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BIOC192 2024 > Lecture 25 > Flashcards

Lecture 25 Flashcards

1
Q

What is the chemical nature of lipids?

A

Hydrophobic or amphiphilic organic molecules

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2
Q

What are the three forms of lipid in the diet?

A

Phospholipid, sterols, triacylglycerol

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3
Q

What is an example of a sterol?

A

Cholesterol

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4
Q

What is the role of cholesterol in the body?

A

A range including membranes, signalling (hormones) and forming bile salts

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5
Q

What is the chemical structure of cholesterol?

A

A hydrophobic ring structure

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6
Q

What is an example of a triacylglycerol (TAGs)?

A

Fatty acids

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7
Q

What is a fatty acid?

A

Carbon chain attached to a carboxylic acid

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8
Q

What is a free fatty acid (FFA)?

A

A fatty acid not bound to any other molecule

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9
Q

What is the chemical nature of the carbon chain in fatty acids?

A

Hydrophobic

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10
Q

What is the chemical nature of the carboxylic acid in fatty acids?

A

Hydrophilic

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11
Q

What is the structure of a triagylglycerol?

A

1x Glycerol (3C) with 3x fatty acids (acyl groups) attached

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12
Q

What component of the TAG is polar?

A

Glycerol

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13
Q

What component of the TAG is non-polar?

A

fatty acid (acyl group)

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14
Q

What type of enzyme breaks down TAGs?

A

Lipase

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15
Q

What does lipase do to TAGs?

A

Hydrolyses it to release the free fatty acids (FFAs)

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16
Q

What are bile acids?

A

Salts synthesised from cholesterol in the liver

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17
Q

How are bile acids synthesised?

A

By adding hydroxyl and/or carboxyl groups to create a hydrophilic face

18
Q

What do bile acids form?

A

Micelles, multiple bile acids come together to form a hydrophobic core of TAGs inside to be absorbed into epithelial cells

19
Q

What are exogenous fatty acids?

A

Fatty acids ingested from the diet

20
Q

What is the path of exogenous fatty acid transport to the blood stream?

A

Consumed in diet fats exist as TAGs, pancreatic lipase breaks these down into MAG and 2FFAs which are then rearranged to form a micelle (with bile salts on the outside) for transportation to SI lining for absorption. Once absorbed MAG and 2FFAs are rearranged back into a TAG which are packaged into chylomicrons along with apoproteins to enter capillaries.

21
Q

What is a chylomicron?

A

A type of large lipoprotein involved in TAG transport with low protein:lipid (~1:50)

22
Q

What is a lipoprotein?

A

A type of ‘delivery system’ for lipid transportation, to help solubilise them

23
Q

What are the components of a lipoprotein?

A

Phospholipids, unesterified cholesterol, esterified cholesterol, TAGs and apoproteins

24
Q

What is unesterified and esterified cholesterol

A

Cholesterol without and with FFAs attached (respectively)

25
Q

What is an apoprotein?

A

The protein component of the lipoprotein that can have several roles including; structural, ligand for receptors and enzyme co-factors

26
Q

What are the classes of lipoprotein?

A

Chylomicron, VLDL, LDL, HDL

27
Q

What is a VLDL?

A

Very low-density lipoprotein involved in TAG transport with medium lipid:protein (~1:9)

28
Q

What is a LDL?

A

Low-density lipoprotein involved in cholesterol transport

29
Q

What is a HDL?

A

High-density lipoprotein involved in cholesterol regulation

30
Q

What happens to the chylomicron once it enters the blood stream?

A

Lipoprotein lipase hydrolyses the TAG into monoacylglycerol and fatty acids to enter the tissue

31
Q

What is lipoprotein lipase activated by?

A

ApoCll

32
Q

What remains in the blood after TAG hydrolysis in the chylomicron?

A

A chylomicron remnant

33
Q

What do defects by mutation is ApoCll or lipoprotein lipase cause?

A

Elevated levels on chylomicrons in the blood and plasma triacylglycerol

34
Q

Where is the LPL found?

A

On the endothelial surface of capillaries

35
Q

What type of muscle cell prefers to use fat at fuel?

A

Red muscle cells

36
Q

Why are fats the primary energy stored in mammals?

A

Because less space is required to store the same amount of fuel as fats are more reduced than carbohydrates

37
Q

How is excess glucose stored as fat in the body?

A

Glucose → Pyruvate (via glycolysis)
Pyruvate → Acetyl-CoA (in mitochondria)
Acetyl-CoA → Fatty acids (if energy needs are met)
Fatty acids + glycerol → Triacylglycerol (TAG)
TAG stored in fat cells for future energy use

38
Q

What happens to the chylomicron remnants in the liver?

A

Liver recycles the remnants to make VLDL to be released into the blood and bile salts + cholesterol to break down exogenous lipids

39
Q

What happens to VLDL in the blood?

A

LPL breaks down further to send FFAs into the tissue and releases the remaining as a VLDL remnant

40
Q

What happens to the VLDL remnant?

A

50% is absorbed back into the liver to be recycled and 50% is converted to an LDL to be used by peripheral tissues and also recycled by the liver

BIOC192 2024 (36 decks)

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