Lecture 17

Question 1

What is energy?

Answer 1

Capacity to do work

Question 2

What does ATP (adenosine triphosphate) do?

Answer 2

medium of energy exchange i.e. the energy currency of the cell

Question 3

What generates the most ATP?

Answer 3

Glucose and fatty acid metabolism

Question 4

What generates a relatively little amount of ATP?

Answer 4

Amino acids

Question 5

Where else is ATP generated?

Answer 5

some ATP generated by glycolysis and krebs cycle

Question 6

What reducing equivalents are produced by glycolysis, beta oxidation and krebs cycle?

Answer 6

NADH and FADH2

Question 7

What do NADH and FADH2 do?

Answer 7

supply protons (H+) & electrons (e-) to the electron transport chain where most of the ATP is made

Question 8

How can ATP be produced anaerobically (without 02)

Answer 8

• ATP can also be generated without O2
• Phosphocreatine (PCr) degradation
• 9-10 seconds worth
  ATP → ADP + Pi
  PCr + ADP + H+ → ATP + Cr
• ATP is rebuilt by adding a phosphate to ADP
• Glycolysis will also continue to produce ATP (end product is lactate in anaerobic conditions e.g. sprints)

Question 9

How does fat store energy?

Answer 9

Most energy stored as triglycerides in adipocytes

Question 10

How do carbohydrates store energy?

Answer 10

• Stored as glycogen in liver (~150g) – most concentrated since liver is only ~2kg
• Stored as glycogen in muscle (~350g) – ~40% body mass is muscle
• Only ~30g of glucose found in blood i.e. not much

Question 11

How do proteins store energy?

Answer 11

• Large potential energy source
• Protected but will be used in starvation or caloric restriction

Question 12

What are the pro’s of using carbohydrates as fuel?

Answer 12

• Aerobically, can generate ATP slightly faster than fat
• Can generate ATP anaerobically (3x faster than aerobic)

Question 13

What are the cons of using carbohydrates as fuel?

Answer 13

• Holds a lot of water i.e. heavier & less energy-dense than fat

Question 14

What are the pro’s of using fat as fuel?

Answer 14

• Doesn’t hold water i.e. more than 2x as energy-dense as carbohydrate
• Most abundant energy reserve

Question 15

What are the cons of using fat as fuel?

Answer 15

• Can’t provide energy anaerobically i.e. must have oxygen

Question 16

What happens during the absorptive state regarding energy homeostasis?

Answer 16

• First 3-4 hours after a meal
• Energy (macronutrients) are stored i.e. anabolism
• Excess macronutrients stored i.e. anabolic state
• Glycogen (carbohydrate) stored in liver & muscle
• Triglycerides (fat) stored in adipose tissue, liver, & muscle
• Excess calories in the form of glucose or amino acids converted to fat

Question 17

What happens during the postabsorptive state (fasting) regarding energy homeostasis?

Answer 17

• Stored macronutrients are mobilized for energy i.e. catabolic state
• Glucose is spared for nervous system

Question 18

What is normal fasting blood glucose range?

Answer 18

~4 – 5.5 mmol/L (very narrow
range

Question 19

What is fasting hyperglycemia glucose level?

Answer 19

glucose > 7 mmol/L

Question 20

What is fasting hypoglycemia glucose level?

Answer 20

glucose ~< 3.5 mmol/L

Question 21

Why is glucose maintained so tightly?

Answer 21

• Many cells require glucose
• Maintain osmotic balance (i.e. optimal concentrations of electrolytes & non-electrolytes)
• Hyperglycemia can cause glycosylation of amino acids in kidneys, peripheral nerves, & lens of the eye, causing damage

Question 22

When is insulin released?

Answer 22

When blood glucose is elevated
ex. after a meal

Question 23

When is glucagon released?

Answer 23

When blood glucose is low
ex. fasting

Question 24

What does prolonged, lower intensity excercise rely on?

Answer 24

Relies more on plasma-derived substances, particuarly free fatty acids but also some blood glucose

Question 25

What is needed when excercise intensity increases?

Answer 25

As excercise intensity increases, increased need to mobilize energy stores (substrates) within the muscle itself i.e. glycogen and triglycerides

Question 26

What is the predominant fuel used during high intensity excercise?

Answer 26

Muscle glycogen

Question 27

Prolonged, low intensity e.g. walking, slow
jog. What is the major contributing fuel?

Answer 27

Mainly blood glucose & fatty acids; some
triglycerides & glycogen

Question 28

Moderate to high intensity e.g. cycling,
jogging/running at 60 – 90% VO2 max. What is the major contributing fuel?

Answer 28

Mainly muscle glycogen & triglycerides;
blood glucose & fatty acids

Question 29

Very high intensity e.g. sprinting,
weightlifting i.e. large anaerobic component. What is the major contributing fuel?

Answer 29

Muscle glycogen, phosphocreatine (PCr)