Bio 111 Cellular Respiration

cellular respiration

transfers energy from food to our cells/the movement of electrons from molecules

can you harvest energy all at once

no, a lot of energy would be lost, so it needs to be squeezed out bit by bit

catabolic steps

syphon energy out; most energy from food is first transferred as electrons, the electrons’ energy is later used to make ATP; some energy from food is used to drive direct synthesis in ATP

in what form is energy typically transferred in

electrons

coupled reactions

what respiration is a series of, redox reactions

redox reactions

coupled oxidation/reduction reactions, electrons move as part of a hydrogen atom (so track the hydrogen atom in electrons); LEO GER (less electrons is oxidation, gain electrons is reduction)

oxidation

lose electrons (in hydrogen)

reduction

gain electrons (in hydrogen)

electron carriers

temporarily store energy by transferring electrons, bad at holding electrons, so they stay higher in energy due to these weak bonds, energy is harnessed to make ATP

goals of cellular respiration

energy transfer

1) take stored energy in food and temporarily transfer that energy has high energy electrons (transfer energy stored in bonds of glucose into NADH/FADH2)

2) take energy stored in high energy electron carriers and temporarily store energy as an electrochemical gradient  (transferring energy stored in NADH/FADH2 into a proton gradient)

3) convert energy in electrochemical gradient to ATP, and the ATP is now a usable energy currency to do stuff (transfer the energy stored in the proton gradient into ATP)

broad overview of stages of cellular respiration

1) glycolysis, pyruvate oxidation, and the citric acid cycle

transferring energy stored in the bonds of glucose into NADH/FADH2 (and a bit into ATP), serves the first goal- energy transfer, squeezing out (catabolically breaking down and storing electron carriers)

2) oxidative phosphorylation

transferring the energy stored in NADH/FADH2 gradients into a proton gradient, transferring the energy stored in the proton gradient into ATP, serves the second 2 energy goals

what happens to macromolecules during stages 1-3 of cellular respiration

they are reduced molecules that become gradually oxidized (lose hydrogen/electrons/energy) through a bunch of little reactions

energy syphoning

done by exergonic/catabolic reactions that break down glucose bit by bit to gradually syphon off high energy electrons to be put into high energy electron carriers that will be paid off in stage 4, and a little ATP is made along the way

stage 1

glycolysis

glycolysis

oxidation of glucose; at cytosol- glucose in, pyruvate out, ATP is made directly, NADH is made, energy is stored in ATP, NADH, and pyruvate at the end

stage 2

pyruvate oxidation

pyruvate oxidation

at mitochondrial matrix- pyruvate in, acetyl CoA and CO2 out, ATP is not directly made, NADH is made, energy is stored in acetyl CoA and NADH at end

stage 3

citric acid cycle

citric acid cycle

at mitochondrial matrix- acetyl CoA in, CO2 out, ATP is directly made, NADH and FADH2 are made, energy is stored in ATP, NADH, and FADH2 at end

where is most of the energy stored at the end of stages I-III

most of the energy is stored in NADH2 and FADH2, but we still need to get energy out of the cell (will be done through ATP)

ATP in glycolysis

we get net 2 ATP; some ATP is paid, but we get some ATP out; 2 ATP in, 4 ATP out

electron carrier in glycolysis

the electron acceptor, 2NAD+, goes in and 2NADH, the electron carrier comes out along with 2 pyruvate

pyruvate

a product of glycolysis, from when glucose is broken down

phases of glycolysis

investment

-phosphorylation (add ATP)

-cleavage (break glucose into 2 molecules, why we end up with 1 glucose and 1 pyruvate)

payoff

-oxidation (harvesting the energy)

oxidation of glucose

the goal is to pull high energy electrons off molecuels so they can be used, so electrons (and therefore energy) are stripped from the macromolecules

glycolysis energy investment

add ATP, energy investment traps glucose in cell and destabilizes glucose molecule so it breaks into 2 pieces

partial oxidation of carbon molecule

transfer energy from carbon to energy on NADH, so reduction of NAD+ to NADH, then ATP is made by taking a phosphate group on the carbon molecule and transferring it to ADP→ results in pyruvate (2× 3 carbon sugars)

where does ATP come from

1) substrate level phosphorylation

-stages 1 & 3 (glycolysis and citric acid cycle)

-phosphate breaks off C molecule and attaches to ADP to make ATP

2) oxidative phosphorylation

-stage 4 only

-uses ETC

what makes the mitochondrion so powerful

-has a lot of membrane → has 2 layers = separate compartments we can gather electrochemical gradient, has many folds = lots of surface area for machinery that will carry out respiration

