Chapter 9 : Cellular Respiration

Energy flows into an ecosystem as sunlight, and leaves as heat.
How does energy flow into and out of an ecosystem?
The breakdown of organic molecules is…
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Partial degradation of sugars that occurs WITHOUT oxygen.
Consumes organic molecules and oxygen yields ATP.
Aerobic Respiration
Consumes compounds without oxygen, but similar to aerobic respiration.
Anaerobic Respiration
Does cellular respiration include both aerobic and anaerobic respirations?
C6H12O6 + 6 O2 = 6 CO2 + 6 H2O + Energy (ATP and Heat)
What is the equation for cellular respiration?
Oxidation. (substance becomes oxidized)
A loss of hydrogen or electrons…
Reduction. (substance becomes reduced)
*amount of positive charge is reduced
A gain of hydrogen or electrons…
Does the transfer of electrons during chemical reactions release energy stored in organic molecules? Is this energy used to synthesize ATP?
Chemical reactions that transfer electrons between reactants are called?
Is oxidized and is called a reducing agent.
Electron Donor
Is reduced and is called the oxidizing agent.
Electron Receptor
Do not transfer electrons but change the electron sharing in covalent bonds.
Ex. Reaction between O2 and methane
Redox Reactions
Glucose is being oxidized (losing hydrogen).
Oxygen is being reduced (gaining hydrogen).
In cellular respiration, is the glucose being oxidized or reduced? Is Oxygen being oxidized or reduced?
Coenzyme; is an electron acceptor functioning as an oxidizing agent during cellular respiration.
Reduced form of NAD+; represents stored energy that is tapped to synthesize ATP.
Does NADH pass electrons to the ETC (electron transport chain)?
TRUE OR FALSE. The ETC passes electrons in a series of steps instead of one uncontrolled explosive reaction
FALSE; Oxygen pulls electrons up the ETC chain.
TRUE OR FALSE. Oxygen pulls electrons up the ETC chain in an energy yielding tumble.
Breaks down glucose into two molecules of pyruvate.
Completes the breakdown of glucose
Citric Acid Cycle/ Krebs Cycle
Accounts for most of the ATP synthesis; by chemiosmosis.
Oxidative Phosphorylation
Oxidative Phosphorylation generates most of the ATP and is powered by redox reactions. (90% of ATP)
What process in cellular respiration generates the most ATP?
Glycolysis, and the Citric Acid Cycle/Krebs Cycle by substrate level phsophorylation.
Smaller amounts of ATP are formed in what processes?
Energy Investment Phase = EA
Energy Payoff Phase = ATP and NADH
What are the phases of Glycolysis?
Where does glycolysis occur?
If Oxygen is present, pyruvates (3 carbon C-H-O) enter the mitochondria
What happens if Oxygen is present?
TRUE OR FALSE. Before the Krebs Cycle can begin, the pyruvate must be converted to Acetyl CoA.
*Acetate + Coenzyme A *
Acetate=two carbon C-H-O
Coenzyme A=carrier molecule
Acetyl CoA
Mitochondrial Matrix.
Citric Acid Cycle occurs where?
How much ATP and NADH and FADH2 is generated per turn of the cycle?
2 Turns per glucose from glycolysis.
How many turns does the Krebs Cycle have to go through from glycolysis per glucose?
8 steps.
How many steps in the Krebs Cycle?
The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate (OAA) and forms citrate; citric acid.
What is the first step in the Krebs Cycle/Citric Acid Cycle?
The next seven step involve the break down of citrate and regeneration of OAA’ making the process a cycle.
What do the next seven steps involve?
They carry electrons extracted from food to the ETC in the mitochondrial cristae membrane.
What do the NADH and FADH2 produced from the Krebs Cycle do?
NADH and FADH donate electrons to ETC which powers ATP synthesis via oxidative phosphorylation.
Where do NADH and FADH donate electrons and why?
Cristae Membrane of Mitochondrion.
Where is the electron transport chain?
Carriers alternate reduced and oxidized states as they accept and donate electrons
Redox in ETC carriers (Electron Transfer)
The Electrons drop in free energy as they go down the chain and are finally passed to O2 forming H2O (waste).
What happens to electrons when they go down the ETC?
NADH and FADH2; electrons are passed along the cristae membrane through a number of proteins including cytochromes (each with an iron atom) to O2. (ETC generates no ATP)
How are electrons transferred to the ETC?
The chain’s function is to break the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts.
What is the ETC’s function?
Redox in ETC causes protein to pump H+ from the mitochondrial matrix to the inter membrane space creating a proton H+ gradient.
What does the electron transfer; redox, in ETC cause?
In ATP Synthase H+moves back across membrane passing through ATP Synthase channels. ATP Synthase then uses the exergonic flow of H+ to drive phosphorylation of ATP
Where does H+ fit in with ATP synthase?
The use of energy in a H+ gradient to drive ATP Synthase.
FALSE, it is a proton-motive force; emphasizing it’s capacity to do work.
TRUE OR FALSE. The H+ gradient is a electron-motive force.
ETC Redox and Chemiosmosis
Two steps in Oxidative Phosphorylation =
10 NADH x2.5 (25 ATP)
2FADH^2 x1.5 (3 ATP)
Amount of energy being made in cell. resp.
Pyruvate Ox.
Krebs Cycle
Ox. Phosphor.


Glucose > NADH > Electron Transport Chain > Proton-motive Force > ATP
How does energy flow in cellular respiration?
38 ATP
How much energy is made in cellular respiration?
In absence of O2, glycolysis couple with fermentation and anaerobic respiration to produce ATP.
How does glycolysis produce ATP without O2?
Fermentation consists of glycolysis plus reaction that regenerate NAD+; which can be reused by glycolysis.
What does fermentation consist of?
Pyruvate is converted to ethanol in two steps, with the first releasing CO2.
Alcohol Fermentation
Pyruvate is reduced to NADH (forming lactate as a product) with no release of CO2
Lactic Acid Fermentation
Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce, meaning there is an O2 debt. This reaction is reversible when O2 is available.
Example of Lactic Acid Fermentation in Human Muscle Cells
ACR nets 38 ATP per glucose molecule vs Fermentation nets only 2 ATP per glucose molecule
Aerobic Cellular Respiration vs. Fermentation in energy production
Carry out fermentation or anaerobic respiration and cannot survive without the presence of O2.
Obligate Anaerobes
can survive using either fermentation or cellular respiration
Facultative Anaerobes
Fermentation was evolved to recycle NAD+ back to glycolysis so ATP production could continue in the absence of O2.
Why was fermentation evolved?
Energy is released
When electrons move closer to a more electronegative atom…
Oxygen becomes reduced
In the reaction glucose + oxygen…

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