Cell Membranes

Question 1

what causes the separation that is crucial for selective permeability,
ion gradients, signal transduction in cells?

Answer 1

cell membranes

Question 2

Phospholipids are predominant class of lipid in the cell/plasma membrane and are comprised of:
— Phosphatidyl???
— Phosphatidylserine (cytosolic)

Answer 2

Phosphatidylcholine

Question 3

TRUE or FALSE: Amphiphilic nature of lipids leads to spontaneous
assembly into self-sealing compartments

Answer 3

TRUE

Question 4

Typically of the two hydrophobic tails of the glycerol backbone, one is ‘saturated’ (with hydrogen; only ???-bonds) whilst the other contains one double-bond (unsaturated)

Answer 4

single

Question 5

What prevents tight packing of lipids, which results in more fluidity and flexibility of the membrane?

Answer 5

the unsaturation of phospholipids

Question 6

Higher abundances of cholesterol within phospholipid bilayer of plasma membrane will result in more ‘packed’ membranes, increasing or decreasing (?) rigidity

Answer 6

increasing rigidity

Question 7

TRUE or FALSE: High fluidity means lipids and proteins can move more freely within the plane of the membrane

Answer 7

TRUE

Question 8

Movement of molecules is interrupted by ??? junctions

Answer 8

tight junctions

Question 9

Membrane lipids are primarily synthesised by enzymes in the smooth ???

Answer 9

endoplasmic reticulum

Question 10

membrane lipids are assembled from glycerol, fatty acids, phosphate
groups, other small molecules on the ??? surface of the ER. Flippases then selectively transfer some molecules to achieve both even growth and deliberate asymmetry

Answer 10

cytosolic

Question 11

The lipid bilayer is asymmetrical i.e Interior (cytosolic) face is different to the side protruding into the ??? space

Answer 11

extracellular

Question 12

??? also adds glycans (sugars) to lipids, but only on the ‘exterior’ face of the membrane

Answer 12

Golgi apparatus

Question 13

Phosphatidylserine is predominantly found on the cytosolic face in most cell types, due to activity of ATP-dependent ???

Answer 13

flippases

Question 14

phosphatidylserine facilitates signal transduction by providing a docking site for ??? enzymes such as protein kinase C

Answer 14

cytosolic

Question 15

which lipid provides membrane curvature, phosphatidylcholine or phosphatidylserine?

Answer 15

phosphatidylserine

Question 16

Phosphatidylserine is translocated to the other side of membrane during ???. Scramblase enzymes redistribute PS

Answer 16

apoptosis

Question 17

what serves as a specific ‘eat me’ signal for phagocytes and enables rapid, controlled clearance of dying cells?

Answer 17

phosphatidylserine translocating to the other side of membrane

Question 18

membrane glycosylation occurs when the ??? receives lipids from ER, Glycosyltransferases sequentially add sugar moieties to the lipid backbone (both simple and complex sugars are added ONLY to the non-cytosylic face)

Answer 18

Golgi apparatus

Question 19

membrane ??? plays an important role in cell-cell communication such as host-recognition and Blood group antigens

Answer 19

membrane glycosylation

Question 20

TRUE or FALSE: membrane glycosylation provides protective glycocalyx: Mechanical and environmental protection and prevents non-specific adhesion by other molecules

Answer 20

TRUE

Question 21

Concentrations of important ions are
maintained at different levels via active transport = concentration ???

Answer 21

gradients

Question 21

Non-polar molecules are permeable
through the mostly hydrophobic
bilayer, exception = ??? because it is small and also due to aquaporins

Answer 21

H2O

Question 22

Glucose, to be absorbed across the gut, requires sodium electrochemical gradient (actively maintained via Na+/K+ pumps)
▪ This gradient is implemented to drive Na+ into the cell (??? its gradient) along with glucose
— Via glucose-Na+ symporter
— This occurs at the apical side
▪ At the luminal face, glucose exits via passive diffusion
— Via facilitated diffusion
— Known as glucose uniporter

Answer 22

down