Lipids

Question 1

Lipids

Answer 1

• Non-polar and hydrophobic
• Insoluble in water but soluble in organic solvents
• Can be: simple, complex or steroids & sterols

Question 2

Glycerol

Answer 2

• Alcohol with 3 -OH groups
• Soluble in water since -OH can interact with water

Question 3

Fatty acids

Answer 3

Consists of
- Hydrophilic carboxylic acid group
- Hydrophobic hydrocarbon chain

Question 4

Triglyceride

Answer 4

1 glycerol + 3 fatty acids

Question 5

Phospholipid

Answer 5

• 1 glycerol + 2 fatty acids + 1 phosphate group
• Hydrophobic hydrocarbon tail
• Hydrophilic phosphate head

Question 6

Ethanol emulsion test

Answer 6

1. Crush sample, place into test tube
2. Add ethanol to approx 2cm³ above sample
3. Shake thoroughly
4. Allow solid to settle
5. Decant ethanol into another test tube
6. Add 2cm³ of deionised water to into 2nd test tube
7. If layer of cloudy white suspension forms, lipids present

Question 7

Fluid mosaic model

Answer 7

Fluid → phospholipids and proteins exhibit lateral movement within the bilayer
Mosaic → proteins scattered in a “patchwork” arrangement within the bilayer

Question 8

Components of cell membrane

Answer 8

1. Phospholipids
2. Cholesterol
   Increases stability of membrane
3. Proteins
4. Carbohydrates
   Cell-to-cell adhesion

Question 9

Factors affecting membrane fluidity

Answer 9

1. Temperature
2. Length of hydrocarbon tails
3. Degree of saturation of hydrocarbon tails
4. Presence of cholesterol

Question 10

Facilitated diffusion

Answer 10

• Molecules diffuse through transport proteins
• For charged/polar molecules
• Protein channels and carriers can help shield them from the hydrophobic core of bilayer

Question 11

Channel protein

Answer 11

• Forms a water-filled pore
• Hydrophilic core

Question 12

Carrier protein

Answer 12

• Has specific binding site for specific solute
• Solute binds to one side of carrier protein, triggering a conformational change that exposes binding site to other side of membrane. Solute released, protein reverts

Question 13

Osmosis

Answer 13

• Net movement of water down a concentration gradient through a selectively permeable membrane
• Water can pass through membrane through the lipid bilayer or aquaporins

Question 14

Aquaporin

Answer 14

Integral membrane proteins acting as water channels

Question 15

Active transport

Answer 15

• Movement of molecules up a concentration gradient
• Uses energy
• Requires carrier protein pumps

Question 16

Exocytosis

Answer 16

-Transport of substances out of the cell in vesicles
- For large/hydrophobic molecules Eg proteins, polysaccharides

Question 17

Endocytosis

Answer 17

• Transport of substances into cell in vesicles
• Can be either:
  a) Pinocytosis (drinking)
  b) Phagocytosis (eating)
  c) Receptor mediated

Question 18

Pinocytosis

Answer 18

• Droplets of extracellular fluid taken in by tiny vesicles
• Non selective

Question 19

Phagocytosis

Answer 19

• Engulfs large particles by sending pseudopodia
• Pseudopodia join to form phagosome
• Lysosome fuses with phagosome and hydrolytic enzymes digest substance