Lipids

Question 0

Lipid classes?

Answer 0

Glycerol based - 1. Simple lipids - esters of fatty acids + glycerol (fats & oils) 2. Compound lipids - esters of FAs + non-lipid molecule (P, CHO, protein)
Non-glycerol based (steroids, waxes…)

Question 1

Functions of lipids..?

Answer 1

Carrier molecules
Vitamin absorption
Membrane structures
Energy stores
Plants - structural & storage

Question 2

Factors that determine physical properties of lipids?

Answer 2

Chain length & degree of saturation
Double bonds increase boiling point
Highest MP: stearic acid
Lowest MP: arachidonic acid

Question 3

Properties of glycolipids?

Answer 3

2 alcohol groups esterified + 1 sugar residue (linoleic & linolenic) - unsaturated

Question 5

What are essential FAs? Give examples.

Answer 5

EFAs cannot be synthesised - must be supplied in the diet eg. Linoleic & linolenic acid

Question 6

EFAs needed for…?

Answer 6

membranes
lipid transport
enzymes
prostaglandins

Question 7

Rich source of EFAs?

Answer 7

oilseeds

Question 8

T or F - EFA deficiencies are rare in grazing animals

Answer 8

true

Question 9

bile salt synonym?

Answer 9

amphipath

Question 10

What are the 4 phases of lipid assimilation?

Answer 10

1. Emulsification
2. Hydrolysis
3. Micelle formation
4. Absorption

Question 11

Briefly list steps of lipid digestion & absorption in monogastrics

Answer 11

1. TGs emulsified in SI by bile (duodenum)
2. Pancreatic lipases hydrolyse TGs -> monoglycerides & FFAs
3. Micelles formed by lipase & bile carry monoglycerides & FFAs -> luminal surface
4. Micelles release monoglycerides & FFAs near epithelial surface -> passive diffusion thru lipid bilayer

Question 12

Major fats in grains?

Answer 12

TGs (mainly linoleic acid)

Question 13

Major fats in forages?

Answer 13

galactoglycerides (mainly linolenic acid)

Question 14

T or F - long chain FAs can be absorbed across the rumen

Answer 14

false

Question 15

Steps in ruminant fat digestion & absorption

Answer 15

1. Microbial extracellular lipases hydrolyse -> glycerol, LCFAs, galactose
2. Biohydrogenation (unsaturated FAs -> saturated FAs) - > CLA -> stearic acid

Question 16

Biohydrogenation of linoleic acid (glycolipid) results in…?

Answer 16

Formation of conjugated linoleic acid (CLA)

Question 17

Fate of CLA

Answer 17

Most is hydrogenated to stearic acid

Some -> SI -> adipose & milk fat

Question 18

Why do we care about CLA?

Answer 18

Inhibition of carcinogenesis

Reduction of carcass fat deposition & milk fat production

Question 19

Action of dietary fat on forage digestibility?

Answer 19

Inhibitory action if > 5-6%

Caused by antimicrobial activity of LCFA -> reduce intake & digestibility

Question 20

How can the effects of antimicrobial LCFA be overcome?

Answer 20

Add calcium hydroxide to diet -> immobilises LCFA