I CAN’S/
YOU MUST KNOW
The difference between fermentation & cellular
respiration
The role of glycolysis in oxidizing glucose to two
molecules of pyruvate
The process that brings pyruvate from the cytosol
into the mitochondria & introduces it into the citric
acid cycle
How the process of chemiosmosis utilizes the
electrons from NADH & FADH2 to produce ATP
9.1
Catabolic pathways release energy by oxidizing
organic fuels
Occur when molecules are broken down
Releases the molecules’ energy
2 types of catabolism
1) Fermentation
Partial degradation of sugars that occurs without O2
2) Cellular Respiration
Most prevalent & efficient catabolic pathway
Uses O2 as a reactant with the organic fuel
Known as AEROBIC RESPIRATION
CAN also use anaerobic respiration
Carbs, Fats, & Proteins are all broken down in
cellular respiration
Glucose is the primary nutrient molecule used:
C6H12O6 + 6O2  6CO2 + 6H2O + ENERGY (ATP/heat)
The exergonic release of energy from glucose is
used to phosphorylate ADP to ATP
Life processes constantly consume ATP
Cellular respiration burns the organic fuels &
uses the energy to regenerate ATP
Redox Reactions
Electrons are transferred from one reactant to
another
Reduction = substance gains electrons & energy
(reduced + charge)
Oxidation = substance loses electrons & energy
(oxidized)
LEO GER
The electron donor is called the reducing agent
The electron receptor is called the oxidizing
agent
Some redox reactions do not transfer electrons
but change the electron sharing in covalent
bonds
During cellular respiration, the fuel (such as
glucose) is oxidized, and O2 is reduced:
At key steps in cellular respiration:
Electrons are stripped from glucose
Each electron travels with a proton (forms
hydrogen)
The hydrogen atoms are not transferred directly to
oxygen (formula shows that) – they are passed to
an electron carrier
Electron Carrier:
Coenzyme NAD+
NAD+ accepts 2 electrons + the stabilizing
hydrogen ion to form NADH
NADH has been reduced & has gained energy
Stored energy used later to make ATP
More than: C6H12O6 + 6O6  6CO2 + 6H2O + ENERGY
Cellular respiration has three stages:
Glycolysis (breaks down glucose into two molecules of
pyruvate)
The citric acid cycle (completes the breakdown of
glucose)
Oxidative phosphorylation (accounts for most of the
ATP synthesis)
9.2
Glycolysis
Occurs in cytosol
The degradation of glucose begins as it is
broken down into two PYRUVATE molecules
The 6-Carbon glucose molecule is split into TWO
3-Carbon sugars through a long series of steps
2 major phases:
Energy (ATP) consuming phase
Energy (ATP) producing phase
Energy consuming
2 ATP are used
Destabilize glucose & makes it more reactive
Energy producing
Later in glycolysis, 4 ATP are made
Results in net gain of 2 ATP
2 NADH are also made – used later
NET gain of 2 ATP & 2 NADH
Most potential energy is still in the 2 pyruvates
Pyruvates will then move to step 2 – citric acid
cycle
9.3
Kreb’s (Citric Acid) Cycle
When O2 is present, pyruvates enter the
mitochondria
Before Kreb’s begins, pyruvate is converted to
acetyl CoA
1) Pyruvate uses a transport protein to move into
the matrix of the mitochondria
2) When there, an enzyme complex removes a
CO2, strips away electrons to convert NAD+ to
NADH, & adds coenzyme A to form acetyl CoA
3) Two acetyl CoA’s are produced per glucose.
It now enters the citric acid cycle
Kreb’s (Citric Acid)
8 steps – each catalyzed by a specific enzyme
The job of breaking down glucose is completed
with CO2 released as waste
Each turn of the cycle requires the input of one
acetyl CoA
Must make 2 turns before the glucose is
completely oxidized
One turn produces:
2CO2, 3NADH, 1FADH2 & 1 ATP
Thus 2 turns produce:
4CO2, 6NADH, 2FADH2 & 2 ATP
At the end of the Kreb’s cycle all 6 carbons from
glucose have been released as CO2
Only 2 ATP have been produced
The rest is held in the electrons in the NADH &
FADH2
Utilized in the Electron Transport Chain
9.4
ETC
The electron carriers will donate electrons to
power ATP synthesis through OXIDATIVE
PHOSPHORYLATION
In the cristae of the mitochondria
The ETC itself produces no ATP (comes from the
products of the ETC)
4 Step Process of ETC
1) ETC is embedded in the inner membrane of
the mitochondria
Has 3 transmembrane proteins that act as
hydrogen pumps
2 carrier molecules that move electrons between
hydrogen pumps
2) ETC is powered by electrons from NADH &
FADH2
As electrons flow, the loss of energy is used to
pump protons across the inner membrane
At the end of the ETC, the electrons combine with
2 hydrogen ions & Oxygen to form water
Oxygen is the final electron acceptor – if none is
available, the ETC STOPS!!!
3) Hydrogen ions flow down their gradient
through ATP synthase (channel in protein)
ATP synthase harnesses proton motive force (the
gradient of protons) to phosphorylate ADP
The proton motive force exists because inner mit.
Membrane is impermeable to hydrogen ions
4) The movement of the proton motive force is
called chemiosmosis
Energy-coupling mechanism that uses energy from
the proton gradient to drive cellular work
The ETC & chemiosmosis compose OXIDATIVE
PHOSPHORYLATION
ATP yield per molecule of glucose is between 36
& 38 ATP
32-34 comes from oxidative phosphorylation
Process
NADH
ATP
FADH2
TOTAL ATP
Glycolysis
2 (3 ATP
each in
ETC)
4 (2 net)
X
8
Pyruvic acid
 acetyl CoA
2
X
X
6
Kreb’s Cycle
6 (3 ATP
each in
ETC)
2
2 (2 ATP
each in
ETC)
24
ATP Totals:
30
4
4
38
9.5
Fermentation allows a cell to produce ATP
without Oxygen (anaerobic)
Consists of glycolysis (2 net ATP) & reactions
that regenerate NAD+
Oxygen not required to accept electrons
Types of fermentation
1) Alcohol
Pyruvate is converted to ethanol
Releases CO2 & oxidizing NADH to create more
NAD+
2) Lactic acid
Pyruvate is reduced by NADH (NAD+) formed
Lactate is a waste product
Facultative anaerobes
Organisms that make ATP by aerobic respiration if
oxygen present
Can switch to fermentation in anaerobic conditions
9.6
Proteins & fats are used to generate ATP through
cellular respiration
Organic molecules are used in biosynthesis (the
building of macromolecules)
Amino acids from the hydrolysis of proteins can be
incorporated into the consumer’s own proteins