Bio I Exam 3 Chapter 9
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What is the primary source of energy of cell
What do the terms oxidation and reduction refer
- Oxidation is the loss of electrons. Reduction is
- the gain of electrons
What kind of reactions are responsible for
metabolism? What catalyzes these reactions? What happens to the electrons
- Metabolism is a series of exergonic, redox
- reactions catalyzed by enzymes. High energy electrons are transferred to
- low-energy states
Describe the process of a redox reaction.
- A high electron donor (reducing agent) is
- oxidized when it transfers electrons to an electron acceptor (oxidizing agent)
What are the electron donors involved in cell
respiration? What are they oxidized to? For photosynthesis?
- Organic molecules are oxidized to CO2 in
- respiration. In photosynthesis, H20 is oxidized to O2
What are the electron acceptors involved in cell
respiration? What are they reduced to? For photosynthesis?
- O2 is reduced to H2O in respiration. In photosynthesis,
- CO2 is reduced to macromolecules
What is the organelle responsible for
photosynthesis? What is the primary product of photosynthesis? What is the
byproduct of this process?
Chloroplasts; ATP; Oxygen
What organelle is responsible for respiration?What is the primary product of respiration? What is the byproduct?
Mitochondria; ATP; H2O
What is the electron carrier of photosynthesis?
NADPH (think of P for plants); NADH
What in metabolism drives ATP synthesis? What sets this up?
- H+ gradient; electron transport chain sets up
- the H+ gradient
Photosynthesis and respiration are similar in
that both use an ___________
(exergonic/endergonic) step-wise energy release from ________ (high/low)
energy electrons to drive synthesis.
What is the primary source of energy in
photosynthesis? In respiration?
Light energy; chemical energy
What is broken down by respiration? What is
Organic molecules; ATP and Heat
What is the electron receptor in aerobic
What is the difference between aerobic
respiration and anaerobic respiration?
- Aerobic respiration uses oxygen and anaerobic
- respiration does not use oxygen
What is a predominant source of chemical energy?
- Molecules with lots carbon and hydrogen (organic
What happens when electrons are transferred?
- Energy is released which is used to do work and
- make ATP
What kinds of organisms make use of aerobic respiration?
- Both prokaryotes and eukaryotes, most large
- organisms, humans
Why aren’t electrons directly released to reduce
oxygen? How are they released?
- The direct combination would be explosive.
- Instead, electrons are passed down an electron transport chain from NADH to
- oxygen in a stepwise function. Potential energy is lost along the way.
How many molecules of ATP are produced from one
glucose molecule in aerobic respiration?
What are the four different steps of aerobic
respiration? What is the basic function of
- Glycolysis – 6 carbon glucose molecule is broken
- down into two 3-carbon molecules; pyruvate oxidation – 3-carbon molecule
- oxidized to 2-carbon molecule and CO2 is exhaled; citric acid cycle – 2-carbon
- molecule made into CO2; electron transport chain – electrons from previous 3
- steps used to drive ATP synthesis, O2 accepts final electron to form H2O
Where do the different steps of aerobic
respiration take place?
- Glycolysis happens in the cytosol, the others
- take place within the mitochondria
What sources of chemical energy are used as
electron receptors in respiration?
NAD+/NAHD, FAD/FADH2, ADP/ATP
What do the energy molecules NADH and FADH2
- Nicotinamide adenine dinucleotide; flavin
- adenine dinucleotide
What happens in the investment stage of
- A glucose molecule is phosphorylated twice by
- ATP and becomes fructose biphosphate. The fructose biphosphate is then split
- into two phosphorylated 3-carbon molecules
What are the products from the investment phase
of glycolysis? Which one is used further? What happens with the other one?
