Lecture 18 Flashcards
Energy is defined as
the capacity to do work
Adenosine Triphosphate (ATP)
Energy Currency of the Cell, medium of energy exchange
what do glucose and fatty acid metabolism generate?
most of the ATP … relatively little
from amino acids (but still some)
Some ATP is generated by
glycolysis and Kreb’s cycle
Glycolysis, beta oxidation and Kreb’s cycle produce
reducing equivalents …
NADH and FADH2
NADH and FADH2 supply
protons (H+) and electrons (e-) to the electron transport chain. THIS is where most of the ATP is
made.
ATP can also be generated WITHOUT O2 by:
Phosphocreatine (PCr) degradation, about 9-10 seconds worth
ATP → ADP + Pi
PCr + ADP + H+ → ATP + Cr
ATP is rebuilt by adding a phosphate to ADP
end products in anaerobic
conditions
lactate, E.g sprints
most energy is stored as
triglycerides (a form of fat)
in our adipocytes
Carbohydrate stored as
- Glycogen in liver (~150 g); most concentrated as liver is only ~2 kg
- Glycogen in muscle (~350 g); ~40% body mass is muscle (varies highly based on genetics and body type)
- Only ~ 30 g of glucose is found in the blood – not much (body rids blood of glucose quickly)
Protein also represents
a large potential energy source (~40% body mass is muscle)
This is obviously protected, but will be used in starvation or
caloric restriction
potential energy source means..
not the first source of energy, not broken down first. Stored for emergency - starvation or muscle breakdown
Carbohydrate, aerobically
can generate ATP slightly
faster than from fat
Carbohydrate, anaerobically
Can also generate ATP, 3x
faster than aerobic
carbs hold
a lot of water i.e. “heavier”;
less energy dense than fat
Fat doesn’t hold
water, more than twice
as energy dense as carbohydrate
fat represents
our most abundant
energy reserve
fat cannot
provide energy
anaerobically (must have oxygen!
Absorptive State:
First 3-4 hours after a meal
Energy (macronutrients) are stored (anabolism)
Excess nutrients taken up will be stored i.e. anabolic state in
- Glycogen (carbohydrate) stored in liver and muscle
- Triglycerides (fat) stored in adipose tissue, liver and muscle
Excess calories in the form of glucose or amino acids can get converted into
fat
during Postabsorptive State / Fasting…
Stored macronutrients are mobilized for energy (catabolism); Glucose is spared for nervous system
Gluconeogenesis
making glucose from non-
carbohydrate precursors (occurs in the liver -primarily – but also kidneys)
Glycogenolysis
breakdown of glycogen, a stored form of glucose, into glucose molecules (fasted state)
Normal fasting blood glucose is
~ 4 – 5.5 mmol/L (very narrow range!)
free fatty
acids
the other major circulating fuel, vary from 0.2 - 2 mmol/L
Fasting hyperglycemia:
Glucose > 7 mmol/L
Fasting hypoglycemia:
Glucose ~ < 3.5 mmol/L
Why is blood glucose maintained so tightly?
- Many cells require glucose e.g. neural tissue, kidney
- Maintain osmotic balance (optimal concentrations of electrolytes and
non-electrolytes are maintained) - Hyperglycemia can cause glycosylation of amino acids in kidneys,
peripheral nerves, lens of the eye, causing damage
glucose regulation via insulin happens when
blood glucose is elevated, after a meal / post absorptive state
or
when blood glucose is low
This could be induced by fasting
glucagon is decreased during
post absorptive state, insulin to glucagon ratio
increases
why don’t we want glucogenolysis process to occur after eating a meal
process in which liver makes glucose, don’t need this, blood sugar is already high
insulin is decreased during
fasted state, glucagon to insulin ratio increases
reciprocal changes in______ and _____ are more important than the change in one of these hormones
insulin and glucagon
what is used for energy during prolonged low intensity exercise? (Cycling, jogging, swimming)
plasma-derived substrates mostly fatty acids, some blood glucose
as exercise intensity increases what is used for energy? (heavy weight lifting + sprinting)
increased need to mobilize energy stores (substrates) within the muscle itself, muscle glycogen (mostly) + triglycerides used
