Metabolic Rate Flashcards
(141 cards)
1
Q
True or false: the metabolic rate of an animal impacts every other aspect of the animal’s physiology
A
True
2
Q
How is breathing affected by metabolic rate?
A
Breathing»_space; how much oxygen is needed»_space; how much energy is needed»_space; metabolic rate
3
Q
How is nervous physiology impacted by the metabolic rate?
A
Nervous tissue is energetically expensive»_space; complex nervous systems must find a way to increase max metabolic rate to be able to sustain the nervous system
or must find ways to reduce energy expending in other physiological processes in order to maintain the nervous system
4
Q
Ingested chemical energy
A
total amount of energy that is contained within all the foodstuffs that the animal is eating
5
Q
What is the goal of digestion?
A
take large complex molecules from ingested food and break them down into simpler organic molecules that can be absorbed into animal’s body
6
Q
Absorbed (assimilated) Chemical energy
A
Total energy contained into animal’s body after digestion occurs and the smaller/simpler molecules are absorbed into the animal’s body
7
Q
Fecal chemical energy
A
Represents the energy that was ingested but was not absorbed into the body
8
Q
True or false: feces are nothing but waste products
A
False. Feces do largely contain waste products, but mostly they contain any energy/molecules that were not able to be absorbed into the body
9
Q
What are some reasons that some nutrients were not able to be properly absorbed by the body?
A
- Some organic molecules are resistant to digestion, and if they can’t be digested easily they can’t be absorbed. Instead they will just be pooped out, and the enrgy they contained will be in the poop
- If food moves too rapidly through the digestive tract (diarrhea) there’s not enough time to absorb all the nutrients so lots of energy (even simple ones) being pooped out
10
Q
True or false: feces contain no energy
A
False. Feces DO contain energy but its just stuff that can’t be absorbed by the animal
11
Q
Why is absorbed/assimilated chemical energy considered energy input and not Ingested chemical energy?
A
Because the gut cavity (mouth + anus) is continuous w the external environment and is not considered to be a part of the body. It is only once the energy has absorbed that its gone from gut cavity into the living tissues/cells in our body –> thats when we consider it a part of our body
12
Q
What is the formula for absorption efficiency?
A
(Absorbed chemical energy / ingested chemical energy) x 100%
13
Q
What is considered a ‘good’ mean value of assimilation efficiency for animals
A
About 70-80%
14
Q
which foods are typically easier to digest?
A
Animal based foods and seeds
15
Q
Which foods are typically harder to digest?
A
Plant based foods (stems, leaves, fruits)
16
Q
Why are animal based foods and seeds easier to digest than stems, leaves, fruits, etc?
A
Animal based: more simple molecules like fats and more molecules that are not very resistant to digestion
Plants: large portion of organic molecules contained in plants are difficult to digest and break down (cellulose, lignins) –> animals have a harder time digesting and absorbing from them
17
Q
Do herbivores or carnivores tend to have higher absorption efficiencies, and why?
A
Herbivores tend to have lower absorption efficiencies than carnivores do (around 30-40%) because plants are harder to digest than animals are
18
Q
What does an animal’s absorption efficiency say about their feeding habits?
A
The higher the absorption efficiency is for an animal, the less time they need to spend eating.
time spent feeding = time spent being exposed to being preyed upon
so the more you eat, the more time you spend at risk of being eaten
as a result, herbivores tend to spend more time feeding (can spend a third of their day feeding) bc its so much harder for them to digest their foods
19
Q
Is it good to have a very high or very low absorption efficiency?
A
Very high: No. Too high puts you at risk of obesity, which puts you at risk of being preyed upon
Very low: No, very low means you must spend a majority of your time eating, which puts you at risk of being preyed upon
20
Q
Why is fat the preferred method of storing energy?
A
It is the most efficient method of storing energy per unit of weight. Almost 10x more energy is stored in a gram of fat than in a gram of glycogen or protein
21
Q
What makes fat so energy dense?
A
Lipids (fats) are more reduced than other fuel types –> more electrons present to be passed onto oxygen –> so the fact that it is more reduced makes it more energy dense
22
Q
How is energy derived in most animals?
A
energy is derived by taking electrons from molecules and giving them to oxygen
23
Q
What makes glycogen and proteins less efficient at storing energy than lipids?
