Lecture 4 Flashcards
Energy balance in terms of biological terms is described by the following equation:
Energy intake = internal heat produced (+external +internal work)
You don’t get _____% of calories consumed
100%
Cuz your body uses energy from food intake to absorb + process the nutrients
What does the body use the energy from calories for?
Breaking down food, generating heat, or lost as waste
Describe the law of thermodynamics
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
what happens to energy that’s lost in the form of heat (a form of energy)?
it is used to maintain core body temp
what is energy input? what happens during this?
energy in ingested food (chemical energy). cells capture portion in high-energy bonds of ATP; we capture these high energy bonds to produce ATP
what is energy output
aka external work. it’s the energy expended during muscle contraction to move external objects, or to move the body
energy from nutrients that is not used to perform work is? is this considered energy output or energy input?
transformed into thermal energy or heat. this is considered energy output
what percent of chemical energy in food is used to for biological work? what happens to the remainder?
25%, the rest is converted to heat which is used to maintain body temp
what kind of work (internal/external) is energy storage?
internal work
what is internal work
all other forms of bio energy expenditure that do not accomplish mechanical work outside the body
what’s an example of internal work, in terms of skeletal muscles
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
internal work is largely ____ stores
fat
what three possible states of energy balance are there?
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
what is the difference between basal metabolic race and metabolic rate?
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
what increases our energy expenditure
external work (muscles require more of that energy in order to perform a certain task)
what is the largest part of our energy need?
Metabolic rate
____ is more metabolically costly than any other tissues. Why?
muscle
it has high energy demands during contractions, and it utilizes energy even at rest to perform basic functions (ion transport, posture contractions)
to perform a BMR test, what are the following conditions that must be met?
- 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
why do we want to avoid consuming food 12 hours prior to the test?
digestion, absorption, and nutrient processing adds to energy expenditure and leads to an overestimation of your true BMR
what are some other factors that can increase metabolic rate ?
- 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
what is the primary determinant of BMR
thyroid hormone levels
what are factors influencing metabolic rate?
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
what is the rate at which energy is expended when you’re awake/lying still, and when you’re sitting at rest?
77 kcal/hr
100 kcal/hr
all of the chemical reactions that take place inside cells are part of our _____ _______
cellular metabolism
what can the potential energy stored within chemical bonds be harnessed for?
to perform work for biological processes
all reactions in out body require what to get started?
a certain amount of activation energy
what can we use enzymes for? what does this do?
a catalyst to lower the activation energy required for a certain chemical reaction to occur
it increases the reaction rate
T/F enzymes are all we need to fulfill a reaction
F we still need some input energy
what’s the most common input energy reactions use?
heat
T/F an enzyme is used to carry out multiple chemical reactions
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
why is it necessary to exhibit an enzyme
to reduce a reaction rate
explain competitive inhibition
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
explain non-competitive inhibition
an inhibitor molecule binds to the enzyme at a location other than the active site (allosteric site)
what does the inhibitor molecule do to the enzyme
it changes its shape, but the inhibitor is no longer in optimal position to catalyze the reaction
why would the noncompetitive inhibitor be less receptive to the binding site?
cuz it cam bind to another site
explain the metabolic regulation graph
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
why is it necessary to have a high rate of reaction?
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
what are allosteric activators
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
many enzymes only work when bound to non-protein helper molecules called ______ ________. what do these molecules do? what’s the most common one?
cofactors and coenzymes (on/off switch)
binding to these molecules promotes optimal conformation and function
the most common coenzymes are dietary vitamins
what is feedback inhibition? what has it been useful for?
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
does feedback inhibition stop the reaction all together?
no it only blocks the initial reaction. when enzymes have a greater effect then the substrate will eventually stop the reaction
in order to maintain chemical equilibrium ____
some products inhibit the enzymes will some reactants activate them
