L4 - Lipids Flashcards

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1
Q

Describe the properties of lipids. (x7)

A
  • Large biomolecules
  • Formed from C, H, O and sometimes, P
  • Not polymers
  • Largely non-polar (as there are mostly C-H and C-C bonds)
  • Largely insoluble in water
  • Soluble in non-polar solvents
  • Hydrophobic interactions cause lipids to group together in water
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2
Q

What are triglycerides made up of?

A
  • 1 Glycerol

- 3 Fatty Acids

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3
Q

What bond is formed between fatty acids and glycerol?

A

Ester bond

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4
Q

Describe the digestion of triglycerides.

A
  • Broken down by hydrolysis
  • Requires intestinal enzyme, triglyceride lipase + H2O
    = FFAs more easily absorbed in the gut and transported
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5
Q

What are the 2 classes of fatty acids?

A
  • Saturated

- Unsaturated

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6
Q

What are saturated fatty acids?

A

Fatty acids that contain only single C-C bonds.

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7
Q

What are unsaturated fatty acids?

A

Fatty acids that contain one or more double bonds (C=C).

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8
Q

What are Free Fatty Acids (FFAs)

A

Fatty acids that are not part of a triglyceride.

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9
Q

Name the 2 fatty acids that are essential and cannot be synthesised in the body.

A
  • Omega 3

- Omega 6

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10
Q

How are omega FFAs named?

A

By the location of the first double bond, counted from the methyl end (= omega end).

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11
Q

What types of triglycerides do saturated and unsaturated fatty acids form, and what state are they in at room temperature?

A
  • SFAs form compact, closely packed triglycerides = solid at RTP
  • UFAs form loosely packed triglycerides (due to cis double bonds) = liquid at RTP
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12
Q

Describe the properties of steroids.

A
  • Steroids are lipids
  • Basic structure is 4 fused carbon rings with various side groups attached
  • Lanosterol is the building block for all steroids
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13
Q

What is the building block for all steroids?

A

Lanosterol

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14
Q

How is lanosterol formed?

A

By the cyclisation of squalene.

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15
Q

Name 4 examples of steroids.

A
  • Cholesterol
  • Sex Hormones
  • Corticosteroids
  • Vitamin D (Cholecalciferol) = a secosteroid
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16
Q

What are 2 functions of corticosteroids?

A
  • Anti-Inflammation

- Fluid balance

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17
Q

Where are corticosteroids produced?

A

In the adrenal cortex

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18
Q

Name 2 examples of corticosteroids, and classify what type of steroids they are.

A
  • Aldosterone (mineralocorticoid)

- Cortisol (glucocorticoid)

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19
Q

Name 3 sex hormones that classify as steroids.

A
  • Oestrogen
  • Progesterone
  • Testosterone
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20
Q

What are phospholipids?

A

Lipids with a phosphate group (PO42-) covalently bonded to the glycerol backbone, instead of a fatty acid.

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21
Q

Describe the properties of the phosphate group in a phospholipid.

A
  • Acts as a ‘head’
  • Polar
  • Soluble in water (hydrophilic)
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22
Q

Describe the properties of the fatty acid groups in a phospholipid.

A
  • Acts as a ‘tail’
  • Non-Polar
  • Insoluble in water (hydrophobic)
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23
Q

Name the 5 different substances that the group ‘X’ on phosphate can be, and describe what product is formed as a result.

A
  • Hydrogen = Phosphatidic Acid
  • Ethanolamine = Phosphatidylethanolamine
  • Serine = Phosphatidylserine
  • Choline = Phosphatidylcholine
  • Inositol = Phosphatidylinositol
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24
Q

How do phospholipids organise themselves in water?

A
  • Hydrophilic heads point outwards

- Hydrophobic tails point inwards

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25
Q

What are micelles?

A

Spherical arrangement of lipid molecules

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26
Q

What is a bilayer?

A

Composed of 2 layers of lipids organised as a sheet

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27
Q

What is the purpose of the cell membrane?

A

Complex structure that physically separates the interior of the cell from the outside environment to confer protection from the surroundings.

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28
Q

What is the role of the cell membrane?

A

Role in anchoring to extracellular structures and other cells required for tissue formation.

29
Q

What is a glycolipid?

A

A lipid covalently attached to an oligosaccharide.

30
Q

What parts of the cell do glycolipids form?

A
  • Cell membrane

- Glycocalyx

31
Q

What is a lipoprotein?

A

Soluble complexes that transport lipids and are synthesised in the liver.

32
Q

What components are part of the spherical particles with central hydrophobic cores?

A
  • Triglycerides
  • Esterified cholesterol (cholesteryl ester)
  • Small amounts of other lipids and fat soluble vitamins
33
Q

What components are part of the external hydrophilic layer?

A
  • Phospholipids
  • Cholesterol (OH functional group outermost)
  • Apoproteins which stabilise the structure and regulate enzymatic activity at the lipoprotein interface
34
Q

Name the lipoproteins in ascending order of size.