A
water content –> lipids have v small amount of water (5% of a fat store is comprised of water bc lipids/fats are hydrophobic) –> so fats are stored in a dry state.
glycogen and proteins store much more water along with them (hydrophilic) –> when stored they MUST be stored in a wet form –> adds more weight to storage molecules without adding any extra energy
24
Q
True or false: fats are inherently more energetic than glycogen and proteins
A
True. lipids have 2x energy per unit energy mass dry weight
25
Do all organisms prefer fat as their storage molecule?
No. Sessile organisms and organisms experiencing periodic anoxia prefer other storage molecules
26
Why do sessile organisms not use fat as their preferred storage molecules?
Because unlike motile organisms, sessile organisms don't have to worry about their weight impacting them. They don't need to stay light weight to avoid predators like motile organisms do
27
Why do organisms experiencing periodic anoxia not use fat as their preferred storage molecules?
only way to derive energy from fat is aerobically --> so if youre periodically anaerobic (anoxic) then you dont wanna store energy as fat --> instead you might prefer glycogen bc you can derive energy from it both aerobically and anaerobically
28
Describe the basic physical structure of a mitochondrion
Has an outer and inner membrane. The inner membrane is highly folded to increase its surface area. Embedded within the inner membrane are components of electron transport to produce ATP
29
Why are storage molecules so important to the organism in terms of energy use?
Storage molecules like fats can also be oxidized and converted into ATP molecules, especially in between meals or during periods of fasting
30
Biosynthesis
Synthesis of biological molecules
31
What are the 2 major reasons an organism might undergo biosynthesis?
1. Growth and maintenance
| 2. Exported organic matter
32
Describe the relationship between ATP and growth and maintenance
1. for growth and maintenance --> if an animal wants to grow it must build or enlarge its cells --> must build proteins, phospholipids (for cell membrane) --> powered by energy contained within ATP
2. maintenance --> biological molecules break down over time, must then be replaced --> so even if not growing, the animal must still do lots of biosynthesis to replace any worn down biological molecules w/in the body --> some proteins only last a day or two before needing to be replaced --> ATP being used to build the new molecules
3. any biological molecules we've built can also be oxidized and converted into ATP at some point --> important during fasting n stuff --> or when theres organs that arent being used the body starts to break them down (like muscle atrophy --> turn the muscles into ATP)
33
Exported organic matter
represents a way that energy can flow out of animal bodies
energy contained in bonds of all the molecules that are being exported out of the body
34
Describe the relationship between exported organic matter and biosynthesis
biological molecules that are produced by the animal, are ultimately lost from the animal body
milk and hair
milk: female mammals make milk --> contains fats, proteins etc --> bio molecules the female produced and are incorporated into milk --> but then its lost when the lady feeds her baby
hair: synthesize lots of bio molecules in hair --> constantly losing hair all of the time
gametes: sperm --> male animals build sperm and then ejaculate it into females or just onto some eggs in an environment
offspring: bio molecules theyre taking up from the mom, then leave the body
urine: lots of bio molecules end up in the urine (amino acids n other N containing molecules) which then flows out into the environment
35
Work
Force x Distance
or
Change in kinetic or potential energy
36
What are the 2 types of work that animals can do?
Internal and external work
37
Describe internal work
work taking place inside animal body --> pumping blood or ions.
blood: blood is moving thru the circulatory system, moving against force of friction (up against blood vessel walls) so heart does work to push the blood against the friction force --> uses atp to contract muscles to generate pressure gradients to accomplish flow of blood against the blood vessels
ions: ion pump taking Na+ and pumping it across cell membrane thats already + charged --> moving an ion against he electrical gradient --> energy is required to do so (from ATP)
38
Describe external work
work of moving the body itself/moving objects outside of the body
running, flying, swimming, lifting things
39
Is the metabolism of animals aerobic or anoxic?
Aerobic. Storage molecules are converted to ATP through chemical oxidation when electrons are taken off of compounds and donated to oxygen molecules, which releases energy which is then converted into ATP molecules
40
What are the 2 laws of thermodynamics in terms of biological energy use
1. The quantity of energy in the universe is constant. This does not prohibit energy transductions from occurring
2. Every time a process occurs, the quality of energy int he universe decreases. Some amount of high quality is transformed into low quality energy whenever a process occurs
41
Free energy
Energy that is available to do work. Also known as high quality energy. This includes every type of energy in the universe except for heat energy
42
Is heat energy considered high quality energy?
