Chapter 5: bio

Use the graph and your knowledge of enzymes to identify the three true statements about enzymes.

Enzymes lower the overall energy input needed for a reaction to occur. By binding to reactant molecules, enzymes make it easier for the bonds in the molecules to break apart. Reactants cannot convert to products without an initial input of energy to start the reaction.

The membrane is referred to as a "fluid mosaic" structure. Which of the following statements is true?

The fluid is phospholipid, and the mosaic is protein.

An enzyme speeds up reactions by lowering the

activation energy

An enzyme is considered a(n) ____ because it speeds up a chemical reaction without being used up.

catalyst

During enzymatic reactions, substrates are converted to products. A property of enzymes that facilitates this reaction is that they are catalysts and therefore _____.

change the rate of a reaction without being consumed by the reaction

A _______ which is often a vitamin, binds to an enzyme and plays a role in catalysis

coenzyme

Azidothymidine (AZT) is an antiretroviral drug used in the treatment of HIV. It shares a structural similarity to a nucleotide. What might be the mode of action for this drug?

competitive inhibition

High temperatures or changes in pH can _____ an enzyme, causing it to lose its shape and biological activity.

denature

The secretion of neurotransmitters out of the nerve cell, from small vesicles at the end of the axon, can be considered an example of _____.

exacytosis

1. The ideal osmotic environment for an animal cell is a(n) ______ environment.

isotonic

A plant cell surrounded by a(n)________ solution will be flaccid (limp).

isotonic

If the tertiary structure of an enzyme is changed, _____.

its substrate may not fit properly in the active site

Which curve shows the course of the reaction in the presence of an enzyme--the black curve or the red curve? Which line represents the activation energy for that reaction--a, b, or c?

red curve, line b

In a catalyzed reaction, a reactant is often called a(n)

substrate

What substance is transported by aquaporins?

water

A plant cell placed in a(n)_________ solution will lose water and plasmolyze.

hypertonic

There is a net diffusion of water out of an animal cell when it is placed in a(n) ______ solution

hypertonic

An animal cell placed in a(n)_______ solution will gain water, swell, and possibly burst.

hypotonic

If the volume of a cell increases when it is placed in an aqueous solution, that solution is said to be _____ to the cell.

hypotonic

The ideal osmotic environment for a plant cell is a(n)______ environment.

hypotonic

The ____ between an active site and its substrate often strains bonds and helps the reaction proceed.

induced fit

Which of the following statements is true about passive transport?

Passive transport requires no expenditure of cellular energy.

A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via _____.

The temperature should be raised.

Lactase is essential for digesting lactose in milk. This enzyme is specific for this sugar. Why?

There is a precise compatibility between the active site and the lactose molecule.

An enzyme is specific because the shape of its ______ matches only particular reactants.

active site