Respiration Flashcards
located in the lipid interior of the membrane, ferries electrons from Complex I to Complex III, which contains cytochrome b
Ubiquinone/coenzyme Q (CoQ)
plays a critical role in both catabolic and anabolic processes and represents a major “hub” of metabolic activities in the cell
citric acid cycle
can undergo glycolysis once they have been converted to glucose 6-phosphate or fructose 6-phosphate
Carbohydrates other than glucose, including glycogen, starch, various disaccharides, and a number of monosaccharides
a peripheral membrane protein on the intermembrane-space side that shuttles back and forth between Complexes III and IV
cytochrome c
non-heme iron proteins that are additional components of the electron transport chain
iron-sulfur proteins
(exergonic) various pathways by which different organic molecules are broken down to yield energy
catabolism
is a key intermediate in cellular energy metabolism because it can be utilized in one of several pathways
Pyruvate
Electrons Removed from the Glucose Molecule Are Transferred to Oxygen
a series of electron carriers, each of which holds the electrons at a slightly lower energy level than the previous carrier
electron transport chain
phase that requires an energy investment of 2 ATP per glucose molecule. This stage ends with the splitting of the six-carbon sugar molecule into two three-carbon molecules.
Preparatory Phase
– was originally known as the Krebs cycle in honor of Sir Hans Krebs, whose research group was largely responsible for its elucidation; Krebs cycle is more commonly called the citric acid cycle or the TCA (tricarboxylic acid) cycle today, because it begins with the formation of citric acid, or citrate, which has three carboxylic acid (—COO-) groups
citric acid cycle
central to the biosynthetic processes of life
pyruvate or the acetyl group of acetyl CoA
which receives two electrons from NADH and passes them to CoQ
flavin mononucleotide (FMN)
Oxidizes the Acetyl Groups of the Acetyl CoA Molecules
citric acid cycle
depends on a gradient of protons (H+ ions) across the mitochondrial membrane and the subsequent use of the free energy stored in that gradient to form ATP from ADP and phosphate
Oxidative Phosphorylation
serve as an intermediate between two-electron carriers and one-electron carriers
ubiquinone, also called coenzyme Q (CoQ)
represent the cell’s net energy harvest from glycolysis
ATP & NADH
phase that produces an energy yield of 4 ATP and 2 NADH—a substantial return on the original investment. The net ATP yield is therefore 2 molecules of ATP per molecule of glucose.
payoff phase
drives the formation of ATP from ADP and Pi by oxidative phosphorylation
proton gradient
two distinct events take place in chemiosmotic coupling:
(1) a proton gradient is established across the inner membrane of the mitochondrion, and
(2) potential energy stored in the gradient is used to generate ATP from ADP and phosphate
the complete oxidation of sugars or other organic molecules to carbon dioxide and water
Respiration
the combination of the acetyl group and CoA and is the form in which carbon atoms from glucose enter the citric acid cycle
acetyl CoA
the overall reaction for the complete oxidation of glucose
C6H12O6 + 6O2 ⎯→ 6CO2 + 6H2O + Energy
— a large molecule consisting of a nucleotide linked to pantothenic acid, one of the B-complex vitamins
— often written as CoA-SH to indicate its sulfur group, where bonding occurs
coenzyme A (CoA)
electron acceptor; the first component of the electron transport chain
flavin mononucleotide (FMN)
can move freely within the lipid bilayer of the membrane and thus can shuttle electrons between other, less mobile carriers.
ubiquinone, also called coenzyme Q (CoQ)
– The term “chemiosmotic,” coined by Peter Mitchell, reflects the fact that the production of ATP in oxidative phosphorylation includes both chemical processes (the “chemi” portion of the term) and transport processes across a selectively permeable membrane (the “osmotic” portion of the term)
chemiosmotic coupling
the oxidation of pyruvate to acetyl CoA yields
two molecules of NADH
The Strategy of Energy Metabolism
catabolism
anabolism
– the mechanism by which oxidative phosphorylation is accomplished
– mechanism of ATP synthesis
chemiosmotic coupling
(endergonic) are the pathways by which cells synthesize the diversity of molecules that constitute a living organism
anabolism
takes place in the cytosol, and in the presence of oxygen yields 2 molecules of ATP directly plus 2 molecules of NADH per molecule of glucose. The net yield from reoxidation of the 2 NADH molecules is only 4 molecules of ATP, rather than the 6 that would otherwise be expected.
