The breakdown of organic molecules is ________.
exergonic
____________ is a partial degradation of sugars that occurs without oxygen
fermentation
___________ _____________ consumes organic molecules and oxygen and yields ATP
aerobic respiration
aerobic respiration reactants and products
reactants: glucose and oxygen
products: carbon dioxide, water, and energy
Anaerobic respiration is similar to aerobic respiration but consumes compounds other than _________
oxygen
__________ ___________ includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration
cellular respiration
The transfer of ________ during chemical reactions releases energy stored in organic molecules, which is ultimately used to synthesize ____
electrons, ATP
Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or _________ reactions.
redox
In ___________, a substance loses electrons, or is oxidized.
oxidation
In ___________, a substance gains electrons, or is reduced (the amount of positive charge is reduced).
reduction
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 ________ bonds.
covalent
During cellular respiration, the fuel is _______ and O2 is _______.
oxidized, reduced
Organic molecules with an abundance of _________ are excellent sources of high-energy electrons
hydrogen
Energy is released as the electrons associated with hydrogen ions are transferred to oxygen, a _______ energy state.
lower
First Step of Cellular Respiration: Electrons from organic compounds are usually first transferred to ______, a coenzyme.
NAD+
As an electron acceptor, NAD+ functions as an ________ agent during cellular respiration.
oxidizing
Each NADH represent stored energy that is tapped to synthesize ______
ATP
NADH passes the electrons to the ______ _______ ______.
electric transport chain
The ETC passes electrons in a series of _____ instead of one explosive reaction.
steps
_____ pulls electrons down the chain in an energy-yielding tumble.
O2
The energy yielded from the ETC is used to...
regenerate ATP
Harvesting of energy from glucose has three stages...
1. glycolysis
2. citric acid cycle
3. oxidative phosphorylation
Glycolysis breaks down glucose into two molecules of _______.
pyruvate
Where in the cell does glycolysis occur?
cytoplasm
What are the two major phases of glycolysis?
1. energy investment phase
2. energy payoff phase
Does glycolysis occur whether or not O2 is present?
yes
What is the net product of glycolysis?
2 pyruvate, 2 ATP, 2 NADH, 2 H2O
Before the citric acid cycle can begin, pyruvate must be converted to ________ ________, which links glycolysis to the citric acid cycle.
acetyl coenzyme A (acetyl CoA)
Pyruvate is converted to acetyl coA through a multi-enzyme complex that catalyzes three reactions:
1. Oxidation of pyruvate and release of CO2
2. Reduction of NAD+ to NADH
3. Combination of the remaining two carbon fragment and coenzyme A to form acetyl CoA
Where does pyruvate oxidation occur?
mitochondrial matrix
The citric acid cycle completes the breakdown of _______ to _____.
pyruvate to CO2
What is the citric acid cycle also known as?
Krebs cycle
Where does the citric acid cycle occur?
mitochondrial matrix
The cycle oxidizes organic fuel derived from pyruvate, generating...
1 ATP, 3 NADH, and 1 FADH2
How many steps does the citric acid cycle have?
8 steps, each catalyzed by a specific enzyme
The acetyl group of acetyl CoA joins the cycle by combining with ____________, forming _______
oxaloacetate forming citrate
What do the next seven steps of the cycle do?
decompose the citrate back to oxaloacetate
The ______ and ______ produced by the cycle relay electrons extracted from food to the electron.
NADH and FADH2
Following glycolysis and the citric acid cycle, _____ and ______ account for most of the ______ extracted from food.
NADH and FADH2, energy
These two electron carriers...
donate electrons to the electron transport chain
The electrons donated to the ETC by NADH and FADH2 power ATP synthesis via...
oxidative phosphorylation
Where is the electron transport chain located?
inner mitochondrial membrane (cristae)
What is most of the ETC made out of?
proteins (which exist in multiprotein complexes)
During the ETC, electrons drop in free energy as they go down the chain and are finally passed to ____, forming ______.
O2 forming H2O
Electron carriers alternate between ________ and _________ states as they accept and donate electrons.
reduced, oxidized
Electrons are passed through a number of proteins including _________ to O2
cytochromes
Does the electron transport chain generated any ATP directly?
no
The energy released as electrons are passed down the ETC is used to...
pump H+ from the mitochondrial matrix to the inter-membrane space
H+ then moves down its concentration gradient back across the membrane, passing through the protein complex _____ _________
ATP synthase
H+ moves into binding site of ATP synthase, causing it to...
spin in a way that catalyzes phosphorylation of ADP to ATP
The binding of H+ to ATP synthase is an example of ___________, the use of energy in a H+ gradient to drive cellular work
chemiosmosis
Certain electron carriers in the ETC accept and release ____ along with the electrons.
H+
The energy stored in a H+ gradient across a membrane couples the ______ ___________ of the ETC to ATP synthesis.
redox reactions
The H+ gradient is referred to as a ____________.
proton motive force
Oxidative phosphorylation accounts for most of the...
ATP synthesis
The process that generates almost 90% of the ATP is called ________ _________ because it is powered by redox reactions.
oxidative phosphorylation
A smaller amount of ATP is formed in glycolysis and the citric acid cycle by ____________ _______________.
substrate-level phosphorylation
During cellular respiration, most energy flows in this sequence:
glucose -> NADH -> ETC -> proton-motive force -> ATP
About _____% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about ____ ATP
34%, 32 ATP
Maximum amount of ATP produced per glucose...
about 30 or 32
What are the three reasons why the number of ATP is not known exactly?
1. photophosphorylation and the redox reactions are not directly coupled; the ratio of NADH to ATP molecules is not a whole number
2. ATP yield varies depending on whether electrons are passed to NAD+ or FAD int he mitochondrial matrix
3. the proton-motiv
Most cellular respiration depends on electronegative _________ to pull electrons down the transport chain.
oxygen
Anaerobic respiration uses an ETC with a final electron acceptor other than ________, for example sulfate.
oxygen
Fermentation uses _____________ _________________ instead of an electron transport chain to generate ATP.
substrate-level phosphorylation
Fermentation consists of glycolysis plus reactions that generate _____, which can be reused by glycolysis
NAD+
Fermentation produces __ ATP per glucose molecule
2
Two common types of fermentation...
alcohol fermentation and lactic acid fermentation
_________ is the most widespread metabolic pathway on Earth.
glycolysis
_______ ________ carry out fermentation or anaerobic respiration and cannot survive in the presence of O2.
obligate anaerobes
Yeast and many bacteria are __________ _______, meaning that they can survive using either fermentation or cellular respiration.
facultative anaerobes
Glycolysis accepts a wide range of __________, including starch, glycogen, and several disaccharides.
carbohydrates
Proteins that are used for fuel must be digested to _____ ____ and their ______ _____ must be removed.
amino acids, amino groups
Fats are digested to _________ and ________ _____
glycerol and fatty acids
Fatty acids are broken down by ______ __________
beta oxidation
What does beta oxidation of fatty acids yield?
CoA, NADH, and FADH2