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Preliminary Objectives - Chapter 6, Part 1

Terms in this set (13)

Describe what is meant by the "coupling" of exergonic and endergonic reactions, and explain how conversions between ATP and ADP would be involved in a coupled reaction
Watch video & refer to lecture slides.
To carry out the many metabolic processes needed to sustain life, cells must release & reuse the energy contained in chemical bonds. The energy-coupling coenzymes, ATP & NADH, play roles in the transfer of energy b/w cellular reactions that release energy (catabolism) and those that require energy (anabolism)

Catabolism (exergonic): releases energy by oxidation & this energy can be trapped by reduction of coenzymes such as NAD+

Anabolism (endergonic): ATP supplies the energy for many energy-requiring processes

*Most energy-releasing reactions produce NADH, but most energy-consuming reactions require ATP
Describe what happens to electrons in a redox reaction, and how repeated redox reactions of what was originally a molecule of glucose generates ATP.
Redox reaction: When molecule loses an electron and gives the electron to another molecule
Cells use NAD as an electron carrier in redox reactions. The reduction of NAD is highly endergonic, & within the cell, the (e-) don't remain in NADH. Oxygen is highly electronegative & readily accepts (e-) from reduced NADH molecule. The oxidation of NADH by oxygen is highly exergonic
In a description or diagram of a redox reaction, identify which reactant was reduced, and which was oxidized.
NAD ---> NADH
<---
-NAD is the reactant that is reduced, it gained an electron.
-NADH is the reactant that is oxidized, it lost an electron

FAD ---> FADH
-FAD is the reactant that is reduced
-FADH is the reactant that is oxidized

NAD & FAD
Oxidized: Intermediary forms of glucose
Glucose serves as a donor of (e-) to NAD & FAD

NADH & FADH
Reduced: Oxygen is reduced to H2O and is the final electron acceptor

3 Pathways that use Reduction:
1) Glycolysis
2) Citric Acid Cycle
3) Pyruvate Oxidation
Describe the difference between substrate-level phosphorylation and oxidative phosphorylation
Substrate-level phosphorylation: Simple Chemical Rx, from one reactant from ATP, to form ADP

Oxidative phosphorylation: Take energy in (e-), donate (e-) to Oxygen and donate to ATP; Electron carriers (NADH & FADH2) lose (e-) and they supply energy of active transport of hydrogen ions & then diffusion of H ions, through a protein allows for ATP to be created
For the metabolic pathways of 1) glycolysis, 2) alcohol fermentation, 3) lactic acid fermentation, 4) the electron transport chain, 5) the citric acid cycle, and 6) pyruvate oxidation, do the following:
o Identify the correct order in which they occur during 1) cellular respiration and 2) fermentation.
o Identify which organisms carry out these each individual pathway.
o Identify where each pathway occurs in 1) eukaryotic cells and 2) prokaryotic cells
o Provide their inputs (reactants) and outputs (products)
o Identify which metabolic pathways their inputs came from, and which metabolic pathways their products go to.
o Recall whether coenzymes are being either reduced or oxidized during this pathway.
o Recall which of these pathways use substrate level phosphorylation, and which use oxidative phosphorylation (electron transport) to produce ATP.
Glycolosis:
Who: All living organisms carry out Glycolosis
Where: Cytoplasm
Inputs: 2 NADH
Outputs: 2 Pyruvate, 4 ATP

Pyruvate Oxidation:
Who: All eukaryotes/many but not all prokaryotes
Where: Eukaryotes - Matrix Mitochondria
Prokaryotes - Cytoplasm
Inputs: 2 Pyruvate, NADH, and CO2
Outputs:

Citric Acid Cycle:
Who: All eukaryotes/many but not all prokaryotes
Where: Eukaryotes - Matrix Mitochondria
Prokaryotes - Cytoplasm
Inputs:
Outputs: NADH, CO2, 2ATP, and FADH2

Electron Transport Chain:
Who: Everything that carries out cellular respiration
Where: Eukaryotes: Inner-membrane of mitochondria
Prokaryotes: Cell membrane
Inputs: NADH, FADH2, H2O, and O2
Outputs:
In Glycolysis
o Distinguish between the events that occur in 1) the Energy Investment Stage and 2) the Energy Harvesting Stage
o Name the functions of the enzymes phosphofructokinase and pyruvate kinase, and which stage of Glycolysis they are used.
1) Energy Investment Stage: Take phosphates of 2 ATP, and make Fructose 1,6 Biphosphate
Phosphofructokinase is an important enzyme used in the Energy Investment Stage. What does it do?

