Fat

Question 1

How many calories does 1 kg of fat contain?

Answer 1

roughly 7,700 kCal

Question 2

Can fat be used as an energy source?

Answer 2

Yes it can form Acetyl CoA and be used in the krebs cycle

Question 3

What limits fat oxidation?

Answer 3

Lipolysis
FA > blood
Transport by blood
Blood > muscle
Cytosol > mitochondria
beta oxidation

Question 4

What is lipolysis?

Answer 4

Activation of hormone sensitive lipase (HSL)
glycerol release (exercise initiates mobilsation of fatty acids)

Question 5

What is re esterification?

Answer 5

at rest 70% of free fatty acids released from lipolysis are re esterfied. This takes a long time so it is happening all the time

Question 6

FFA > blood

Answer 6

dependent on blood flow to adipose tissue and the amount of albumin in that blood.
each albumin has 3 binding sites for FFAs
Unlikely to be a limiting factor

Question 7

FA> muscle cell

Answer 7

Two transports
FABP (fatty acid binding protein)
FAT/CD36 (Fatty acid transporter)

FABPc moves FFa to mitochondria

Question 8

What is the main limiting step for fat?

Answer 8

When CHO is being oxidated because we need glucose to break down fat which is why a low carb diet inhibits fat metabolism

Question 9

Lipolysis during exercise

Answer 9

Lipolysis starts to decrease during exercise.
It increases initially as blood flow to the area increases. But not really because it requires ATP and during exercise the ATP is being used

Question 10

Why can CHo and Fat have the same limiting process?

Answer 10

At rest it all works out as nothing is really driving glucose metabolism and what we eat is being stored but during exercise CHO is more oxygen efficient so it makes sense that the CHO will be used as it does not require so much ATP or oxygen to break down as fat does

Question 11

Do fasting or high fat diets work?

Answer 11

No because glycogen gets depleted and because you need CHO for fat to be burnt

Question 12

What is intramuscular fat?

Answer 12

IMTG. Lipid droplets within the muscle. Important energy source during exercise
in well trained individuals IMTG is near the mitochondria. Thought to be oxidised by the muscle rather than being released into the blood etc

Question 13

What happens during endurance training?

Answer 13

Increase in mitochondria size, number and efficiency which results in an increase in mitochondrial enzymes and enhanced enzymatic activity.
Number of capillaries around muscle fibers increases.
Increase in absolute quantity of lipid oxidized at a given exercise level (still small relative to CHO)
Increased release of fatty acid from adipose tissue
Increased amount of IMTG