Chapter 6: Bioenergetics Flashcards
What is the molecular structure of ATP?
Adenine and ribose attached to three phosphates.
How does ATP store and release energy?
The two bonds between the three phosphates store energy, and release energy when broken
What is the law that states that energy can be changed from one form to another but cannot be created or destroyed?
The first law of thermodynamics
Law of conservation of energy
What metabolic reactions are the cornerstone of human physiology?
Anabolic: the building process
Catabolic: The breakdown process
What is the enzyme that breaks the bond between the second and third phosphates to release the stored energy?
ATPase
What is dephosphorylation?
The process of removing a phosphate using water
How many acidic protons are released during the breakdown of ATP to ADP?
one
What is rephosphorylation?
The process of reattaching or adding a phosphate (Pi)
What enzyme is needed for rephosphorylation?
ATP synthase
What’s the process of breaking of ATP while in the presence of water to release energy stored within its bonds?
ATP hydrolysis
What is metabolic acidosis? What is it caused by?
When ATP hydrolysis causes the muscle to accumulate protons (H+) faster than the muscle can remove them as waste
What is the short-term effect of metabolic acidosis?
Impairs muscle power and energy production
What happens to cellular ph during acidosis?
It becomes lower
When happens with ADP to AMP?
the two remaining phosphate ions in the ADP bond can be used to generate cellular energy
What is the enzyme that converts two ADP into one ATP?
adenylate kinase
What is the chemical reaction for AMP to ADP?
AMP + Pi + energy
Pi is a phosphate ion
Why is AMP is not an ideal molecule to have in the cells?
An accumulation of phosphates can cause muscle fatigue and limit physical performance
It can also break down even further and create ammonia, which is toxic
What’s the advantage of burning a higher percentage of stored fat as fuel?
It does not result in cellular acid buildup
What are the 3 energy systems?
The phosphagen system
Anaerobic glycolysis
Aerobic glycolysis
What is the phosphagen system?
The combination of a muscle’s stored ATP plus its phosphocreatine, used to create up to 30 seconds’ worth of energy
What is the molecule found in muscle and brain tissue that donates its phosphate to ADP to form ATP during the phosphagen system?
Phosphocreatine
What is anaerobic glycolysis?
Producing ATP from glucose
What us glucose? What is it used for?
The smallest molecule a carbohydrate can be broken down into and used as an energy source
What is pyruvate?
A three-carbon structure formed by splitting a glucose molecule
Why does anaerobic glycolysis produce a decline in muscle power?
From a production of protons (H+) that increase cellular acidity
What is the end product of glycolysis?
Lactic acid
What is aerobic glycolysis?
The breakdown of fuels to form ATP in the presence of oxygen
What is the gel-like material that makes up all inner components of every cell within the human body?
Cytoplasm
What is sarcoplasm?
The cytoplasm of a muscle cell
What is the cell nucleus?
An organelle that controls a cell and the deoxyribonucleic acid (DNA)
What is deoxyribonucleic acid (DNA)?
A molecule that contains genetic instructions for growth, development, reproduction, and functioning
What’s the only part of the cell that is not considered part of the cytoplasm?
The nucleus
What is the chemical structure of phosphocreatine?
One phosphate molecule connected to one molecule of creatine
What molecule assists in the re-formation of ATP from ADP?
Creatine
How does creatine work?
It donates its phosphate to ADP to form ATP
What enzyme that catalyzes ADP to ATP, as well as creatine to phosphocreatine?
Creatine kinase
Why is the creatine kinase reaction critical for muscular contraction?
It keeps the ATP-ADP cycle running
What happens the longer the creatine kinase reaction runs?
More protons will build up in the cytoplasm, reducing the cellular pH of the cell and leading to metabolic acidosis
What is the limitation on the phosphagen system?
The supply of phosphocreatine in the body
Where is creatine synthesized?
In the kidney, pancreas, and the liver
What does the supplementation of creatine allow?
More stored creatine in the cells
complements the phosphagen system
Helps delay muscle fatigue and increase muscular output for short-duration efforts
Why can a more conditioned individual replenish cellular phosphocreatine within 5–10 minutes?
