Cell membrane

Question 1

What is diffusion?

Answer 1

Molecules move down their concentration gradient passively

Question 2

What affects diffusion rate? What quantifies this?

Answer 2

Surface area
Concentration gradient
Distance
Temperature

Fick’s Law

Question 3

What is osmosis?

Answer 3

Water moves down its water potential gradient across a partially permeable membrane

Question 4

What is solubility?

Answer 4

The ability of a substance to dissolve in a solvent

Question 5

What is the difference between a channel and a carrier?

Answer 5

Channel:
Passive diffusion.

No binding site, open to both environments at the same time.

Can be gated and only open under certain conditions.

Can also be selective with selectivity filters.

Carriers:
Passive or active.

Have binding site, undergo a conformational shape change to present the solute on the other side of the membrane.

Carriers are saturable.

Question 6

What makes a carrier work actively?

Answer 6

Require ATP hydrolysis to undergo the conformational shape change

Question 7

What is the main constituent of a cell membrane?

Answer 7

Phospholipids

Question 8

What arrangement do phospholipids form in the membrane?

Answer 8

Bilayer

Question 9

What property of phospholipids allows them to form a bilayer?

Answer 9

Amphipathic

Question 10

What does amphipathic mean?

Answer 10

Hydrophilic and hydrophobic properties

Question 11

What are the 3 parts of a phospholipid?

Answer 11

Phosphate head
Glycerol
Two fatty acid tails

Question 12

Which part of the phospholipid is hydrophilic and what part is hydrophobic?

Answer 12

Hydrophobic head

Hydrophilic tail

Question 13

What are the three most prevalent lipids in the cell membrane?

Answer 13

Phosphatidylserine: Head contains serine residue (PS)

Phosphatidylcholine: Head contains choline residue (PC)

Sphingomyelin (SM), is a type of sphingolipid

Question 14

Where is sphingomyelin especially present?

Answer 14

Membranous myelin sheath that surrounds some nerve cell axons

Question 15

What does sphingomyelin consist of?

Answer 15

Phosphocholine head group, a sphingosine, and a fatty acid

Question 16

Is sphingomyelin synthesised from glycerol?

Answer 16

No

Question 17

How are the 3 lipid constituents arranged on the inside and outside?

Answer 17

Inside layer containing more PS and the outside layer containing more PC and SM

Question 18

What is cholesterol?

Answer 18

Unsaturated alcohol (sterol)

Question 19

What does cholesterol’s interaction with phospholipids result in?

Answer 19

Cholesterol increases membrane packing, which both alters membrane fluidity and maintains membrane integrity so that animal cells do not need to build cell walls

Question 20

What is the glycocalyx?

Answer 20

A glycoprotein and glycolipid covering that surrounds the cell membranes

Question 21

What conjugation results in the formation of the glycocalyx?

Answer 21

Glycosylation of the proteins and lipids

Question 22

What does the fluid mosaic model refer to?

Answer 22

The fluidity and dynamic nature of the membrane

Question 23

What are three ways a protein can be positioned in a membrane?

Answer 23

Surface proteins

Transmembrane proteins: integral membrane protein that spans the entirety of the cell membrane.

Anchored proteins: proteins located on the surface of the cell membrane that are covalently attached to lipids embedded within the cell membrane.

Question 24

What do surface proteins often contribute to?

Answer 24

Often are glycosylated and make up glycoproteins in the glycocalyx.

Question 25

What is a uniporter, symporter and antiporter?

Answer 25

Carrier proteins

Uniporters (move one substance in one direction)

Symporters (move two substances in the same direction)

Antiporters (move two substances in opposite directions) .