No, heat energy is considered to be low quality energy because it cannot do biosynthesis or work within biological systems. Thus, heat energy is also not considered to be free energy
43
Thermodynamics
The study of energy and its transductions. Quality and quantity of energy are governed by the laws of thermodynamics
44
Metabolic rate
The rate at which animals convert absorbed chemical energy into heat energy, external work, and exported organic matter. The rate at which energy flows through animal bodies. Also known as metabolic power
45
Why is metabolic rate also known as metabolic power?
Power = energy use per unit of time
| which is the same thing as rate
46
What are the 2 fates of heat energy in the body?
1. stored in the body (body heat)
| 2. flows out of animal body --> flows to the surrounding environment
47
What are the 3 major ways that energy flows out of the body?
1. exported organic matter
2. external work
3. heat energy
48
True or false: when animals do internal/external work and that work gets undone it results in heat
True. ex: if a Na+ ion is pumped thru a membrane and then leak back from where it came from down its electrical gradient --> then the internal work is being undone, which leads to the production of heat
so heat can also manifest from the undoing of internal work
external work: when its undone it also results in heat --> heat that comes from external work being undone is already outside of the body bc thats where its being produced, so the heat isnt leaving the body in that case since it already left when the work was initially done
ex 2: ex: throwing a ball --> giving it kinetic energy --> it is caught --> that energy is dissipated as heat
49
Calorimetry
Measures heat given off by animal body, a major way of measuring the metabolic rate of an animal
50
Direct calorimetry
Directly measures the metabolic rate of an animal by measuring the heat production/heat loss by the body
51
How does a direct calorimeter work?
Experimental animal is placed into a chamber, which is surrounded by 2 ice jackets. The inner jacket empties out into a pot. As the animal metabolizes it gives off heat to the environment, which melts the inner ice jacket. The outer ice jacket is used to intercept environmental heat and prevent overestimation of the metabolic rate of the animal
52
How do we measure metabolism through direct calorimetry?
Since we know how much heat energy it takes to melt 1g of ice into water, we can measure the weight of water melted by the heat of the animal over a set period of time, to then calculate the metabolic rate in Watts.
ex. if 10g of water = 3340J needed to melt over a unit of time --> convert the time into seconds --> we can use that to calculate the metabolic rate in Watts
53
What is the latent heat of melting
The amount of heat energy required to melt 1g of ice into water, 334 J/g
54
Antoine Lavoisier
Created direct calorimetry and respirometry
55
Indirect calorimetry
A way of estimating how much energy is flowing out of the body without directly measuring the energy. Used because calorimetry is very complex
56
What are the basic methods used in respirometry?
Measure oxygen consumption rates to infer the metabolic rate of the animal. Do this by using a tube to send air with a known oxygen concentration into a chamber, and then comparing that to another tube taking air out and measuring how much oxygen came out of the chamber
57
What are some limitations to respirometry?
Assumes that all the energy the animal is producing is flowing out of the body. It is possible that
58
What is another way that metabolic rate is measured using direct calorimetry
Evaporation within the chamber is measured. it takes a certain amount of heat energy to evaporate water, and water is constantly evaporating from our bodies,. Water vapour won't melt the ice in the inner jacket so we can't measure this directly with the calorimetry device, instead we measure the increase in water vapour over the same period of time. We can do his since we also know the latent heat of evaporation
59
What is a drawback to respirometry?
Very complex, and neglects the 2 other ways that energy is coming out of the body
60
Does respirometry overestimate or underestimate metabolic rates when the animal is growing/storing energy?
Overestimate, because it assumes all energy is flowing out of the body, not remaining inside the body
61
What are the fundamental assumptions we must make when using respirometry?
1. Metabolism is fully aerobic
2. Stored oxygen is not being used
3. All energy flows out of the body and is not being stored or used for growth
62
Under what circumstances would we underestimate the metabolic rate when using respirometry?
If the organism is using anaerobic respiration.
63
Do aerobic or anaerobic metabolic pathways have longer endurances?
