Exam 2 Microbiology Part 1

What's the inputs and outputs of cellular respiration?

Input: Glucose and O2
Output: CO2, H2O, and ATP

Why do all enzymatic reactions need activation energy?

Energy is required to disrupt a substrate's stable electron configuration

What is meant by the statement "Enzymes are biological catalysts"?

Enzymes speed up the chemical reactions in living cells

Why are enzymes important to biological systems?

Enzymes decrease the amount of activation energy required for chemical reactions to occur.

Energy that is not used in Metabolism is given off as what kind of source?

Heat

What kind of reaction is involved in producing larger compounds from smaller compounds?

Anabolism

Where does the energy required for anabolic reactions come from?

Catabolic reactions

What kind of reaction is using amino acids to make proteins?

Anabolism

How does a competitive inhibitor slow enzyme catalysis?

They compete with the substrate for the enzyme's active site.

What enables competitive inhibitors to bind to a specific enzyme?

Competitive inhibitors have structures that resemble the enzyme's substrate.

What's the purpose of competitive inhibitors?

decrease the rate of enzyme activity

How does a noncompetitive inhibitor reduce an enzyme's activity?

The inhibitor binds to the enzyme in a location other than the active site, changing the shape of the active site.

What would be the likely outcome if you increased the concentration of substrate for an enzyme in the presence of a noncompetitive inhibitor?

No change in enzyme activity would be observed.

Where would you expect to find electron transport chains in a prokaryote?

Along the plasma membrane

Which compounds provide electrons to the electron transport chain?

NADH and FADH2

What does oxygen get reduced to at the end of the electron transport chain?

Water

What does the electron transport chain do to the concentration of hydrogen ions (protons)?

The concentration of protons is higher outside the membrane than inside.

What is referred to as the process of generating ATP using a proton gradient?

chemiosmosis.

Why is ATP required for glycolysis?

ATP makes it easier to break apart glucose into two three-carbon molecules

What does Glycolysis mean?

sugar splitting

How many net ATPs can be made from one molecule of glucose in glycolysis?

two

What carbon molecules remain at the end of glycolysis?

Pyruvic acid

What is the reaction if ΔG0 is negative?

exergonic and energy will be released.

What is one major difference between anaerobic and aerobic respiration?

electron acceptor

What is one example of an electron acceptor that can be used in anaerobic respiration?

Nitrate

What happens if an oxidation reaction occurs?

simultaneous reduction of a different compound will also occur, because electrons do not generally exist alone in solution.

What is the function of NAD+/NADH in the cell best described?

a way to increase the types of redox reactions that occur in the cell by acting as an intermediary between dissimilar compounds

What is Activation energy?

energy required for a chemical reaction to begin.

The Embden-Meyerhof-Parnas pathway is another name for?

glycolysis.

Where does most of the carbon in amino acid biosynthesis comes from?

citric acid cycle intermediates and glycolysis products.

Which intermediate compound(s) in the citric acid cycle is/are often used for biosynthetic pathways as well as carbon catabolism?

α-ketoglutarate, oxaloacetate, and succinyl-CoA

For a carbon source, chemoorganotrophs generally use compounds such as?

citrate, fumerate, and glucose.

Glycolysis produces energy in which form?

NADH and ATP

Which step is the step for which glycolysis is named?

fourth step

What is meant by substrate-level phosphorylation?

Production of ATP by transferring phosphates directly from metabolic products to ADP

What is the driving force of energy production in steps 6 and 7 in glycolysis?

The oxidation of three-carbon compounds

What is the net production of ATP in glycolysis?

two ATP

The net gain of ATP per molecule of glucose fermented is?

2

Applying your knowledge of metabolism, glycolysis starts with one molecule of glucose (6C) and produces a net total of?

two pyruvates; 2 NADH; 2 ATP

From the standpoint of fermentative microorganisms, the crucial product in glycolysis is?

ATP and regenerated NAD+; the fermentation products are waste products.

What fermentation products are made following glycolysis as a result of reactions?

oxidize NADH so that NAD+ can be reused again in glycolysis

What are the steps of fermentation?

1. Organic compounds are uptaken
2. Turns into energy-rich compound
3. Substrate-level phosphorylation
4. Oxidized compound
5. Fermentation product gets excretion
6. Redox Cycling

What is the role of pyruvic acid in fermentation?

It takes the electrons from NADH, oxidizing it back into NAD+.

What is the fate of the NAD+ newly regenerated by fermentation?

It returns to glycolysis to pick up more electrons.

Which of the following is an acid produced by fermentation?

Lactic acid and propionic acid

What is the intermediate product formed by pyruvic acid during alcoholic fermentation?

Acetaldehyde

What happens during electron transport reactions?

OH- accumulates on the inside of the membrane while H+ accumulates on the outside.

