L6 - Cell Membranes

Question 1

What are monosaccharides? (2)

Answer 1

Monomer for carbohydrates

• hydroxylated aldehydes and ketones
• ‘building blocks’ of other sugars

Question 2

What are disaccharides?

Answer 2

Oligosaccharide
Formed by linking monosaccharides together with a glycosidic bond

Question 3

What is glycogen? + extra info (3)

Answer 3

Example of polysaccharide
- can contain up to 100,000 glucose molecules
- highly branched
- has a linear chain (a-1,4-bond) and a branch point (a-1,6-bond)

Question 4

How does the body use sugar? (2)

Answer 4

Glucose is the major monosaccharide found in the blood

• glycogen is the reservoir of available energy, stored in the chemical bonds within individual glucose monomers
• hydrolysis, releases glucose monomers, prevents blood glucose from decreasing to dangerously low levels

Question 5

How do the cells use sugars? (2)

Answer 5

• extracellular matrix
  = scaffold for cell attachment (glycosaminoglycans GAGs)
  = transmits info to cells growing, differentiating and migrating
• glycolysation
  = glycoproteins
  = glycolipids

Question 6

What are lipids?

Answer 6

Molecules predominantly H, C linked by nonpolar covalent bond

Question 7

What are roles of lipids in the body? (3)

Answer 7

• major compoonent of cell membranes
• provide source of energy
• important signaling moleciules

Question 8

What are the 4 types of lipids?

Answer 8

• steroid
• fatty acid
• triglyceride
• phospholipid

Question 9

Features of steroids: (3)

Answer 9

• 4 ring structures (ABCD, 6:6:6:5) with side chains
• dif. arise due to functionalisation of the rings and changing the side- chains
• cholesterol, oestrogen, testosterone, corticosteroids, bile acids

Question 10

What are fatty acids?

Answer 10

carboxylic acids with long alkyl side chains (lipophilic)

Question 11

Features of triglycerides: (3)

Answer 11

• importatnt energy stores
• glycerol esterified with 3 FAs
• interconverted by hydration/dehydration

Question 12

Features of phospholipids: (2)

Answer 12

• several dif phospholipids each with a specialised role
• amphipathic

Question 13

Features of the cell membrane structure: (4)

Answer 13

• lipid bilayer
• polar head-groups face water, lipophilic side chains each other
• contains cholesterol and proteins
• fluid sctructure (lipids and entities dissolved within layer can diffuse)

Question 14

Membrane structure and function: (5)

Answer 14

• boundaties between cells and environment
• selective barrier to molecules
• detect chemical signals
• anchor cells to adj cells and extracellular matrix
• highly specialised for functions

Question 15

What factors affect the rate of diffusion? (2)

Answer 15

• ionic charge
• size

Question 16

What are the ways of moving molecules across membranes? (4)

Answer 16

• diffusion
• osmosis
• protein transporters/carriers
• endocytosis/exocytosis

Question 17

What is diffusion?

Answer 17

Passive diffusion down a conc grad (high to low)
- net flux takes into acc diffusion in both directions

Question 18

What is osmosis?

Answer 18

Water transport across membranes down a conc grad until eq is reached
- diffusion/facilitated difussion (by aquaporins)

Question 19

What are protein transporters/carriers?

Answer 19

Membrane proteins that can perform both passive and active transport of selected molecules
- often undergo a conformational (shape) change

Question 20

Give an example of active transport

Answer 20

The Na+/K+ pump
- powered by ATP, moves Na+ and K+ ions in opp directions, against its conc grad

Question 21

What is endocytosis/exocytosis?

Answer 21

Vesicular bulk transport into/out of the cell, often receptor mediated