Chapter 2 exercise phys

Substrates 

fuel sources from which we can make energy 

Bioenergetics

How each cell converts substrates into energy that the cell can use

Metabolism

All of the chemical reactions in the body

What is a calorie?

1 calorie is the amount of heat energy needed to raise 1 gram of water 1 degree C, from 14.5 degrees C to 15.5 degrees C

How is energy expressed in humans?

Kilocalories (kcal)

When is energy released? 

When chemical bonds are broken

How much of ATP comes from fat at rest?

About 60%

What is used during anaerobic activities

Carbohydrates

What is used during aerobic activities?

Carbs and fat

What are most carbs converted into? 

Glucose (a monosaccharide), which is transported through the blood to all body tissues.

Where are ingested carbohydrates stored under resting conditions?

In the muscles and liver in glycogen (a polysaccharide)

Where is glycogen stored?

In the cytoplasm of muscle cells, the cells use it for ATP.

Extra glycogen is stored in the liver. When the body needs energy, the liver turns this glycogen into glucose and sends it through the blood to the muscles and other tissues, where it is used for energy.

Why is fat less readily available for cellular metabolism? 

It must first be broken down from its complex form, triglyceride, into glycerol and free fatty acids. Only the fatty acids are used to make energy (ATP). 

What must proteins be converted into to be used as a minor energy source (protein can supply up to 10% of the energy needed to sustain prolonged exercise)?

glucose

Gluconeogenesis

protein or fat being converted into glucose

Lipogeneis

Converting protein into fatty acids

What is the usable storage form of energy within the cells?

ATP

How much do carbs and protein provide in kcals of energy per gram? What about fat?

4.1 kcal energy/gram, and fat 9.4 kcal energy/gram 

Fat

stored as triglycerides in adipose tissue, and triglycerides are broken down into free fatty acids, which are converted to energy.

What controls the rate of metabolism and energy production?

Enzymes speed up the breakdown (catabolism) of chemical compounds by lowering the activation energy required to begin the reaction.

What is the rate at which free energy must be released from a chemical compound determined by?

Enzyme activity and availability of the primary substrate (mass action effect).

rate-limiting enzyme

An enzyme early in the pathway controls how fast the whole reaction goes. It can be slowed down by negative feedback from products made later in the pathway, which reduces the reaction rate

How does ATP release energy?

When ATP is mixed with water and helped by an enzyme called ATPase, it loses one of its phosphate groups. This releases a lot of energy and turns ATP into ADP and a separate phosphate (P).

Phosphorylation

A phosphate is added to ADP to make ATP.

Oxidative phosphorylation 

When oxygen is used to help make ATP (energy) from ADP and phosphate. It happens in the mitochondria and makes most of the cell’s energy.

What is one way cells generate ATP?

ATP-PCr system

1) The enzyme creatine kinase breaks apart phosphate groups from phosphocreatine. The energy from this process is used to add the phosphate to ADP, making ATP.

2) Anaerobic system

3) Maintain ATP levels early in exercise. Energy yield is 1 mol of ATP/1 mol of Pcr.

Talk about how energy is formed through ATP-PCr system

1) During the first few seconds of sprinting, the amount of ATP stays the same, but phosphocreatine (PCr) goes down because it’s used to make more ATP.
2) By the time you get really tired, both ATP and PCr are low and can’t give the muscles energy anymore.
3) This system can keep the muscles working hard for about 3 to 15 seconds during a full sprint.

Glycolytic system

1) This process is called glycolysis. It breaks down glucose or glycogen step-by-step to make pyruvic acid.
If there’s no oxygen, pyruvic acid changes into lactic acid.
Breaking down one glucose makes 2 ATP, and one glycogen makes 3 ATP.

Glycogenolysis 

Glycogenolysis is the process where glycogen (stored sugar) is broken down into glucose to be used for energy.

What must happen before glucose or glycogen can be used to generate energy?

1) Must be converted into a compound called glucose-6-phosphate.

2) In glycolysis, it requires the input of 1 ATP

3) Glycogen requires no energy expenditure.

What does glycolysis require for the breakdown of glycogen to pyruvate?

10-12 enzymatic reactions, which are converted into lactic acid

Breakdown of 1 glucose molecule to 2 three-carbon molecules of pyruvic acid

1) Glucose-net gain is 2 mol ATP

2) Glycolysis-3 mol of ATP

Is the glycotic system aerobic or anaerobic and what is its by-product?

