IB BIO II
Cell Respiration
Van Roekel
Cell Respiration Review
Cellular Respiration
1. What is Cellular respiration?
Controlled release of energy from organic compounds to produce ATP
2. What is the formula for Aerobic Respiration?
C6H12O6 + 6O2  6CO2 + 6H2O + Energy (ATP)
3. Draw a molecule of ATP and list some of its uses in the body.
Muscle Contraction, Protein Synthesis, Active Transport, DNA Replication, etc..
4. Explain why cellular respiration is considered an oxidation-reduction reaction?
Glucose molecules are being oxidized and oxygen molecules are being reduced during the
reaction.
5. What occurs (what is gained/lost) during oxidation? Reduction?
Oxidation is the loss of electrons/hydrogens. Reduction is the gain of electrons/hydrogens
Oxidation is the gain of oxygen. Reduction is the loss of oxygen.
Glycolysis
1. Where does glycolysis occur? Why does this make Glycolysis the universal energy harvesting
process?
Glycolysis occurs in the cytoplasm. All organisms have a cytoplasm, so all organisms perform
cellular respiration to harvest energy.
2. What does glycolysis mean?
Glycolysis is the splitting of a sugar molecule into two pyruvate molecules through
phosphorylation, oxidation, and substrate-level phosphorylation.
3. Draw and annotate a simplified diagram of glycolysis. (focus on reactions and products more
than intermediates)
Glucose is broken down into 2 pyruvates through a series of reactions that produce 2 molecules
of NADH, and a net production of 2 ATP. First glucose is phosphorylated to fructose 1,6biphosphate. Then it is split into two molecules of glyceraldehyde 3-phosphate, and finally it is
oxidized (producing NADH) and undergoes substrate level phosphorylation (producing ATP).
4. What is substrate level phosphorylation?
An enzyme transfers a phosphate group from a substrate molecule directly to ADP forming ATP.
5. What are the final net products of glycolysis?
2 pyruvates. 2 NADH. 2 ATP.
Link Reaction/Krebs Cycle
1. Where does pyruvate go in the presence of oxygen?
Mitochondrion
2. Specifically, where does the link reaction and the Krebs cycle take place?
Matrix of Mitochondria
3. What occurs during the link reaction? (focus on reactions and products)
Each Pyruvate molecule is decarboxylated, releasing CO2 and becomes an acetyl group. The
acetyl group is oxidized, producing NADH, and joins with coenzyme A to form acetyl CoA.
IB BIO II
Cell Respiration
Van Roekel
4. What molecules can result in the formation of Acetyl CoA?
2 NADH, 2 CO2, 2 Acetyl CoA
5. Draw and annotate a diagram of the Krebs Cycle (focus on reaction and final products)
Acetyl CoA combines with oxaloacetate to form Citrate (6 carbon compound). Citrate is then
oxidized and decarboxylated (producing NADH and CO2) into a 5 carbon compound (Alpha
Ketoglutarate), which again is decarboxylated and oxidized (producing NADH and CO2) into a 4
carbon compound (Succinyl-CoA). The 4 carbon compound undergoes substrate level
phosphorylation (producing ATP) and is oxidized two more times (producing NADH and FADH2)
to return to the starting molecule of oxaloacetate. This will happen two times for every glucose
molecule.
6. What are the final net products of the Krebs cycle?
2 ATP, 6 NADH, 2 FADH2
Electron Transport Chain & Chemiosmosis
1. What it the electron transport chain?
Collection of molecule embedded in the inner mitochondrial membrane that are oxidized and
reduced to provide energy for chemiosmosis and oxidative phosphorylation.
2. What molecules are electron carriers?
NADH and FADH2 are electron carriers that donate their electrons from glycolysis, the link
reaction, and the Krebs Cycle to protein carriers in the electron transport chain.
3. What is produced after the electrons have passed through the electron transport chain?
Oxygen acts as the final electron acceptor in the electron chain and will combine with two
molecules of hydrogen to form water.
4. Describe the process of chemiosmosis (discuss role of electron transport chain, concentration
gradient, proton-motive force, ATP Synthase, etc)
Chemiosmosis is the coupling of the electron transport chain with ATP synthase to provide a
means for oxidative phosphorylation to occur. As the proteins in the electron transport chain
accept electrons, they will pump hydrogen ions from the matrix to the inter-membrane space,
creating a hydrogen ion concentration gradient. This gradient results in proton-motive force,
which allows the hydrogen ions to power ATP synthase as the move down their concentration
gradient, back into the matrix. ATP synthase undergoes conformational changes and will then
combine ADP and phosphate to form ATP.
5. What is oxidative phosphorylation and how is it related to/powered by chemiosmosis?
Oxidative phosphorylation is the combination of ADP and a phosphate group to form ATP,
powered by the redox reactions and the transfer of electrons to oxygen. It is powered by
chemiosmosis because as listed in the steps above, chemiosmosis powers ATP synthase, which
is an enzyme that combines ADP and phosphate to make ATP.
Anaerobic Respiration/Fermentation
1. What happens if no oxygen is present after glycolysis?
Pyruvate will stay in the cytoplasm of the cell and go through anaerobic respiration, using
fermentation, and produce 2 ATP.
2. What is fermentation?
IB BIO II
Cell Respiration
Van Roekel
Fermentation is an extension of glycolysis that regenerates NAD+ from NADH, by reducing
pyruvates or derivatives of pyruvates.
3. Describe the process of alcoholic fermentation (2 steps)
Glycolysis breaks glucose down into pyruvate producing 2 ATP. Alcoholic fermentation first
converts pyruvate into acetaldehyde through decarboxylation, releasing CO2. It is then reduced,
gaining electrons from NADH, into ethanol and regenerating NAD+.
4. Describe the process of lactic acid fermentation
Glycolysis breaks down glucose into pyruvate, producing 2 ATP. Lactic acid fermentation then
reduces pyruvate, gaining electrons from NADH (which is oxidized) and producing lactate. This
regenerates NAD+.
5. Compare and contrast Aerobic and Anaerobic Respiration
Both start with glucose, use glycolysis, produce ATP, produce pyruvate, and produce CO2.
Aerobic pathways use oxygen, use the link reaction, krebs cycle, and electron transport chain,
uses electron transport chain to recycle NADH into NAD+, and produces a large amount of ATP
(36).
Anaerobic pathways do not require oxygen, produce lactic acid/lactate through lactic acid
fermentation, produces ethanol through alcoholic fermentation, occurs only in the cytoplasm of
the cell, and uses fermentation to recycle NADH into NAD+, and produces a small amount of ATP
(2)
Mitochondria
Know parts and functions of mitochrondria
Outer Mitochondrial Membrane
Separates contents of mitochondrion from rest of cell.
Controls entry/exit of materials
Matrix
Cytosol like area of mitochondria…enzymes for Kreb’s
cycle and link reaction
Cristae
Tubular regions of IMM increases surface area for
oxidative phosphorylation
Inner Mitochondrial Membrane
Contains carriers for the ETC and ATP synthase for
chemiosmosis.
Space between inner and outer membranes
Reservoir for H+ ions (necessary for chemiosmosis)