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Year 2 - Endocrinology > Lipid Metbabolism > Flashcards

Lipid Metbabolism Flashcards

1
Q

Name three dietary lipids

A

Triglycerides
Cholesterol
Phospholipids

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2
Q

What is the differences between saturated, unsaturated and polyunsaturated fats?

A

Unsaturated/polyunsaturated fats have one or more double bonds between their Carbons in their fatty acid tail

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3
Q

Names the components and the bonds involved in triglycerides.

A

One glycerol molecule
Three fatty acids
Glycerol connected to the three fatty acids with three ester bonds

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4
Q

Where does lipid digestion occur?

A

Small intestine

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5
Q

Which enzymes break down triglycerides in the intestine, and what does it break them down into?

A

Pancreatic lipase and coplipase

Triglycerides are broken down into 2 fatty acids and one monoglyceride

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6
Q

What is the function of bile salts?

A

Emulsify fats to smaller fat droplets so that lipase can act easier on them

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7
Q

What happens to emulsified fat once it’s been acted upon by bile salts?

A

They are broken down by lipase, colipase and more bile salts to become micelles
- micelles are water soluble collections of phospholipids, cholesterol, fatty acids and monoglycerides

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8
Q

What happens to fat once it’s been absorbed?

A

Triglycerides reform in intestinal cells and are packaged with cholesterol, lipoproteins and other lipids to form chylomicrons
Chylomicrons are released into the lymphatic system by exocytosis

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9
Q

How does lipid from the chylomicrons enter adipose tissue?

A

It’s acted upon lipoprotein lipase when it passes adipose tissue
LPL breaks fatty acids off the chylomicrons, which enters the tissue
The remaining chylomicrons carriers on round the system, towards the liver

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10
Q

Name four possible uses of fatty acids when it enters adipose tissues?

A

Storage (TAG)
Structural - phospholipids
Oxidation to ATP (beta-oxidation)
Ketone body synthesis

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11
Q

Briefly describe the endogenous lipid transport, starting in the liver

A

The liver releases VLDL which travel in the blood, giving off lipids as it goes, until it becomes IDL
The IDL then carriers on, either reentering the liver (LDLR) or becoming a LDL
LDLs then attach to a LDLR on either the liver or an extra hepatic cell

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12
Q

What are the ways in which lipids can travel in the blood?

A 
Plasma TAG (lipoproteins)
Free fatty acids - bound to albumin
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13
Q

What is beta-oxidation?

A

Generation of energy from fatty acids

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14
Q

What is the first step of beta-oxidation?

A

Fatty acids are first added to acetyl-CoA to form fatty acetylchol-CoA

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15
Q

Where does beta-oxidation occur, and how do the fatty acids get there?

A

Within the mitochondria
Fatty acids must cross the inner mitochondrial membrane with a carrier molecule (carnitine)
- derived from lysine and methionine
- high in muscles

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16
Q

Describe beta-oxidation, once fatty acetyl-CoA is in the mitochondria.

A

Fatty acyl-CoA are degraded by oxidation at the beta-carbon

This occurs in rounds, constantly shortening the acyl chain 2 carbons at a time

17
Q

What are the end products of beta-oxidation per turn?

A

1 FADH2
NADH
Acetyl-CoA

18
Q

What happens to the acetyl-CoA produced by beta-oxidation?

A

It can be entered into the Krebs cycle to produce 3 NADH and an FADH2 (11 ATP)

19
Q

What are the two most important enzymes in triglyceride synthesis?

A 
Lipoprotein Lipase (LPL) - hydrolysed TAG in chylomicrons/VLDL
Diacylglycerol acyl transferase (DGAT) - This re-esterifies to TAG
20
Q

Where does glycerol used in TAG esterification come from?

A

Glycolysis (DHAP - becomes glycealdehyde-3-phosphate, which forms TAG)

21
Q

What is the hormones responsible for TAG breakdown in adipose tissues, and how is it activated?

A

Hormone sensitive lipase

  • activated by cAMP-dependent phosphorylation in response to adrenaline (in fasted state)
  • inhibited by insulin
22
Q

What are the regulatory enzymes for fatty acid synthesis?

A

Acetyl-CoA carboxylase - forms malonyl CoA

Fatty acid synthase

23
Q

Describe malonyl CoA formation from acetyl CoA.

A

Acetyl CoA uses one ATP and CO2 to form malonyl CoA

Acetyl CoA carboxylase is used as a catalyst

24
Q

What is the function of malonyl CoA?

A

It is used to inhibit fatty acid beta-oxidation

- inhibits the carnitine transporter

25
Q

What is required for fatty acid synthesis?

A

Acetyl CoA coupled to malonyl CoA, NADPH, followed by 7 successive steps by fatty acid synthase

26
Q

How does beta-oxidation lead to formation of ketone bodies?

A

When beta oxidation is in action, there is substantial amount of acetyl CoA production
The extra acetyl-CoA left over from each fatty acid is put into the Krebs cycle
When oxaloaceteate isn’t present, it can’t enter the Krebs cycle and will be converted to ketones

27
Q

Give three examples of ketone bodies

A

Acetoacetate (which can be converted to the other two)
Beta-hydroxybutyrate
Acetone

28
Q

How are phospholipids formed?

A

Diglyceride is formed, and then combined with an alcohol

29
Q

Names some different phospholipids.

A

Phosphatidylserine
Phosphatidylglycerol
Phosphatidyllinositol
Phosphatidylethanolamine

30
Q

What are the functions of essential fatty acids?

A

Cell membrane functions
Growth and development
Brain and nerve function
Precursors for inflammatory response

31
Q

What are the possible ways essential fatty acids can reduce risk of CV disease?

A

Lowers LDL

Reduce plasma triglycerides?

32
Q

Which hormones regulate lipid metabolism, and how do they do it?

A 
Insulin
- stimulates fatty acids synthesis, and triglyceride synthesis
- inhibits lipolysis 
Noradrenaline 
- stimulates lipolysis
33
Q

What does insulin specifically stimulate inside the adipose tissues?

A

GLUT-4 mediated transport of glucose into the cell
Acetyl-CoA carboxylase activity
Fatty acid synthase expression
Increases LPL activity

34
Q

What does (nor)adrenaline specifically stimulate within the adipose tissue?

A

Stimulates cAMP synthesis and cAMP-dependent kinase (PKA) activation
PKA-mediated phosphorylation and activation of hormone sensitive lipase

35
Q

How does insulin inhibits lipolysis?

A

Insulin stimulates breakdown of cAMP - adrenalin can’t stimulate lipolysis

36
Q

What are the effects of elevated fatty acids?

A

Impaired insulin action in the liver, muscle and adipose tissues
- increases lipolysis - Gluconeogenesis
- decreased glucose uptake and glycogen synthesis
Impaired insulin secretion by the beta-cells
HYPERGLYCAEMIA

Year 2 - Endocrinology (14 decks)

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