High School Biology : Cell Functions

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #2 : Understanding The Electron Transport Chain

The electron transport chain is responsible for generating the proton gradient that powers the production of ATP. To where do the proteins of the electron transport chain pump these protons?

Possible Answers:

The mitochondrial matrix

The intermembrane space

The cytosol

The outer mitochondrial membrane

Correct answer:

The intermembrane space

Explanation:

As electrons move down the electron transport chain, protein pumps are provided the energy to pump protons into the intermembrane space of the mitochondrion.

The result is a high concentration of protons in the intermembrane space and a low concentration in the mitochondrial matrix. The difference in concentration and charge balance results in an electrochemical gradient, pulling protons into the mitochondrial matrix. ATP synthase is able to use this pulling force to activate enzymatic activity and generate ATP.

Example Question #3 : Understanding The Electron Transport Chain

Which of the following is not critical in ATP formation through aerobic respiration?

Possible Answers:

Electron carriers

Double membrane

Proton gradient

ATP synthase

Lactic acid

Correct answer:

Lactic acid

Explanation:

This question primarily tests your knowledge of the Electron Transport Chain, which is responsible for the majority of ATP synthesis. The Electron Transport Chain relies on the delivery of electrons from electron carriers. ATP is formed through the movement of protons down their gradient through a ATP synthase protein. The formation of the proton gradient is accomplished via a double membrane in the mitochondria. Lactic Acid is not present in aerobic respiration, instead it is a derivative of fermentation. 

Example Question #1 : Understanding The Electron Transport Chain

Which of the following is the final electron accepter of the electron transport chain?

Possible Answers:

ATP

Oxygen

Hydrogen

NADH

Correct answer:

Oxygen

Explanation:

Molecular oxygen——is the final electron accepter in cellular respiration and acts as an oxidizing agent. 

Example Question #1 : Photosynthesis

Which of the following is a product of photosynthesis?

Possible Answers:

Oxygen

Hydrogen

Carbon dioxide

Nitrogen

Water

Correct answer:

Oxygen

Explanation:

Photosynthesis is the biological process by which plants convert sunlight energy into chemical energy. The main product is the simple sugar glucose. The bonds in glucose can be broken and used for energy by the plants. The formula for photosynthesis is:

The reactants are carbon dioxide, water, and light energy. The products are glucose and oxygen.

Example Question #1 : Photosynthesis

In the given chemical process, what does  represent?

Possible Answers:

Chlorophyll

Carbonated water

Carbon hydroxide

Carbohydrate

Correct answer:

Carbohydrate

Explanation:

Carbohydrates are formed from carbon chains with a single oxygen group (either an aldehyde or a ketone). Carbohydrates have the general empirical formula . This formula can be used to designate a nonspecific carbohydrate molecule.

The process described is the conversion of light energy to chemical energy through photosynthesis. Chlorophyll serves as a functional pigment in this process, but is not involved in the net reaction. Carbonated water is formed from dissolved carbon dioxide in water, and is actually a solution of the two compounds. Carbon hydroxide is a misnomer, and does not refer to a real compound.

Example Question #1 : Photosynthesis

During the light-dependent reaction, the electron in __________ is __________ before the electron in  _________.

Possible Answers:

photosystem I. . . removed. . . photosystem III

photosystem II. . . excited. . . photosystem I

photosystem II. . . oxidized. . . photosystem III

photosystem I. . . excited. . . photosystem II

Correct answer:

photosystem II. . . excited. . . photosystem I

Explanation:

Contrary to their assigned numbers, the electron in photosystem II is excited before the electron in photosystem I. Their numbers are a reflection of the order in which they were discovered. 

Example Question #1 : Understanding The Calvin Cycle

Which of the following does not show a simplified version of the photosynthesis reaction?

Possible Answers:

Correct answer:

Explanation:

There are several ways that the photosynthesis reaction is often written. A common form shows carbon dioxide and water combining, with the help of energy from the sun, to produce sugar and oxygen.

Often the reaction will be simplified to remove the coefficients of the molecules, or the reaction will be written in words instead of chemical symbols. NADP is converted to NADPH during photosynthesis, but may or may not be included in the reaction.

The incorrect reaction in the answer choices reverses the carbon dioxide and oxygen. Remember that the reaction must contain carbon on both sides of the equation in order to be balanced; carbon dioxide cannot be on the same side as glucose. The overall purpose of photosynthesis is to convert carbon, in the form of carbon dioxide from the air, into usable sugar. In terms of a reaction equation, this means that carbon dioxide is a reactant on the left side and sugar is a product on the right side.

Example Question #1 : Understanding The Calvin Cycle

Which of the following statements about the Calvin cycle is false?  

Possible Answers:

The Calvin cycle releases oxygen as a byproduct

The Calvin cycle occurs within the stroma of the chloroplast

The Calvin cycle is the second set of reactions in photosynthesis

The Calvin cycle binds carbon atoms from carbon dioxide sources into organic compounds

Correct answer:

The Calvin cycle releases oxygen as a byproduct

Explanation:

The Calvin cycle is the second set of biochemical reactions in photosynthesis and follows the light reactions. The light reactions function to use photons and water to generate NADPH, oxygen, and water. The NADPH can then be used to power the Calvin cycle, which uses the energy stored in ATP and NADPH during light reactions to generate organic molecules for energy. The light reactions take place in the chloroplasts, but the Calvin cycle takes place in the stroma and is not dependent on light. The final result of the Calvin cycle is to use energy to bind reactant carbon dioxide to produce glyceraldehyde 3-phosphate (G3P), a three-carbon sugar. G3P is then used to build sucrose, starch, and cellulose for energy storage and metabolism.

Example Question #2 : Photosynthesis

What is the function of rubisco during the Calvin cycle?

Possible Answers:

It catalyzes the carboxylation of RuBP

It carries the prepared glucose to surrounding cells

It produces G3P molecules 

It regenerates RuBP

It captures photons and uses them to generate ATP

Correct answer:

It catalyzes the carboxylation of RuBP

Explanation:

Rubisco is an enzyme that helps add carbon dioxide to RuBP molecules. This in turn forms an unstable inermediate compound, which immediately breaks into two 3-PGA molecules. 

Example Question #1 : Photosynthesis

Some plants can fix carbon through an alternative pathway called the C4 pathway. What is the key advantage of the C4 pathway?

Possible Answers:

Fixing carbon with less water loss compared to C3 plants

It provides a feedback mechanism to split more water during the light reaction

Production of more RuBP to fuel the Calvin cycle

The combination of both C3 and C4 pathways allows the plant to grow faster

Correct answer:

Fixing carbon with less water loss compared to C3 plants

Explanation:

The key characteristic of the C4 pathway is that is produces oxaloacetate and four-carbon sugars from carbon dioxide, compared to the Calvin cycle of most plants, which generates glyceraldehyde 3-phosphate and three-carbon sugars.

The Cpathway fixes carbon dioxide into four-carbon compounds, thus the name. Pores on the plant called stomata regulate how much carbon dioxide, oxygen, and water enter and leave the plant and are usually partially closed during the hottest part of the day to conserve water. This yields a low carbon dioxide level and high oxygen level, which inhibits carbon fixation by the Calvin cycle. Plants that use the C4 pathway have an enzyme that can efficiently fix carbon to four-carbon compounds when the carbon dioxide level is low. The four-carbon compounds are then transported to other cells, where carbon dioxide is released and can enter the Calvin cycle.

Plants that use the C4 pathway are better adapted to hot and dry conditions, as they can fix carbon with less loss of water. Examples of C4 plants are corn and crabgrass.

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