Learn: Exercise Physiology Knowledge Festival 2

What is metabolism?

The sum of all chemical reactions that occur in the body.

What are anabolic reactions?

Reactions involving the synthesis of molecules.

What are catabolic reactions?

Reactions involving the breakdown of molecules.

What is bioenergetics?

Conversion of fats, proteins, and carbohydrates into energy.

What is the function of the cell membrane?

A semipermeable membrane separating the cell from the extracellular environment.

What is the function of the nucleus?

Contains genes that regulate protein synthesis.

What is the cytoplasm?

The fluid portion of the cell that contains organelles.

What is oxidation?

Removal of an electron.

What is reduction?

Addition of an electron.

What is the relationship between oxidation and reduction?

They are always coupled reactions.

If a molecule loses hydrogen, what happens to it?

It loses an electron and is oxidized.

What is the oxidized form of NAD?

NAD+.

What is the reduced form of NAD?

NADH.

What is the oxidized form of FAD?

FAD.

What is the reduced form of FAD?

FADH2.

What is the major role of NAD and FAD?

They transfer electrons/hydrogens during metabolism.

What is the general function of an enzyme?

A catalyst that regulates reaction speed.

How do enzymes speed up chemical reactions?

They lower the energy of activation.

How does a small rise in body temperature affect enzyme activity?

It increases enzyme activity.

How can altered pH affect enzyme activity?

Changes in pH can reduce enzyme activity.

What does the lock-and-key model describe?

Enzymes interact with specific substrates.

What do kinases do?

Add a phosphate group.

What do dehydrogenases do?

Remove hydrogen atoms.

What do oxidases do?

Catalyze oxidation-reduction reactions involving oxygen.

What do isomerases do?

Rearrange the structure of molecules.

Why can blood enzyme levels indicate tissue damage?

Damaged cells release enzymes into the blood.

Elevated lactate dehydrogenase or creatine kinase may indicate what?

Tissue damage such as myocardial infarction.

What three components make up ATP?

Adenine, ribose, and three linked phosphate groups.

What reaction synthesizes ATP?

ADP + Pi + energy → ATP.

What are the three major energy systems emphasized in class?

Phosphocreatine, glycolysis, and oxidative phosphorylation.

Which energy system provides an immediate source of ATP?

Phosphocreatine (ATP-PC).

What is another name for the phosphocreatine system?

ATP-PC system.

Which enzyme is associated with the ATP-PC reaction?

Creatine kinase.

Which energy systems can produce ATP anaerobically?

ATP-PC and anaerobic glycolysis.

Which major ATP-producing pathway is aerobic?

Oxidative phosphorylation.

What enzyme was highlighted in the energy-investment phase of glycolysis?

Phosphofructokinase (PFK).

What do reducing equivalents transport?

Hydrogens and their associated electrons.

Where can reducing equivalents carry hydrogen during aerobic metabolism?

Into mitochondria for ATP generation.

How are reducing equivalents involved under anaerobic conditions?

They participate in conversion of pyruvate to lactate.

What happens to NAD+ when it accepts hydrogen/electrons?

It becomes NADH + H+.

What happens to FAD when it accepts hydrogen?

It becomes FADH2.

Why must NADH produced during glycolysis be converted back to NAD?

NAD must be regenerated so glycolysis can continue.

What are two ways NAD can be regenerated after glycolysis?

Convert pyruvate to lactate or shuttle H+ into mitochondria.

Where is the H+ shuttle system located?

In the mitochondrial membrane.

What happens when pyruvic acid accepts two hydrogens?

NAD is regenerated and lactic acid is formed.

What is lactate in relation to lactic acid?

The conjugate base of lactic acid.

What happens to lactic acid after it is produced?

It rapidly dissociates into lactate and H+.

What happens to pyruvate before entering the Krebs cycle?

3-carbon pyruvate is converted to 2-carbon acetyl-CoA.

What is released when pyruvate is converted to acetyl-CoA?

CO2.

What combines with acetyl-CoA to begin the Krebs cycle?

4-carbon oxaloacetate.

What 6-carbon molecule is formed from acetyl-CoA and oxaloacetate?

Citrate.

What happens to citrate through the Krebs cycle?

It is metabolized back to oxaloacetate.

How many CO2 molecules are released during one turn of the Krebs cycle?

