chapter 6 problem sets (micro)

During glycolysis, a single 6-carbon molecule of glucose is converted to two 3-carbon pyruvate molecules. During the later steps in this process, how many molecules of ATP are generated?

4

During the electron transport chain, ATP will be made from

ADP + Pi

The Calvin Cycle uses ______ and ______, produced in the light reactions of photosynthesis, to drive the fixation of carbon dioxide

ATP and NADPH

Consider how an aerobically respiring bacterial cell uses glycolysis, the TCA cycle, and oxidative phosphorylation to break apart and oxidize glucose. What are the three main benefits these central metabolic pathways yield to the cell?

ATP, reduced electron carriers, and precursor metabolites.

Consider the biochemical pathway: A → B → C Enzyme 1 catalyzes A → B Enzyme 2 catalyzes B → C If enzyme 2 is inactive, which of the following compounds will accumulate

B Only

You are studying the metabolism of the phototrophic green sulfur bacterium Chlorobaculum tepidum and realize that it is running a reversed TCA cycle! How do you explain this observation?

C. tepidum is using the reversed TCA cycle to fix carbon dioxide.

Scientists isolated a new species of bacteria growing in sediments collected from a 63 meter deep site at the bottom of Lake Washington in Seattle This species, named Labrys methylaminiphilus, is capable of obtaining its carbon and energy needs from methylamine (CH3NH2), a derivative of ammonia (NH3) in which one H atom is replaced by a methyl (CH3) group. L. methylaminiphilus grows at a temperature range of 10-35°C, with optimal growth at 28-30°C, and a pH range of 4.0-9.5, with optimal growth at 5.0-7.0. Because methylamine is a single carbon compound resulting from the breakdown of decaying organic matter, methylotrophic ("methyl-feeding") bacteria like L. methylaminiphilus play an important role in carbon cycling in lake sediments and other environments. Consider the growth of L. methylaminiphilus on methylamine. How would you classify this species based on its metabolism?

Chemoorganoheterotroph

Some enzymes require a cofactor or a coeznyme in order to be active. What is the difference between cofactors and coenzymes?

Cofactors are non-protein components that assist enzymes and are typically trace elements; coenzymes are organic cofactors that loosely carry molecules or electrons.

Which of the following contain a metal ion that can accept and donate electrons?

Cytochromes

Where do NADH and FADH2 go after being produced in the TCA cycle?

Electron transport chain

Consider the image you labeled showing a metabolic pathway under allosteric regulation. Which enzyme in this pathway is most likely under allosteric control?

Enzyme a

Which of the following compounds can be generated from precursor metabolites in the TCA cycle?

Glycerol, a component of lipid; Peptidoglycan, a component of bacterial cell walls; Some amino acids like aspartate, glutamate, and proline, All the amino acids; Fatty acids.

Which of the following compounds can be generated from precursor metabolites produced during glycolysis?

Glycerol, a component of lipids.

What happens to carbon dioxide after it is released during reactions of the TCA cycle?

It diffuses out of the cell.

The two 3-carbon molecules glucose is split into are converted through a series of steps into pyruvate. During these steps

NAD+ is converted to NADH

Hydrogen is transported from other reactions to the electron transport chain by ______.

NADH and FADH2

Catechol oxidase causes the browning seen when fruits and vegetables like apples, bananas, and potatoes are damaged or cut. Catechol oxidase oxidizes catechol to form benzoquinone. A compound called phenylthiourea (PTU) is able to bind to catechol oxidase. You perform an experiment to test the effect of PTU on the enzymatic reaction. You set up enzyme reactions in 2 test tubes. In tube 1, you add 11 mL water + 1 mL potato juice (contains catechol oxidase), while in tube 2 you add 10 mL water + 1 mL potato juice (contains catechol oxidase) + 1 mL PTU. After adding 1 ml catechol to both tubes, you observe a color change (browning) in tube 1 and no color change in tube 2. You set up a third test tube containing 8 mL water, 1 mL PTU, 1 mL potato juice, and 3 mL catechol. If this third test tube turned brown, this would suggest which of the following?

PTU is a competitive inhibitor of catechol oxidase.

Catechol oxidase causes the browning seen when fruits and vegetables like apples, bananas, and potatoes are damaged or cut. Catechol oxidase oxidizes catechol to form benzoquinone. A compound called phenylthiourea (PTU) is able to bind to catechol oxidase. You perform an experiment to test the effect of PTU on the enzymatic reaction. You set up enzyme reactions in 2 test tubes. In tube 1, you add 11 mL water + 1 mL potato juice (contains catechol oxidase), while in tube 2 you add 10 mL water + 1 mL potato juice (contains catechol oxidase) + 1 mL PTU. After adding 1 ml catechol to both tubes, you observe a color change (browning) in tube 1 and no color change in tube 2. The results of your test tubes suggest which of the following?

PTU is an inhibitor of catechol oxidase.

Anabaena is a genus of filamentous cyanobacteria commonly found in aquatic environments, where it harvests energy from sunlight and fixes both carbon dioxide and nitrogen. Knowing this, how would you classify Anabaena?