Glycolysis
the principal electron carriers of the chain
flavin mononucleotide (FMN) - which receives two electrons from NADH and passes them to CoQ
coenzyme Q (CoQ) - located in the lipid interior of the membrane, ferries electrons from Complex I to Complex III, which contains cytochrome b
cytochromes b, c, a, and a3
consists overall of glycolysis, the citric acid cycle, and the electron transport chain
Respiration
(from glyco-, meaning “sugar,” and lysis, meaning “splitting”), the six-carbon glucose molecule is split into two molecules of pyruvate
Glycolysis
In many bacteria, fungi, protists, and animal cells, this oxygenless, or anaerobic, process results in the formation of lactate, a three-carbon compound similar in structure to pyruvate.
Lactate Fermentation
the universal energy currency in living organisms
ATP
occurs in a series of 10 steps, each catalyzed by a specific enzyme
an anaerobic process that occurs in the cytosol
begins with preparatory phase, which requires an input of energy in the form of ATP (steps 1 and 3)
have two phases:
Preparatory phase – Energy investment: 2ATP
Payoff phase – Energy yield: 4ATP and 2NADH
Ends with Most of the Energy of the Original Glucose Molecule Still Present in the Two Pyruvate Molecules
Glycolysis
Is the Chief Source of Energy in Most Cells
glucose
also occurs in the matrix of the mitochondrion, yielding 2 molecules of ATP, 6 of NADH, and 2 of FADH2
Citric acid cycle
is involved in the formation of ATP using energy supplied to electrons by the sun. It can also be used to power other transport processes
chemiosmotic power
The two-step process by which pyruvate is converted anaerobically to ethanol. In the first step, carbon dioxide is released. In the second, NADH is oxidized and acetaldehyde is reduced
Alcohol Fermentation
Completes the Metabolic Breakdown of Glucose to Carbon Dioxide
citric acid cycle
Is Achieved by the Chemiosmotic Coupling Mechanism
Oxidative Phosphorylation
the yield of the citric acid cycle
2 ATP
two molecules of FADH2
six molecules of NADH
occurs in the matrix of the mitochondrion, yielding 2 molecules of NADH for each molecule of glucose
Conversion of pyruvate to acetyl CoA
uses the energy of protons moving down their gradient to produce ATP
ATP synthase
In yeast and most plant cells, however, pyruvate is converted to ethanol (ethyl alcohol) and carbon dioxide.
Alcohol Fermentation
protein molecules with an iron-containing porphyrin ring, or heme group, attached
cytochromes
Glycolysis (from glucose to pyruvate) can be summarized by the overall equation:
Glucose + 2NAD+ + 2ADP + 2Pi ⎯→ 2 Pyruvate + 2NADH + 2H+ + 2ATP + 2H2O
is the cleavage step from which glycolysis derives its name
step 4
the formation of ATP by the enzymatic transfer of a phosphate group from a metabolic intermediate to ADP, as occurs in steps 7 and 10
Substrate-level phosphorylation
The overall equation for the citric acid cycle is therefore:
Oxaloacetate + Acetyl CoA + 3H2O + ADP + Pi + 3NAD+ + FAD ⎯→ Oxaloacetate + 2CO2 + CoA + ATP + 3NADH + 3H+ + FADH2
The most abundant components of the electron transport chain
quinone molecules
This enzyme complex consists of two major portions, FO, which is contained within the inner membrane of the mitochondrion, and F1, which extends into the matrix.
ATP synthase
reflects the fact that the production of ATP in oxidative phosphorylation includes both chemical processes
chemi
transport processes across a selectively permeable membrane
osmotic
The two-step process by which pyruvate is converted anaerobically to ethanol.
In the first step, carbon dioxide is released. In the second, NADH is oxidized and acetaldehyde is reduced.
alcohol fermentation equation
Glucose + 2ADP + 2Pi ⎯→ 2 Ethanol + 2CO2 + 2ATP + 2H2O
lactate fermentation equation
Glucose + 2ADP + 2Pi ⎯→ 2 Lactate + 2ATP + 2H2O
oxidation
loss of electron
reduction
gain of electron
process for a fat to convert to acetyl CoA and enter the citric acid cycle, the triglyceride molecule is first hydrolyzed to glycerol and three fatty acids. Then, beginning at the carboxyl end of the fatty acids, two-carbon acetyl groups are successively removed as acetyl CoA.
Beta oxidation
protein complex that is not a part of the transfer of electrons from NADH to O2
complex II