They are generally able to take in and use oxygen better than an unconditioned individual
What is the limitation on the replenishment of stored phosphocreatine?
The availability of oxygen
What is glycogen?
The stored form of glucose in liver and skeletal muscle
What happens when stored glycogen runs low?
glucose in the bloodstream is forced into the muscle cells and broken down (aka glycolosis)
What processes produce many times more ATP than the phosphagen system?
Aerobic or anaerobic glycolysis
What are the glyocolytic processes in the absence and presence of oxygen?
In the presence of oxygen: oxidative phosphorylation
In the absence of oxygen: anaerobic glycolysis
What happens to the glucose molecule during anaerobic glycolosis?
Its split into two pyruvate molecules
What coenzyme regulates the split between two pyruvate molecules?
nicotinamide adenine dinucleotide (NAD+)
What is the reduced form of NAD+ that necessary for energy production that comes from glycolysis?
NADH
What causes “muscle burn”?
The buildup of lactate and protons when the phosphagen system is phasing into anaerobic metabolism
What causes a decrease in muscular output during high intensity activities?
The inability to allow enough oxygen to enter the mitochondria for the exercise to be predominantly aerobic
What 3 conditions produce larger quantities of lactate?
- Lack of oxygen in the mitochondria
- Quick increase in exercise intensity
- Recruitment of type II muscle fibers
What are the three primary benefits to the muscles of lactate?
acts as a buffer to slow acidosis
cotransporter from the sarcoplasm and the bloodstream, taking a proton along with it
can be transported to the liver and converted back into glucose through the lactic acid cycle
What is gluconeogenesis?
The formation of glucose from noncarbohydrate sources, usually in the liver
What is the the preferred source of energy for the cardiac muscles of the heart?
lactate
What are the conditions under which lactate is used?
- Normal resting heart activity
- Submaximal exercise (~40–60 percent of VO2 max)
What happens when intensity is increased to around 55 to 65 percent of a person’s VO2 max?
The rate of lactate accumulation exceeds the muscle’s ability to clear it aka the lactate threshold
What does the lactate threshold signal?
The physiological point where the central nervous system and muscle fibers will be affected by the excess of protons because lactate cannot be buffered
What causes lactate to rise, and corresponds with an increase in H+ and blood acidity?
Increasing power output (i.e., work rate)
What are the by-products of anaerobic glycolysis in cellular energy production?
Lactate and H+
What happens as acidosis causes an increase in lactate concentration and free protons?
Declines in muscular performance and increases in muscle soreness
How can acidosis (and the associated muscle soreness) be minimized?
With an appropriate recovery intensity between bouts of high-intensity exercise
Why is it a light run after a sprint a good idea?
Because when recovery is near or at the individual’s lactate threshold, optimal lactate and proton clearance from the sarcoplasm and the blood occurs
why is anaerobic glycolysis effective only for high-intensity activities of a relatively short duration?
because In the absence of oxygen, only 2 ATP molecules are produced for each molecule of glucose
What affects the exact timing of oxidative phosphorylation taking over as the energy system?
- The conditioning of the individual
- Highly trained athletes can access their aerobic metabolism at full capacity in 60 seconds
- Unconditioned individuals may take up to 4 minutes to become completely aerobic
What is aerobic metabolism?
The breakdown of fuels to form ATP in the presence of oxygen
What is acetyl coenzyme A (acetyl-CoA)?
The central metabolite that initiates the aerobic metabolism process within the mitochondria, regardless of fuel source
What is the the first stage of aerobic metabolism?
The Krebs Cycle
What is the metabolic pathway within mitochondria where the majority of ATP molecules are formed during aerobic metabolism?
electron transport chain
What’s another name for the electron transport chain?
Oxidative phosphorylation
What are the three reasons mitochondria are essential for maintaining performance?
1) They produce ATP during exercise, especially when the activity lasts more than a few minutes
2) During the first 10 to 30 seconds of maximal activity, mitochondria absorb protons (H+)
3) mitochondria help athletes recover more quickly between intermittent bursts of powerful activity
How do strength training and cardiovascular training positively affect the mitochondria?
Strength training increases the the organelle’s ability to produce ATP
Cardiovascular training increases substrate concentrations and increases in the number of mitochondria in each cell
What are the 4 fuel sources for aerobic metabolism?
