CH 9: Cellular Respiration
H+ then moves back across the membrane, passing through the protein complex called ______________.
ATP synthase
Redox reactions
Chemical reactions that transfer electrons between reactants
Pyruvate Oxidation
Conversion of pyruvate to acetyl CoA and CO2 that occurs in the mitochondrial matrix in the presence of O2.
NAD+ as an electron shuttle
Electrons from organic compounds are usually first transferred to NAD+, a coenzyme
Stages of Cellular Respiration
Glycolysis (breaks down glucose into two molecules of pyruvate) The citric acid cycle (completes the breakdown of glucose) Oxidative phosphorylation (accounts for most of the ATP synthesis)
Cellular respiration
Includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration
Glycolysis: energy investment phase
Input: glucose, 2 ATP Output: pyruvate, 2 net ATP, 2 NADH
Glycolysis: energy payoff phase
Input: glucose, 2 ATP, 2 NAD+ Output: 2 pyruvate, 2 net ATP, 2 NADH
Citric Acid Cycle inputs and outputs
Inputs: 2 pyruvate -->Acetyl-CoA; 2 oxaloacetate Outputs: 6 CO2, 2 ATP, 8 NADH, 2 FADH2
Glycolysis inputs and outputs
Inputs: glucose, 2 ATP Outputs: 2 pyvare, 2 net ATP (4 ATP), 2 NADH
In lactic acid fermentation, pyruvate is reduced by NADH, forming
NAD+ and lactate as end products, with no release of CO2
Stepwise Energy Harvest via NAD+ and the Electron Transport Chain
NADH passes the electrons to the electron transport chain
Glycolysis occurs whether or not _______ is present.
O2
______________ is the the process that generates almost 90% of the ATP
Oxidative Phosphorylation
ATP yield per molecule of glucose at each stage of cellular respiration
Review pg. 177
Free energy change during electron transport chain
See Pg. 174
H3C-CH3 --> H2C=CH2 Oxidation or Reduction?
Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds. Methane is reducing agent (electron donor) and oxygen is oxidizing agent (electron acceptor)
Accounts for the smaller amount o ATP is formed in glycolysis and cytric acid cyle
Substrate-level phosphorylation
The Pathway of the Electron Transport
The electron transport chain is in the inner membrane (cristae) of the mitochondrion Most of the chain's components are proteins, which exist in multi-protein complexes (cytochromes) Electrons drop in free energy as they go down the chain and are finally passed to O2, forming H2O
Substrate-level phosphorylation
The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism.
Oxidative Phosphorylation
The production of ATP using energy derived from the redox reactions of an electron transport chain.
H+ then move into binding sites on the rotor of ATP synthase, causing it to spin in a way that catalyzes __________________.
phosphorylation of ADP to ATP
Fermentation and anaerobic respiration enable cells to
produce ATP without the use of oxygen
The energy released as electrons are passed down the electron transport chain is used to
pump H+ from the mitochondrial matrix to the inter membrane space
a substance gains electrons is
reduced
Transfer of electrons during chemical reactions
releases energy stored in organic molecules
Fermentation uses __________________ instead of an electron transport chain to generate ATP
substrate level phosphorylation
Feedback inhibition
the most common mechanis for metabolic control
Chemiosmosis
the use of energy in a H+ gradient to drive cellular work
Citric Acid Cycle (Krebs Cycle)
- 2 Pyruvates enter the mitochondrion - releases 2 ATP, 6NADH, and 2 FADH2 for each glucose
Proton motive force (PMF)
- potential energy stored across a membrane - cell actively pumps hydrogen ions out of the cytoplasm creating a charge across the membrane
In alcohol fermentation, pyruvate is converted to ethanol in two steps
1st: Releases CO2 from pyruvate 2nd: Produces NAD+ and ethanol Fermentation by yeast used for brewing, wine, baking
____________ and _____________ are two type of fermentation
alcohol fermention; lactic acid fermentation
Dehydrogenase
an enzyme that catalyzes the removal of hydrogen atoms from a particular molecule, particularly in the electron transport chain reactions of cell respiration in conjunction with the coenzymes NAD and FAD.
Glycolysis ("sugar splitting")
breaks down glucose into two molecules of pyruvate
Control of ____________ is based on regulating the activity of ___________ at strategic points in the catabolic pathway
catabolism; enzymes
Without oxygen, the electron transport chain will
cease to operate. In that case glycolysis couples with anaerobic respiration or fermentation to produce ATP
During oxidative phosphorylation
chemiosmosis couples electron transport to ATP synthesis
Where does glycolysis occur?
cytoplasm
Most cellular respiration depends on
electronegative oxygen to pull electrons down the transport chain
Catabolic pathways funnel _________from many kinds of organic molecules into ___________________
electrons; cellular respiration
Two major phases of glycolysis
energy investment phase and energy payoff phase
Anaerobic respiration uses an electron transport chain with a_______________________other than oxygen, such as sulfate.
final electron acceptor
Flow of energy in cellular respiration
glucose --> NADH --> ETC --> proton-motive force --> ATP
Fermentation consists of __________ plus reactions that generate ________, which can be reused by glycolysis
glycolysis; NAD+
A substance loses electrons is
oxidized
About 34% of the energy in a glucose molecule is
transferred to ATP during cellular respiration, making about 32 ATP. The rest of the energy is lost as heat.