Flashcards in Chapter 4-6 Deck (96):
what is the AVERAGE heat of combustion of CHO, fats, protein in bomb calorimetry vs in body
CHO 4.2 kcal/g
fats 9.4 kcal/g
protein 5.65 kcal/g
CHO 4 kcal/g
fats 9 kcal/g
protein 4 kcal/g
why is the average heat of combustion so different for proteins in bomb calorimetry compared to the human body ?
5.65 vs 4
it is due to the NH2 group.
We do not combust NH2 in our body, we produce urea from breaking it down, therefore it won't be in our body's heat of combustion
what is a bomb calorimeter ? go through the steps of its usage
apparatus that has pressurized O2 in a shell surrounded by water and fiberglass.
flip switch to set off ignition to start combustion
calorimeter will measure the heat that is produced as you combust different things (eg 1g fat or 1g CHO)
what property of the thing being combusted does heat of combustion depend on ?
it depends on the structural composition and the arrangement of atoms. also, for protein, the heat of combustion will depend on the relative nitrogen content.
what do the average heats of combustion tell us about the liberation of energy per gram for the three different macromolecules ?
CHO 4.2, fats 9.4, protein 5.65
lipid oxidation liberates significantly more energy than carb or protein metabolism (65% more than protein and 120% more than carbs)
why does lipid oxidation release more energy ?
it has to do with the number of hydrogen atoms in different macromolecules. lipids have more H available for cleavage and subsequent oxidation than other macromolecules.
what is coefficient of digestibility ?
it takes energy to digest, so it takes away approx 5% of energy store. therefore when we ingest a macromolecule we are only using 95% of it, for example.
percentage of ingested food digested and absorbed to meet metabolic needs.
what substance reduces the coefficient of digestibility?
A high-fiber meal has less total energy absorbed than a fiber free meal or a low fiber.
what is the average coefficient of digestibility for carbs, fats, proteins ?
if a person wishes to lose weight, what sort of food with what sort of coefficient of digestibility is recommended ?
coefficient of digestibility = percentage of ingested food digested and absorbed to meet metabolic needs.
therefore, if we want less food to make it into metabolism, we would choose a food with a lower coefficient, for example vegetables (plant proteins have a lower coefficient of digestibility than 92)
what are Atwater general factors ?
net energy (digestibility % * heat of combustion) available for consumption
what is the digestibility and net energy for protein ?
heat of combustion 5.65 avg
digestibility from 97 (animals, net energy 4.27)
to 83 (vegetables, net energy 3.11)
what is the digestibility and net energy for fats ?
heat of combustion 9.4 avg
digestibility from 95 (animals, net energy 9)
to 90 (vegetables, net energy 8.37)
what is the digestibility and net energy for carbs ?
heat of combustion 4 avg
digestibility from 98 (animals and cereals, net energy 4.11) to 90 (fruits, net energy 3.6)
is cellular respiration exergonic or endergonic ?
exergonic- it releases potential energy in the form of ATP
how is ATP used to create macromolecules ?
ATP, created with exergonic reaction of cellular respiration, can then be used to aid endergonic reactions.
glucose + ATP = glycogen
glycerol + fatty acids + ATP = TG
amino acids + ATP = protein
what is the mechanical, chemical, and transport work that ATP does ?
mechanical - in muscles
chemical- in endergonic reactions
transport- in active transport, like the sodium and potassium pump.
where does cellular respiration occur ?
in the mitochondria of the cell
what is the formula of cellular respiration ?
glucose (C6H12O6) + 6O2 ---> 6H2O + 6CO2 + ATP
what is oxidation ?
transferring O2, H, or electrons, causing a loss in electrons
what is reduction ?
what is a reducing agent ?
substance that donates or loses electrons as it oxidizes
what is an oxidizing agent ?
electron acceptor, gains electrons or reduces them
what is the configuration of the inner membrane ? how does it encourage transfer of chemicals through it ?
70% lipid 30% protein, so it's lipophilic and; enables chemicals to come through
what are cytochromes ?
enzymes that take electrons and pass them to one another down a chain. NAD donates electrons to electron acceptors on these cytochromes.
what is ATP composed of ?
adenosine (ribose + adenine) triphosphate (3 phosphates)
the 3 phosphates lead to high energy phosphate bonds between the groups which are released in hydrolysis.
how does ATP work as an energy transfer agent ?
it traps original food's potential energy and readily transfers this trapped energy to other compounds to raise their energy level
what is the formula of ATP hydrolysis ?
ATP + H2O ---> ADP + Pi - 7.3 kcal/mol (released free energy available for work)
what is the formula for pyruvate going to lactate ? what kind of reactions are there ?
pyruvate + NADH ---> lactate + NAD+
basically oxidation is losing electron so
NADH ---> NAD+ + H+ +2e-
reduction, gaining electron
pyruvate + 2e- --> lactate
how ATP is stored at any time in the body ?
