Biologcal Molecules: Lipids

Question 1

Properties of lipids?

Answer 1

Non polar
Hydrophobic
Insoluble

Question 2

What makes up triglycerides? And function?

Answer 2

Glycerol and 3 fatty acids (RCOOH)
- energy store

Question 3

What are two types of fatty acids?

Answer 3

UNSATURATED - have double bonds (can be MONO (one double bond) or Poly UNSATURATED ( more than 1 double bond)
SATURATED - NO DOUBLE BONDS

Question 4

What are phospholipids made up of? And function?

Answer 4

2 fatty acids, glycerol and phosphate ion

-PHOSPHATE is polar —> HYDROPHILIC
-FATTY ACID tails are NON POLAR —-> HYDROPHOBIC

• cell membrane component (bc of their amphipathic nature)

Question 5

How does an ester bond form?

Answer 5

• forms between -OH of glycerol and -COOH group of fatty acid
• by condensation reaction - water molecule is RELEASED
  H in glycerol bonds to OH in COOH group to form water

Question 6

Why are triglycerides good energy stores?

Answer 6

• Hydrocarbon chains are OXIDISED in respiration , causing bonds to break , releasing energy to produce ATP
• triglycerides are HYDROPHOBIC so don’t cause osmotic water uptake so more can be stored

Question 7

Why are triglycerides good for insulation?

Answer 7

• triglycerides form part of myelin sheath that surrounds nerve fibres —> provides insulation , increasing speed of transmission of impulses
• triglycerides compose part of the adipose tissue layer below skin —> prevent heat loss

Question 8

How are triglycerides good for buoyancy?

Answer 8

• low density of fat tissue increases ability of animals to float

Question 9

How do triglycerides provide protection?

Answer 9

• adipose tissue contains stored triglycerides —> protects organs

Question 10

How is fluidity of cell membrane affected by the type of fatty acid?

Answer 10

Saturated fatty acids- membrane is LESS fluid
Unsaturated fatty acid - membrane is MORE fluid

Question 11

How does cholesterol’s structure allow them to exist in the bilayer of membrane?
How does it effect the cell membrane ?

Answer 11

Have hydrophobic and hydrophilic regions

• affects FLUIDITY and PERMEABILITY
  —> disrupts close packing of phospholipids (increasing flexibility of membrane)
  —> acts as a barrier , fitting in spaces between phospholipids- preventing water soluble substances diffusing

Question 12

What is cholesterol used for?

Answer 12

To produce steroid-based hormones (oestrogen, testosterone and progesterone)

Question 13

Function of phospholipids?

Answer 13

• control membrane protein orientation - weak hydrophobic interactions between phospholipids/membrane proteins hold proteins in membrane, but allow movement

Forms phospholipid bilayer - presence of hydrophobic fatty acid tails, means a hydrophobic core is created
The core acts as a barrier to water-soluble molecules

hydrophilic phosphate heads form H-bonds with water,so cell membrane can be used to compartmentalise - cells can organise specific roles into organelles

Question 14

Functions of triglycerides ?

Answer 14

Buoyancy
Energy store/source
Insulation
Protection

Question 15

Function of fatty acids ?

Answer 15

Form phospholipids - form bilayer
Form membranes

Fatty acids respired to release energy - More triglycerides more energy released
Energy used for cell production / production of named cell component

Question 16

Test for lipids?

Answer 16

Shake substance with ethanol /pour into water
- solution turns milky is lipid present