Cellular respiration

Goal of cellular respiration

breakdown glucose into energy that is used for ATP synthesis

is cellular respiration endergonic or exergonic?

exergonic

• releases usable energy to drive ATP synthesis

is cellular respiration catabolic or anabolic?

catabolic

• breakdown of large molecule

chemical formula (overall)

C₆H₁₂O₆+6O₂→6CO₂+6H₂O+ATP

Reducing equivalent

• NADH and FADH₂

• accepts and stores electrons

• carries stored electrons to the ETC

Electrons carry _____

energy

substrate level phosphorylation

directly adding a phosphate group to ADP

oxidative phosphorylation

• indirect

• electrons from reducing equivalents provide the energy used to eventually make ATP in the ETC

main function of glycolysis

breakdown glucose into 2 pyruvate molecules

important steps in energy investment phase

steps 1,3: energy coupling of ATP hydrolysis and phosphorylation of a sugar

• 1) ATP hydrolysis and phosphorylation of glucose

• 3) ATP hydrolysis and phosphorylation of glucose intermediate (PFK-1)

explain energy coupling

a favorable, exergonic reaction (releases energy) is paired with an unfavorable, endergonic reaction (absorbs energy)

• exergonic rxn provides the energy needed for endergonic rxn to proceed

important steps in energy payoff phase

6) Reduction of NAD+

7 & 10) substrate level phosphorylation

main function of pyruvate oxidation

oxidation of 2 decarboxylated (CO2 removed) pyruvate molecules → 2 acetyl-CoA

output

2 acetyl-CoA + 2 NADH

• energy by way of electrons is stored in reducing equivalent

By the end of the citric acid cycle, what has happened?

all energy form original glucose molecules has been extracted in form of electrons to either make ATP directly or be stored in reducing equivalents

• 6 NADH

• 2 FADH₂

input (per glucose) to the ETC

• 10 NADH → 2 glycolysis, 2 pyruvate oxidation, 6 citric acid cycle

• 2 FADH₂ → citric acid cycle

• 6O₂ → accepted by final e- terminal acceptor

function of reducing agents in the ETC

pass electrons to final e- acceptor by way of redox reactions

• specifically, reducing agents continuously give their electrons away to protein complexes until reaching the final electron terminator (oxygen)

how is the proton motive force created?

during the redox reactions, some energy from electrons is used to pump H+ ions against the electrochemical gradient → creating a PMF

the PMF is created by way of

active transport

movement along the PMF is _______ and _________ energy

favored (exergonic), releases (i,e. electrons)

chemiosmosis

a) movement of H+ ions in chemiosmosis

b) ATP formation (how does PMF play a role?)

• 4H+ ions passively flow through membrane via ATP synthase

• energy released from PMF is used to rotate ATP synthase when H+ ions pass through, creating ATP

why does NADH have a higher ATP production rate?

NADH electrons pass through 3 proton-pumping complexes, whereas FADH₂ passes through 2 proton-pumping complexes

ATP / reducing equivalent

2 ½ ATP / NADH

1 ½ ATP / FADH₂

main regulatory molecule of cellular respiration

phosphofructokinase

• acts in glycolysis

what is the role of phosphofructokinase?

the rate of phosphofructokinase activity tells the cell to either

• increase production of ATP

• reduce production of ATP

molecules that allosterically regulate phosphofructokinase (i.e. what does phosphofructokinase respond to?)

ATP, AMP and citrate

ATP and citrate ________ phosphofructokinase activity = cell _______ ATP production

inhibits, decreases

AMP ________ phosphofructokinase activity = cell ______ ATP production

stimulates, increases

Fermentation pathways

1. Ethanol fermentation

2. Lactic acid fermentation

Main function of fermentation

• Recycle NADH → NAD+ via electron transfer to pyruvate molecules

• solely relies on substrate level phosphorylation