BISC 1111 Study Guide - Quiz Guide: Citric Acid Cycle, Acetyl-Coa, Oxidative Phosphorylation

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8 Feb 2017

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Samuel Mohebban Exam 3
Study guide, Chapters 8.1-8.4, 9, 10.1-10.3, 11.1-11.4.
Catabolic pathways (“Downhill”)- Release energy by breaking down complex molecules to simpler
o Cellular respiration
Glucose and other organic fuels are broken down in the presence of O2 CO2 and
Anabolic pathways (“Uphill”)- consumer energy to build molecules from simpler ones
o Synthesis of amino acid from simpler molecules
o Synthesis of a protein from amino acids
Energy released from the downhill reactions of catabolic pathways can be stored and then used to
drive the uphill reactions of anabolic pathways
Chemical energy- potential energy available for release in a chemical reaction
o Glucose is high in chemical energy (reactions above)
Exergonic- expends energy
o change is G is negative
o Magnitude represents max amount of work
Endogenic- absorbs energy
o change is G is positive
Spontaneous chemical reaction occurs without the need of outside energy
o If sucrose was dissolved in water, it would sit for years at room temp.
However, if an enzyme was added, then the sucrose can be hydrolyzed in seconds
Sucrose- Sucrase
Activation energy- energy required to push uphill, in order to start downhill
o Lowered when if enzymes are added
Substrate- reactant in enzyme
Active site- place where substrate binds
Enzyme-substrate complex- when an enzyme binds to a substrate
Enzyme changes shape from interaction between the substrate’s chemical groups and chemical
groups on the side chains of amino acids that form the active site
o Becomes tighter and brings chemical groups of the active site into positions that enhance
their ability to catalyze the chemical reaction
Substrate is held in the active site by weak bonds (H & Ionic)
R groups of amino acids in the active site catalyze the conversion of substrate to product
o Product then departs from the active site
Enzyme can catalyze either forward or reverse reactions
o Depending on which direction has a negative (Change in G)
Fermentation- partial degradation of sugars or other molecules without the use of O2
Cellular respiration- consists both aerobic and anaerobic processes
o Organic compounds + O2 CO2 + H2O + Energy
o Brings Hydrogen and oxygen together to form water
Stages of cellular respiration
o 1) Glycolysis-
Breaking of glucose (6-carbon sugar) into two 3-carbon sugars
The 2 3-carbon sugars are then oxidized to form pyruvate (ionized form of
pyruvic acid)
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Samuel Mohebban Exam 3
Glycolysis divided into 2 phases:
1) Energy investment phase
o ATP is used
2) Energy payoff phase
o ATP uses in first phase then is produced using substrate-level
o NAD+ is reduced to NADH by electrons released from th
oxidation of glucose
No carbon is released and occurs without Oxygen
However, if O2 is present, the chemical energy stored in pyruvate and
NADH can be extracted by pyruvate oxidation, the citric cycle, and
oxidative phosphorylation
o 2) Pyruvate Oxidation and the Citric Acid Cycle
Pyruvate Cycle
Pyruvate is first converted to a compound called acetyl coenzyme A (acetyl
In Pyruvate Oxidation, multi-enzyme complex that catalyzes 3 reactions:
1) pyruvates carboxyl group (COO-) is removed and given off as a
molecule of CO2. (First step where CO2 is released)
2) remaining 2-carbon fragment is oxidized to form acetate (CH3COO-,
which is the ionized form of acetic acid)
o Extracted electrons are transferred to NAD+, storing energy in
the form of NADH
3) CoA (sulfur-rich compound), is attached via its sulfur atom to
acetate acetyl CoA, which is high in potential energy
Citric Acid Cycle
o 3) Oxidative Phosphorylation- electron transport and chemiosmosis
Mode of ATP synthesis
Electrons are combines with molecular O and H ions to form water
Substrate-level phosphorylation- occurs when an enzyme transfers a P-group
from a substrate molecule to ADP, rather than adding an inorganic phosphate to
ADP as in oxidative phosphorylation (Less energy)
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