Lipids

Question 1

Biological functions of lipids

Answer 1

Stored form of energy, steroid hormones, signalling molecules, structural element of membranes

Question 2

Lipid classes

Answer 2

Fatty acids, triacylglycerol, phospholipids, glycolipid, steroids

Question 3

Unsaturated fatty acids

Answer 3

One or more double bonds that kink hydrocarbon chain

Question 4

Saturated fatty acids

Answer 4

Solid, no double bonds

Question 5

Naming fatty acids

Answer 5

Number of carbons, place of double bond, number of double bonds present

Question 6

Good fats

Answer 6

High in polyunsaturated fats eg olive oil sunflower oil

Question 7

Bad fats

Answer 7

High in saturated fats eg beef

Question 8

Really bad fats

Answer 8

Trans fatty acids (result from hydrogenation of vegetable oil) eg hard margarine

Question 9

Humans cannot ingest double bonds beyond carbon

Answer 9

9

Question 10

Omega 3 fatty acids

Answer 10

Derived from linolenic acids as essential fatty acids. Lower cholesterol levels, prevents obesity, reduces inflammation. Found in fish

Question 11

Omega 6 FA

Answer 11

found in linoleic. Does not have benefits

Question 12

Essential fatty acid deficiency

Answer 12

Depression, ADHD, scaly dermatitis etc

Question 13

Triacylglycerols

Answer 13

Esters (neutral uncharged lipids) of fatty acids and glycerol. Major lipid component of adipose tissue. Dietary fuel and insulation

Question 14

Phospholipids

Answer 14

2 fatty acids and phosphate group, amphipathic, in membrane, help with digestion as they are emulsifiers

Question 15

What affects the melting points of fatty acids

Answer 15

Number of carbons and degree of unsaturation

Question 16

Are lipids water soluble

Answer 16

No

Question 17

What is the main dietary lipid

Answer 17

Triacylglycerol

Question 18

How are lipids digested

Answer 18

In small intestine. Use of pancreatic enzymes. Promoted by emulsification (dispersion) by bile salts and peristalsis

Question 19

Bile salts

Answer 19

Biological detergents that form emulsions and mixed micelles, saves lipids coalescing in an aqueous environment. Derivatives of cholesterol

Question 20

How are triacylglycerols digested

Answer 20

Degraded by lipases to monoacylglycerol and fatty acids

Question 21

Cholesterol esters are broken down into

Answer 21

Cholesterol and free fatty acid by pancreatic cholesterol esterase

Question 22

What do products if lipid digestion form and where do they go

Answer 22

Form mixed micelles with bile salts and then approach brush border membranes of enterocytes and release lipid products that enter by diffusion . Only long chain FA need micelles

Question 23

Gall bladder secretes

Answer 23

Bile

Question 24

Chylomicrons

Answer 24

Intestinal cells that are packaged with apoB-48 which is a solubilising protein. They are then exported from small intestine by exocytosis into lymph then blood

Question 25

What happens once chylomicrons reach tissue

Answer 25

• free FA used for energy or reesterified for storage
• if depleted of triacylglycerols they go to liver (chylomicrons remnants)
• lipoprotein lipase found in capillaries of muscle, adipose and skeletal tissue hydrolyse the TAG to fatty acids and glycerol

Question 26

How are fatty acids release from storage in adipose tissue

Answer 26

By hormone sensitive lipase when it is activated phosphorylation in response to high epinephrine levels

Question 27

What stops fatty acids from being released from TAG in adipose tissue

Answer 27

When plasma glucose and insulin levels are high and they promote dephosphorylation of lipase

Question 28

Fatty acids are transported in blood by

Answer 28

Serum albumin ( plasma protein with 2-7 binding sites for FA)

Question 29

If fatty acids are esterified how are they carried in blood

Answer 29

Lipoproteins

Question 30

Beta oxidation pathway

Answer 30

Degrades fatty acids two carbons at a time and occurs in mitochrondrial matrix. Produces acetyl CoA and NADH and FADH2

Question 31

Stages of beta oxidation

Answer 31

Activation of fatty acids in cytosol,
transport into mitochondria by carnitine shuttle,
degradation to two carbon fragments in the mitochondrial matrix- energy!

Question 32

Carnitine shuttle

Answer 32

Major site of regulation, prevents synthesis and degradation from happening at same time, get it from diet or made from lysine or methionine

Question 33

4 main steps of metabolism part of B oxidation

Answer 33

Dehydration to produce FADH2
Hydration
Dehydration to produce NADH
Thiolysis (cleaved) to produce acetyl CoA

Question 34

When fasting/starving/diabetes what happens to acetyl CoA

Answer 34

Not enough oxaloacetate to be used in the citric acid cycle so the acetyl CoA is converted into ketone bodies

Question 35

Where does ketogenesis occur and why

Answer 35

In liver and because it depends on the activity of rate limiting enzyme HMG CoA synthase which is found in liver (liver cannot use the ketone bodies but it makes them)

Question 36

Are ketone bodies soluble in blood

Answer 36

Yes. Do not need albumin or lipoprotein

Question 37

What uses ketone bodies for energy

Answer 37

Cardiac and skeletal muscles, kidney, brain cells

Question 38

Excessive ketone bodies can cause

Answer 38

Ketonemia, ketonuria, acidemia

Question 39

Ketone bodies are acidic or alkaline

Answer 39

Acidic

Question 40

Fatty acid synthesis occurs in cytosol in what tissues/ organs

Answer 40

Liver, adipose tissue, lactating mammary gland

Question 41

When does citrate shuttle occur

Answer 41

When citrate concentration in mitochondria is high. It allows acetyl CoA to cross membrane from mitochondrion to cytosol

Question 42

What is the key regulatory enzyme in fatty acid production

Answer 42

Acetyl CoA carboxylase. transfers acetyl coA to TCA

Question 43

What activates and deactivates Acetyl Coenzyme Carboxylase

Answer 43

citrate activates, palmitoyl CoA deactivates. (Short term) Insulin activates, glucagon and epinephrine deactivates (long term)

Question 44

What is malonyl CoA

Answer 44

inhibitor of carnitine shuttle. prevents split up of acyl and coA. Substrate that provides the carbon for the formation of palmitate (product of fatty acid synthesis)