W6L2 Energy Balance

Question 1

What is the difference between metabolism and metabolic rate?

Answer 1

Metabolism = chemical reactions in body

Metabolic rate = heat liberated in body

Question 2

1 calorie is how many Joules?

Answer 2

4.2 Joules

Question 3

What is the energy content of 1 gram of carbohydrates? (in Joules)

Answer 3

17.2 kJ / gram

Question 4

What is the energy content of 1 gram of fat? (in Joules)

Answer 4

39 kJ / gram (the most efficient per weight)

Question 5

What is the energy content of 1 gram of protein? (in Joules)

Answer 5

17. 2 kJ / gram

Question 6

If total energy expenditure is greater than the energy content of food, what is this condition called?

Answer 6

“negative energy balance”

Characterized by weight loss

(the opposite is positive energy balance)

Question 7

What percentage of ATP production ends up as heat?

Answer 7

35%

he said in the lecture that we don’t have to know this figure, but maybe good to just see it once and mark it 5

Question 8

Direct calorimetry of total energy expenditure can be measured how?

Answer 8

While not performing any external work, total energy expenditure = heat production. So measure the heat produced by the stationary animal.

(slide has a rat in a box melting ice)

Question 9

Indirect calorimetry is measured how?

Answer 9

Because almost all energy released in our body is derived from reactions where oxygen participates, using 1 L oxygen -> 21 kJ energy released. So we just measure oxygen consumption in liters and multiple it by 21.

Question 10

What is BMR?

Answer 10

Basal Metabolic Rate = Minimal energy expenditure required to exist in the awake state, without any physical activity

Question 11

What are some prerequisites to measuring BMR?

Answer 11

Usually measured in morning, no physical activity, neutral temperature (20 C), fasting, no emotional stress / stimuli, no drugs

Question 12

What are normal BMR values for women and men?

What is the normal value per square meter of body surface area?

Answer 12

Women = 6000 kJ / day.

Men = 7000 kJ / day.

170 kJ / square meter / hour.

Question 13

What percentage of total energy expenditure is BMR usually?

Answer 13

50-70%

Question 14

What is DIT?

What percentage of TEE is it?

Answer 14

Diet-Induced Thermogenesis = heat production increase after a meal. Results from GI motility and secretions, hormones, and direct effect of food.

8-15% of TEE

Question 15

What percentage of TEE is spent on physical activity if a person is not very physically active?

Answer 15

15-30%, depending on lifestyle/ work of person (still referring to a low activity person / bro who doesn’t even lift)

Question 16

Why are brown adipocytes brown?

Answer 16

They’re brown because they have less fat than white adipocytes + have mitochondria

Question 17

What is the function of brown adipocytes, and how does it work?

Answer 17

They generate heat as a result of expressing uncoupling protein (UCP1), in the inner membrane of their mitochondria.

UCP breaks down the electrochemical gradient between intermembrane space and matrix, resulting in heat generation

Question 18

When do humans express brown adipocytes? What similar tissue is more common in humans?

Answer 18

Brown adipocytes are only in newborn humans.

Beige adipocytes (somewhere between white and brown adipocytes as far as fat content / mitochondria) are present in adult humans, and are stimulated by cold and catecholamines