S18) Energy Production III — Lipids, β-Oxidation & Ketone Bodies Flashcards

1
Q

Identify and describe the three different classes of lipids

A
  • Fatty acid derivatives – fatty acids and triacylglycerol
  • Hydroxy-methyl-glutaric acid derivatives – ketone bodies, cholesterol
  • Vitamins – ADEK
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Explain how energy storage varies between a healthy and obese man

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the structure of triacyglycerol

A

Triacylglycerols are hydrophobic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe the storage of TAG

A
  • Stored in an anhydrous form
  • Stored in adipose tissue
  • Storage / mobilisation under hormonal control
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Identify three circumstances where triacylglycerols are used

A
  • Prolonged exercise
  • Starvation
  • Pregnancy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Identify the tissues involved in triglyceride metabolism and illustrate their role

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where does stage 1 of TAG metabolism occur?

A

Gastrointestinal tract (extracellular)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What occurs in stage 1 of TAG metabolism?

A
  • Extracellular hydrolysis of dietary lipids (TAG) in small intestine by pancreatic lipases
  • Fatty acids and glycerol are formed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

In 5 steps, describe what happens in TAG metabolism after absorption int the GI tract

A

⇒ Converted back to triglycerides in GI tract

⇒ Packaged into lipoprotein particle (chylomicrons)

⇒ Released into circulation via lymphatics

⇒ Carried to adipose tissue

⇒ Stored as triglyceride

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe fat mobilisation

A
  • Fatty acids are released when needed
  • They are carried to tissues as albumin-fatty acid complex
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Fat mobilisation is under hormonal control.

Describe this

A

Hormone-sensitive lipase:

  • Increases with glucagon/adrenaline
  • Decreases with insulin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Which consumer tissues are fatty acids not mobilised to?

A
  • Cells without mitochondria e.g. RBC
  • Brain; fatty acids do not easily pass blood-brain barrier
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

In 5 steps, describe and illustrate the triglyceride/fatty acid cycle in adipose tissue

A

1 – Glucose transport

2 – Glycolysis

3 – Esterification

4 – Lysis

5 – Re-esterification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What causes the release of fatty acids as alternative fuel?

A

Low extracellular [glucose]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe the molecular structure of fatty acids

A

Amphipathic: contain hydrophilic & hydrophobic groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the two types of fatty acids?

A
  • Saturated: no double bonds between neighbouring C-atoms
  • Unsaturated: 1/more double bonds between neighbouring C-atoms
17
Q

Where does stage 2 of fatty acid metabolism occur?

A

Mitochondrion

18
Q

In three steps, describe what occurs in fatty acid catabolism

A

⇒ FA is activated outside the mitochondrion

⇒ FA is transported across the inner mitochondrial membrane using a carnitine shuttle

⇒ FA cycles through sequence of oxidative reactions, with C2 removed each cycle

19
Q

Fatty acid activation occurs outside the mitochondria, in the cytoplasm.

Describe how this occurs

A
  • Activated by linking to coenzyme A by the action of fatty acyl CoA synthase
  • Activated fatty acids (fatty acyl~CoA) do not readily cross the inner mitochondrial membrane (carnitine shuttle)
20
Q

Carnitine shuttle transports fatty acyl~CoA across the mitochondrial membrane.

Describe how and why this process is regulated

A
  • Regulated, so controls the rate of FA oxidation
  • Inhibited by malonyl~CoA (biosynthetic intermediate)
21
Q

Fatty acid catabolism is also called β oxidation.

Identify three key features of this process

A
  • H+ and e- transferred to NAD+ and FAD
  • Stops in absence of O2
  • No ATP synthesis
22
Q

Briefly describe glycerol metabolism

A

Glycerol can be transported in the blood to the liver, where it is metabolised

23
Q

Acetyl-CoA the main convergence point for catabolic pathways.

What is its function?

A

Acetyl~CoA is the most important intermediate in both catabolic and anabolic pathways

24
Q

Three ketone bodies produced in the body.

What are they?

A
  • Acetoacetate: CH3COCH2COO- (liver)
  • Acetone: CH3COCH3
  • β-hydroxybutyrate: CH3CHOHCH2COO- (liver)
25
Describe the physiological and pathological variation in the plasma concentration of ketone bodies
- **Normal** \< 1 mM - **Starvation** = 2-10 mM (physiological ketosis) - **Untreated Type 1 diabetes** \> 10 mM (pathological ketosis)
26
Briefly outline the pathways in which ketone bodies are synthesised by liver mitochondria
27
How is acetone formed?
**Acetone** is formed from the spontaneous (non-enzymatic) decarboxylation of acetoacetate
28
Explain how ketone body production is controlled in the liver
29
Outline the pathways involved in ketone metabolism
30
Explain how ketone bodies synthesis is regulated by the insulin:glucagon ratio in fed and starvation states
- **Fed state:** high insulin:glucagon inhibits lyase and activates reductase → cholesterol synthesis - **Starvation state:** low insulin:glucagon inhibits reductase and activates lyase → ketone body synthesis
31
Illustrate how ketone bodies spare glucose in early starvation/diabetes
32
Illustrate how ketone bodies spare glucose in late starvation/diabetes
33
How are excess ketone bodies excreted from the body?
Above renal threshold, excreted in urine (**ketonuria**)
34
How is acetone excreted from the body?
Volatile acetone may be **excreted via the lungs** (characteristic smell of acetone on breath)