How is anaerobic respiration different from aerobic respiration?

The terminal electron acceptor in anaerobic respiration is not oxygen.

What occurs at the bridge step?

Decarboxylation of pyruvic acid

How many electron carriers are reduced in the Krebs cycle only?

4

What is the function of GTP?

An energy carrier

What is the fate of metabolites during respiration?

They are oxidized completely to carbon dioxide and water.

Why does lack of oxygen result in the halt of ATP synthesis?

The chain shuts down and can no longer pump hydrogen ions across the membrane, and the proton gradient cannot be maintained.

Why might some cells uncouple the electron transport chain?

Cells can use the energy from the proton gradient for functions other than producing ATP, such as heat generation.

How does cyanide poisoning result in the decrease of ATP production?

Cyanide permanently reduces cytochrome a3, preventing other components to change into the oxidized state. This causes the proton gradient to break down, stopping ATP synthesis.

Which of the following is needed as a reactant for the first step of the citric acid cycle?

Oxaloacetic acid

Where does the energy come from to power the formation of GTP?

Succinyl CoA

Which step involves the release of carbon dioxide in the Kreb cycle?

The third and fourth steps

How many molecules of ATP can be generated from one molecule of NADH?

3

Which step(s) of the Krebs cycle does (do) not produce any usable energy?

The second and seventh steps

What are the 8 steps in the kreb cycle?

1. Condensation of acetyl CoA with oxaloacetate to form citrate.
2. Isomerization of citrate into isocitrate.
3. Oxidative decarboxylations of isocitrate
4. Oxidative decarboxylation of α-ketoglutarate
5. Conversion of succinyl-CoA into succinate.
6. Dehydration of succinate to fumarate.
7. Hydration of fumarate to malate.
8. Dehydrogenation of L-malate to oxaloacetate

In aerobic respiration, the final electron acceptor is?

Oxygen

Some hydrogen oxidizers synthesize two forms of the enzyme hydrogenase, one that is embedded in the cytoplasmic membrane and one that is soluble in the cytoplasm. Other hydrogen oxidizers get by with only one form of hydrogenase. Given the roles of each type of hydrogenase, what are the implications for the latter type of organism?

Hydrogen oxidizers with only membrane-integrated hydrogenases must use reverse electron transport to reduce NAD+ to NADH for autotrophy.

Why does FADH2 yield less ATP than NADH?

FADH2 electrons enter the electron transport chain at a lower energy level.

Which of the following can be used as a final electron acceptor for aerobic respiration?

Molecular oxygen

What is one difference between ubiquinones and cytochromes?

Ubiquinones are not made of protein; cytochromes are.

How does the proton gradient help ATP synthase to make ATP?

Protons move from outside the membrane to inside the membrane.

What are the sequence of steps as energy is extracted from glucose during cellular respiration?

glycolysis → acetyl CoA → citric acid cycle → electron transport chain

What is the correct general equation for cellular respiration?

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP energy

Which of the following processes takes place in the cytosol of a eukaryotic cell?

glycolysis

In what organelle would you find acetyl CoA formation, the citric acid cycle, and the electron transport chain?

mitochondrion

What best describes glycolysis?

This process splits glucose in half and produces 2 ATPs for each glucose

What best describes the citric cycle?

This process produces some ATP and carbon dioxide in the mitochondrion.

What best describes the electron transport chain?

This process uses energy captured from electrons flowing to oxygen to produce most of the ATPs in cellular respiration

Which of the following equations represents photosynthesis?

6CO2 + 6H2O → C6H12O6 + 6O2

What organelles does photosynthesis take place?

Chloroplast

What connects the two photosystems in the light reactions?

An electron transport chain

What two molecules are produced by the light reactions and used to power the Calvin cycle?

ATP and NADPH

What provides electrons for the light reactions?

Water

What provides the carbon atoms that are incorporated into sugar molecules in the Calvin cycle?

Carbon dioxide (CO2)

What transports electrons from the light reactions to the Calvin cycle?

NADPH

Where does light reaction take place?

thylakoids

Where does the Calvin cycle take place?

Stroma

What are each steps in the Calvin cycle?

1. Energy input
2. Reduced power
3. Removal of 6 carbons to biosynthesis
4. Various sugar rearrangements
5. Regeneration of CO2 acceptor and energy input

Which of the following is a common energy storage polymer in microorganisms?

glycogen

What could a bacterium running low on NADPH do?

invoke the pentose phosphate pathway to generate more of this coenzyme.

Gluconeogenesis is the process of synthesizing what?

glucose from other compounds

Since glucose, a hexose, is the major source of energy for most prokaryotes, why would they need to have pentose sugars available?

Pentose sugars are needed for nucleic acid synthesis.

What is an example of the Pentose Phosphate Pathway?

anabolism