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Science for Medicine > Lipids > Flashcards

Lipids Flashcards

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1
Q

Lipids are

A

heterogenous organic molecules that exist in a few different forms and have several purposes

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2
Q

Give 3 functions of lipids

A
  • a stored form of energy
  • a structural component of cell membranes
  • needed as enzyme cofactors
  • used in hormones
  • used for the synthesis of Vitamins A, D, E and K
  • used as signalling molecules
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3
Q

What are the major lipid classes?

A
  • fatty acids
  • triacylglycerides
  • phospholipids
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4
Q

What are fatty acids?

A

Hydrocarbon chains with a carboxylic group at one end

  • can be saturated or unsaturated
  • nomenclature defines which is which
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5
Q

What are the four types of fatty acids?

A

Essential fatty acids - must be obtained from plants

Good fats - high in polyunsaturated fatty acids

Bad fats - high in saturated fatty acids

Really bad fats - trans fatty acids

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6
Q

Give an example of an essential fatty acid

A
  • Linoleic acids

- A-Linoleic acids

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7
Q

Give an example of a good fat

A

Plant oils e.g. sunflower oil

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8
Q

Give an example of a bad fat

A

Stearic acid

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9
Q

Give an example of a really bad fat

A

Margarine

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10
Q

Essential fatty acids must be obtained via

A

our diet, since humans cannot introduce double bonds beyond carbon nine

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11
Q

What are triacylglycerides?

A

Esters of fatty acids and glycerol - water insoluble

  • coalesce into droplets in water
  • major component of adipose tissue
  • act as insulation and dietary fuel
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12
Q

What are phospholipids?

A

Glycerol bonded to two fatty acids and a phosphate group

  • amphipathic
  • form basic structure of the cell membrane
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13
Q

What is the main dietary lipid?

A

Triglycerols

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14
Q

Where does most digestion of triglycerols take place? Through the use of what?

A

Small intestine

pancreatic enzymes, emulsification by bile salts and peristalsis

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15
Q

Most triglycerols are digested by ___ into ___

A

pancreatic lipase

monoacylglycerol and two fatty acids

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16
Q

Cholesterol esters are broken down to

A

cholesterol and a fatty acid

17
Q

Phospholipids are hydrolysed to

A

a fatty acid and lysophospholipid

18
Q

Mixed micelles release their contents when they

A

approach the brush border

19
Q

The intestinal cells repackage ___
into ___
which are released ___

A

TAG, fatty acids and cholesterol esters

chylomicrons

into the blood via the lymphatic system

20
Q

When lipids reach the tissues, TAG is hydrolysed to ___

by ___

A

fatty acids and glycerol

lipoprotein lipase

21
Q

The resulting free fatty acids are used for ___

or ___

A

energy

re-esterified into TAG for storage

22
Q

Free fatty acids are transported in lipoproteins in a complex with

A

serum albumin

23
Q

Fats are also transported in

A

high and low density lipoproteins

24
Q

LDLs carry

A

cholesterol from the liver to other tissues

25
Q

HDLs

A

pick up cholesterol from tissues and bring it back to the liver for elimination

26
Q

The beta-oxidation pathway degrades ___

to form ___

A

fatty acids two carbons at a time

Acetyl CoA, NADH and FADH2

27
Q

The beta-oxidation pathway occurs in the

A

mitochondrial matrix

28
Q

What are the three stages of the beta-oxidation pathway?

A
  • activation
  • transport
  • degradation
29
Q

What happens in the activation stage of the beta-oxidation pathway?

A

The fatty acids are activated to form fatty acyl CoA in the cytoplasm

30
Q

What happens in the transport stage of the beta-oxidation pathway?

A
  • carnitine shuttle transfers long chain fatty acyl CoA from the cytoplasm to inside the mitochondrion
  • carnitine is a non-essential amino acid
  • carnitine fatty-acyl transferase is inhibited by malonyl CoA, used in fatty acid synthesis
  • therefore synthesis and degradation cannot occur simultaneously
31
Q

What happens in the degradation stage of the beta-oxidation pathway?

A
  • fatty acyl CoA is dehydrogenated to form FADH2 and another intermediate
  • this intermediate is then hydrated
  • the resulting intermediate is dehydrogenated again to form NADH
  • finally, thiolysis occurs to form Acetyl CoA that feeds into the CAC
32
Q

Each beta-oxidation cycle forms

A
  • 1 Acetyl CoA
  • 1 NADH
  • 1 FADH2
  • Carbon species 2 carbons shorter than the original
33
Q

No fatty acid is

A

gluconeogenic

34
Q

During fasting or starvation, glucose supplies run low and so excess Acetyl CoA from fat metabolism can be made into

A

ketone bodies

35
Q

What cells can use ketone bodies?

A
  • cardiac muscle cells
  • skeletal muscle cells
  • brain cells during times of starvation
36
Q

Ketogenesis occurs in the

A

liver

37
Q

What is also produced in ketogenesis?

A

Acetone (but is expelled during expiration)

38
Q

What are the main ketone bodies?

A

Acetoacetate

3-Hydroxybutarate

Science for Medicine (24 decks)

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