Term
| What is glycolysis, what are the two phases and what comes in and out? |
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Definition
◦ ‘sugar splitting’
◦ Two phases:
Energy investment
IN: Glucose, 2ATP
OUT: 2G3P
Energy payoff
IN: 2G3P
OUT: 4 ATP, 2 NADH,
2 Pyruvate |
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Term
| Describe the steps of the citric acid cycle |
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Definition
Step 1: Synthesis of Citric Acid.
This step of the Krebs cycle is a Aldol condensation reaction and it is irreversible reaction. Oxaloacetic acid and the acetyl CoA condense to form citric acid in the presence of the enzyme citrate synthase. The net effect of this reaction is to join a two-carbon with a four-carbon molecules which yields a six-carbon molecule which is the citric acid. This is called the synthesis of citric acid.
Step 2: Dehydration of citrate
It is a reversible reaction. Under the action of the enzyme acotinase, citrate is isomerized to form isocitrate.
Step 3: Oxidation and Decarboxylation of isocitrate
This reaction is catalyzed by the emzyme isocitrate dehydrogenase. This is an irreversible reaction where isocitrate undergoes oxidative decarboxylation yielding 3 NADH molecules. These are first NADH molecules produced in the cycle and also CO2.
Step 4: Oxidative decarboxylation of α-ketoglutarate
The enzyme α-ketoglutarate dehydrogenase complex catalyzes the conversion of α-ketoglutarate to succinyl CoA. This reaction produces the second CO2 and also the second NADH of the cycle. The coenzymes that are required in the reaction are thiamine pyrophosphate, lipoic acid, FAD, NAD+ and CoA.
Step 5: Substrate level phosphorylation
The This reaction is catalyzed by the enzyme succinyl-CoA synthetase. This reaction is exothermic and is GTP molecule which is equivalent to ATP is generated in this reaction. The product of this reaction is succinic acid and GTP.
Step 6: Oxidation
This reaction is catalyzed by the enzyme succinate dehydrogenase. In this reaction the final electron acceptor is the FAD coenzyme. This reaction yields two ATP molecules from the electron transport chain.
Step 7: Hydration
The hydration reaction is catalyzed by the enzyme fumarase. The fumarate is hydrated to form L-Malate.
Step 8: Oxidation
This is reversible reaction, catalyzed by the enzyme malate dehydrogenase. The malate is oxidized to form oxaloacetic acid. This is the final point of entry to the electron transport chain. This reaction generates the NADH and oxaloacetate. |
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Term
| What comes in and out of Citric Acid Cycle? |
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Definition
Summary so far (net changes):
IN: Glucose
OUT: 6 CO2
, 10 NADH, 2 FADH2
, 4 ATP |
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Term
| What are the two steps of oxidative phosphorylation |
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Definition
I. Passing electrons generated by earlier steps in cellular
respiration down an electron transport chain to generate a
proton gradient
II. Using this proton gradient to generate ATP |
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Term
| Where does oxidative phosphorylation occur? |
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Definition
Takes place in mitochondria
Cristae provide increased
surface area
Structure/function |
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Term
| Describe how electrons move across the electron transport chain |
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Definition
◦ Pass electrons to progressively less energetic
configurations, using the energy to pass protons
across membrane, establishing gradient
Releases energy slowly
Creates ‘proton motive force’ |
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Term
| What is the electron transport chain made up of? |
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Definition
Electron transport chain
◦ Complexes of proteins and
prosthetic groups
◦ Mobile electron carriers
◦ Oxygen is final electron
acceptor
Progressive redox reactions
◦ (Not the same as the
Photosynthesis ETC) |
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Term
| Where does NADH and FADH2 electrons enter the Electron Transport Chain? |
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Definition
◦ NADH and FADH2 electrons enter at different points – different
proton yields
NADH – complex I, translocating protons
FADH2 – complex II, no proton translocation
Both pass to complex III & IV, which translocate additional protons |
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Term
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Definition
◦ Using proton gradient across membrane to drive
formation of ATP |
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Term
| Describe ATP synthase in the the mitochonrial matrix |
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Definition
◦ Multi-protein complex
Inner mitochondrial membrane
◦ Protons move down their
gradient
◦ Catalytic domain uses energy
to form ATP from ADP and Pi |
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Term
| What comes in and out of cellular respiration |
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Definition
IN: Glucose, O2
OUT: 6 CO2
, 30-32 ATP |
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Term
| What is cellular metabolism? |
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Definition
◦ Many other biomolecules can be broken down for
use in the pathway
◦ Respiratory pathways are
part of the wider biochemistry
of the cell
◦ The breakdown products
other macromolecules feed
into this pathway at various
points |
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Term
| What is an obligate anaerobe? |
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Definition
Anaerobic respiration
Use electron transport chain
Pass electrons to some other acceptor, such as SO4
2-
Fermentation |
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Term
| What is a facultative anaerobe? |
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Definition
| Can choose to use cellular respiration or fermentation |
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Term
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Definition
◦ Pyruvate occupies central position in energy harvest
from breakdown of glucose
◦ Regulated switch based on oxygen levels
◦ Implications for endosymbiosis theory
◦ Anaerobic respiration
Uses glycolysis only to produce ATP
Regenerated NAD+ by other reactions
◦ Two types:
Alcohol
Lactic acid |
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Term
| Describe what happens if you have no O2? |
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Definition
It’s about electrons and dinucleotide cofactors
• Anaerobic Respiration passes electrons from respiratory
chain to some other acceptor
• Fermentation regenerates cytoplasmic NAD+ from NADH,
to allow glycolysis to produce a small amount of ATP |
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Term
| Describe lactic acid fermentation |
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Definition
◦ Converts pyruvate into lactate using NADH
Restores NAD+ pool needed for Glycolysis
◦ Only produced the 2 ATP from Glycolysis
A little is better than none
◦ Reversible if O2
restored |
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Term
| Describe alcohol fermentation |
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Definition
◦ Converts pyruvate into acetaldehyde
◦ Converts acetaldehyde to ethanol using NADH |
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Term
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Definition
| Much less ATP, but a little is better than none |
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Term
| What are implications of fermentation implications of? |
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Definition
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Term
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Definition
◦ Photosynthesis & Cellular Respiration both
the sun doesn’t shine all the time
the roots don’t get any light, yet still require energy
The product of the Calvin Cycle, G3P, can
immediately enter Energy Payoff phase of
Glycolysis |
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