Lipids 1 Flashcards

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1
Q

What is the structure of a fatty acid?

A

Polar (soluble) carboxylic acid ‘head’.

Non-polar (insoluble) hydrocarbon chain ‘tail’.

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2
Q

What are the two types of unsaturated fatty acids?

A

Monounsaturated (MUFAs) - only one double bond in chain.

Polyunsaturated (PUFAs) - multiple double bonds in chain.

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3
Q

What does the stability of a fatty acid depend on?

A

Length, degree of saturation.

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4
Q

What is the difference between cis and trans double bonds?

A

Cis = two hydrogen atoms on the same plane.

Trans = two hydrogen atoms in opposite planes.

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5
Q

Describe the storage lipid triacylglycerol (TAG).

A

Formed of three fatty acid chains joined in a glycerol backbone by ester bonds.

Neutral - do not carry charge, are not soluble in water.

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6
Q

How are membrane lipids categorised?

A

Initially into phospholipids and glycolipids.

Then by backbone group - glycerol or sphingosine.

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7
Q

Describe the structure of the phospholipid bilayer.

A

Hydrophilic heads on the outside, facing water. Hydrophobic tails on the inside.

This dual nature of the same molecule means they are classed as amphipathic.

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8
Q

What are the 2 main categories of hormone?

A

Eicosanoids and steroids.

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9
Q

What molecule are steroid hormones formed from?

A

Cholesterol.

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10
Q

What are the classifications of steroid hormones?

A

Sex hormones, glucocorticoids, mineralocorticoids, synthetic steroids.

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11
Q

How are fatty acids produced?

A

Acetyl CoA + CO2 + ATP + biotin -> Malonyl CoA (by acetyl-CoA carboxylase)

Fatty acid synthase donates 2 carbons from malonyl CoA to acetyl CoA, with addition of 4 hydrogens and 2 electrons.

Continues until palmitate (16 carbons) is formed.

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12
Q

Where does the process of lengthening fatty acid chains take place?

A

Smooth endoplasmic reticulum / mitochondria.

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13
Q

Describe the process of desaturation of fatty acids.

A

Fatty acid desaturated by fatty acyl-CoA desaturase, NADPH molecule oxidised to produce 2H2O molecules.

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14
Q

Describe the formation of eicosanoids.

A

Phospholipids + phospholipase A2 -> Arachindonate

Arachidonate + cyclooxygenase -> prostaglandin G2 -> prostaglandin H2

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15
Q

What are the precursors of TAGs?

A

Fatty acyl-CoA, glycerol 3-phosphate.

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16
Q

What does insulin promote the conversion of into TAGs?

A

Dietary carbohydrates and proteins.

17
Q

How are TAGs formed?

A

Phosphatidic acid -> 1,2-diacylglycerol (by phosphatidic acid phosphatase).

Diacylglycerols -> triacylglycerols by transesterification with a third fatty acyl-CoA.

18
Q

How are glycerophospholipids formed?

A

Phosphatidic acid -> 1,2-diacylglycerol (by phosphatidic acid phosphatase).

Head group attached to phosphate group.

19
Q

Describe the steps of formation of sphingolipids.

A
  1. Synthesis of backbone molecule (glycerol / sphingosine).
  2. Attachment of fatty acid(s) to backbone through ester / amide linkage.
  3. Addition of hydrophilic head group to backbone through phosphodiester linkage.
  4. Alteration / exchange of head group to yield final phospholipid product.
20
Q

How is cholesterol formed?

A

3 acetate molecules -> mevalonate

-> 2 activated isoprenes

6 activated isoprenes -> squalene

  • > four-ring steroid nucleus
  • > lanosterol -> cholesterol