Chapter 7 Flashcards
Living cells require ___ from outside sources.
energy
Energy flows into an ecosystem as ______ and leaves as ____.
sunlight, heat
Central process to cellular respiration
Catabolic pathways involving electron transfer
Fermentation
partial degradation of sugars that occurs without O2.
Aerobic respiration
consumes organic molecules and O2 and yields ATP
Cellular respiration
includes aerobic and anaerobic processes but often refers to aerobic respiration.
transfer of electrons during chemical reactions
releases energy stored in organic molecules
redox reaction
chemical reactions that transfer electrons between reactants
redox reactions are also called
oxidation-reduction reactions
oxidation
a substance loses electrons
reduction
a substance gains electrons
reducing agent
electron donor
oxidizing agent
electron acceptor
Some redox reactions do not transfer electrons but ______.
change the degree of electron sharing in covalent bonds
a redox reaction that moves electrons from less electronegative atom to a more electronegative atom ________.
releases energy that can be used to do work.
during cellular respiration, fuel (such as __) is ______ and O2 is _____
glucose, oxidized, reduced
As hydrogen (with its electrons) is transferred to oxygen, ________.
energy is released that can be used in ATP synthesis
In cellular respiration, what is broken down in a series of steps?
glucose and other organic molecules
electrons from organic compounds are usually first transferred to?
NAD+, a coenzyme
As an electron acceptor, ________ during cellular respiration.
NAD+ functions as an oxidizing agent
NADH
high energy electron carrier
Each NADH represents?
stored energy tapped to make ATP
NADH is the reduced form of?
NAD+
dehydrogenases
enzymes that facilitate the transfer of two electrons and one hydrogen ion to NAD+ forming NADH
What is released during dehydrogenases?
one hydrogen ion
NADH passes electrons to ____?
electron transport chain
electron transfer to oxygen occurs in ______ instead of one explosive reaction.
a series of energy-releasing steps
Reactants of cellular respiration
glucose and oxygen
Products of cellular respiration
carbon dioxide, water, ATP
glycolysis
breaks down glucose into two molecules of pyruvate in the cytosol
pyruvate oxidation and citric acid cycle
completes the breakdown of glucose in the mitochondrial matrix
oxidative phosphorylation
accounts for most of the ATP synthesis and occurs in the inner membrane of the mitochondria
Oxidative phosphorylation function
transfer of inorganic phosphates to ATP
Oxidative phosphorylation accounts for?
almost 90% of the ATP generated by cellular respiration
What is formed by substrate level phosphorylation?
smaller amount of ATP formed in glycolysis and the citric acid cycle
substrate level phosphorylation
an enzyme transfers a phosphate group directly from a substrate molecule of ADP.
Glycolysis breaks down glucose into?
two molecules of pyruvate
glycolysis occurs in?
cytoplasm
2 major phases of glycolysis
-energy investment phase
-energy payoff phase
What is the net energy yield per glucose molecule?
2 ATP plus 2 NADH
Glycolysis occurs whether or not ______ is present.
O2
If O2 is present in glycolysis then
the energy stored in pyruvate and NADH is extracted by pyruvate oxidation, citric acid cycle, and oxidative phosphorylation.
In eukaryotic cells, if O2 is present then____.
pyruvate enters the mitochondira to complete glucose oxidation
_______ is released and _____ is converted to ____ before entering the citric acid cycle.
CO2, pyruvate, acetyl coenzyme A
Another name for acetyl coenzyme A?
acetyl Co A
Glucose oxidation yields ____per pyruvate
1 NADH
Glucose oxidation yields ____ per glucose molecule
2 NADH
The citric acid cycle
completes the breakdown of pyruvate to CO2
Each turn of the citric acid cycle does what?
oxidizes molecules derived from one pyruvate molecule.
How many turns does the citric acid cycle do?
2
What does the citric acid cycle produce per glucose molecule?
2 ATP, 6 NADH, and 2 FADH2
The acetyl group of acetyl Co A joins the citric acid cycle by?
combining with oxaloacetate forming citrate
The NADH and FADH2 produced by the cycle relay?
electrons extracted from food to the electron transport chain.
Glycolysis and the citric acid cycle only produce ____.
4 ATP molecules by substrate-level phosphorylation
What accounts for most of the energy extracted from glucose?
NADH and FADH2
NADH and FADH2 electron carriers donate _______ which powers ________.
electrons to the electron transport chain, ATP synthesis via oxidative phosphorylation.
Where is the electron transport chain located in eukaryotic cells?
the inner membrane of the mitochondrion
Where is the electron transport chain located in prokaryotic cells?
plasma membrane
Most of the electron transport chains components are?
complexes of proteins with electron carriers numbered I to IV
Most of the proteins in the electron transport chain are?
cytochromes
cytochromes
proteins with attached heme groups that transport electrons and are involved in redox catalysis.
Electrons alternate between reduced and oxidized states as they?
accept and donate protons
What is not produced directly by the electron transport chain?
ATP
The energy released by electrons being transferred in the chain is used to?
pump H+ into the intermembrane space
The energy released by the electrons being transferred in the chain establishes?
an H+ gradient across the inter mitochondrial membrane
ATP synthase
H+ can only cross the inner membrane through protein complexes
ATP synthase uses ______ to drive phosphorylation of ATP.
exergonic flow of H+
ATP synthase driving the phosphorylation of ATP is an example of?
chemiosmosis
chemiosmosis
the use of energy in a H+ gradient to drive cellular work.
The H+ gradient is referred to as a?
proton-motive force
proton-motive force
emphasizing its capacity to do work
The remaining energy from glucose other than ATP is ____?
lost as heat
What will stop operating without oxygen?
electron transport chain and oxidative phosphorylation
alcohol fermentation
pyruvate is converted to ethanol
2 steps of alcohol fermentation
-acetaldehyde is formed
-acetaldehyde is reduced by NADH to ethanol.
Acetaldehyde
CO2 is released from pyruvate
In alcohol fermentation, NADH is oxidized regenerating?
NAD+
Lactic acid fermentation
pyruvate is converted directly to lactate without producing CO2
lactate
an ionized form of lactic acid
In fermentation, aerobic respiration, and anaerobic respiration what is the oxidizing agent?
NAD+
NAD+ does what during glycolysis?
accepts electrons from food
How does NADH oxidation differ in fermentation?
the final electron acceptor is an organic molecules such as pyruvate or acetaldehyde.
How does NADH differ in cellular respiration?
electrons are transferred from NADH to a carrier molecule in the ETC
obligate anaerobes
use only fermentation or anaerobic respiration, cannot survive in presence of O2
facultative anaerobes
yeast and many bacteria use cellular respiration in the presence of O2 or fermentation when O2 is not present
As glycolysis is the most common metabolic pathway, it likely?
evolved early in the history of life
Due to low O2 availability on early earth, early _?
prokaryotes likely relied entirely on glycolysis.
Glycolysis occurs in the cytosol, indicating that it likely evolved?
before mitochondria
beta oxidation
fatty acids are broken down to two-carbon fragments
beta oxidation yields
acetyl CoA
What is oxygen’s role in oxidative phosphorylation?
maintains a low H+ gradient in the matrix because oxygen is the final e- acceptor making H2O
