Lipids

Question 1

What are some properties of lipids

Answer 1

Heterogeneous organic molecules
Hydrophobic
Exist in cell membranes, as lipid droplets in adipose tissue, as lipoproteins in blood

Question 2

What is the biological function of lipids

Answer 2

Stored form of energy
Structural element of membranes
Enzyme cofactors
Hormones
Vitamins A D E K
Signalling molecules

Question 3

Lipid classes

Answer 3

Fatty acids
Triacylglycerol (TAG)
Phospholipids
Glycolipids
Steroids

Question 4

What are the two types of fatty acids and what is the difference between them

Answer 4

Unsaturated - one or more double bond that kink hydrocarbon chain
Saturated - solid with no double bonds

Question 5

Which fatty acids are essential

Answer 5

Linoleic and alpha linolenic

Question 6

Where do you get essential fatty acids from

Answer 6

Plants

Question 7

What are some ‘good fats’ and what makes them so

Answer 7

Vegetable oil e.g. olive or sunflower

They’re high in polyunsaturated fatty acids

Question 8

What are some ‘bad fats’ and why

Answer 8

Stearic (beef)

High in saturated fatty acids

Question 9

What is a ‘really bad fat’ and why is it so

Answer 9

Trans fatty acids, result from hydrogenation of vegetable oils e.g. man made hard margarine

Question 10

After which point can humans not introduce double bones

Answer 10

Carbon 9

Question 11

What are omega 3 fatty acids derived from

Answer 11

Linolenic acid

Question 12

What does omega 3 FA do

Answer 12

Lowers plasma cholesterol, prevents atherosclerosis, lowers TAG, prevents obesity, reduces inflammation

Question 13

Classis symptoms of essential fatty acid deficiency

Answer 13

Growth retardation
Reproductive failure
Skin lesions
Kidney and liver disorders
Subtle neurological and visual problems

Question 14

What are triacylglycerols

Answer 14

Esters of fatty acids and glycerol

Question 15

Function of triacylglycerols

Answer 15

Dietary fuel
Insulation
Water insoluble TAG coalesce into lipid droplets in adipose tissue
Major lipid component of adipose tissue

Question 16

What are phospholipids composed of

Answer 16

Glycerol bonded to 2 fatty acids and a phosphate group

Question 17

Describe amphiphatic nature of phospholipids

Answer 17

Positively charged head is hydrophilic

Hydrophobic tail repels water

Question 18

What is the main dietary lipid

Answer 18

Triacylglycerol

Question 19

Where is the main site of digestion

Answer 19

Small intestines

Question 20

What are some other dietary lipids

Answer 20

Phospholipids, cholesterol, free fatty acids and cholesterol ester

Question 21

What digests lipids and what is it promoted by

Answer 21

Lipids are digested by pancreatic enzymes called lipases and is promoted by emulsification by bile salts and peristalsis

Question 22

What are bile salts

Answer 22

Derivatives of cholesterol
Saves lipids coalescing in an aqueous enviroment
Act as a biological detergents to form emulsions and mixed micelles

Question 23

How do we digest TAG

Answer 23

Most degraded in small intestine by pancreatic lipase to monoacylglycerol and 2 FA

Question 24

What are cholesterol esters digested to

Answer 24

Cholesterol and free FA

Question 25

How are phospholipids digested and what too

Answer 25

Converted to FAs and lysophospholipids by hydrolysation

Question 26

Which of short, medium and long FAs require micelles for absorption

Answer 26

Long

Question 27

What is steatorrhea

Answer 27

Excess fat in faeces, stools float, have oily appearance and are foul smelling

Question 28

What happens if the gallbladder is removed

Answer 28

Inhibition of digestion and absorption of fats

Question 29

How is TAG stored in adipose cells

Answer 29

Droplets that constitute the depot fat

Question 30

Why is TAG the most efficient storage form of fuel

Answer 30

It's highly reduced, nearly anhydrous

Question 31

How are FA released from stored TAG in adipose tissue

Answer 31

Hormone Sensitive Lipase (HSL) activated by phosphorylation in response to epinephrine. High plasma glucose and insulin promote dephosphorylation of lipase (deactivation)

Question 32

How are FA transported in the blood

Answer 32

Free FA transported through blood in complex with serum albumin

Question 33

What is the most abundant plasma protein and how many FA binding sites does it have

Answer 33

Albumin, 2-7

Question 34

What occurs when there is too much LDL

Answer 34

Atherosclerosis, lipid develops into fatty streaks and plaque within an artery

Question 35

What does the beta oxidation pathway do

Answer 35

Degrades fatty acids 2 carbons at a time | Produces acetyl CoA and NADH and FADH2

Question 36

Where does beta oxidation occur

Answer 36

Mitochondrial matrix

Question 37

What happens in beta oxidation?

Answer 37

Three stages: 1. activation of fatty acids in cystole 2. transport by carnatine shuttle into the mitochondria 3. degradation to 2 carbon gragments (as acetyl CoA) in the mitochondrial matrix - energy

Question 38

What happens in fatty acid activation

Answer 38

Fatty acid activated to form fatty acyl CoA in cytoplasm

Question 39

What is the Carnitine shuttle

Answer 39

Major site of regulation Prevents synthesis and degradation occurring simultaneously Carton from diet or made from lysine/methionine in liver/kidney

Question 40

What is CAT-1

Answer 40

Carnitine palmitoyl-transferase deficiency A carnatine associated defect in liver fatty acid beta oxidation impairs the livers capacity to use fatty acids as fuels and puts and extra burden on its capacity to generate glucose through glucneogenesis

Question 41

What happens during degradation stage of beta oxidation

Answer 41

1. Dehydrogenation to produce FADHs 2. Hydration 3. Dehydrogenation to produce NADH 4. Thiolysis (cleaved) to produce acetyl CoA