chapter 9: cellular respiration (test 4) Flashcards
Photosynthesis generates ___ and ___, which are used in cellular respiration
Cells use chemical energy stored in organic molecules to generate ATP, which powers work
O2
organic molecules
The breakdown of organic molecules is ___
___ is a partial degradation of sugars that occurs without O2
___ consumes organic molecules and O2 and yields ATP
___ is similar to aerobic respiration but consumes compounds other
than O2
exergonic
Fermentation
Aerobic respiration
Anaerobic respiration
___ includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration
Carbohydrates, fats, and proteins are all consumed as fuel if necessary.
Cellular respiration with glucose
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat)
Cellular respiration
The transfer of electrons during chemical reactions releases energy stored in organic molecules. These reactions are called ___.
This released energy is ultimately used to synthesize ___
In ___, a substance loses electrons,
or is oxidized
In ___, a substance gains electrons, or is reduced (the amount of positive charge is reduced)
redox reactions
ATP
oxidation
reduction
In cellular respiration, glucose and other organic molecules are broken down in a series of steps
Electrons from organic compounds are usually first transferred to ___, a coenzyme or FAD
Each NADH (the reduced form of NAD+) and FADH2 (the reduced form of FAD) represents stored energy that is tapped to synthesize ATP
NAD+
NADH and FADH2 pass the electrons to the ___
Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction
O2 pulls electrons down the chain in an energy-yielding tumble
The energy yielded is used to regenerate ATP
electron transport chain
(The Stages of Cellular Respiration: A Preview)
Harvesting of energy from glucose has three stages
___ (breaks down glucose into two molecules of pyruvate)
___ (completes the breakdown of glucose)
___ (accounts for most of the ATP synthesis). The process is powered by redox reactions.
Glycolysis
The citric acid cycle
Oxidative phosphorylation
___ accounts for almost 90% of the ATP generated by cellular respiration
A smaller amount of ATP is formed in glycolysis and the citric acid cycle by ___
For each molecule of glucose degraded to CO2 and water by respiration, the cell makes up to ___ molecules of ATP
Oxidative phosphorylation
substrate-level phosphorylation
32
(Glycolysis harvests chemical energy by oxidizing glucose to pyruvate)
Glycolysis (“sugar splitting”) breaks down glucose into ___
Glycolysis occurs in the ___ and has two major phases
___
___
Glycolysis occurs whether or not O2 is present
two molecules of pyruvate
cytoplasm
Energy investment phase
Energy payoff phase
(After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules)
In the presence of O2, pyruvate enters the mitochondrion (in eukaryotic cells) where the oxidation of glucose is completed
Before the citric acid cycle can begin, pyruvate must be converted to ___, which links glycolysis to the citric acid cycle
This process yields ___ for every pyruvate that enters the mitochondrion.
acetyl Coenzyme A (acetyl CoA)
1 NADH
(The Citric Acid Cycle)
The citric acid cycle, also called the Krebs cycle, completes the ___
The cycle oxidizes organic fuel derived from pyruvate, generating ___ per turn
breakdown of pyruvate to CO2
1 ATP, 3 NADH, and 1 FADH2
The citric acid cycle has ___ steps, each catalyzed by a specific enzyme
The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate
The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle
The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain
eight
(During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis)
Following glycolysis and the citric acid cycle, ___ account for most of the energy extracted from food
These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via ___
NADH and FADH2
oxidative phosphorylation
(The Pathway of Electron Transport)
The electron transport chain is in the ___ of the mitochondrion
Most of the chain’s components are ___,
which exist in multiprotein complexes
The carriers alternate reduced and oxidized states as they___
Electrons drop in free energy as they go down the chain and are finally passed to ___
inner membrane (cristae)
proteins
accept and donate electrons
O2, forming H2O
Electrons are transferred from ___ to the ___
Electrons are passed through a number of proteins including ___ (each with an iron atom) to O2
The electron transport chain generates no ATP directly
It breaks the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts
NADH or FADH2
electron transport chain
cytochromes
(Chemiosmosis: The Energy-Coupling Mechanism)
Electron transfer in the electron transport chain causes proteins to pump ___ from the mitochondrial matrix to the ___
H+ then moves back across the membrane, passing through the protein complex, ___
ATP synthase uses the exergonic flow of H+ to drive phosphorylation of ATP
This is an example of ___, the use of energy in a H+ gradient to drive cellular work
H+
intermembrane space
ATP synthase
chemiosmosis
The energy stored in a H+ gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis
The H+ gradient is referred to as a ___, emphasizing its capacity to do work
proton-motive force
(An Accounting of ATP Production by Cellular Respiration)
During cellular respiration, most energy flows in this sequence:
glucose → NADH → electron transport chain → proton-motive force → ATP
About 34% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about ___ ATP
32
(Fermentation and anaerobic
respiration enable cells to produce ATP without the use of oxygen)
Most cellular respiration requires ___ to produce ATP
Without O2, the electron transport chain will cease to operate
In that case, glycolysis couples with anaerobic respiration or___ to produce ATP
O2
fermentation
___ uses an electron transport chain with a final electron acceptor other than O2, for example sulfate
*Fermentation uses ___ instead of an electron transport chain to generate ATP
Anaerobic respiration
substrate-level phosphorylation
(Types of Fermentation)
Fermentation consists of glycolysis plus reactions that regenerate ___, which can be___
Two common types are___ and ___
NAD+
reused by glycolysis
alcohol fermentation and lactic acid fermentation
In alcohol fermentation, ___ is converted to ethanol in two steps
The first step releases ___
The second step produces ___
Alcohol fermentation by yeast is used in brewing, winemaking, and baking
pyruvate
CO2
ethanol
In ___, pyruvate is reduced by NADH, forming lactate (lactic acid) as an end product, with no release of CO2
Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt
Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce
lactic acid fermentation
