EXSC 329 Bioenergetics and Energy Production

What are macronutrients converted to and stored as?

carbs → glucose → glycogen

fats → glycerol + fatty acid → triglycerides

proteins → amino acids → (no storage form)

At rest, about how much energy is produced from carbs vs fats?

carbs 50%, fats 50%

What does usage of fat for energy depend on during long duration exercise?

overall intensity, fitness, and duration

What is the production of energy from protein sources called?

gluconeogensis

What does usage of carbs for energy depend on?

availability of glucose/glycogen storage and muscle metabolism

Where is glycogen stored?

in skeletal muscle cytoplasm or in the liver as needed

What are the main characteristics of fat breakdown for energy production?

fat stores are harder to access and less readily available, and have a less efficient, slower rate of energy release compared to carbs

Where is fat stored in the body?

intramuscularly, as subcutaneous fat, or as visceral fat

How is protein used for energy production?

it is converted to glucose or other intermediates of oxidative metabolism

What is the main function of proteins?

enzymes and structural components within the body

What is gluconeogenesis?

forming glucose from non-carb/fat sources such as amino acids or lactate being converted to glucose

What is glycogenesis

forming glycogen from glucose

What is glycogenolysis?

forming glucose from glycogen

What is lipogenesis?

forming fats from glucose

What is lipolysis?

forming glucose from fats

What does the rate of energy production depend on?

availability of substrates and enzyme activity

How do enzymes speed up the rate of reactions?

the do not cause reactions or alter usable energy, but speed up catabolism of chemical compounds by lowering activation energy needed to start a reaction

What is a rate limiting enzyme?

an enzyme that controls a reaction’s overall rate, usually early on in a pathway

What is negative feedback?

when accumulation of products changes enzyme activity to (primarily) slow reactions

What releases the energy from ATP?

splitting off a phosphate group to produce ADP, Pi, H+ and release energy

Generating ATP requires energy? T/F

true, energy is used to add ADP + Pi to create ATP

What are the processes of breaking down and building ATP called?

breaking down: hydrolysis

building: phosphorylation

How are the anaerobic energy systems linked to the aerobic energy system?

byproducts of glycolysis and ATP-PCr systems feed into oxidative phosphorylation

How much exercise does the ATP-PCr system support?

3-15 seconds of all-out exercise using immediately stored ATP and phosphocreatine

Where does glycolysis occur?

in the cell cytoplasm

How much ATP is released per mole of glycogen and glucose?

3 mol ATP/mol glycogen

2 mol ATP/mol glucose

How much exercise does the glycolytic system support?

a few minutes of intense exercise

What supports glycolysis and what limits it?

supports: rapid cycling to produce energy quickly

limited by: rapid acidosis, causing impaired enzyme function and lowered calcium binding capacity in muscle fibers

What is a main product of glycolysis and how is it used?

pyruvate converted to lactate or enters the oxidative system, depending on rate of ATP producted needed

What is the myth about lactic acid and lactate?

there is no lactic acid, and lactate actually consumed H+ to lower pH and regenerates NAD+ to support ATP production

Where does acidosis actually come from?

likely the excess H+ ions produced during ATP hydrolysis

Where does oxidative phosphorylation occur?

in the cell mitochondria

What determines density of mitochondria?

demand for ATP and O2

How much exercise does oxidative phosphorylation support?

low intensity, long duration activity lasting more than a few minutes

What is the main pathway of oxidation?

glycolysis (pyruvate becomes acteyl CoA) → Krebs cycle produces NADH, FADH2, and H+ → electron transport chain passes along electrons to outer mitochondrial compartment to create an unequal concentration gradient → ATP synthase phosphorylates ADP and Pi into ATP

What is beta-oxidation?

the breakdown of triglycerides into glycerol and free fatty acids that can be used for ATP generation

How is ATP used during beta-oxidation?

ATP “activates” FFA for catabolism into acetyl CoA

What are some differences between oxidation of fats vs carbs?

1 FFA = 106 ATP vs 1 glucose = 32 ATP

FFA = 9.4 kcal/g vs glucose = 4.1 kcal/g

What is the downside to using fat oxidation to produce energy?

rate of energy yield is lower and less efficient for every O2 molecule

fat = 5.6 ATP/O2 vs carb = 6.3 ATP/O2

How does oxidation of protein produce energy?

by converting directly to glucose or converting to intermediates of the Krebs cycle

What is the lactate shuttle?

a process for utilizing lactate throughout the body

Where can lactate go to be used as fuel?

in the same cell where there is a high density of mitochondria, in adjacent muscle fibers, and circulating through the blood for oxidation elsewhere

What are monocarboxylase transporters (MCTs)?

transporters that facilitate lactate movement between cells and tissues, usually with H+ to prevent acidosis

What is the Cori cycle?

a process for using blood-circulating lactate in the liver to be converted to pyruvate then glucose, and returned back to the working muscle

Summary of aerobic metabolism:

requires oxygen

located in the mitochondria

uses carbs and fats for fuel

slower rate of reaction

exercise lasting more than a few min

Summary of anaerobic metabolism:

does not require oxygen

occurs in cytosol

uses carbs and phosphocreatine as fuel

faster rate of reaction

shorter duration exercise under 1-2 min