004 Membranes

Question 1

the composition of membranes

Answer 1

lipids
proteins
carbohydrates

Question 2

primary component of biological membranes

Answer 2

phospholipids (PL)

Question 3

amphipathic

Answer 3

hydrophilic head and hydrophobic tail

Question 4

these are attached covalently to some membrane lipids and proteins

Answer 4

carbohydrates

Question 5

meaning of glycosylated

Answer 5

attached to carbohydrate molecules

Question 6

hydrophilic head group contains

Answer 6

phosphate moiety

Question 7

hydrophobic tail made of

Answer 7

fatty acids

Question 8

two types of phospholipids based on their backbone

Answer 8

1. glycerophospholipids (glycerol backbone)

2. sphingolipids (sphingosine backbone)

Question 9

three types of membrane lipids

Answer 9

1. phospholipids (most abundant)
2. glycolipids (sphingosine backbone and carbohydrate/oligosaccharide residue, outer leaflet)
3. cholesterol (embedded in lipid layer, steroid nucleus with hydroxyl group)

Question 10

Outer sheet membrane lipids (faces extracellular environment)

Answer 10

1. phosphatidylcholine
2. sphingomyelin
3. glycolipids

Question 11

inner sheet membrane lipids (faces the intracellular environment)

Answer 11

1. phosphatidylinositol
2. phosphatidylserine
3. phosphatidylethanolamine

Question 12

three types of membrane proteins

Answer 12

1. integral membrane proteins
2. peripheral proteins
3. lipid-anchored

Question 13

integral membrane proteins

Answer 13

embedded in the membrane and firmly stabilized by hydrophobic interactions with lipids

Question 14

transmembrane proteins

Answer 14

span entire lipid bilayer and interact with both intracellular and extracellular
include transporters, ion channels, and receptors

Question 15

integral monotopic proteins

Answer 15

firmly attached to one sheet of the membrane

Question 16

peripheral proteins

Answer 16

loosely bound to the membrane through electrostatic interactions with lipids or proteins

Question 17

lipid anchored

Answer 17

tethered to membranes via a covalent attachment to a lipid molecule

Question 18

glycocalyx

Answer 18

outer sheet of membrane that is covered with a carbohydrate shell due to presence of glycolipids and glycosylated proteins

Question 19

3 functions of glycocalyx

Answer 19

1. protection
2. cell adhesion
3. cell identification (imp in red blood cells)

Question 20

phosphatidylserine as a marker for apoptosis

Answer 20

in healthy cells PS is found in inner leaflet of bilayer
during apoptosis PS is displayed on extracellular side
serves as a label and dying cells recognized and removed by phagocytes

Question 21

Niemann-Pick Disease

Answer 21

rare autosomal recessive
deficiency in sphingomyelinase
so sphingomyelin accumulates in lysosomes of body
enlargement of liver and spleen, cherry red spots in eyes
patients generally do not live past 18 months

Question 22

factors that influence membrane fluidity

Answer 22

temperature
lipid composition
cholesterol

Question 23

at the transition/melting temp (Tm) the membrane is at

Answer 23

optimal fluidity

Question 24

what kind of fatty acids decrease membrane fluidity

Answer 24

long saturated fatty acids

due to tighter packing which strengthens their interaction and reduces mobility

Question 25

these types of fatty acids increase membrane fluidity

Answer 25

short unsaturated fatty acids

the kinks in their fatty acid chains do not allow tight packing between lipid

Question 26

cholesterol can either increase or decrease membrane fluidity based on

Answer 26

the type of fatty acid present ( saturated or unsaturated)

slide 36

Question 27

what allows flip flop movement to occur

Answer 27

translocators and flippases

Question 28

spur cell anemia

Answer 28

hemolytic anemia where there is elevated levels of cholesterol in erythrocyte membrane
decreases fluidity and flexibility of the membrane
causes erythrocytes to lyse membranes as they pass through capillaries
associated with beta lipoproteinemia and advanced alcoholic cirrhosis