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Science for shegs > Lipids > Flashcards

Lipids Flashcards

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1
Q

Where are lipids generally found? (3)

A

Cell membranes

Lipid droplets in adipose

Lipoproteins in blood

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2
Q

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

A

Enzyme cofactors

Hormons

Vitamins

Signalling molecules

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3
Q

What are the 5 classes of lipid?

A 
Phospholipids
Triacylglycerols
Free fatty acids
Glycolipids
Steroids
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4
Q

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

A

17 carbons

3 double bonds

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5
Q

True or false

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

A

False

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

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6
Q

Why must we obtain linoleic and linolenic acids from plants?

A

Essential fatty acid

Can not synthesise it

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7
Q

Why are we unable to make essential fatty acids?

A

Humans cannot introduce double bonds beyond carbon 9

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8
Q

What problems are caused by fatty acid deficiency?

GRSKVDA

A 
Growth retardation 
Reproductive failure
Skin lesions 
Kidney/Liver disorder
Visual problems 
Depression (Omega 3)
ADHD (Omega 3)
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9
Q

What are the main uses of triacyglycerols?

A

Energy
Insulation

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

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10
Q

Where are triacylglycerols stored?

A

Adipose tissue

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11
Q

Describe the basic structure of phospholipids.

A

Glycerol
2 FA
Phosphate

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12
Q

What is the main dietary lipid type?

A

Triacylglycerols

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13
Q

What is the main site of digestion of lipids?

A

Small intestine

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14
Q

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

A

Pancreatic lipases

+ bile salts

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15
Q

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

A

Gallbladder

Cholesterol

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16
Q

What do bile salts do?

A

Emulsify lipids into smaller droplets

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17
Q

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

A

2 FA

1 Monoacylglycerol

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18
Q

Phospholipids are broken down into what?

in small intestine

A

1 FA

1 Lysophospholipid

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19
Q

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

A

Micelles

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20
Q

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

A

Short chain FA can diffuse through membrane directly

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21
Q

What is Steatorrhea?

A

Inadequate lipid absorption

Defects in bile secretion, pancreatic function, intestinal cell uptake

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22
Q

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

A

Re-synthesised

Made into chylomicrons

Exocytosis into lymph

Movement into blood

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23
Q

What is the purpose of apoB-48?

A

Solubilising protein

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24
Q

Describe how the triacyglycerols are transported into tissues.

A

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

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25
Q

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

A

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)

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26
Q

Where is triacylglycerol stored?

A

Adipose cells/tissue

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27
Q

What does Hormone sensitive lipase (HSL) do?

A

Release stored TAG in adipose cells

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28
Q

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

A

Adrenaline (epinephrine)

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29
Q

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

A

FA’s - serum albumin

TAG’s - lipoproteins

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30
Q

Why are lipoproteins needed?

A

TAGs and cholesterol esters are insoluble in water

Cannot travel in blood/lymph

31
Q

True or false

Chylomicrons are examples of lipoproteins

A

True

32
Q

What are the 4 types of Lipoproteins?

A

Chylomicron
VLDL (Very low density lipoprotein)
LDL
HDL

33
Q

What problems are associated with too much LDL?

A

Atherosclerosis

34
Q

Where do VLDLs transport TAGs to and from?

A

Liver to tissues

35
Q

What do LDL’s transport?

A

Mainly cholesterol

Release in extra-hepatic tissues

36
Q

What is the function of HDLs?

A

Transport cholesterol from tissues to liver to be eliminated

37
Q

What is Beta oxidation?

A

Degradation of fatty acids, 2 carbons at a time

Produces Acetyl CoA + NADH + FADH2

38
Q

Where does Beta oxidation occur?

A

Mitochondrial matrix

39
Q

What are the 3 stages of Beta oxidation?

A

Activation
Transport
Degradation

40
Q

What happens in the activation stage of beta oxidation?

A

Fatty acids activated to form fatty acyl CoA

In cytoplasm

41
Q

Describe the transport stage of beta oxidation.

A

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

42
Q

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

A

Carnitine palmitoyl-transferase

1 + 2

43
Q

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

A

Carntine shuttle used for long chain FA

Medium chain FA can pass into mitochondria without shuttle

Patient can carry out Beta Oxidation

44
Q

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

A

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

45
Q

What is the Acetyle CoA produced by thiolysis used for?

A

Feeds into the citric acid cycle

46
Q

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

A

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

47
Q

What are peroxisomes used for?

A

Partial B-oxidation of >22 carbon FA chains

These could not originally pass into Mitochondria via C shuttle but can after leaving peroxisome

48
Q

Why does Acetyl CoA not used in gluconeogenesis?

A

Thermodynamically impossible to convert Acetyl CoA to pyruvate

(only the opposite)

49
Q

What does the body convert Acetyl CoA into during starvation?

A

Ketone bodies

50
Q

Describe why ketone bodies are used?

A

Starving: glucose decreased

Excess Acetyl Coa from metabolism of FA converted to Ketone bodies

Supplies Cardiac + skeletal muscles + brain cells

51
Q

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

A

Brain cannot use FA as fuel source

Brain needs a fuck ton of energy

52
Q

Where are ketone bodies produced?

organelle + organ

A

Mitochondrial matrix of cells in the liver

53
Q

True or false

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

A

True

54
Q

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?

A

Diabetes leads to high ketone concentrations in blood

Ketonemia (blood) + Ketonuria (urine) + Acidemia (acidic blood)

Fruity odour due to Acetone

55
Q

Where does Fatty acid synthesis take place? (3)

A

Liver
Lactating mammary gland
Adipose tissue

56
Q

What organic molecule are fatty acids synthesized from in lipogenesis?

A

Acetyle CoA

57
Q

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

A

ATP

NADPH

58
Q

Why is NADH not used in fatty acid synthesis?

A

NADH is used in FA degredation

59
Q

Where does fatty acid synthesis take place?

A

Cytosol

liver, mammary gland, adipose

60
Q

Where is acetyl CoA produced?

A

Mitochondria

61
Q

How is Acetyle CoA moved to the cytosol?

A

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
62
Q

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

A

Forms malonyl-CoA

Committed step in pathway

63
Q

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

A

4

8 A.CoA : 1 Palmatite

64
Q

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

A

56 NADPH - 28 ATP

each palmatite requires 14 NADPH’s and 7 ATP’s to make

65
Q

True or false

Steroids and Eicosanoids are both derived from cholesterol

A

False

Steroids are derived from cholesterol

Eicosanoids are derived from omega 3 and 6

66
Q

What is cholesterol derived from?

A

Acetyl CoA

67
Q

How do statins reduce cholesterol levels?

A

Inhibit enzyme needed in cholesterol synthesis

Lower LDL levels

68
Q

What vitamins are derived from lipids?

A

A, D, E, K

69
Q

What is beta oxidation?

A

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

70
Q

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

A

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

71
Q

Why does ketogenesis occur?

A

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

72
Q

What tissues can use ketone bodies as a fuel source?

A

Cardiac and skeletal muscle

The brain - this can’t use FA as an energy source

73
Q

Where does ketogenesis take place

A

Liver

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

Science for shegs (28 decks)

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