Aerobic. Aerobic glycolysis can last for 5-7 hours, and aerobic lipolysis can last for days to months in humans.
Anaerobic pathways can last for a few seconds to a few minutes
64
What are 2 major anaerobic metabolic pathways
Creatine Phosphate: pathway for producing ATP from creatine phosphate, capacity is 10-20 seconds, animals don't store large amounts of creatine phosphate, so they quickly exhaust these supplies when using them to make ATP
Lactate fermentation: AKA anaerobic glycolysis. When lactate is present we know that anaerobic metabolism is taking place bc it's a physiologically disturbing molecule. Eliminating lactate from the cell results in acidification of blood. so we can only undergo anaerobic glycolysis for short periods of time, usually a few seconds to minutes
65
Why must we assume that stored oxygen is not being used when conducting respirometry?
Because respirometry measures how much oxygen the animal takes and uses from its environment. If the animal is using stored oxygen then we won't see that with our techniques
66
What is an example of an animal that would be impossible to conduct respirometry on?
A diving marine mammal (like whales or dolphins). When swimming, they use stored oxygen within their blood, lungs, and muscles to power their metabolism
67
RER
Respiratory Exchange Ratio. A way to infer what fuels an animal is oxidizing. Measured as CO2 production rate divided by O2 consumption rate
68
Why are CO2 and Oxygen used to calculate RER?
CO2 is a byproduct of aerobic metabolism, and the ratio of oxygen to CO2 changes depending on what fuel type is being used.
69
What is the usual range for RER
0.7 to 1.0.
for chemical oxidation of steric acid --> 26 mols of o2 consumed to produce 28 mols of co2 --> RER of 0.7
for glucose oxidation: for every mol of oxygen consumed there is a mol of co2 produced --> RER for animal only oxidizing carbs = 1.0
70
What does it mean if the RER is between 0.7 and 1.0?
A mix of carbs and fats are being oxidized, not just one or the other
71
True or false: RER values never go outside of the range (0.7 to 1.0)
False
72
What might an RER value of 0.85 suggest?
Normally this would mean a good mix of fats and carbs are being used as a fuel source, but if there is reason to believe the animal is starving itself then there is a good chance the animal is oxidizing proteins, not fats or carbs
73
What are exceptions to the following statement: "Animals do not generally oxidize proteins for energy?"
1. When starved or fasting, animals will oxidize significant numbers of proteins, usually proteins are in functional tissues and muscles, not stored in reserves, leading to muscle atrophy
2. When excess protein is present in a diet, animals will start to oxidize these proteins for energy
74
What does a lower RER value suggest?
Suggests that the organism is oxidizing more fats
75
What happened when mice were fed a plant with anti obesity properties?
They saw a significant decrease in their RER whether or not they were fed high/low fat diets. This suggests a shift towards more fat oxidation and less carbohydrate oxidation, which helps animals lower their body weight by encouraging them to oxidize their fatty acids instead of just storing them
76
Why can't we be sure of what fuel an animal is oxidizing even if we know the exact composition of its diet?
There is no guarantee that when an animal is feeding on a particular diet that it is oxidizing from that diet, it could be storing those food molecules and metabolizing other stored molecules
77
What must we do when an RER value is well outside of the expected range?
We must hypothesize why this may be the case with other given info
78
Overall dynamic body accelerometry
another form of indirect calorimetry. measures the acceleration of an animal
79
Why do we measure the acceleration of an animal to determine its metabolism?
```
Work = force x distance
energy = work
energy = the capacity to do work
```
```
force = mass x acceleration
energy = mass x acceleration x distance
```
if we measure acceleration of organism it should be proportional to energy the animal is spending
over fixed amount of time --> proportional to energy use of animal over same period of time --> energy over time = metabolic rate
so as movement speed increases, total amount of acceleration measured also increases, so the metabolic rate also increases
80
What is a downside to overall dynamic body accelerometry?
