Lecture 17 Flashcards
What is energy?
Capacity to do work
What does ATP (adenosine triphosphate) do?
medium of energy exchange i.e. the energy currency of the cell
What generates the most ATP?
Glucose and fatty acid metabolism
What generates a relatively little amount of ATP?
Amino acids
Where else is ATP generated?
some ATP generated by glycolysis and krebs cycle
What reducing equivalents are produced by glycolysis, beta oxidation and krebs cycle?
NADH and FADH2
What do NADH and FADH2 do?
supply protons (H+) & electrons (e-) to the electron transport chain where most of the ATP is made
How can ATP be produced anaerobically (without 02)
- 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)
How does fat store energy?
Most energy stored as triglycerides in adipocytes
How do carbohydrates store energy?
- 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
How do proteins store energy?
- Large potential energy source
- Protected but will be used in starvation or caloric restriction
What are the pro’s of using carbohydrates as fuel?
- Aerobically, can generate ATP slightly faster than fat
- Can generate ATP anaerobically (3x faster than aerobic)
What are the cons of using carbohydrates as fuel?
- Holds a lot of water i.e. heavier & less energy-dense than fat
What are the pro’s of using fat as fuel?
- Doesn’t hold water i.e. more than 2x as energy-dense as carbohydrate
- Most abundant energy reserve
What are the cons of using fat as fuel?
- Can’t provide energy anaerobically i.e. must have oxygen
What happens during the absorptive state regarding energy homeostasis?
- 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
What happens during the postabsorptive state (fasting) regarding energy homeostasis?
- Stored macronutrients are mobilized for energy i.e. catabolic state
- Glucose is spared for nervous system
What is normal fasting blood glucose range?
~4 – 5.5 mmol/L (very narrow
range
What is fasting hyperglycemia glucose level?
glucose > 7 mmol/L
What is fasting hypoglycemia glucose level?
glucose ~< 3.5 mmol/L
Why is glucose maintained so tightly?
- 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
When is insulin released?
When blood glucose is elevated
ex. after a meal
When is glucagon released?
When blood glucose is low
ex. fasting
What does prolonged, lower intensity excercise rely on?
Relies more on plasma-derived substances, particuarly free fatty acids but also some blood glucose