80-100g (a very small amount)- enough to power a few seconds of maximal all out activity
how does ATP overcome its storage limitation ?
by constantly resynthesizing to never deplete levels in skeletal muscle except under extreme physical activity conditions
what are the 3 main sources for ATP synthesis ?
glycogen, fats, and phoshocreatine
6 fuel sources for ATP
- TG and glycogen in muscle
- blood glucose derived from liver glycogen
- intramuscular and liver derived carbon skeletons
- anaerobic reactions in cytosol
-phosphorylation of ADP with PCr with creatine kinase and adenylate kinase.
what enzyme is needed for step 1 of glycolysis ? what are its 3 functions ?
step 1 is ATP donating Pi to glucose to become glucose 6-phosphate.
HEXOKINASE needed to speed up the process and to take up glucose and create G-6-Pi
in step 2 of glycolysis what happens with G-6-pi (glucose 6-phosphate)? what enzyme is needed ?
in step 2 we need glucose 6-phosphate isomerase in order for G-6-Pi to become F-6-Pi.
in step 3 of glycolysis what happens to fructose 6-phosphate ? what enzyme is needed ?
in step 3 ATP donates another Pi to fructose 6-phosphate for it to become fructose 1,6-diphosphate. needs PFK for that.
what is the rate limiting substance in glycolysis ?
PFK, activated by ADP and Pi
if it's not maximally activated process of glycolysis stops there.
at what step of glycolysis can it stop if it doesn't have enough activation of the rate-limiting substance ?
rate limiting substance = PFK
step 3 of glycolysis cannot happen without maximal activation of PFK.
which two steps of glycolysis utilize 2 ATP ?
1 ATP at step 1 (when glucose goes to glucose 6-phosphate with the help of hexokinase)
1 ATP at step 3 (when fructose 6-phosphate goes to fructose 1,6-diphosphate with the help of PFK)
what inhibits the production of PFK and by which mechanism ? what sort of buildup would occur ?
negative feedback inhibits PFK production when there is a high [ATP]. therefore glucose 6-phosphate would buildup without a reaction.
what happens with fructose 1,6-diphosphate in step 4 of glycolysis ?
with aldolase, the 6 carbon sugar splits in 2.
becomes two 3-phosphoglyceraldehyde, basically two 3 carbon sugars with a phosphate group each.
in step 5, which enzyme converts the two 3-phosphoglyceraldehydes between themselves ?
in step 6 of glycolysis, what coenzyme is produced ? with the help of which enzyme ?
NAD is reduced, NADH is produced with the help of glyceraldehyde 3-phosphate dehydrogenase, making the two 3-phosphoglyceraldehydes into two 1,3-diphosphoglycerates. (also need to add phosphate with Pi)
in which step is 2 ATP produced first ?
in step 7, when phosphoglycerate kinase enables 1,3-diphosphoglycerate to become 3-phosphoglyceric acid x 2
in step 8 of glycolysis, which enzyme converts 3-phosphoglyceric acid into 2-phosphoglyceric acid ?
when is water produced in glycolysis ?
in step 9, with enolase, 2-phosphoglyceric acid becomes 2-phosphoenolpyruvate
in step 10, what happens ?
2-phosphoenolpyruvate becomes pyruvate with pyruvate kinase. 2 ATP produced
in which steps are the 4 ATP produced ?
in step 7, 2 ATP when 1,3-diphosphoglycerate goes to 3-phosphoglyceric acid with the help of phosphoglycerate kinase
in step 10, 2 ATP when phosphoenolpyruvate becomes pyruvate with pyruvate kinase.
what is the net ATP balance of glycolysis
2 (2 used, 4 produced)
list the 10 enzymes needed for glycolysis
5) triosephosphate isomerase
6) glyceraldehyde 3-phosphate dehydrogenase
7) phosphoglycerate kinase
8) phosphoglycerol mutase
10) pyruvate kinase
list the products of glycolysis step by step
1) glucose 6-phosphate
2) fructose 6-phosphate
3) fructose 1,6-diphosphate
4 and 5) 3-phosphoglyceraldehyde x 2 and dihydroxyacetone phosphate
7) 3-phosphoglyceric acid
8) 2-phosphoglyceric acid
10) pyruvate kinase
how many ATP is formed from 1 Acetyl CoA ? break them down .