Only accounts for energy expended via movement, so we can't know if the animal's metabolic rate increased for non-movement related reasons
81
Doubly-Labelled water technique
Measures the field metabolic rate of animals by injecting DL water into an animal, releasing it, and then recapturing it. After recapture a blood sample is taken to measure how much of the isotopes from the DL are left in the body to measure the rate at which they disappeared from the body. then compare the initial amount of DL isotopes to the final amount of DL isotopes to determine the rate
82
How does the doubly-labelled water technique work
Relies on the fact that DL water is made up of 2 heavy isotopes, O18 and H2. DL water is much rarer - regular water (H1 and O16) makes up 99.9% of all existing water, so scientists are able to track it much easier
83
Field metabolic rate
The metabolic rate of an animal in its natural environment as it goes about its regular behaviours
84
What is the main drawback to Doubly-Labelled Water Technique?
Super expensive bc not many labs produce the heavier isotopes to produce the DL water.
and
its often impossible to recapture every single animal after the initial capture
85
How do the isotopes from DL water exit the body?
In the form of CO2 and H20
| CO2 is breathed out, water is evaporated off the body and excreted in the urine.
86
How do the isotopes from the DL water end up in CO2?
CO2 and water are in equilibrium with each other in the body
CO2 and H2O react together to form carbonic acid
when carbonic acid returns into H2O and CO2 --> dont know which oxygen molecule ends up where --> so it could go back to a water molecule OR go back to a CO2 molecule
87
Why is it important for animals to try to maintain constant sizes for their energy stores throughout their life?
too big = obesity
too small = during periods of fasting/starving you may starve to death --> cant sustain your body if you dont have good energy stores
88
Energy balance
When the amount of energy used by the animal is equal to the amount of energy absorbed
89
How do animals ensure that their energy stores remain constant throughout their life?
Ensure energy intake matches energy expenditure
90
Which homeostatic signals allow us to regulate and maintain our energy stores?
leptin, ghrelin, insulin --> provide info to body abt how much fat (leptin), carbs (insulin) and food energy in the digestive tract (ghrelin) there are --> 3 major energy stores in our body
send signals to the brain to tell ithow much of each stores there are to regulate energy intake and expenditure
too low: decrease energy expenditure or increase energy intake (by triggering hunger) to bring in more energy stores
91
What are a few situations where it would be useful to know an organism's energy balance requirements?
Vets: treating obesity in pets
Zoos: knowing how much to feed animals
Astronauts: desire to send ppl to mars, and we know thats a long trip, and you gotta make sure theres enough food on the ship to meet the expenditure demands of the ppl on the trip relatively healthy --> if we know metabolic rate of humans we can put enough food on the ship but also not more food than necessary bc that can lead to obesity AND lead the ship to becoming too heavy
92
BMR
Basal metabolic rate. Lowest level of metabolic rate that is compatible with conscious lif
93
True or false: if an animal goes below BMR they will die
False. Torpid metabolic state is lower than BMR, and occurs wen animals go into torpor (hibernation)
94
Torpid metabolic rate
Lowest level of MR an animal can achieve whilst still maintaining life. Reduced capacity to respond to stimuli
95
Supramaximal metabolic rate
Anaerobic, unsustainable. The highest MR an animal can achieve, but only lasts a short period of time
96
Maximal (peak) metabolic rate
Maximum metabolic rate that an animal can sustain for long periods of time via aerobic metabolism. Can last longer, only limiting factor is energy stores
97
Resting metabolic rate
Rate at which animal is resting, Must be conscious but not active
98
Aerobic scope
Rate of rate of energy utilization available for activities above BMR/SMR (e.g., thermogenesis, locomotion, feeding, reproduction, etc.) The rate at which animals can do anything is dependant on the aerobic scope.
99
What does the aerobic scope of an animal determine?
Its ability to utilize energy --> the rate at which it can do so. The reason that even if an individual has lots of energy stored it can't run super fast -- must have an aerobic scope that allows for fast energy utilization in order to be fast
100
How is aerobic scope calculated?
Take animal's maximal MR and subtract the BMR
101
True or false: the field metabolic rate of an animal remains stagnant
False. It could be anywhere between resting and maximal metabolic rate value, depends on how active the animal species is
102
How is Maximal metabolic rate determined?
a common way of measuring this is just putting an animal on a treadmill and increasing the speed to see how fast they can go and sustain for a while
103
How is MMR measured in fish?
ircular system of tubes, the removable test section is where the fish gets placed
propellor spins, causes water to flow thru the tubes, pushing the fish
fish needs to swim to stay within the test section and not get slammed against the screen
increase propellor speed over time to speed up water flow rate
keep turning up until fish cant swim any faster, then measure metabolic rate of fish at the fastest speed it can go
also oxygen sensors built in --> so use respirometry to measure the MR
104
How can we be sure that MMR has been achieved when examining a blood sample?
