energy systems (chapter 2)

primary goal of all energy systems

to make ATP, which fuels cellular energy production

metabolic balance

balance between anabolism (building molecules, energy storage) and catabolism (breaking molecules, energy release)

when does energy breakdown dominate

during exercise (more catabolism than anabolism)

when does energy building dominate

during recovery/eating (more anabolism than catabolism)

why is ATP so important

ATP powers both anabolic (building) and catabolic (breaking down) reactions in the body

how much ATP do we store in the body at once

only about 100g

how fast can we burn ATP at the start of strenuous exercise

about 450g per minute

how much ATP do we break down in a whole day

around 45 kg

what is the fastest energy system

phosphagen (PCr) system

how does phosphocreatine make ATP

PCr + creatine kinase -> splits into creatine + inorganic phosphate -> energy released to make ATP

does the phosphagen system use carbs, fats, or protein

no, it doesn't use macronutrients

when is the phosphagen system used

short, powerful bursts (ex: sprints, heavy lifting, jumps))

what happens during anaerobic glycolysis

glucose is broken down quickly -> produces 2-3 ATP, 2 pyruvate, 2 NADH

which enzyme controls glycolysis

phosphofructokinase (PFK) responds to ATP:ATP ratios

what happens to pyruvate in anaerobic glycolysis

if mitochondria can handle it, it goes to Krebs cycle (if not its converted into lactate)

what actually causes the burn in muscles during exercise

hydrogen ions (H+), not lactate (lactate actually buffers hydrogen and helps delay fatigue

what is aerobic metabolism

energy production using oxygen (produces the most ATP and keeps the body functioning normally)

where does aerobic metabolism occur

in the mitochondria

what is the meeting point of all macronutrients

Acetyl-CoA, which enters the Krebs cycle

what does oxaloacetate do in the Krebs cycle

combines with Acetyl-CoA to form citrate (starting the cycle)

how much ATP is produced from one glucose molecule aerobically

around 30-32 ATP

what drives ATP synthase in the electron transport chain

a hydrogen gradient created by electron transport (chemiosmotic coupling)

how are carbs used for energy

glycolysis -> Krebs cycle -> ETC

why are carbs important for fat metabolism

carbs provide oxaloacetate, which is needed to keep the Krebs cycle running

what happens if glucose is too low

oxaloacetate is used for gluconeogenesis -> Krebs slows -> Acetyl-CoA becomes ketones

why are fats considered the highest energy molecule

they yield the most ATP when broken down

what is the process of fat breakdown called

beta-oxidation

what are the products of each beta-oxidation cycle

1 Acetyl-CoA, 1 NADH, 1 FADH2

when is fat breakdown limited

starvation or very low carbs (not enough oxaloacetate)

low-carb diets (harder to burn fat efficiently)

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