-where stages 2 & 4 of cellular respiration happen

goal of pyruvate oxidation

move pyruvate into matrix and partially oxidize it (strip some electrons off it)

goal of citric acid cycle

complete oxidation of remaining carbon molecules- suck remaining energy out of carbon and use remaining energy from that to reduce electron carriers and make some ATP through direct transfer of phosphate from carbon to ADP

how much energy is left in glucose at the end of the citric acid cycle/stage 3

all of the energy has been squeezed out of glucose, so energy is temporarily put in NADH+ and FADH2 in the form of high energy electrons

NADH+ and FADH2

bad for long term energy storage, and cannot be used as energy currency, so ATP is needed

stage 4

oxidative phosphorylation

oxidative phosphorylation

at inner mitochondrial membrane- electron carriers in (FADH2, NADH, and O2- breathed directly in), ATP, NAD+, FADH, and H2O out

what is the big idea of oxidative phosphorylation

ATP synthesis via ETC; use a lot of redox reactions to create a protein gradient that protons move on to power synthesis of ATP via ATP synthase

electron transport chain (ETC)

series of coupled redox reactions between big protein complexes that are embedded in the inner mitochondrial membrane; movement of electrons to higher affinity and lower energy acceptors

during cellular respiration, where is the majority of ATP produced

stage 4/oxidative phosphorylation

what are electrons passed to in the ETC

to something that has a tighter hold (higher affinity) than the previous thing on the chain, if it is holding it tighter/closer it has lower energy (more stable) which will slowly decrease the energy in electrons

if an electron is carried by FADH2, what complex does it enter at

complex II

protons pumped and ETC

energy is harnessed from electron movement is used to pump protons (H+)

what protein complexes have protein pumps

I, III, IV and as electron moves to something lower in energy, the difference in energy is used to push protons against their gradient

why do protons move down their concentration gradient

they need to concentrate on one side, they are high in the inter membrane space and low in the matrix

CoQ and cytochrome C

they are like little electron carriers, they are mobile enzymes that accept and donate electrons

how are protons moved in oxidative phosphorylation

they are first pumped from the matrix to the inter membrane space, then they flow back into the matrix through ATP synthase and use that energy to synthesize ATP

inter-membrane system

potential energy of H+ gradient → kinetic energy of H+ moving down gradient thru ATP synthase (stored potential energy of ATP); protons flow through ATP synthase to give ATP synthase the energy it needs to make ATP

what happens if there are holes in the membrane

it can keep doing redox reactions and move electrons and pump protons, BUT protons will diffuse down hole instead of gradient (so it won’t get to ATP synthase to make ATP)

analogy- if there are holes in a dam, all of the H2O will pour through instead of being harnessed for electricity

cellular respiration in review

glucose is oxidized into pyruvate, which is oxidized into acetyl coA which is oxidized into CO2 (each time it oxidizes, a small amount of ATP is made through substrate level phosphorylation in stages I & III)

all of that is coupled to the reduction of NAD+ to NADH and FADH to FADH2, which carry high energy electrons to make ATP via ETC and oxidative phosphorylation in stage IV

substrate level phosphorylation

an enzyme removes the phosphate group on a carbon molecule and attaches it to ADP creating ATP

what does glycolysis produce

pyruvate, ATP, NADH from glucose

what does pyruvate oxidation produce

acetyl CoA, CO2, NADH from pyruvate

what does the citric acid produce

CO2, ATP, NADH/FADH2 from acetyl CoA

what does oxidative phosphorylation produce

ATP from oxidation of NADH to NAD+ and FADH2 to FADH

what happens if cytochrome c is broken

it puts a wall between complex III and IV, so nothing can be passed along in I-III which causes a buildup of NADH/FADH2 since they have no where to put their electrons because the complexes and CoQ are full of electrons, that means no electrons can get to oxygen so it never gets used

why would ATP synthesis stop

electrons aren’t moving, protons aren’t pumped, no gradients, no ATP and oxygen builds

anaerobic respiration

glycolysis produces ATP, stages II-IV don’t happen

fermentation

reduces pyruvate for the sake of oxidizing NADH to regenerate NAD+ so glycolysis can continue; what you do when you can’t back to glycolysis

lactic acid fermentation

in animals and bacteria

ethanol fermentation

in plants and fungi (yeast)