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Science For Medicine BenJ > Lipids finak > Flashcards

Lipids finak Flashcards

1
Q

What are Lipids?

A

Hydrophobic heterogeneous organic molecules

Soluble in organic solvents

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2
Q

What do lipids make up?

A

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

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3
Q

What do lipids provide?

A
  • Store of energy
  • Membrane structural elements
  • Source of Vit ADEK
  • Signalling molecules
  • Hormones
  • CoFactors
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4
Q

What re the 5 mian classes of lipids?

A
  • Fatty Acids
  • Glycolipids
  • Steroids
  • Phospholipids
  • Triacylglycerols
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5
Q

How do we number FA?

A

Number of Carbons:no.doublebonds (where the bonds are)

e.g. 18:2 (9,12)

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6
Q

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

A

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

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7
Q

What are hte 2 essetial FA?

A

Linoleic Acid & linolenic Acid

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8
Q

Why are they essential?

A

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

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9
Q

What kind of fat is ‘good’?

A

Polyunsaturated Fats e.g. Veg Oil

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10
Q

What fat is ‘bad’?

A

Saturated Fats e.g. Beef

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11
Q

What fats are relaly fucking awful for ya?

A

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

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12
Q

What does linoleic acid provide?

A

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

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13
Q

What does Linolenic acid provide?

A

Omega-3 FA

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14
Q

What is the use of Omega-6 FA?

A

Lower plasma cholesterol & TAG

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15
Q

What are the symptoms of an essential FA deficiencY?

A
  • ADHD
  • Depression
  • Chronic intersitnal disease
  • Reproductive failure
  • Kidney/liver disease
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16
Q

How are FA released from TAG?

A

Epinephrine activates HSL

Hormone sensitive Lipase releases FA

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17
Q

What inihbits HSL?

A

Insulin & High plasma glucose

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18
Q

How are FA transported in the blood?

A

Free FA are complexed with albumin

Most FA is esterified & carried in lipoproteins

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19
Q

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

A
  • Chylomicron
  • Very low density lipoprotein (VLDL)
  • Low Density Lipoprotein (LDL)
  • High density lipoprotein (HDL)
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20
Q

What is in chylomicrons & VLDL?

A

TAG

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21
Q

What is stored in LDL & HDL?

A

Cholesterol

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22
Q

Where do chylomicrons go?

A

Transport FA from intestines to tissues

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23
Q

Where does VLDL go?

A

Transports TAG from liver to tissue

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24
Q

Where does LDL go?

A

Takes cholesterol to extrahepatic tissues (very bad)

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25
Q

Where does HDL go?

A

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

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26
Q

What causes atherosclerosis?

A

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

27
Q

What are the products of B-oxidation?

A

Acetyl CoA
NADH
FADH2

28
Q

Where does B-oxidation occur?

A

Mitochondrial Matrix

29
Q

What are the 3 phases of B-oxidation??

A

Activation in cytosol
TRansport into matrix
Degradation

30
Q

How is the FA activted in beta-oxidation?

A

Activated in cytosol to a fatty acyl CoA

31
Q

How does the carnitine shuttle work?

A

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
Q

How is the carnitine shuttle inhibited?

A

CAT inhibited by Malonyl-CoA.

The main agent for FA synthesis so ensures they dont occur simultaneously

33
Q

What deos a CAT-1 deficiency cause?

A

Little B-oxidation leading to hypoglycaemia

34
Q

How do you treat a CAT-1 deficiency?

A

Treat immediately with IV glucose

Long term with medium chain FA that dont need a carnitine shuttle

35
Q

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

A

Oxidation
Hydration
Oxidation
Thiolysis (Cleavage)

36
Q

What is produced for every B-oxidation cycle?

A
  • An acyl group 2 carbons shorter than before
  • An Acetyl-CoA group
  • 1 NADH
  • 1 FADH2
37
Q

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

A 
Every:
- FADH2 -> 2ATP
- NADH -> 3ATP
- Acetyl CoA -> 12ATP
Remember to remove 2 for the production of palmitoyl-CoA at the start
38
Q

What happens to FA over 22 carbons inlenth?

A

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

39
Q

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

A

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

40
Q

Why is no FA gluconeogenic?

A

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

41
Q

What happens to excess Acetyl-CoA?

A

Becomes Ketone Bodies in liver

42
Q

What are ketones used for?

A

Fuels the brain, cardiac muscle & skeletal muscle

43
Q

What happens if theyres excess ketone bodies?

A

Ketonemia
Ketonuria
Acidemia
Fruity breath from acetone

44
Q

What is diabetes ketosis?

A

When theres a lack of insulin HSL isnt inhibited

  • > increased lipolysis
  • > increased blood FA
  • > more B-oxidation
  • > increased Acetyl-CoA
  • > Ketonemia, ketonuria, acidemia
45
Q

Where does FA synthesis occur?

A

Cytosol of:
Liver
Mammary glands
Adipose tissue

46
Q

What enzyme controls FA synthesis?

A

Fatty Acid Synthase

47
Q

What FA is produced in FA synthesis?

A

Palmitate (palmitic acid)

48
Q

What is the overall equation for Palmitate syntehsis?

A 
8 Acetyl-CoA + 14 NADPH + 14H+ + 7ATP
                         |
                         |
                        V
Palmitate + 8 CoA + 14 NADP+ + 7ADP + 7Pi + 7 H2O
49
Q

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

A

The citrate shuttle

50
Q

What else is produced in the citrate shuttle?

A

NADPH

51
Q

What is the building block of FA syntehiss?

A

Malonyl-CoA

Made from Acetyl-coA

52
Q

What are the reactions in FA syntehsis?

A

Condensation
Reduction
Dehydration
Reduction

53
Q

What carries the intermediates dring FA syntehsis?

A

ACP (Acyl carrier Protein)

54
Q

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

A

Thiosterase

55
Q

What is TAG made of?

A

Triacylglycerols are esters of FAs & glycerol

56
Q

What are phospholipids made of?

A

2 FA & a glycerol

57
Q

What are bile salts derived from?

A

Cholesterol

58
Q

What part of digestion occurs in the small intestine?

A 
Pancreatic enzymes (lipases) break down lipids.
PRomoted by emulsification by bile salts & peristalsis
59
Q

How are products of lipid digestion absorbed?

A

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
Q

What happens if lipid malabsorption occurs?

A

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

61
Q

How are lipids transported from the intestine?

A

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

62
Q

What happens to TAG at tissue?

A

Its hydrolysed to FA & glycerol by lipoprotein lipase

63
Q

What happens to the FA & glycerol at tissues?

A

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

Science For Medicine BenJ (35 decks)

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