Glucose, fatty acids, lactate, and ketones
What are the 3 locations that fat is stored around the body?
Visceral fat - around the midsection, in the area between the abdominals and organs
Subcutaneous fat - directly beneath the skin
Intramuscular fat
What are triglycerides?
The stored form of fatty acids
What is lipolysis?
The breakdown of triglycerides into fatty acids to be used for energy
What roles does the hormone epinephrine (adrenaline) play during exercise?
It attaches to receptors on fat cells, which breaks down triglycerides into fatty acids
Allows them to flow into the blood, which transports them to the muscles
How do fatty acids reach the muscle cell?
They move into the sarcoplasm and then into the mitochondria
What is beta-oxidation (β-oxidation)?
The process of transforming fatty acids into acetyl-CoA
What are the two ways lactate can be used for energy?
Remain in the muscle
Move to other areas
What happens when lactate remains in the muscle?
It converts back to pyruvate and then enters the mitochondria to produce ATP
How does lactate move through the body?
It enters the bloodstream and flows into another working muscle, including the heart or the liver
What happens when lactate enters the liver?
It’s converted to pyruvate, then to glucose, and then sent back through the bloodstream to wherever it’s needed
What are ketones?
An acidic by-product of fatty acid metabolism, produced in the liver when glucose isn’t available
What hormones control ketones?
insulin and glucagon
What is insulin?
A hormone produced in the pancreas that regulates the metabolism of carbohydrates, fats, and proteins
What is glucagon?
hormone produced in the pancreas that increases levels of glucose and fatty acids in blood
What conditions force the liver to metabolize large amounts of fatty acids?
starvation, a severe illness or infection, or a chronic disease like diabetes
What happens if ketones remain elevated too long?
It can lead to ketoacidosis, a potentially fatal health problem
During exercise, ketones don’t typically play a significant role in ATP production. But when will they will have an effect?
A diet very low in carbohydrates
An ultralow calorie diet
An ultramarathon or another extreme endurance event
What percent of the brain’s ATP needs do ketones meet after 3 days and then several weeks without carbs?
30 and 70
Regardless of the fuel source, acetyl-CoA is the central metabolite that . . .
initiates the aerobic metabolism process within the mitochondria
The Krebs cycle is also referred to as the . . .
citric acid cycle
How many steps are in the citric acid cycle?
Eight
What are crucial products that contribute electrons to aerobic metabolism?
NADH and FADH2
What is the electron transport chain?
The stage where most of the ATP (32) is produced in aerobic metabolism
What happens during rephosphorylation?
The additional phosphate is broken down again for quick energy as part of the ATP-ADP cycle
What happens to the glucose molecule during anaerobic glycolosis?
It is split into a pair of pyruvate molecules to produce two ATP
Where is creatine found, and what do average stores depend upon?
Creatine is naturally found in muscle tissue
Average stores maintained will depend on overall muscle mass
Where is creatine synthesized?
in the liver and kidneys
What amino acids synthesize creatine?
methionine, glycine, and arginine
What is the long-term effect of metabolic acidosis?
Reprograms the cell to recycle ADP faster and reduce the oxidative stress of the process
What happens when lactate enters the liver and it’s not needed?
the glucose is converted to glycogen and stored in the muscles or liver to fuel future activity
What is the muscle’s primary potential source of H+ accumulation?
ATP hydrolysis
What is the goal of endurance training?
To develop the body’s ability to use stored fat as the primary fuel source, since fat provides a virtually limitless supply of energy
What happens as ATP-ADP cycle keeps running?
More protons build up in the cytoplasm, reducing the pH of the cell
How long does Full replenishment of stored phosphocreatine take after maximum effort exercise?
15–25 minutes
What is the currency of the human body that allows it to continually function?
Adenosine triphosphate (ATP)
How much ATP can the human body store?
Very little. Skeletal muscles have enough stored ATP to contract vigorously for just one or two seconds
What is muscle’s second fastest source of ATP?
Glucose
When stored glycogen runs low, glucose in the bloodstream is forced into the muscle cells and broken down in a process called glycolysis