A

HDL < LDL < IDL < VLDL < Chylomicron

35
Q

Name the lipoproteins in ascending order of density.

A

Chylomicron < VLDL < IDL < LDL < HDL

36
Q

Name the lipoproteins in ascending order of triglyceride vs. cholesterol ester content.

A

HDL < LDL < IDL < VLDL < Chylomicron

37
Q

Name the lipoproteins in ascending order of lipids vs. proteins on the surface.

A

HDL < LDL < IDL < VLDL < Chylomicron

38
Q

What is the main apoprotein in a chylomicron?

A

Apoprotein B-48

39
Q

What is the main apoprotein in a VLDL?

A

Apoprotein E

40
Q

What is the main apoprotein in a IDL?

A

Apoprotein E

41
Q

What is the main apoprotein in a LDL?

A

Apoprotein B-100

42
Q

What is the main apoprotein in a HDL?

A

Apoprotein A-1

43
Q

How are Very Low Density Lipoproteins (VLDL) made and what is their role?

A
  • Produced in the liver from synthesised triglycerides and cholesterol esters
  • Carry fat to target tissues
44
Q

How are Low Density Lipoproteins (LDL) and Intermediate Density Lipoproteins (IDL) formed from Very Low Density Lipoproteins (VLDL)?

A

Triglycerides are gradually removed from circulating VLDL which become IDL and then LDL.

45
Q

What is the role of High Density Lipoproteins (HDL)?

A

Carries cholesterol to the liver (good cholesterol reducing atherosclerosis.

46
Q

What is atherosclerosis?

A

Serious condition where arteries become clogged with fatty material (sites of fatty deposition called plaques)

47
Q

Describe the properties of triglycerides. (x3)

A
  • TGs and FFAs have energy-rich C-H bonds available for chemical reactions within cells
  • TGs are largely non-polar and relatively compact
  • TGs are stored as lipid droplets in the cytoplasm of adipocyte cells in adipocyte tissue
48
Q

What are the uses of White Adipose Tissue? (x4)

A
  • Provides insulation
  • Protects internal organs from temperature changes
  • Shock absorber
  • Reduces skin heat loss
49
Q

Where 2 types of fat pads are adipose tissues located in?

A
  • Visceral fat pads

- Subcutnaeous fat pads

50
Q

Where is adipose located? (x8)

A
  • Epicardial
  • Mesenteric
  • Omental
  • Retroperitoneal
  • Gonadal
  • Subcutnaeous abdominal
  • Gluteal
  • Femoral
51
Q

How does excess adipose cause disease?

A
  • Involved in causing atherosclerosis, thrombosis, stenosis and aneurysms
  • Exerts undue pressure on organs
  • Major endocrine organ produces pro-inflammatory hormones such as leptin and cytokines
  • These lead to cardiovascular disease
52
Q

What is thrombosis?

A

The clotting of circulating blood.

53
Q

What is stenosis?

A

Abnormal narrowing of a body passage (e.g. blood vessel).

54
Q

What is an aneurysm?

A

Blood-filled bulge in a blood vessel wall.

55
Q

Describe the role of lipids as insulation in neurones.

A
  • Phospholipids form the myelin insulation around nerve fibres
  • Myelin increases speed of nervous impulses
  • Schwann cells produce myelin peripherally
  • Oligodendrocytes produce myelin centrally
56
Q

Describe the properties of some vitamins. (x2)

A
  • Fat soluble

- Lipid / steroid derived

57
Q

What else is Vitamin A referred to as? (x3)

A
  • Retinol
  • Retinoic Acid
  • Carotenoids
58
Q

What are the uses of Vitamin A? (x3)

A
  • Healthy teeth
  • Healthy skin
  • Sight
59
Q

What else is Vitamin D referred to as?

A

Cholecalciferol

60
Q

What is Vitamin D used for?

A

Helps body absorb Ca2+ for healthy bones

61
Q

What else is Vitamin E referred to as?

A

Tocopherol (antioxidant found in oils)

62
Q

What is Vitamin E used for? (x2)

A
  • Antioxidant

- Protects cell from damage

63
Q

What else is Vitamin K referred to as? (x2)

A
  • Phylloquinone

- Menaquinone

64
Q

What is Vitamin K used for?

A

Important for coagulation of blood

65
Q

What are hormones?

A

Chemical messengers

66
Q

Name 2 types of hormones and describe what they are derived from.

A
  • Steroidal hormones derived from cholesterol

- Eicosanoids derived from omega-3 and omega-6 fatty acids

67
Q

Name 3 eicosanoids and describe what they are responsible for.

A
  • Prostaglandins (inflammation, vascular tone)
  • Leukotrienes (asthma and allergy)
  • Thromboxanes (vascular tone, platelet aggression)
68
Q

Explain the role of lipids in preventing moisture loss and give two examples of this in the body.

A
  • Lipid layers can inhibit evaporation of water
  • Skin moisture loss reduced by lipid layers
  • Lipid layer on tear film reduces moisture loss from cornea