Two.

How many NADH are produced per acetyl-CoA in the Krebs cycle?

Three.

How many FADH2 are produced per acetyl-CoA in the Krebs cycle?

One.

How much GTP is formed per acetyl-CoA in the Krebs cycle?

One GTP.

Where does oxidative phosphorylation occur?

In the mitochondria.

What happens to electrons from NADH and FADH2 in the ETC?

They pass along a series of carriers called cytochromes.

How much ATP does one NADH produce according to these slides?

2.5 ATP.

How much ATP does one FADH2 produce according to these slides?

1.5 ATP.

What is oxygen's role in the electron transport chain?

It is the final electron acceptor and helps form water.

What does the ETC do to H+ across the inner mitochondrial membrane?

Pumps H+ across the membrane, creating a gradient.

How does the H+ gradient lead to ATP formation?

Energy is released as H+ diffuses back across the membrane.

What is the chemiosmotic hypothesis?

ATP formation driven by an H+ gradient across the inner mitochondrial membrane.

What is a rate-limiting enzyme?

An enzyme that regulates the rate of a metabolic pathway.

How do high ATP levels affect ATP production?

They inhibit ATP production.

How do low ATP and high ADP + Pi affect ATP production?

They stimulate ATP production.

How can calcium affect aerobic ATP production?

Calcium may stimulate aerobic ATP production.

What is beta-oxidation?

Conversion of fatty acids into acetyl-CoA through repeated 2-carbon removal.

What must happen to fatty acids before they can be used as fuel?

They must be converted to acetyl-CoA.

Where does activated fatty acyl-CoA go for beta-oxidation?

Into the mitochondrion.

What happens to a fatty acid during beta-oxidation?

It is chopped into 2-carbon fragments that form acetyl-CoA.

Where does acetyl-CoA from beta-oxidation go?

Into the Krebs cycle.

Why does fat oxidation require more O2 than glucose oxidation?

A fatty acid contains more carbon.

How many acetyl-CoA result from the C16 fatty acid example?

Eight acetyl-CoA.

How many beta-oxidation cuts occur for the C16 fatty acid example?

Seven cuts.

What does each beta-oxidation cut generate?

1 NADH + H+ and 1 FADH2.

What is the net ATP yield of the C16 fatty acid example in the slides?

106 ATP.

How can glycerol from triglycerides be metabolized?

It enters the glycolytic pathway.

How much ATP does glycerol yield according to the slides?

19 ATP.

What total ATP yield is given for a triglyceride containing three C16 fatty acids?

337 ATP.

At rest, approximately what percentage of ATP is produced aerobically?

Almost 100%.

What is normal resting blood lactate according to the slides?

Less than 1.0 mmol/L.

What is resting O2 consumption in L/min?

About 0.25 L/min.

What is resting O2 consumption relative to body mass?

About 3.5 mL/kg/min.

What happens to ATP production immediately when exercise begins?

It increases immediately.

What happens to oxygen uptake when exercise begins?

It increases rapidly.

How long does it typically take to reach steady state after exercise begins?

About 1-4 minutes.

Once steady state is reached, how is the ATP requirement primarily met?

Through aerobic ATP production.

Which pathways supply much of the initial ATP when exercise begins?

ATP-PC and glycolysis.

What is oxygen deficit?

The lag in oxygen uptake at the beginning of exercise.

What supplies energy during the oxygen deficit?

Intramuscular high-energy phosphates and glycolysis.

When does the oxygen deficit effectively end?

When steady-rate energy transfer matches exercise energy demand.

Do energy systems simply switch on and off during exercise?

No; they blend smoothly and overlap considerably.

What are the two proposed explanations for O2 deficit in the slides?

Slow O2 delivery and lack of a signal because PCr initially supplies energy.

Why is O2 delivery relevant to oxygen deficit?

O2 is the final electron acceptor in aerobic metabolism.

What is oxygen uptake kinetics?

The study of O2 uptake during the transition from rest to exercise.

What does Phase I of oxygen uptake kinetics represent?

The cardiodynamic phase.

Does Phase I primarily reflect increased muscle VO2?

No; it reflects metabolite washout from increased pulmonary blood flow.

What does Phase II of oxygen uptake kinetics reflect?

The ability to deliver/use O2 to meet the new exercise demand.