2) Energy Harvesting Stage: From the 1, 6 Biphosphate, it splits into two pyruvate (G3P)
4 ATP + 2 Pyruvate + NADH
Pyruvate kinase is an important enzyme in the Energy Harvesting Stage and it helps create ATP
In Pyruvate Oxidation
o Recall that each molecule of pyruvate, after reacting with coenzyme A, forms a molecule of Acetyl coenzyme A (Acetyl CoA)
Read the text.
NADH ---> Electron Transport Train
Acetyl CoA ---> Citric Acid Cycle
In the Citric Acid Cycle:
o For the first step of this pathway, name the two reactants used and the product they form
o Name the final product after one "turn" of this cycle
o Name the product of the final reaction of this cycle that is used as a reactant in the first reaction of this cycle
Read the text.
Oceleoacetate --> Citrate (reduces NAD & FADH)
Final products: Reactant in 1st step becomes the product in the last step? Oceleoacetate is regenerated
*w/o NAD, no citric cycle
In the Electron Transport Chain and Chemiosmosis:
o Identify the roles of oxygen, hydrogen ions, and donated electrons, and identify what product they become.
o Identify whether 1) ATP synthase OR 2) "other membrane proteins" are involved in:
• the active transport (pumping) of hydrogen ions
• simple diffusion of hydrogen ions
• the oxidation of NADH or FADH
• the donation of electrons to oxygen
• the synthesis of ATP.
Read the text.
Chemiosmosis: Hydrogen ions diffuse through protein channel: ATP synthase, then form 28 ATP (?)
For obligate aerobes, obligate anaerobes, and facultative aerobes
o Identify whether they die in the presence of oxygen, or in the absence of oxygen.
o Identify whether prokaryote and/or eukaryote species are included in that category.
o Identify if they can carry out cellular respiration or fermentation, and if these pathways are used for both growth and cellular energy, or just for cellular energy.
Obligate aerobes: Must have oxygen to survive

Obligate anaerobes: Must not have oxygen present if they're going to survive

Facultative aerobes: May use oxygen or can survive without it
Read text to find answer for last bullet
Distinguish between catabolic and anabolic interconversions
Catabolic Interconversions: Polysaccharides, proteins, and lipids can be broken down to provide energy

Polysaccharides - Can be hydrolyzed to glucose. Glucose passes through Glycolysis, pyruvate oxidation, & the respiratory chain, where energy is captured in ATP

Proteins - Hydrolyzed into amino acid building blocks. 20 amino acid building blocks feed into glycolysis or the citric acid cycle at different points.
e.g. Amino acid, glutamate, converted to alpha-ketoglutarate. Alpha-ketoglutarate is an intermediate in the citric acid cycle

Lipids - Broken down into glycerol & fatty acids. Glycerol is converted into dihydraxyacetone phosphate. Fatty acids are highly reduced molecules converted to acetyl CoA during Beta-oxidation, catalyzed by series of oxidation enzymes inside the mitochondrion

Anabolic Interconversions: Many catabolic pathways can operate in reverse w/ some modifications
e.g. Gluconeogenesis, Glycolytic & citric acid cycle intermediates can be reduced & used to form glucose instead of being oxidized to form CO2
Describe the process of gluconeogenesis
"New formation of glucose"
Gluconeogenesis: When Glycolytic & citric acid cycle intermediates can be reduced and used to form glucose

Acetyl CoA is used to form fatty acids
Some citric acid intermediates can form nucleic acids
Distinguish between an example of a positive feedback mechanism, and a negative feedback mechanism
(?)
Negative feedback: Occurs when the rate of the process decreases as the concentration of the product increases

E.g. In a metabolic pathway, a high concentration of the final product can exhibit the enzyme that catalyzes commitment step. With ATP (product of glucose catabolism) feedback inhibits key enzymes in both glycolysis and the citric acid cycle

Positive feedback: The rate of the product increases as the concentration of the product increases

E.g. Feedback involves the product of one pathway speeding up reactions in another pathway. Feedback regulation generally occurs rapidly, affecting a pathway within minutes
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