- Dihydroxyacetone phosphate and Glyceraldehyde
- 3-phosphate (G3P). G3P is used further; Isomerase can convert dihydroxyacetone
- phosphate into G3P as the equilibrium shifts
What happens in the energy payoff phase of
- Glyceraldehyde 3-phosphate dehydrogenase (GAPDH)
- catalyzes the removal of electrons to form NADH from NAD+ and phosphorylate
- G3P. Phosphoglycerate kinase then catalyzes the transfer of a phosphate group
- to ADP to form ATP. Pyruvate kinase then transfers the second phosphate group
- to another ADP to form another ATP molecule
What is the final product from the energy payoff
phase of glycolysis? What is it’s chemical composition? How many ATP molecules
are produced from the process?
Pyruvate; a carboxyl, , and hydrocarbon; 2
Is glycolysis a net endergonic or exergonic
Exergonic, although parts of it are endergonic
What happens in the pyruvate oxidation phase?
- It enters the mitochondria. The carboxyl group
- is removed to form CO2 and electrons are removed to form NADH. The acetyl group
- then attaches to the sulfur atom of coenzyme A
Citrate acid is formed when what two molecules
- Acetyl (after shedding COA) and 4-carbon
What happens to the carbon molecules of citrate
acid as it moves through the citric acid/krebs cycle?
- 2 carbons are removed as CO2 and 4-carbon
- oxaloacetate is reformed
What happens to electrons of the citrate acid
molecule as it passed through the citric acid/Krebs cycle?
- They are removed to form 3 NADH molecules and 1
- FADH2 molecule
CoA is removed at the beginning of the citric
acid/Krebs cycle but reappears later in the cycle. What does it attach to and
why does it reappear?
- It attached to 4-carbon succinyl to aid in
- phosphorylation and help form ATP or GTP
What products and how many of each are produced
in the citric acid/Krebs cycle?
3 NADH, 1 FADH2, 1 ATP or GTP, 2 CO2
How are fats transformed into energy?
- 2 carbons are removed from the fatty acid which
- are then turned into an acetyl group in a process that also yields NADH and
- FADH2. The acetyl group then attaches to CoA and enters the citric acid/Krebs
Why do fats have high caloric content?
- They contain lots of carbon and can make lots of
- acetyl groups which then go on to be processed and create energy in the citric
- acid/Krebs cycle
What is the net change in free energy from the
respiration of one glucose molecule? Order steps from most energy to least
- About -700; Citric acid cycle, pyruvate
- oxidation, glycolysis
Where do the different phases of respiration
- Glycolysis takes place in the cytosol, pyruvate
- oxidation and citric acid/Krebs cycle take place in the matrix of the
- mitochondria, electron transport chain takes place in the cristae of the
What is the electron transport chain in
respiration made from and where is it located?
- It is a chain of proteins located on the inner
- mitochondrial membrane (cristae)
What molecules donate electrons to the electron
transport train in respiration? Where are they delivered to? What happens to
- NADH and FADH2; membrane proteins; they are
- energized to perform active transport a proton against the gradient
Where does a high proton concentration
accumulate during cellular respiration?
In the intermembrane space of the mitochondria
What membrane proteins are mostly responsible
for the transport of electrons in respiration?
Cytochromes and others that contain iron
What acts as the final electron acceptor in
cellular respiration and what does it form once it accepts the electrons?
What is the process of chemiosmosis and what
does it do in respiration? What aids in this process and what is this made
- Chemiosmosis is the facilitated diffusion of
- protons back into the mitochondrial matrix and results in ATP production. ATP,
- made from about 10 proteins, synthase is what helps the proton diffuse.
What are the byproducts of each of the steps in
- Glycolysis = 1 ATP and 1 NADH, Pyruvate
- oxidation = 1 NADH and 1 CO2, Citric Acid Cycle = 3 NADH, 1 FADH2, 1 ATP, 2
- CO2, Oxidative Phosphorylation = 15 ATP
Where does ATP synthase occur in PROKARYOTES?
On the Cell membrane using an ion gradient
What is anaerobic respiration? Where does it
occur? How is it similar/different than aerobic respiration?
- Respiration without O2; prokaryotes; similar to
- aerobic respiration but just with a different final electron acceptor
What is fermentation?
- It is a process to make ATP that includes only
- glycolysis and sometimes pyruvate oxidation. It makes much less ATP than respiration
- because it only includes substrate level phosphorylation
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