AP Biology : Understand enzyme structure and purpose

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #21 : Enzymes

Which of the following does not affect the activity of enzymes?

Possible Answers:

pH

Activation energy

Temperature

Inhibitors

Correct answer:

Activation energy

Explanation:

Enzyme activity can be affected by environmental factors such as temperature and pH. This is because proteins denature and lose their shape at high temperatures and extreme pHs. Most enzymes prefer to act under a temperature close to body temperature. Optimal pH is usually physiologic at pH 6 to 8; however, digestive enzymes prefer lower pH around 2 to 3 (e.g. pepsin, which makes sense because pepsin works in acidic conditions within the stomach). 

Example Question #22 : Enzymes

Which of the following is true about enzymes?

Possible Answers:

They lower the energy of products. 

They are lipids. 

They lower the activation energy of a reaction.

They are not catalysts. 

They lower the energy of reactants.

Correct answer:

They lower the activation energy of a reaction.

Explanation:

Enzymes are all proteins, however there are some RNA molecules that have been found to catalyze reactions, but they are termed ribozymes, not enzymes. They speed up reactions by lowering the activation energy of a reaction and do not change the energy states of the reactants or products. 

Example Question #23 : Enzymes

Which of the following macromolecules has a subcategory that acts to speed up biological reactions in the body?

Possible Answers:

Lipids

Nucleotides

Carbohydrates

Proteins

Correct answer:

Proteins

Explanation:

Proteins commonly act to facilitate reactions that would otherwise not take place. By lowering activation energy, proteins often serve as catalysts. A protein catalyst in a biological reaction is known as an enzyme. All enzymes are proteins.

Example Question #24 : Enzymes

GLUT1 is a type of protein used to facilitate the transport of glucose across the plasma membrane. What protein classification accurately describes GLUT1?

Possible Answers:

Enzyme

Integral protein

Extrinsic protein

Peripheral protein

Correct answer:

Integral protein

Explanation:

GLUT1 is a protein that allows glucose to pass into a cell through the membrane. Glucose is a large polar molecule, meaning that it will require a protein in order to diffuse across the membrane. GLUT1 must span the entire length of the plasma membrane in order to provide a "passage" for glucose to diffuse. As a result, GLUT1 is classified as an integral protein, or a protein that fully transverses the membrane.

Peripheral, or extrinsic proteins, are situated on the surfaces of membranes, and do not span across the bilayer. Enzymes catalyze biological reactions; GLUT1 is a transport protein, and does not catalyze any reactions.

Example Question #11 : Understand Enzyme Structure And Purpose

Which of the following is not a common function of proteins?

Possible Answers:

Cell motility

Transport molecules across the plasma membrane

Catalyze chemical reactions

Encode information

Correct answer:

Encode information

Explanation:

While some proteins (such as histones) can pass down information from generation to generation, typically DNA is the macromolecule associated with encoding information.

Proteins commonly catalyze reactions. When these reactions occur in a biological organism, the proteins are considered enzymes. Proteins can also be embedded in cellular membranes, acting as channels or receptors to allow molecular transport. One protein, tubulin, is used to build cilia and flagella (as well as microtubules) that are essential to cell motility.

Example Question #26 : Enzymes

Which of the following biological molecules is most similar to proteins?

Possible Answers:

Enzymes

Carbohydrates

DNA

RNA

Triglycerides (fats)

Correct answer:

Enzymes

Explanation:

Proteins are organic molecules made of amino acids that are capable of interfacing with certain substrates and facilitating cellular activities. Enzymes are a sub-group of proteins that are used to speed up reactions within the body. Enzymatic proteins are essential to many biological and cellular processes, such as cellular respiration, transcription, and DNA replication.

Example Question #27 : Enzymes

Amylase facilitates the breakdown of glycosidic bonds in carbohydrates. Which functional group will not be present in a molecule of amylase?

Possible Answers:

Correct answer:

Explanation:

You should immediately realize that amylase is an enzyme because it ends in "-ase". Remember that enzymes are proteins; therefore they are made up of amino acids. All amino acids contain a carboxylic acid (-COOH), an amine (-NH2), and a hydrogen (-H) attached to the central carbon. Phosphate groups (-PO3) are more commonly found in lipids and nucleic acids, not in proteins. No amino acids contain phosphate groups, though phosphates can be added to certain amino acids to activate certain proteins and enzymes (phosphorylation).

Example Question #28 : Enzymes

Which of the following describes enzymes?

Possible Answers:

Catalytic proteins

Degradative nucleic acids

Anabolic proteins

Anabolic lipids

Correct answer:

Catalytic proteins

Explanation:

Enzymes are catalysts that function to increase the rate of a reaction. All enzymes are proteins and they are never consumed in a reaction. Another form of biological catalyst is ribozymes, which are made of protein and RNA, but are not classified as enzymes.

Example Question #24 : Enzymes

The total sum of an organism's chemical processes is called __________.

Possible Answers:

catabolism

biochemical process

metabolism

anabolism

Correct answer:

metabolism

Explanation:

An organism's metabolism is the sum of its chemical processes. Catabolism and anabolism are different aspects of metabolism. Catabolism refers to the breakdown of organic molecules, producing useable forms of energy, such as ATP. Anabolism refers to the use of energy to build macromolecules such as proteins, nucleic acids and carbohydrates.  

Example Question #30 : Enzymes

Which of the following is best defined as a chemical agent that changes the rate of a reaction without being consumed by that reaction?

Possible Answers:

Conductor

Modifier

Catalyst

Helper 

Correct answer:

Catalyst

Explanation:

A catalyst is a substance that can change the rate of a reaction without being consumed by the reaction. Catalysts only affect the speed of the reaction. If a reaction would not occur naturally then the addition of a catalyst will have no effect.

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