Energy Prodcution - Lipids

Question 1

What are the three classes of lipids?

Answer 1

• Fatty acids derivatives - fatty acids + TAGS
• **Hyroxy-methyl-glutaric acid derivates* - ketone bodies
• Vitamins - A,D,E,K

Question 2

What are the lipid fuel molecules?

Answer 2

Fatty acids
TAGs
Ketone bodies

Question 3

Are carbs or lipids more reduced?
What does this mean

Answer 3

Lipids are more reduced than carbs
Release more energy when oxidised
Complete oxidation requires O2

Question 4

Compare and contrast the energy storage of TAGs in a healthy and obese man?

Answer 4

Healthy:
15 kg > 600,000kJ energy content

Obese:
80kg > 3,000,000kJ energy content

Question 5

Describe the storage of TAGs

Answer 5

Stored in anhydrous form
Stored in adipose tissue
Under hormonal control

Question 6

When are TAGs broken down?

Answer 6

Low blood glucose;
- Prolonged exercise
- Starvation
- Pregnancy

Question 7

Outline the metabolism of TAGs and the tissues involved

Answer 7

GI tract:
TAGs <> glycerol + fatty acids

Blood:
Glycerol > glycerol
Fatty acids > chylomicrons (packaged into lipoprotein)

Tissues
Glycerol > liver
Chylomicrons > adipose > released as fatty acids into blood > to muscles

Question 8

How are fatty acids carried to tissues?

Answer 8

Bound to albumin
Albumin-fatty acid complex

Question 9

Describe what happens in TAG metabolism after absorption in the GI tract

Answer 9

1- convert back to triglycerides in the GI trac
2- packed into lipoprotein particle > Chylomicron
3- released into blood via lymphatics
4- carried to adipose
5- store as triglyceride

Question 10

What is fat mobilisation controlled by?

Answer 10

Hormone sensitive lipase

Increases with glucagon + adrenaline
Decreases with insulin

Question 11

Where are fatty acids not found?

Answer 11

Brain - cant cross blood brain barrier
Cells without mitochondria - *e.g. RBCs**

Question 12

Outline the steps in triglyceride/fatty acid cycle in adipose

Answer 12

1- glucose transport
2- glycolysis
3- esterification
4- lysis
5- re-esterification

Question 13

Describe beta oxidation

Answer 13

Fatty acid catabolism
Removal of 2C units from FA to generate acetyl coA

Question 14

Describe fatty acid activation

Answer 14

Fatty acid + coA > fatty acyl co A
fatty acyl coA synthase
Transported across mitochondria membrane via carnitine shuttle

Question 15

Describe the carnitine shuttle

Answer 15

Transports fatty acyl CoA across mitochondrial membrane
CAT1+2 - carnitine acyl transferases

Question 16

What inhibits the carnitine shuttle?

Answer 16

Malonyl CoA

Question 17

Identify three features of beta oxidation

Answer 17

H+ and e- transferred to NAD+ and FAD
Stops in the absence of O2
No ATP synthesis

Question 18

Outline glycerol metabolism

Answer 18

In the liver
TAG synthesis
^
Glycerol > glycerol phosphate > DHAP > glycolysis
glycerol kinase

Question 19

Function of acetyl CoA

Answer 19

Most important intermediate in catabolic and anabolic pathways

Question 20

What are the three ketone bodies produced?

Answer 20

Acetone/acetate
Acetoacetate
B-hydroxybutyrate

Question 21

What is the normal plasma conc of ketone bodies?

Answer 21

<1mM

Question 22

Ketone bodies conc. in starvation

Answer 22

2-10mM - physiological ketosis

Question 23

Ketone bods conc. in untreated type1 diabetes

Answer 23

> 10nM - pathological ketosis

Question 24

Outline ketone bodies synthesis

Answer 24

By liver mitochondria

                   Mevalonate > cholesterol 
                          ^ *HMG-CoA reductase*  
                          |

Acteyl coA > HMG-CoA > acetoacetate >acetone or B hydroxybutyrate
synthase lyase

Question 25

How is acetone formed?

Answer 25

The spontaneous decarboxylation of acetoacetate

Question 26

Explain how ketone bodies synthesis is regulated by insulin:glucagon ratio in fed and starved states

Answer 26

Fed state:
High insulin:glucagon ratio
Inhibits lyase
Activates HMG CoA reductase
Increased cholesterol synthesis
Decreased KB synthesis

Starved state
Low insulin:glucagon ratio
Activates lyase
Inhibits HMG CoA reductase
Decreases cholesterol synthesis
Increases KB synthesis

Question 27

How are ketone bodies removed from the body?

Answer 27

When above renal threshold
Excreted in urine > ketonuria

Question 28

How is acetone excrete from the body?

Answer 28

Via a lungs > smell of acetone on breath