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Flashcards in Lipids finak Deck (63):
1

What are Lipids?

Hydrophobic heterogeneous organic molecules
Soluble in organic solvents

2

What do lipids make up?

Phospholipids in membranes
Triacylglycerols in adipose droplets
Lipoproteins (often in blood)

3

What do lipids provide?

- Store of energy
- Membrane structural elements
- Source of Vit ADEK
- Signalling molecules
- Hormones
- CoFactors

4

What re the 5 mian classes of lipids?

- Fatty Acids
- Glycolipids
- Steroids
- Phospholipids
- Triacylglycerols

5

How do we number FA?

Number of Carbons:no.doublebonds (where the bonds are)
e.g. 18:2 (9,12)

6

What can we tell from a FA described as 19:3 (3,5,12)

19 carbon chain
3 C=C bonds
Double bonds at 3=4, 5=6 & 12=13.

7

What are hte 2 essetial FA?

Linoleic Acid & linolenic Acid

8

Why are they essential?

We cant introduce double C=C bonds beyond Carbon 9 so must get them from plants

9

What kind of fat is 'good'?

Polyunsaturated Fats e.g. Veg Oil

10

What fat is 'bad'?

Saturated Fats e.g. Beef

11

What fats are relaly fucking awful for ya?

Transfats e.g. hard margerine man made by hydrogenation of Veg oil.

12

What does linoleic acid provide?

Arachidonic acid which metabolizes to eicosanoids like leukotiren & prostoglandins
Omega-6 FA

13

What does Linolenic acid provide?

Omega-3 FA

14

What is the use of Omega-6 FA?

Lower plasma cholesterol & TAG

15

What are the symptoms of an essential FA deficiencY?

- ADHD
- Depression
- Chronic intersitnal disease
- Reproductive failure
- Kidney/liver disease

16

How are FA released from TAG?

Epinephrine activates HSL
Hormone sensitive Lipase releases FA

17

What inihbits HSL?

Insulin & High plasma glucose

18

How are FA transported in the blood?

Free FA are complexed with albumin
Most FA is esterified & carried in lipoproteins

19

What are the 4 types of lipoprotein in increasing density order?

- Chylomicron
- Very low density lipoprotein (VLDL)
- Low Density Lipoprotein (LDL)
- High density lipoprotein (HDL)

20

What is in chylomicrons & VLDL?

TAG

21

What is stored in LDL & HDL?

Cholesterol

22

Where do chylomicrons go?

Transport FA from intestines to tissues

23

Where does VLDL go?

Transports TAG from liver to tissue

24

Where does LDL go?

Takes cholesterol to extrahepatic tissues (very bad)

25

Where does HDL go?

Takes cholesterol from tissue to the liver for elimination (Very good)

26

What causes atherosclerosis?

Obesity or a genetic defect in LDL receptors can lead to excess LDL which can cause atherosclerosis

27

What are the products of B-oxidation?

Acetyl CoA
NADH
FADH2

28

Where does B-oxidation occur?

Mitochondrial Matrix

29

What are the 3 phases of B-oxidation??

Activation in cytosol
TRansport into matrix
Degradation

30

How is the FA activted in beta-oxidation?

Activated in cytosol to a fatty acyl CoA

31

How does the carnitine shuttle work?

Carnitine Palmitoyl-transferase (CAT) carries the Acyl group thorugh the membrane attached to carnitine then releases it on the other side where it binds to more CoA.

32

How is the carnitine shuttle inhibited?

CAT inhibited by Malonyl-CoA.
The main agent for FA synthesis so ensures they dont occur simultaneously

33

What deos a CAT-1 deficiency cause?

Little B-oxidation leading to hypoglycaemia

34

How do you treat a CAT-1 deficiency?

Treat immediately with IV glucose
Long term with medium chain FA that dont need a carnitine shuttle

35

What are the main reactions in the degradation of a FA?

Oxidation
Hydration
Oxidation
Thiolysis (Cleavage)

36

What is produced for every B-oxidation cycle?

- An acyl group 2 carbons shorter than before
- An Acetyl-CoA group
- 1 NADH
- 1 FADH2

37

How do we determine the energy output of a FA when completely broken down?

Every:
- FADH2 -> 2ATP
- NADH -> 3ATP
- Acetyl CoA -> 12ATP
Remember to remove 2 for the production of palmitoyl-CoA at the start

38

What happens to FA over 22 carbons inlenth?

They undergo a preliminary B-oxidation in a peroxisome which is less efficient because no FADH2 is made

39

What do defects in the peroxisome B-oxidation lead to?

Very Long Chain Fatty Acid (VLC-FA) accumulatin in blood/tissue

40

Why is no FA gluconeogenic?

Because they break down to Acetyl-CoA which cant undergo gluconeogenesis due to the pyruvate->acetyl-CoA reaction being irreversible

41

What happens to excess Acetyl-CoA?

Becomes Ketone Bodies in liver

42

What are ketones used for?

Fuels the brain, cardiac muscle & skeletal muscle

43

What happens if theyres excess ketone bodies?

Ketonemia
Ketonuria
Acidemia
Fruity breath from acetone

44

What is diabetes ketosis?

When theres a lack of insulin HSL isnt inhibited
-> increased lipolysis
-> increased blood FA
-> more B-oxidation
-> increased Acetyl-CoA
-> Ketonemia, ketonuria, acidemia

45

Where does FA synthesis occur?

Cytosol of:
Liver
Mammary glands
Adipose tissue

46

What enzyme controls FA synthesis?

Fatty Acid Synthase

47

What FA is produced in FA synthesis?

Palmitate (palmitic acid)

48

What is the overall equation for Palmitate syntehsis?

8 Acetyl-CoA + 14 NADPH + 14H+ + 7ATP
|
|
V
Palmitate + 8 CoA + 14 NADP+ + 7ADP + 7Pi + 7 H2O

49

Acetyl-CoA is made in the matrix but FA syntehsis occurs in the cytosol. How does it move out the mitochondria?

The citrate shuttle

50

What else is produced in the citrate shuttle?

NADPH

51

What is the building block of FA syntehiss?

Malonyl-CoA
Made from Acetyl-coA

52

What are the reactions in FA syntehsis?

Condensation
Reduction
Dehydration
Reduction

53

What carries the intermediates dring FA syntehsis?

ACP (Acyl carrier Protein)

54

What cleaves the ACP off the acyl group at the end of FA synthesis?

Thiosterase

55

What is TAG made of?

Triacylglycerols are esters of FAs & glycerol

56

What are phospholipids made of?

2 FA & a glycerol

57

What are bile salts derived from?

Cholesterol

58

What part of digestion occurs in the small intestine?

Pancreatic enzymes (lipases) break down lipids.
PRomoted by emulsification by bile salts & peristalsis

59

How are products of lipid digestion absorbed?

Products form mixed micelles with bile salts
Then approach the bursh border membrane where theyre released from the micelle & enter the intestinal cells by diffusion

60

What happens if lipid malabsorption occurs?

Steatorrhea - excess fat in teh faeces causing them to float & take on a shiny appearence

61

How are lipids transported from the intestine?

Lipids resyntehsised into TAG, Phospholipids & cholesterol in intestinal cells.
Then packaged with apoB-48 for solubility into chylomicrons
Then exocytosed into the blood

62

What happens to TAG at tissue?

Its hydrolysed to FA & glycerol by lipoprotein lipase

63

What happens to the FA & glycerol at tissues?

Either reformed to TAg & stored as adipose droplets.
OR:
- the glycerol is converted to G-3-P then put into glycolysis/gluconeogenesis
- The FA undergoes B-oxidation for energy