Lipids

Question 1

Where are lipids generally found? (3)

Answer 1

Cell membranes

Lipid droplets in adipose

Lipoproteins in blood

Question 2

Aside from their use in energy storage and membranes, what are lipids used for in the body? (4)

Answer 2

Enzyme cofactors

Hormons

Vitamins

Signalling molecules

Question 3

What are the 5 classes of lipid?

Answer 3

Phospholipids
Triacylglycerols
Free fatty acids
Glycolipids
Steroids

Question 4

A fatty acid with a 17:3 in the name means what?

Answer 4

17 carbons

3 double bonds

Question 5

True or false

In omega acids, the double bond is counted from the carboxyl end of the molecule?

Answer 5

False

Normal convention is to count from the Coo- end but omega acids are counted from the methyl end

Question 6

Why must we obtain linoleic and linolenic acids from plants?

Answer 6

Essential fatty acid

Can not synthesise it

Question 7

Why are we unable to make essential fatty acids?

Answer 7

Humans cannot introduce double bonds beyond carbon 9

Question 8

What problems are caused by fatty acid deficiency?

GRSKVDA

Answer 8

Growth retardation 
Reproductive failure
Skin lesions 
Kidney/Liver disorder
Visual problems 
Depression (Omega 3)
ADHD (Omega 3)

Question 9

What are the main uses of triacyglycerols?

Answer 9

Energy
Insulation

(TAG’s are the main lipid type in stored fat)

Question 10

Where are triacylglycerols stored?

Answer 10

Adipose tissue

Question 11

Describe the basic structure of phospholipids.

Answer 11

Glycerol
2 FA
Phosphate

Question 12

What is the main dietary lipid type?

Answer 12

Triacylglycerols

Question 13

What is the main site of digestion of lipids?

Answer 13

Small intestine

Question 14

What molecules are used to digest lipids in the small intestine?

Answer 14

Pancreatic lipases

+ bile salts

Question 15

Where are bile salts produced and what are they derivatives of?

Answer 15

Gallbladder

Cholesterol

Question 16

What do bile salts do?

Answer 16

Emulsify lipids into smaller droplets

Question 17

What is produced when Triacylglycerols are broken down in the small intestine?

Answer 17

2 FA

1 Monoacylglycerol

Question 18

Phospholipids are broken down into what?

in small intestine

Answer 18

1 FA

1 Lysophospholipid

Question 19

Bile salts combine with the products of digestion of lipids to form?

Answer 19

Micelles

Question 20

Why do micelles only contain long chain fatty acids and not short/medium chain?

Answer 20

Short chain FA can diffuse through membrane directly

Question 21

What is Steatorrhea?

Answer 21

Inadequate lipid absorption

Defects in bile secretion, pancreatic function, intestinal cell uptake

Question 22

What happens to the products of digestion after they cross into epithelial cells? (4)

Answer 22

Re-synthesised

Made into chylomicrons

Exocytosis into lymph

Movement into blood

Question 23

What is the purpose of apoB-48?

Answer 23

Solubilising protein

Question 24

Describe how the triacyglycerols are transported into tissues.

Answer 24

Chylomicrons broken down into FA + glycerol in capillaries by lipoprotein lipases

These are found mostly in capillaries of skeletal muscle and adipose tissue

Chylomicron remnants transported to liver

Question 25

What are the Fatty acids and glycerol molecules (produced when chylomicrons are broken down) used for?

Answer 25

FA used for energy (skeletal muscle) or resynthesised to make TAG for storage (adipose) Glycerol is used by liver to make G-3-P (glycolysis & gluconeogenesis)

Question 26

Where is triacylglycerol stored?

Answer 26

Adipose cells/tissue

Question 27

What does Hormone sensitive lipase (HSL) do?

Answer 27

Release stored TAG in adipose cells

Question 28

What transmitter is used to trigger Hormone sensitive lipase to start working?

Answer 28

Adrenaline (epinephrine)

Question 29

What is the difference in how fatty acids and triacylglycerols are transported in the blood?

Answer 29

FA's - serum albumin | TAG's - lipoproteins

Question 30

Why are lipoproteins needed?

Answer 30

TAGs and cholesterol esters are insoluble in water Cannot travel in blood/lymph

Question 31

True or false Chylomicrons are examples of lipoproteins

Answer 31

True

Question 32

What are the 4 types of Lipoproteins?

Answer 32

Chylomicron VLDL (Very low density lipoprotein) LDL HDL

Question 33

What problems are associated with too much LDL?

Answer 33

Atherosclerosis

Question 34

Where do VLDLs transport TAGs to and from?

Answer 34

Liver to tissues

Question 35

What do LDL's transport?

Answer 35

Mainly cholesterol | Release in extra-hepatic tissues

Question 36

What is the function of HDLs?

Answer 36

Transport cholesterol from tissues to liver to be eliminated

Question 37

What is Beta oxidation?

Answer 37

Degradation of fatty acids, 2 carbons at a time Produces Acetyl CoA + NADH + FADH2

Question 38

Where does Beta oxidation occur?

Answer 38

Mitochondrial matrix

Question 39

What are the 3 stages of Beta oxidation?

Answer 39

Activation Transport Degradation

Question 40

What happens in the activation stage of beta oxidation?

Answer 40

Fatty acids activated to form fatty acyl CoA | In cytoplasm

Question 41

Describe the transport stage of beta oxidation.

