Ch 8 Microbial Metabolism Flashcards
What is a metabolic pathway
Sequence of chemical reactions each catalyzed by a particular enzyme; anabolic and catabolic
Define metabolism
The sum total of all energy exchanges that occur in cells
What is an anabolic pathway
Consume energy to build larger more complex molecules from simpler ones; can be called biosynthetic pathways; “uphill pathways”
Catabolic pathway
Release energy by breaking down more complex molecules into simpler ones; “downhill pathways”
What is free energy
The portion of a system’s energy that can perform work
Exergonic reaction
Proceeds with a net release of free energy; spontaneous reactions; “downhill reactions” products have less free energy than the reactants; catabolic
Endergonic reactions
One that absorbs free energy from its surroundings; non-spontaneous reactions; “uphill reactions” products have more free energy than the reactants
ATP is made up of what two things
Nucleotide and inorganic phosphate groups (Pi)
What three things make up a nucleotide
Nitrogenous base, ribose, phosphate group
Which nitrogenous base is found in ATP
Adenine (which is a purine)
What is Phosphorylation
Addition of a Pi (an inorganic phosphate group)
Phosphorylation of ADP would form ____ and is a _____ reaction
ATP; it is an endergonic reaction
Hydrolysis
Release of a Pi (inorganic phosphate group)
Hydrolysis of ATP would form ____ and is a _____ reaction
ADP; is and exergonic reaction
Phosphorylated intermediate
Formed from ATP transferring a phosphate group to a specific reactant; becomes more reactive-less stable
Enzymes
A macromolecule, usually a protein that acts as a catalyst; have very specific shapes, are globular proteins and are not consumed in a reaction so they can be used repeatedly
Catalyst
A chemical agent that speeds up a reaction without being consumed by the reaction
What is the activation energy barrier
Amount of energy needed to push the reactants to the top of an energy barrier or uphill so the downhill part of the reaction can occur
What do enzymes do to the amount of activation energy required
Enzymes lower the activation energy required
Transition state
The molecules have absorbed enough activation energy and their bonds can be broken and then reformed into the more stable bonding arrangements
What is the active site of an enzyme
Typically a pocket or groove on the surface of the enzyme where catalysis occurs
What is a substrate
The reactant of an enzyme catalyzed reaction
What is an enzyme-substrate complex
Formed when an enzyme binds to it’s substrates
Name five factors that affect enzyme activity
Temperature, pH, cofactors, coenzymes, inhibitors
What are cofactors
Any nonprotein molecules or ion that is required for the proper functioning of an enzyme. Can be permanently bound to the active site or bind loosely and reversibly along with the substrates
Examples of cofactors
Inorganic; metal ions; Ex: Fe2, Mg2
What are coenzymes
An organic molecule serving as a cofactor
Examples of coenzymes
Organic; most are vitamins; Ex: NAD, FAD, CoA, CoQ, and cytochromes
What are inhibitors? name 2 types
Reduce the productivity of enzymes; competitive and noncompetitive
Describe competitive inhibitors
Reduce the productivity of enzymes by blocking substrates from entering active sites; directly competes with substrates for binding to the active site
Describe noncompetitive inhibitors
Do not directly compete with the substrate to bind to the enzyme and active site; binds to another part of the enzyme
What is oxidation
Loss of electrons and hydrogen ions(H+)
What is reduction
Gain of electrons and hydrogen ions(H+)
LEO the lion says GER
Lose Electrons Oxidation Gain Electrons Reduction
What is an internal acceptor?
An organic molecule that is an intermediate product in the catabolic pathway
What is the name of the catabolic pathway with an internal electron acceptor
Fermentation
What is an external electron acceptor
Other electronegative molecules not produced in the catabolic pathway
What is the name of the catabolic pathway in which an external electron acceptor is used
Respiration
Name two types of respiration and their final external electron acceptor
Aerobic respiration: catabolic pathway, oxygen
Anaerobic respiration: catabolic pathway, non-oxygen
What are cytochromes
Transmembrane proteins in the electron transport chain
Name the four metabolic stages of aerobic or anaerobic respiration
Glycolysis, pyruvate oxidation, citric acid cycle, oxidative phosphorylation
Where does glycolysis occur
In the cytoplasm
Where does pyruvate oxidation occur
In the cytoplasm
Where does the citric acid cycle occur
In the cytoplasm
Where does oxidative phosphorylation occur
At the cell membrane
Two activities that occur during oxidative phosphorylation
Electron transport chain and Chemiosmosis
What is glycolysis
The splitting of sugar. Partial oxidation of glucose to a three carbon intermediate product
Describe the energy investment phase of glycolysis
Invest 2 ATP, produce 2 G3P (a 3 carbon sugar)
Describe the energy payoff phase of glycolysis
Yield 4 ATP, produce 2 pyruvate, 2 NADH+
What is the 3 carbon intermediate product of glycolysis called
Pyruvate
What is substrate level phosphorylation
The enzyme catalyzed formation of ATP by direct transfer of a Pi to ADP from an intermediate substrate in catabolism
What are the NET products of glycolysis
2 ATP
2 NADH
2 pyruvate
During pyruvate oxidation what happens for EACH pyruvate
CO2 is given off and pyruvate is oxidized to form acetyl which combines with CoA to form acetyl-CoA. NAD is reduced to form NADH.
