Respiration

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