Lecture 4

Question 1

Energy balance in terms of biological terms is described by the following equation:

Answer 1

Energy intake = internal heat produced (+external +internal work)

Question 2

You don’t get _____% of calories consumed

Answer 2

100%
Cuz your body uses energy from food intake to absorb + process the nutrients

Question 3

What does the body use the energy from calories for?

Answer 3

Breaking down food, generating heat, or lost as waste

Question 4

Describe the law of thermodynamics

Answer 4

Energy cannot be created or destroyed - energy is moved around, converted from one form to another; therefore there’s always going to be a balance between energy input and energy output

Question 5

what happens to energy that’s lost in the form of heat (a form of energy)?

Answer 5

it is used to maintain core body temp

Question 6

what is energy input? what happens during this?

Answer 6

energy in ingested food (chemical energy). cells capture portion in high-energy bonds of ATP; we capture these high energy bonds to produce ATP

Question 7

what is energy output

Answer 7

aka external work. it’s the energy expended during muscle contraction to move external objects, or to move the body

Question 8

energy from nutrients that is not used to perform work is? is this considered energy output or energy input?

Answer 8

transformed into thermal energy or heat. this is considered energy output

Question 9

what percent of chemical energy in food is used to for biological work? what happens to the remainder?

Answer 9

25%, the rest is converted to heat which is used to maintain body temp

Question 10

what kind of work (internal/external) is energy storage?

Answer 10

internal work

Question 11

what is internal work

Answer 11

all other forms of bio energy expenditure that do not accomplish mechanical work outside the body

Question 12

what’s an example of internal work, in terms of skeletal muscles

Answer 12

muscle activity for purposes other than external work (postural maintenance, contractions shivering)
all the energy-expending activities that go on continuously just to sustain life

Question 13

internal work is largely ____ stores

Answer 13

fat

Question 14

what three possible states of energy balance are there?

Answer 14

neutral energy balance = constant body weight
positive energy balance - energy input is greater than energy output; energy not use is stored primarily as adipose
negative energy balance - energy input is less than energy output; body must use stored energy to supply the body’s needs

Question 16

what is the difference between basal metabolic race and metabolic rate?

Answer 16

BMR is the minimal internal energy expenditure we need to maintain in order to meet basic physiological function in our body
Metabolic rate is the total amount of energy we need to expend (both internal and external) in order to perform a given task

Question 17

what increases our energy expenditure

Answer 17

external work (muscles require more of that energy in order to perform a certain task)

Question 18

what is the largest part of our energy need?

Answer 18

Metabolic rate

Question 19

____ is more metabolically costly than any other tissues. Why?

Answer 19

muscle
it has high energy demands during contractions, and it utilizes energy even at rest to perform basic functions (ion transport, posture contractions)

Question 20

to perform a BMR test, what are the following conditions that must be met?

Answer 20

• person shout be at physical rest - to avoid energy expenditure by your muscles
• person shout be at mental rest - brain utilizes a lot of glucose; increases BMR
• done at a comfortable room temp (body will expend energy to try and maintain body temp otherwise)
• no food consumed within 12 hours - can increase metabolism

Question 21

why do we want to avoid consuming food 12 hours prior to the test?

Answer 21

digestion, absorption, and nutrient processing adds to energy expenditure and leads to an overestimation of your true BMR

Question 22

what are some other factors that can increase metabolic rate ?

Answer 22

• thyroid hormone can increase metabolic rate as it leads to high metabolism
• caffeine increases BMR as it causes u to oxidize more fat
• fedra (form of enphetamine) causes a massive increase in out basal metabolic rate

Question 23

what is the primary determinant of BMR

Answer 23

thyroid hormone levels

Question 24

what are factors influencing metabolic rate?

Answer 24

TH levels
epi/norepi - will use energy to get away in a fligh/fight situation
exercise - BMR increases post-exercise; HR will be elevated=you’ll use more energy than you did right before
- an increase in muscle mass results in an increase in BMR (more calories to burn)
daily activities
sex/gender - men have a higher BMR than women; they also have a higher muscle mass=more calories to maintain itself
age - MR slows down with age; lose muscle mass, hormones goes down

Question 25

what is the rate at which energy is expended when you’re awake/lying still, and when you’re sitting at rest?

Answer 25

77 kcal/hr 100 kcal/hr

Question 26

all of the chemical reactions that take place inside cells are part of our _____ _______

Answer 26

cellular metabolism

Question 27

what can the potential energy stored within chemical bonds be harnessed for?

Answer 27

to perform work for biological processes

Question 28

all reactions in out body require what to get started?

Answer 28

a certain amount of activation energy

Question 29

what can we use enzymes for? what does this do?

Answer 29

a catalyst to lower the activation energy required for a certain chemical reaction to occur it increases the reaction rate

Question 30

T/F enzymes are all we need to fulfill a reaction

Answer 30

F we still need some input energy

Question 31

what’s the most common input energy reactions use?

Answer 31

heat

Question 32

T/F an enzyme is used to carry out multiple chemical reactions

Answer 32

F. each enzyme is only able to control a single type of chemical reaction. if an enzyme is not active the entire pathway will stop working

Question 33

why is it necessary to exhibit an enzyme

Answer 33

to reduce a reaction rate

Question 34

explain competitive inhibition

Answer 34

when an inhibitor molecule is similar enough to a substrate that it can bind to the active site and stop it from binding to the substrate it *competes* with the substrate to bind to the enzyme

Question 35

explain non-competitive inhibition

Answer 35

an inhibitor molecule binds to the enzyme at a location other than the active site (allosteric site)

Question 36

what does the inhibitor molecule do to the enzyme

Answer 36

it changes its shape, but the inhibitor is no longer in optimal position to catalyze the reaction

Question 37

why would the noncompetitive inhibitor be less receptive to the binding site?

Answer 37

cuz it cam bind to another site

Question 38

explain the metabolic regulation graph

Answer 38

in the graph: - the normal enzyme has a high rate of reaction, and it is the fastest to reach that state - the competitive inhibitor is slower to speed the reaction but eventually it reaches the maximum rate of reaction - non competitive inhibitor has a low rate of reaction because its not competing to bind to the enzyme

Question 39

why is it necessary to have a high rate of reaction?

Answer 39

the normal enzyme and competitive inhibitor need a high rate of reaction to be able to lure the substrate - if a normal enzyme had a higher (reaction rate) value than the competing inhibitor, it has a higher affinity to that substrate and will bind to the site

Question 40

what are allosteric activators

Answer 40

they can *increase the reaction rate:* once they bind to the enzyme they induce a conformational change (change in the shape) that increases the affinity of the enzyme’s active site for its substrate

Question 41

many enzymes only work when bound to non-protein helper molecules called ______ ________. what do these molecules do? what’s the most common one?

Answer 41

cofactors and coenzymes (on/off switch) binding to these molecules promotes optimal conformation and function the most common coenzymes are dietary vitamins

Question 42

what is feedback inhibition? what has it been useful for?

Answer 42

when a reaction product is used to regulate its own further production cells have evolved to use feedback inhibition to regulate enzyme activity in metabolism, by using the products of enzymatic reactions to inhibit further enzyme activity

Question 43

does feedback inhibition stop the reaction all together?

Answer 43

no it only blocks the initial reaction. when enzymes have a greater effect then the substrate will eventually stop the reaction

Question 44

in order to maintain chemical equilibrium ____

Answer 44

some products inhibit the enzymes will some reactants activate them