If there is a product of anoxic metabolism (such as lactate), this means that the animal can no longer sustain themselves using only aerobic metabolism --> meaning they went above their MMR
105
True or false: Time spent at MMR is not significant to a fish's life
False. Though many fish only spend up to 5% of their time at MMR, this time is related to their fitness (ex. reproduction, survival, ability to pass genes to next gen)
106
What are the two major hypotheses for what determines the value of MMR?
Central limitations hypothesis and Peripheral limitation hypothesis. These theories are mutually exclusive to one another
107
Central limitation hypothesis
Value of MMR is determined by the capacity of animals to acquire oxygen and nutrients from their environment and deliver them to the tissues of their body --> The central machinery (ex. lungs, heart) are what determines the MMR
108
Peripheral limitation hypothesis
Value of MMR is determined by the capacity of tissues to use nutrients and oxygen delivered to them to produce ATP, and power biosynthesis/work using that ATP
109
How might one test if the Central Limitation Hypothesis is true for a given animal?
Measure the MMR of animals in various ways
ex. thermal exposure, have them lactate, or have them exercise.
according to CLH, the MMR should remain the same each time
110
Symmorphosis
The idea that it doesn't make economic sense for an animal to have a limitation in one part of the body system because that would lead to excess somewhere else. Every step in the biological process/pathway should have equal capacity and shouldn't limit one another
111
What is a major counterpoint to symmorphosis?
Safety margins: if capacity of the mechanism with a higher rate gets knocked down, the MMR won't be negatively impacted. If the levels of each are exactly equal, then having one component be damaged would lead to a decreased MMR
112
Under what conditions must an endothermic animal be when measuring its BMR?
- in its thermoneutral zone
- at its typical body temperature (e.g., not torpid)
- post-absorptive (not post-prandial)
- resting (but awake)
- nonreproductive
- unstressed (acclimated to lab conditions)
113
Why must an animal be post-prandial when measuring its BMR?
Post prandial = just eaten a meal, if theyve just eaten a meal they will be metabolising it so we can't measure its BMR (eating, absorbing, digesting, etc) --> must be post absorptive (same as pre feeding condition)
costly for animals to ingest, digest, absorb their meals
114
True or false: you can measure an animal's BMR if it is in torpor
False. Torpor = not in a conscious state --> Basal metabolic rate = lowest MR possible to maintain conscious life. Torpid = unconscious
115
How does reproduction impact MR?
Reproduction increases MR. Additionally, lactation GREATLY heightens MR bc there's a higher amount of exported organic molecules during that stage
116
How do stressors impact MR?
Positive correlation between change in MR occurred when exposed to stressor and the level of cortisol
more stressed = more cortisol = higher MR
117
Can we use cortisol levels to measure MR?
Yes, bc cortisol directly impacts MR bc it signals the body to start mobilizing resources and raising the MR to deal w the stressor
118
Under what conditions must the SMR of an ectotherm be measured?
post-absorptive
- resting - nonreproductive
- unstressed
- must report the temperature at which SMR was measured -should be acclimated to that temperature
119
What happens if one of the conditions is not met when measuring an animal's BMR/SMR?
It is considered RMR instead
120
Why are the conditions for measuring the BMR/SMR different between endotherms and ectotherms?
Because ectotherms don't use their metabolisms to regulate their body temperature, and we also don't know if they sleep or not.
121
What is the relationship between FMR and BMR?
Positive correlation between the two, meaning that a major factor that contributes to an animal's FMR is its BMR --> which means it's a contributing factor to how much food an animal can get and how much they eat
122
What are the 3 most significant contributors to BMR?
Proton leak (18%), protein synthesis (20-24%), Na/K-ATPase (15-22%)
123
Why does protein synthesis account for such a large portion of BMR?
Native proteins have a fairly short half-life -->30 mins to 43 hours --> so damaged proteins must constantly be replaced and rebuilt
124
Why is it important to have a good amount of protein in our diets?