1) anaerobic, used during exercises that last about 10 seconds to 2 minutes

2) Lactic acid is its by-product (it causes muscle fatigue) 

What is the rate-limiting enzyme in glycolysis?

phosphofructokinase (PFK) an important enzyme in your body that helps control how fast you break down sugar (glucose) to make energy.

ATP-PCr and Glycotic system

gives energy during short-burst activities lasting up to 2 minutes and during the early minutes of longer-duration high-intensity exercise.

Oxidative system

1) Most complex out of the three

2) ATP is made in mitochondria

3) Involves Glycolysis, the Krebs cycle, and the electron transport chain

Input and output in Glycolysis

1 glucose, 2 ATP, and 2 NAD+ to 2 pyruvate, 2 net ATP, and 2 NADH

Does glycolysis play a role in aerobic and anaerobic ATP production? 

Yes, but in the presence of oxygen, the pyruvic acid is converted into acetyl CoA

Kebrs cycle location and inputs and outputs

Mitochondria2

• 1 Acetyl‑CoA

• 3 NAD⁺

• 1 FAD

• 1 ADP + Pi

• 2 H₂O

• 2 CO₂

• 3 NADH

• 1 FADH₂

• 1 ATP (or GTP)

Substrate-level phosphorylation

A way cells make ATP by directly transferring a phosphate group from a high-energy molecule to ADP.

What is the rate limiting enzyme in the krebs cycle?

isocitrate dehydrogenase

Location of electron transport chain and the inputs and outputs

inner mitochondrial membrane

• 10 NADH (from glycolysis, pyruvate oxidation, and the Krebs cycle) Wikipedia+3NCBI+3Food Science Toolbox+3

• 2 FADH₂ NCBI+2Food Science Toolbox+2

• O₂ (oxygen) — the final electron acceptor NCBI+2Wikipedia+2

• ADP + Pi (to make ATP) Wikipedia+3NCBI+3Knowt+3

• ATP — from oxidative phosphorylation

  • NADH → ~ 2.5 ATP each NCBI+2Food Science Toolbox+2

  • FADH₂ → ~ 1.5 ATP each NCBI+2Food Science Toolbox+2

• H₂O (water) — when oxygen accepts electrons and protons NCBI+2Wikipedia+2

• NAD⁺ and FAD — regenerated from NADH and FADH₂

cytochromes

These electron carriers work together to transfer electrons through the ETC leading to production of ATP

End result of oxidation of carbohydrates

H20, CO2, and 32-33 ATP molecules

Oxidation of fat

begin with beta oxidation of FFAs (the process of chopping up fatty acids into small pieces (2 carbon units) to make energy).

triglyceride 

one molecule of glycerol and 3 FFA. The breakdown of this is called lipolysis

Brown adipose tissue

transfer energy from food directly into heat

More in infants; in adults, clavicles

Helps burn calories, may improve metabolism, insulin sensitivity; less brown fat with age

White adipose tissue

Stores extra energy (as fat), cushions organs, insulates body.

lipid storage and breakdown (lipolysis)

generates ATP for energy

energy yield of fat vs carbs

5.6 ATP molecules per oxygen molecule and 6.3 ATP per oxygen molecule

Lactate

Made during anaerobic and aerobic exercise and serves as a fuel source for muscle 

Lactic acid

has an additional H+ ion. not present in any living cell.

cori cycle

a way your body recycles lactate back into glucose, especially important when muscles are working hard and producing a lot of lactate

lactate during exercise

Muscles, the heart, and the brain can utilize lactate by converting it back into pyruvate and subsequently oxidizing it for ATP production. This process is known as the "lactate shuttle." Additionally, lactate can be transported to the liver, where it is converted back into glucose through the Cori cycle, providing a continuous energy supply during prolonged activity.

does fat oxidation or the ATP-Cr system produce unlimited energy?

Fat oxidation 

When running a long distance, is fat or carbs used first?

Carbs

Crossover concept

The relative balance between carbs and fat metabolism during sustained exercise. The crossover point is when fat and carb utilization intersect

What does a muscle’s oxidative capacity depend on?

its oxidative enzyme concentrations, fiber type composition, and oxygen availability.

Krebs cycle enzymes

measured to reflect the aerobic capacity of muscle fibers, specifically succinate dehydrogenase and citrate synthase

the more type one fibers in one’s muscles…

the greater the oxidative capacity of those muscles. 

Endurance training enhances the oxidative capacity of…

all fibers, especially type 2 fibers.