11 from ETC (3 NADH give 3 ATP, 1 FADH2 gives 2 ATP)
1 from GDP (substrate level phosphorylation)
lactic acid =
pyruvate + 2H
what is the limiting factor for lactate production ?
which enzyme converts reversibly pyruvate to lactate ?
what is the difference between lactic acid and lactate ?
lactic acid is formed in anaerobic glycolysis , releases an H+
lactate is [lactic acid + (Na+) - (H+)]
which part of the body does not have mitochondria ? what are the implications of that ?
red blood cells don't have mitochondria, meaning they work anaerobically and produce lactate
at 25% Vo2 max, what is happening with NADH, CHO, lactic acid ?
using CHO as main source of energy.
not a lot of H+, plenty of NAD+ around
NADH goes into ETC in mitochondria
lactic acid little or none
at 90% Vo2max, what is happening with CHO, NADH, lactic acid, PFK ?
increased CHO metabolism meaning that [H+] increases in muscles. cell function is inhibited by the increased acidity, (drops to 6.8) meaning that PFK activity declines due to increased acidity, so we stop using carbs for energy (halt in glycolysis and glycogenolysis since PFK is rate-limiting substance)
we want to maximize our NAD+ usage to prevent acidity.
then, if untrained, there will be a buildup of lactic acid
if trained, utilize other sources.
at what intensity does the Cori cycle usually occur ?
more than 55% Vo2max
what is the main purpose of glycolysis ?
to convert glucose to pyruvate
what is the main purpose of the Cori cycle ?
removes lactate released from active muscles to replenish glycogen stores.
where is glycolysis reversible ?
pyruvate can only go to glucose in the liver.
describe the process of the Cori cycle.
lactate will be transported by the veins into the liver ( that processes 5L/min) and where it will become pyruvate again.
what substances can go to pyruvate in the liver?
glycerol, alanine (if deaminated + hydroxyl + hydrogen), lactate
what is the main purpose of lactate shuttling ?
once fast-twitch anaerobic muscle fibers fatigue, the lactate can be shuttled into slow twitch fibers and other tissues to convert to pyruvate (for aerobic activity)
what site is a major site of lactate production but also of lactate removal via oxidation ?
1 glucose forms how many puruvate ?
what are the three components of aerobic metabolism ?
Krebs, ETC, oxidative phosphorylation
what is the rate-limiting enzyme for Krebs ?
pyruvate dehydrogenase (to go from pyruvate to Acetyl CoA)
what macromolecules can become Acetyl CoA ?
carbs, aa, FFA
what molecule is the "hub" of metabolism ?
how does pyruvate become acetyl coA ?
with pyruvate dehydrogenase,
NAD+ ---> NADH + H+
to acetyl coA
(1 NADH/pyruvate, 2 NADH/glucose)
what are 3 things that aerobic training improves in the Krebs cycle ?
amount of substrate & enzyme
size of mitochondria (greater ETC capacity)
number of mitochondria
what happens to a triglyceride in fat metabolism ? how are its components used ?
hormone sensitive lipase breaks down into FFA and glycerol. if outside the cell, FFA will bind to albumin and be transported to cell. glycerol goes to glucose and is utilized in glycolysis and in Krebs.
how much ATP does 1 glycerol make ?
how much ATP is needed to remove the FFA from cytosol and bring it into mitochondria for fat metabolism ?
1 ATP / FFA
list 4 hormones that augment fat metabolism ?
NE, E, glucagon, and growth hormone.
what is the role of cAMP in fat breakdown ?
it activates HSL and therefore regulates fat breakdown. (stimulated by lipid-mobilizing hormones).
what happens to glycerol after TG breakdown ?
glycolysis utilizes it as 3-phosphoglyceraldehyde
what is the main purpose of beta-oxidation ?
to make FFA into acetyl coA
what fuel is utilized in long-duration exercise ?
when glycogen stores are depleted, fat becomes the main fuel.
what kind of diet would enhance capacity for fat oxidation ?
high fat, low carb
fats can become..... why ?
only amino acids. no carbs becayse you can't convert Acetyl CoA back to pyruvate
carbs can become....
fats or AA
proteins can become...
carbs or fats
how is glutamate made ?
alpha-ketoglutarate (Krebs intermediate) + NH2
when amino acids are glucogenic, what carbs do they yield with deamination ?
pyruvate, oxaloacetate, malate, glutamate
when amino acids are ketogenic, what fats do they field when they are deaminated ?
glycine can yield Acetyl CoA
when would lipogenesis occur ?
with excess stores of carbs and protein.
one glucose molecule will yield how much ATP in complete oxidation ?
32 ATP (24 from Krebs & ETC, 8 (2.5x2 + 1.5x2) from glycolysis)
in extremely elevated FFA metabolism, what does pyruvate do ?
it'll go straight to oxaloacetate instead of converting to pyruvate. (because there is already too much pyruvate that has been created, so product >>>> reactant)
oxaloacetate (4C) then binds with acetyl coa (2C) to create citrate (6C)
what does each Krebs cycle make ?
1 ATP, 3 NADH, 1 FADH2
in a resting high fat metabolism, what will pyruvate and acetyl coa do ?
decreased pyruvate due to lack of carbs
pyruvate won't go to oxaloacetate
can't form any citrate for krebs since there's no oxaloacetate
acetyl coa will then combine to form ketones
what are the two substances ketones can break down to ?
acetone and beta-hydroxybutyric acid