Chapter 9: Cellular Respiration

what is cellular respiration

when chemical energy in organic molecules is harvested to generate ATP

energy flows

linearly

catabolic pathways break down ____ to release ____

glucose, oxygen

what is fermentation

partial degradation of organic compounds, without oxygen

what is aerobic respiration

complete breakdown of organic compounds with oxygen

what is anaerobic respiration

full breakdown of organic molecules without oxygen

what are examples of organic compounds

carbs, fats, proteins

what are redox reactions

the transfer of electrons to release the energy stored in organic molecules

where do electrons move

from a less electronegative atom to a more electronegative atom

what does the released energy from redox reactions create?

ATP

a reactant that is oxidized

is the reducing agent, and loses electrons

a reactant that is reduced

is the oxidizing agent, and gains electrons

what kind of reaction is happening here

redox

some redox reactions don’t transfer electrons, but instead…

change the electron sharing, from nonpolar to polar

as polar covalent bonds are created, electrons fall towards

the more electronegative atom

holding electrons away from an electronegative atom

is an energy consuming process

as electrons move towards electronegative atoms

energy is released

what is oxidized during cellular respiration

the fuel

what is reduced during cellular respiration

oxygen

the oxidation of organic molecules results in

a lot of energy

electrons lose

potential energy

what kind of molecule would result in a great amount of energy change following oxidation

a hydrocarbon

in cellular respiration, where are electrons transferred

to coenzyme NAD+

what is nicotinamide adenine dinucleotide

NAD+

NAD+ accepts

2 electrons and 1 H+

what happened to NAD+ here

it was reduced

NADH molecules represent

stored energy

NAD+ can go between

oxidized and reduced forms

NADH passes electrons to

an electron transport chain

electrons are transferred to atoms of increasing

electronegativity

what is the release of energy from electrons used to regenerate?

ATP

what is this illustrating

the electron path

what are the three stages of cellular respiration

glycolysis and pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation

what is glycolysis

the beginning of the breakdown of glucose

what is the citric acid cycle doing

completing the breakdown of glucose

what is oxidative phosphorylation

using the energy harvested in the first two steps to synthesize ATP

what is this

the steps for cellular respiration

where does glycolysis occur

in cytosol

where do pyruvate oxidation, citric acid cycle, and oxidative phosphorylation occur?

mitochondria

glycolysis breaks glucose down into

2 molecules of pyruvate (C3H4O3)

what are the two phases of glycolysis

energy investment phase, energy payoff phase

glycolysis will occur with or without..

oxygen

to break down glucose, how many ATP are used

2

what is the equation for glycolysis

glucose → 2 C3H4O3 + 2H2O

how many ATP are generated in pyruvate oxidation

4

how many net ATP in pyruvate oxidation

2

what is the NAD+ equation for pyruvate oxidation

2NAD+ + 4 electrons + 4H+ —> 2 NADH + 2 H+

how is ATP made during glycolysis

substrate level phosphorylation

what happens during substrate level phosphorylation

a substrate attaches the phosphate from ADP to form another ATP

what is this 

substrate level phosphorylation

what happens to pyruvate after glycolysis

it is converted to acetyl conezyme A by being oxidized

what is the citric acid cycle

it completes the break down of pyruvate to CO2

the citric acid cycle generates

1 ATP, 3 NADH, and 1 FADH2

how many steps in the citric acid cycle

8

what happens in step 1 of the citric acid cycle

the acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate

what happens in steps 2-8 of the citric acid cycle

decomposing citrate back to oxaloacetate

NADH and FADH2 do what in the citric acid cycle

carry electrons to the next step

energy is in the NADH and FADH2 because of

electrons

how do the electrons get added back to NADH and FADH2

oxidative phosphorylation

what is the final step of cellular respiration

oxidative phosphorylation

substrate level phosphorylation produces how many ATP

2 from glycolysis and 2 from citric acid cycle

where is the remainder of ATP generated

oxidative phosphorylation (24)

majority of the energy from the oxidation of glucose is stored in

the reduced coenzymes

how many NADH in glycolysis

2

how many NADH in pyruvate oxidation

2

how many NADH in the citric acid cycle

6

how many FADH2 in the citric acid cycle

2

oxidative phosphorylation accounts for what percent of ATP

90%

oxidative phosphorylation is powered by

redox reactions

what are the two major processes of oxidative phosphorylation

electron transport chain and chemiosmosis

what is the electron transport chain

Collection of molecules embedded in the inner membrane of the mitochondrion

the increased surface area of the chain means

there are 1000s of copies of it

most components of the ETC are

proteins in numbered complexes

what are the non-proteinous groups of the ETC

prosthetic groups necessary for catalysis

electrons are passed down the ETC to…

O2

electron carriers oscillate between

reduced and oxidized states

why does NADH enter the chain earlier than FADH2

it is associated with greater free energy

water is formed when reduced oxygen atoms…

pick up hydrogen ions from the aqueous environment

the ETC generates

no ATP directly, and rather, releases free energy

what is chemiosmosis

proton diffusion from high to low concentration (exergonic) coupled with the formation of ATP (endergonic)

electron transfer in the ETC causes proteins to pump

H+ across the inner membrane

H+ is pumped from

the matrix to the intermembrane space (low to high concentration)

H+s diffuse across the membrane, passing through

ATP synthase

what is ATP synthase

an enzyme that drives ATP production

what is this?

ATP synthase

how does energy flow in cellular respiration

glucose —> NADH —> ETC —> proton motive force —> ATP

why is the number of ATP not known exactly?

several reasons, including 1 NADH = 2.5 ATP, phosphorylation and redox are not directly coupled

34% of energy is transferred to ATP, where does the other amount go?

lost to heat

anaerobic respiration uses the ETC, but uses which electronegative acceptor?

SO4 2-

fermentation produces ATP via

substrate level phosphorylation

what are the two common types of fermentation

alcohol fermentation and lactic acid fermentation

pyruvate is converted to ethanol in

alcohol fermentation

what is the first step of alcohol fermentation

CO2 released to create acetaldehyde

what is the second step of alcohol fermentation

Redox reaction reduces acetaldehyde to
ethanol, and oxidizes NADH

in lactic acid fermentation, pyruvate is reduced directly to

lactate

human muscles use lactic acid when

O2 is scarce

lactic acid fermentation by fungi and bacteria is used to make

cheese and yogurt

fermentation and respiration use

glycolysis

fermentation and respiration have

different mechanisms for oxidizing NADH and produce different amounts of ATP

what is fermentation’s mechanism for oxidizing NADH

an organic molecule acts as a final electron acceptor