

what do we call carbohydrates attached to lipid

Answer 17

glycolipids

Question 18

what are glycoproteins?

Answer 18

proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains.

Question 19

what is glycosylation?

Answer 19

process of adding sugar molecule to protein molecule is known as glycosylation.

Question 20

function of glycoprotein

Answer 20

facilitate intercellular interaction and interaction between cells and environment

Question 21

what are advanced glycation end products (AGEs)

Answer 21

proteins or lipids that become glycated as a result of chronic exposure to sugars(can be a factor in aging or degenerative diseases)

Question 22

2 examples of glycoprotein

Answer 22

collagens and proteoglycans

Question 23

where is glycolipid assembled and embedded

Answer 23

it is assembled in the Golgi apparatus and embedded in the surface of a vesicle which is then translocated to the cell membrane

Question 24

role of glycolipid

Answer 24

maintain stability of cell membrane and to facilitate cellular recognition?

Question 25

2 major types of proteins

Answer 25

peripheral and integral

Question 26

peripheral protein characteristics

Answer 26

• adhere tightly to extracellular or cytoplasmic surface

- can be removed from the membranes by very high/low salt concentration

Question 27

integral proteins properties

Answer 27

• in lipid bilayer
• some are tansmembrane protein
• some are embedded in the membrane without crossing it
• special detergent is used to remove

Question 28

glycophospholipid - linked proteins

Answer 28

attached to membrane by covalent bonds

Question 29

function peripheral proteins

Answer 29

acts as membrane skeleton,provides mechanical support and provide anchor

Question 30

cell adhesion molecules (CAMs)

Answer 30

integrins and cadherins-maintain cell shape,growth,locomotion

Question 31

what is the basement membrane

Answer 31

thin,fibrous,extracellular matric of tissue that separates the lining of an internal or external body surfaces

Question 32

3 layers of cells lining the surface

Answer 32

epithelium,mesothelium,endothelium

Question 33

basement layers are

Answer 33

basal lamina and reticular lamina

Question 34

2 layers of basal lamina

Answer 34

lamina lucida and lumina densa

Question 35

role of basement membrane

Answer 35

• anchor down epithelium to its loose connective tissue
• provides structural support and polarity
• mechanical barrier

Question 36

diseases associated with basement membrane

Answer 36

Alport Syndrome,Goodpasture’s syndrome,epidermolysis bullosa