Photoautotroph

Greenlake is a small lake in Seattle, WA that sometimes experiences blooms of cyanobacteria, photosynthetic nitrogen-fixing bacteria that typically grow as filaments. These blooms are especially likely to occur during warm summer weather and result in the production of large quantities of biomass that then dies off and decomposes, leading to unpleasant odors. In addition to the aesthetic problems, some strains make toxins that can be dangerous to ingest, leading to the closing of the lake. Treatment of the water with alum (aluminum sulfate) to remove phosphorus from the water has helped to limit growth of cyanobacteria. How would you classify the cyanobacteria from Greenlake in terms of their carbon and energy sources?

Photoautotroph

You inoculate fern spores onto the surface of a growth medium in Petri dishes and wait for them to develop into gametophytes, a stage in the life cycle of a fern. The medium contains sources of nitrogen, phosphate, and a number of other macro- and micro-nutrients, but no carbon. After a few weeks, you see a contaminant growing on your plates. Assuming the organism is not digesting the agar itself, which of the following is most likely your contaminant?

Photoautotrophic species of bacteria, archaea, or protists.

Which of the following statements accurately describe biochemical pathways? Choose all that apply.

They convert an initial substrate through a series of steps into an end product; They are well-organized and structured; They can be linear, branched, or cyclical;They are carefully regulated.

How many molecules of NADH are generated for each turn of the TCA cycle?

Three

A hydrogen atom consists of

a proton and an electron

The electron carrier proteins in the electron transport chain shuttle electrons to

a terminal electron acceptor.

The energy released during the reactions of glycolysis is used to form ______.

adenosine triphosphate

The rate of growth in flask 2 is substantially faster than that in flask 1, but somewhat slower than that in flask 3. You detect the production of nitrite. The E. coli in this tube can be most accurately described as undergoing ______.

anaerobic respiration

Early in glycolysis, two phosphates are added to the glucose molecule. These phosphates come from

breaking down ATP

The coenzyme NADH is generated by

by oxidation reactions in glycolysis and the Krebs cycle.

Metabolism can be separated into two catergories

catabolism and anabolism

Glycolysis takes place in the ______.

cytoplasm

The TCA (Krebs) cycle takes place in the mitochondria of eukaryote cells. Where does it take place in prokaryote cells?

cytoplasm

Where does the TCA cycle take place in bacteria?

cytoplasm

An enzyme speeds up a chemical reaction in the cell, but can only be used once.

false

True or false: In prokaryotes and eukaryotes, the TCA cycle takes place in the mitochondria.

false

true or false: In anaerobic respiration, the terminal electron acceptor would also be oxygen.

false

Streptococcus pneumoniae lacks an electron transport chain. Therefore, S. pneumoniae generates ATP via ______.

fermentation

In eukaryotic cells undergoing respiration, protons are pumped

from the mitochondrial matrix to the intermembrane space.

Glycolysis is the central metabolic pathway that involves the breakdown of ______.

glucose

central metabolic pathways

glycolysis, pentose phosphate pathway, tricarboxylic acid cycle

After glycolysis, pyruvate can be converted into ______ under anaerobic conditions.

lactic acid

In bacteria, proton pumps are protein complexes that

move protons from the interior of the cell to the exterior

Hydrogen consists of

one proton and one electron.

Cells obtain energy by ______ food molecules such as glucose.

oxidizing

The terminal electron acceptor in aerobic respiration is ______.

oxygen

The main purpose of cellular respiration is to

produce energy

Enzymes are usually ______.

proteins

The enzyme ATP synthase uses energy from ______ to make ATP

protons re-entering the cell

During the electron transport chain in bacteria, protons are

shuttled to the outside of the cell membrane

Which of the following binds to the active site of an enzyme?

substrate

In aerobic respiration, oxygen acts as

terminal electron acceptor

What is oxidation?

the loss of electrons from a molecule

Cells prefer to use carbohydrates as energy sources because

they are such good donors of hydrogen and electrons

Glyceraldehyde-3-phosphate and 3-phosphoglycerate are three-carbon molecules produced during the Calvin Cycle.

true

Plastoquinone is the primary electron acceptor for electrons leaving photosystem II.

true

The energy captured in the phosphorylation of ADP to ATP comes from the proton motive force created in respiration

true

Whenever a molecule is oxidized, another molecule must be reduced

true

For each glucose molecule that enters glycolysis, how many times does the TCA cycle "turn"?

two

How many ATP molecules are produced in the TCA cycle for each glucose molecule that enters glycolysis?

two

The electrons excited by photons of light are replaced by electrons from ______ in photosystem II, and by electrons from ______ in photosystem I.

water; photosystem II

Which of the following represents the correct sequence of events during photosynthesis

Photosystem II (ATP production) --> Photosystem I (NADPH production)

Pasteur set up the following experiment: he prepared a solution of sugar, ammonia, mineral salts, and trace elements, and added some yeast cells to it. He then measured the number of yeast cells as well as the sugar and alcohol levels over time. He noted that as the yeast cells multiplied, sugar levels decreased and alcohol levels increased, suggesting that the yeast cells were converting the sugar to alcohol. What do think would be an appropriate control for this experiment?

Preparing a solution of sugar, ammonia, mineral salts, and trace elements, but not adding any yeast cells to the solution.

At the beginning of the Calvin cycle, carbon dioxide is attached to ______.

RuBP

Eventually Eduard Buchner showed that crushed (destroyed) yeast cells could convert sugar to ethanol and CO2. What did this experiment show?

Something was released frm the crushed cells that could still convert sugar to alcohol.