Proteins are lost from animal bodies over time, such as in urine, the skin, in hair, gametes, and in milk. Its important to have proteins in our diet to be able to reduce proteins within our bodies
125
Why does Na/K ATPase contribute so much to BMR?
in every single animal cell membrane in body --> uses energy of ATP to pump Na+ out of cell and into extracellular fluid, pump K ions into cell
create Na/K electrochemical gradient
for all cells, Na/K electrochemical gradient are v important --> cell membrane isnt perfectly impermeable to these ions --> can leak across, flow down their electrochemical gradient and undo the work of the pump --> the pump must keep repumping the ions across the cell membrane --> so we have constant expenditure of energy here --> represents major energy expenditure pathway
126
Gluconeogenesis
making glucose from noncarbohydrate precursors --> energy requiring process and only happens under conditions when not feeding --> post absorptive state to help build glucose when not consuming it
127
Why does proton leak contribute so heavily to BMR?
The e- transport system in the mitochondrion membrane oxidizes foodstuffs and uses the released energy to move protons across the inner mitochondrial membrane space to generate a proton gradient. Sometimes sometimes protons go back across the inner mitochondrial membrane via ATP synthase independent routes, which contributes almost 20% to BMR bc when they leak in this way the ET system must expend more energy to pump the protons back into intermembrane space to maintain high proton motive force to allow for ATP production to occur
128
Proton leak
when electrons move back across the inner mitochondrial membrane via ATP synthase independent routes
129
Membrane pacemaker hypothesis
Major factor in determining BMR is the leakiness of its cellular membranes, which is related to its composition. The more unsaturated fatty acids there are in a membrane, the leakier it will be, and the higher the BMR will be, because you need to expend more energy to pump the ions back across the membrane
130
Explain the difference in saturated and unsaturated fatty acids
Saturated: all carbons on the hydrocarbon tail are fully saturated (have no double or triple bonds). Allows them to stack together closely
Unsaturated: One or more of the carbons on the hydrocarbon tail have a double or triple bond. Leads to a kink in the tail, which makes it harder for them to pack closely together, creating leakiness
131
Which glands have the highest effect on BMR?
Pituitary and thyroid. The adrenal and gonads/ovaries don't impact BMR bc:
adrenal: cortisol - for stress
gonads/ovaries: reproductive hormones
animal can't be stressed or reproductive when measuring BMR
132
What effect do thyroid hormones have on BMR?
T3 and T4 (thyroxin) lead to an increase in mass independent BMR
positive correlation between T3 in blood plasma and mass independent BMR --> but remember that if an animal wants to MINIMIZE BMR they will also minimize the amount of thyroid hormones in the blood
133
Is T3 or T4 more potent and which has a greater effect on BMR?
T3
134
What does the scaling coefficient describe?
It's the slope of the line, determines whether or not there is a linear relationship between 2 perameters
135
Positive allometry
Scaling coefficient is greater than 1. means that as one variable increases, the other increases at a faster rate
136
Negative allometry
When scaling coefficient is between 0 and 1. Means that as one variable increases the other increases as well, but the slope of the line starts to increase less and less
137
isometric scaling
when the scaling coefficient = 1. a linear relationship
138
What is the scaling coefficient of the relationship between body mass and BMR?
0.69 --> negative allometry. Means that as animal size increases, its mass specific basal metabolic rate decreases --> smaller animals have higher BMR relative to larger animals
139
Does BMR scale with negative allometry for non mammals as well as mammals?
Yes, for ectotherms, endotherms, and unicellular organisms, all slopes displayed negative allometric scaling, meaning that in all cases, smaller organisms have higher BMRs per gram in relation to organisms with higher masses. this is a universal feature of life
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What does the surface law try to explain?
Tries to explain why BMR/SMR scale with negative allometry. Earliest hypothesis to explain this phenomenon
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Surface law
The reason there's a negative allometric relationship between body mass and BMR is because of geometric principles. As shapes (and animals) get bigger, their surface area to volume ratio gets smaller, as volume increases faster than volume. Since body mass is proportional to volume, and volume determines body weight, the two are proportional. Additionally, BMR is proportional to heat loss, and heat loss is proportional to surface area. So surface area is proportional to length of a shape squared, meaning the scaling exponent that relates body mass to BMR should be 2:3, or 0.67
