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Example Questions
Example Question #1 : Carbohydrate Metabolism
In photosynthesis, what is the purpose of absorbing light into chloroplasts?
The energy from the absorbed light causes the generation of NADH from the electron of water molecules, ultimately setting up a proton gradient
The energy from the absorbed light moves the electrons from NADPH to water molecules, ultimately setting up a proton gradient
The energy from the absorbed light generates NADPH from the electrons of water molecules, ultimately leading to the creation of carbon dioxide
The energy from the absorbed light causes all of the electrons in the chloroplast to jump to higher energy levels
The energy from the absorbed light generates NADPH from the electrons of water molecules, ultimately setting up a proton gradient
The energy from the absorbed light generates NADPH from the electrons of water molecules, ultimately setting up a proton gradient
In photosynthesis, light is absorbed in order to move electrons from water molecules to NADPH. The reduction of to NADPH is accompanied by the movement of protons across a membrane which sets up a gradient similar to that of oxidative phosphorylation. The protons eventually run through ATP synthase and ATP is formed.
Example Question #76 : Catabolic Pathways And Metabolism
Photosynthesis consists of a light phase and a dark phase. The light phase precedes the dark phase and supplies it with __________.
During photosynthesis, the light phase is responsible for creating which the dark phase then consumes as a part of its process. In addition to
is used in the dark phase as a high energy substrate to work properly.
Example Question #2 : Carbohydrate Metabolism
In photosynthesis, if photosystem II absorbs 12 photons, how many molecules of would be produced?
Absorbing four photons by photosystem II creates one oxygen molecule, so absorbing 12 would produce 3 molecules of .
Example Question #78 : Catabolic Pathways And Metabolism
During photosynthesis there is both a light phase and a dark phase. If the light phase were to continue unabated, but the dark phase came to a halt, which of the following is most likely to occur?
Increased sensitivity of the chloroplast to incoming light
A proportional decrease in
An increase in the production of carbohydrates
Decreased sensitivity of the chloroplast to incoming light
Decrease in the level of
Decrease in the level of
During photosynthesis, the dark phase follows the light phase. The light phase produces which, along with
, is fed into the dark phase where it is consumed (becomes
and
). If the light phase continues working, but the dark phase does not, the
and
created during the light phase will not be consumed. Thus, there will be a decrease in the level of
and
(the correct answer). The relative proportion of
will actually increase.
Carbohydrate production is a result of the dark phase working properly, so their levels would decrease in this instance. The sensitivity of the chloroplast to light would not change.
Example Question #1 : Carbohydrate Metabolism
What happens during stage 1 of the Calvin cycle?
2 ATP molecules react with 3-phosphoglycerate to form 1,3-bisphosphoglycerate
NADPH and 1,3 bisphosphoglycerate react to form glyceraldehyde-3-phosphate
Carbon dioxide and ribulose 1,5-bisphosphate react to form 3-phosphoglycerate
Fructose-6-phosphate becomes ribulose 5-phosphate
ATP reacts with ribulose 5-phosphate to become ribulose 1,5-bisphosphate
Carbon dioxide and ribulose 1,5-bisphosphate react to form 3-phosphoglycerate
All of the answer choices are steps in the Calvin cycle, but the only one that describes the first stage - fixation - is and ribulose 1,5-bisphosphate reacting to form 3-phosphoglycerate.
Example Question #1 : Calvin Cycle
What are the three stages of the Calvin cycle?
Fixation, oxidation, and regeneration
Fixation, carboxylation, and regeneration
Fixation, reduction, and regeneration
Reduction, oxidation, and regeneration
Carboxylation, reduction, and regeneration
Fixation, reduction, and regeneration
The stages of the Calvin cycle in the order that they occur are fixation, reduction, and then regeneration. While carboxylation does occur as a part of the first stage, it is not what defines that stage.
Example Question #1 : Other Calvin Cycle Concepts
Which of the following is not true of the Calvin cycle?
NADPH and ATP are required to initiate the Calvin cycle
The Calvin cycle does not need light to function
The first step of the Calvin cycle is carbon fixation
The Calvin cycle occurs in the stroma of a chloroplast
All of these are true of the Calvin cycle
The Calvin cycle does not need light to function
Despite the Calvin cycle's other name (light independent reactions), light is indirectly required for this process to function. All other choices are true of the Calvin cycle.
Example Question #1 : Glycolysis Enzymes
Which of these enzymes catalyzes the first reaction in glycolysis?
Triose phosphate isomerase
Aldolase
Pyruvate kinase
Hexokinase
Hexokinase
The first step in glycolysis is the conversion of glucose to glucose-6-phosphate through the consumption on one ATP molecule. Glucose is reacted upon by the enzyme hexokinase to carry out this step. Kinases are a group of enzymes that add phosphate groups by removing them from an ATP. All of these other enzymes catalyze subsequent reactions in glycolysis.
Example Question #2 : Glycolysis Enzymes
Dihydroxyacetone is converted to glyceraldehyde-3-phosphate by what category of enzyme?
Dehydrogenase
Kinase
Isomerase
Enolase
Isomerase
Dihydroxyacetone phosphate (DHAP) is converted to glyceradehyde-3-phosphate (G3P) by the enzyme triose phosphate isomerase. As the name suggests, this enzyme catalyzes the isomerization of a three-carbon sugar into another three-carbon sugar. Since the molecular formulas of DHAP and G3P are the same, we know that they are isomers of each other.
The balance between DHAP and G3P is extremely important in regulating overall cell metabolism. DHAP is a precursor to triglycerides, and is used in their synthesis, while G3P is an intermediate in glycolysis, an ATP-producing process. In order to favor the conversion of DHAP into G3P, and not the opposite, the cell must keep G3P levels low (Le Chatelier's Principle). Consider the following equilibrium: . This should make sense: if there is lots of ATP around in the cell, there is no need for glycolysis to proceed. Thus the equilibrium will be pushed to the left, increasing the concentration of DHAP in the cell. In humans, DHAP is converted into triglycerides, which get stored as fat. One way to shift this equilibrium to the right is to "create" an ATP need. This can be done by exercising. Exercise utilizes ATP and will thus pull the equilibrium to the right, removing DHAP (which was destined to be converted into fat) and facilitates its conversion into G3P to proceed with cellular respiration.
Example Question #1 : Carbohydrate Metabolism
The enzyme pyruvate kinase is responsible for catalyzing the conversion of phosphoenolpyruvate into __________.
dihydroxyacetone
glucose-6-phosphate
glucose
pyruvate
pyruvate
The tenth and final reaction of glycolysis involves the conversion of phosphoenolpyruvate (PEP) into pyruvate. This step is catalyzed by the enzyme pyruvate kinase. This kinase is going to remove a phosphate group from PEP and put it on ADP to yield ATP. Pyruvate, a three-carbon molecule, is the end product of glycolysis. It can be sent to the pyruvate dehydrogenase complex to be turned into acetyl-CoA, which enters the Krebs cycle. Alternatively, it can be reduced into lactate and/or ethanol (depending on the organism) to regenerate for glycolysis via anaerobic respiration.
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