Chapter 2 Flashcards
What are substrates?
fuel sources from which we make energy
What are the 3 sources of fuel?
carbohydrates, fats, and proteins
What are bioenergetics?
chemical pathways that convert substrates to energy
What level are bioenergetics performed at?
the cellular level
What is metabolism?
chemical reactions in the body
How is energy measured in biological systems?
calories
What does 1 calorie (1 cal) = ?
the amount of heat energy needed to raise 1 g of water 1 degree celsius
How is energy expressed in humans?
kilocalories (kcal)
1 kcal = ?
1,000 cal, which also = 1 Calorie (dietary)
How is energy used in myofibrils?
it causes the sliding of actin and myosin filaments resulting in muscle action and force generation
When is energy released?
when chemical bonds are broken
Why is food not used directly for cellular operations?
the molecular bonds in substrates are weak and provide little energy when broken
How is energy in food’s molecular bonds released?
they are chemically released within our cells and then stored in the form of ATP
What energy does the body need at rest?
50% carbs and 50% fats
What substrate provides little energy for metabolism?
proteins
How do proteins help with energy?
important for enzymes that aid chemical reactions and are structural building blocks
During intense, short-term exercise, what substrate is being used?
more carbs are used
During longer, less intense exercise what substrate is being used?
more fats and less carbs
What percentage of carbs are being used in high intensity exercise?
95% CHO
What is a major benefit of HIIT training
a bigger calorie expenditure compared to continuous exercise
What substrate is used more in anaerobic exercise?
carbs
What substrate is used more in aerobic exercise?
fats
What are all carbs converted to?
glucose
How much energy do carbs give you?
4.1 kcal/g
How many kcals of carbs are stored in the body?
2500 kcals
Where is extra glucose stored in the body?
the liver and muscle
What is the extra glucose in the liver and muscle called?
glycogen
Where is glycogen stored?
in the cytoplasm of muscle cells until those cells use it to form ATP
When are muscle and liver glycogen stores limited?
when the diet has an insufficient amount of carbs and can be depleted during prolonged, intense exercise
What do we rely on to replenish our carb reserves?
starches and sugars
What happens to muscles when there isn’t a sufficient carb intake?
muscles are deprived of their primary energy source
What energy source is used by brain tissue?
carbs
Severe carb depletion causes what in the brain?
negative cognitive effects
How do fats contribute to energy?
they provide a large portion of energy used in prolonged, less intense exercise
How much energy do fats give you?
9.4 kcals/g
How many kcals of fats are stored in the body?
+70,000 kcal stored in the body
Why is fat less readily available for cellular metabolism?
it must be broken down to its basic components of glycerol and 3 free fatty acids (FFAs)
What is only used in fats to form ATP?
FFAs
How does fat have a high net ATP yield?
more energy is derived from breaking down a gram of fat than from the same amount of carbs
Why can’t fat meet all the energy demands of intense muscular activity?
the rate of energy released from fat is too slow
When is protein used as an energy source?
in the case of severe energy depletion
What does protein need to be converted to before it produces energy?
glucose
What is gluconeogenesis?
when protein or fat is converted into glucose
What is lipogenesis?
the process of converting protein into fatty acids
Why is lipogenesis used?
for energy storage and cellular energy substrate
What percentage of energy can protein supply to the body to sustain prolonged exercise?
10%
What basic unit of protein can be used for energy?
amino acids
How much energy does protein give you?
4.1 kcal/g
Free energy has to be released from what?
chemical compounds at a controlled rate
What is the controlled rate determined by?
the availability of the primary substrate and enzyme activity
What does the availability of a substrate do for the controlled rate?
it increases the activity of that particular pathway
What is mass action effect?
the influence of substrate availability in the rate of metabolism
What is catabolism?
enzymes speeding up the breakdown of chemical compounds
How do enzymes speed up reactions?
by lowering the activation energy required to begin the chemical reaction
Most enzymes end with what suffix?
-ase
What enzyme breaks down ATP and releases stored energy?
ATPase
Each step in a biochemical pathway requires what?
to be catalyzed by a specific enzyme
What happens when there is an increase in enzyme activity?
an increased rate of product through a metabolic pathway
What is a rate limiting enzyme?
an enzyme in a metabolic pathway in control of the reaction’s overall rate
What is the activity of a rate limiting enzyme determined by?
the accumulation of substances down the pathway that decreases enzyme activity through negative feedback
Negative feedback is like what for ATP?
it’s like a thermostat. it either kicks on or kicks off ATP
What is the immediately available source of energy for almost all bodily functions?
ATP
What is an ATP molecules composed of?
adenosine and 3 inorganic phospate (Pi) groups
How is ATP broken down to release energy?
ATP molecules combine with water and are acted on by ATPase then the last phosphate group splits away, rapidly releasing free energy
What is phosphorylation?
when a phosphate group (Pi) is added to a low energy ADP to generate ATP
What is substrate-level phosphorylation?
when ATP is generated without oxygen availability
What is oxidative phosphorylation?
when ATP is generated with oxygen
How much ATP can cells store?
only limited amounts of ATP because it must constantly generate new ATP to provide energy
What three metabolic pathways do cells use to generate ATP?
the ATP-PCr system, the glycolytic system, and the oxidative system