What are the NET products of pyruvate oxidation
2 CO2
2 NADH
2 Acetyl-CoA
During the citric acid cycle explain how to get from acetyl-CoA to citrate
Each acetyl-CoA enters the citric acid cycle by joining with a 4 carbon molecule of oxaloacetate (OA) to form a 6 carbon IP called citrate. CoA departed.
How many carbons are left at the end of the citric acid cycle and why
Cycle will completely oxidize the carbon compounds recycling back into the OA receiver; CO2 is given off, so NO carbons continue into the next phase.
How is ATP produced during the citric acid cycle
By using substrate level phosphorylation (SLP)
What are the NET products of the citric acid cycle
4 CO2
2 ATP
6 NADH
2 FADH2
During the citric acid cycle which IP is oxidized
Citrate
What happens during the first step of the electron transport chain
NADH & FADH deliver the electrons and H+ to the transmembrane proteins (cytochromes) to the ETC.
What is the second step in the electron transport chain
Electrons move from one carrier to another in the chain. The transfer of electrons occurs from a carrier with less electronegativity to a carrier that has more EN
The ETC is a ______ reaction resulting in a ______ of free energy
Spontaneous downhill reaction resulting in a release of free energy
What is the final electron acceptor in the ETC during aerobic respiration?
Oxygen
What happens at the final electron acceptor in the ETC
As oxygen receives the electrons and combines with 2 H+ a molecule of water is formed
If the final electron acceptor was not oxygen what would the process be called
Anaerobic respiration
What happens to the free energy released from the ETC
Is used to power proton pumps embedded in the cell membrane
Proton pumps embedded in the cell membrane pump protons (H+) out of the ______ into the ______
Proton pumps embedded in the cell membrane pump protons out of the cytoplasm into the periplasmic space
The pH of the cytoplasm will be ______ compared to the _____ pH of the periplasmic space
The pH of the cytoplasm will be low compared to the high pH of the periplasmic space
Explain the proton motive force
The electrochemical gradient created by the proton pumps; source of potential energy to power the chemiosmosis that will follow
Explain how chemiosmosis works
Protons flow back through the cell membrane to relieve the proton motive force gradient through a channel protein/enzyme called ATP synthase
What does ATP synthase do
Harnesses the proton motive force energy to phosphorylate ADP to form ATP
What are the NET products of the ETC
10 NAD+
2 FAD
6 H2O
What are the NET products of chemiosmosis
3 ATP per NADH = 30 ATP
2 ATP per FADH2 = 4 ATP
TOTAL = 34 ATP
Explain the difference between aerobic respiration and anaerobic respiration
Anaerobic respiration follows the same metabolic pathway as aerobic except that a non-oxygen final electron acceptor is used. Products are variable and ATP yields are much less
Name the three non-oxygen final electron acceptors used in anaerobic respiration
Nitrate, sulfate, carbonate
What is the product when nitrate is reduced during anaerobic respiration
Nitrogen gas + ammonia + 4 ATP
What is the product of sulfate reduction using anaerobic respiration
Hydrogen sulfide + 3 ATP
What is the product of carbonate reduction in anaerobic respiration
Methane + 2 ATP
What is the internal electron acceptor used for fermentation
Pyruvate
During fermentation ____ gets reduced and ______ gets oxidized
During fermentation pyruvate gets reduced and NADH gets oxidized
Acid fermentation produces what
Lactic acid or mixed acids
Alcohol fermentation produces what
Ethyl alcohol (ethanol) + CO2
What is the first step of fermentation
Glycolysis
What is the function of fermentation
To regenerate the NADs to allow glycolysis to continue
How many carbons does G3P have
3
How many carbons does pyruvate have
3
How many carbons does oxaloacetate (OA) have
4
How many carbons does citrate have
6
How many carbons does acetyl-CoA have
2
How many NADH and FADH2 arrive at the ETC
10 NADH
2 FADH