Answer 41

*Carnitine shuttle* Fatty acyl CoA moves across outer mitochondrial membrane CoA group removed, Carnitine group added Fatty acyl Carnitine moves across inner membrane Carnitine removed, CoA added forming Fatty acyl CoA

Question 42

What is the enzyme used to for adding/removing the Carnitine /CoA groups in the transport stage of Beta oxidation?

Answer 42

Carnitine palmitoyl-transferase | 1 + 2

Question 43

Why does therapy for CAT-1 deficiency include giving medium chain Fatty acids?

Answer 43

Carntine shuttle used for long chain FA Medium chain FA can pass into mitochondria without shuttle Patient can carry out Beta Oxidation

Question 44

There are 4 steps in the degradation stage of Beta oxidation, what are they?

Answer 44

Dehydrogenation - produce FADH2 Hydration Dehydrogenation - produce NADH Thiolysis - cleavage to produce Acetyl CoA

Question 45

What is the Acetyle CoA produced by thiolysis used for?

Answer 45

Feeds into the citric acid cycle

Question 46

What would be the product of complete beta oxidation of a 18:0 Fatty acid?

Answer 46

18 carbons Each cycle produces 1 Acetyl CoA and a FA that is 2 C's shorter 00-00-00-00-00-00-00-00-00 8 'splits of -' are needed 8 NADH + 8 FADH2 + 9 Acetyl CoA

Question 47

What are peroxisomes used for?

Answer 47

Partial B-oxidation of >22 carbon FA chains These could not originally pass into Mitochondria via C shuttle but can after leaving peroxisome

Question 48

Why does Acetyl CoA not used in gluconeogenesis?

Answer 48

Thermodynamically impossible to convert Acetyl CoA to pyruvate (only the opposite)

Question 49

What does the body convert Acetyl CoA into during starvation?

Answer 49

Ketone bodies

Question 50

Describe why ketone bodies are used?

Answer 50

Starving: glucose decreased Excess Acetyl Coa from metabolism of FA converted to Ketone bodies Supplies Cardiac + skeletal muscles + brain cells

Question 51

Why must Fatty acids be converted to ketone bodies to supply the brain with energy?

Answer 51

Brain cannot use FA as fuel source Brain needs a fuck ton of energy

Question 52

Where are ketone bodies produced? | organelle + organ

Answer 52

Mitochondrial matrix of cells in the liver

Question 53

True or false The liver manufactures ketone bodies, but can not use them itself

Answer 53

True

Question 54

A stranger in the street collapses in a manner similar to extreme drunked-ness You approach to help but notice a strong fruity odour The stranger is a diabetic What is wrong with the stranger?

Answer 54

Diabetes leads to high ketone concentrations in blood Ketonemia (blood) + Ketonuria (urine) + Acidemia (acidic blood) Fruity odour due to Acetone

Question 55

Where does Fatty acid synthesis take place? (3)

Answer 55

Liver Lactating mammary gland Adipose tissue

Question 56

What organic molecule are fatty acids synthesized from in lipogenesis?

Answer 56

Acetyle CoA

Question 57

What is used to provide energy for making FA's in lipogenesis? (2)

Answer 57

ATP | NADPH

Question 58

Why is NADH not used in fatty acid synthesis?

Answer 58

NADH is used in FA degredation

Question 59

Where does fatty acid synthesis take place?

Answer 59

Cytosol | liver, mammary gland, adipose

Question 60

Where is acetyl CoA produced?

Answer 60

Mitochondria

Question 61

How is Acetyle CoA moved to the cytosol?

Answer 61

Acetyle CoA reacted with oxaloacetate to make citrate Citrate passes through membrane Reverse reaction done so oxaloacetate + Acetyle CoA made on cytosol side - ULTRA BASIC - A.CoA turned to citrate, goes through and is turned back into A.CoA

Question 62

Why is Acetyl CoA carboxylase a key enzyme in fatty acid synthesis?

Answer 62

Forms malonyl-CoA Committed step in pathway

Question 63

You have 32 molecules of Acetyl CoA, how many molecules of palmatite can you obtain from fatty acid synthesis?

Answer 63

4 8 A.CoA : 1 Palmatite

Question 64

How many molecules of ATP and NADPH are used to produce 4 molecules of palmatite?

Answer 64

56 NADPH - 28 ATP each palmatite requires 14 NADPH's and 7 ATP's to make

Question 65

True or false Steroids and Eicosanoids are both derived from cholesterol

Answer 65

False Steroids are derived from cholesterol Eicosanoids are derived from omega 3 and 6

Question 66

What is cholesterol derived from?

Answer 66

Acetyl CoA

Question 67

How do statins reduce cholesterol levels?

Answer 67

Inhibit enzyme needed in cholesterol synthesis Lower LDL levels

Question 68

What vitamins are derived from lipids?

Answer 68

A, D, E, K

Question 69

What is beta oxidation?

Answer 69

Catabolism of Fatty acids to generate NADH, FADH2 and Acetyl CoA

Question 70

What are the possible fates of Acetyl CoA, produced from Beta oxidation?

Answer 70

1) Feed into CAC 2) Ketogenesis 3) Lipogenesis (reverse)

Question 71

Why does ketogenesis occur?

Answer 71

Fasting/starvation Low blood glucose means energy is needed Fatty acids are not gluconeogenic so can not make glucose, so are converted to ketone bodies which can be used as an energy source that isn't glucose

Question 72

What tissues can use ketone bodies as a fuel source?

Answer 72

Cardiac and skeletal muscle The brain - this can't use FA as an energy source

Question 73

Where does ketogenesis take place

Answer 73

Liver But the liver can't use ketone bodies as an energy source