Biology 6.4 Reading Quiz

Why doesn't amylase break down cellulose?

A different bonding pattern between the glucose molecules of cellulose prevents them from fitting into the enzyme's active site.

What does the process of enzymes speeding up the rate of chemical reactions relate to?

A rock climber ascending a steep cliff by finding a series of hand-and footholds that allow her to scale it one small step at a time. Similarly, a series of reaction steps, each requiring a small amount of activation energy and each catalyzed by an enzyme that lowers activation energy, allows the overall reaction to surmount it's high overall activation energy "cliff" and to proceed at body temperature.

What do the majority of enzymes catalyze?

A single reaction involving specific molecules, while leaving even very similar molecules unchanged.

What do catalysts provide in heavy traffic situations?

A specialized surface upon which O2 and CO combine more readily, hastening the conversion of CO to CO2 and reducing air pollution.

What is contained within these specialized cells?

ATP and the fluorescent chemical luciferin.

What is the enzyme used when energy is required to drive endergonic reactions?

ATP is broken down by ATPase.

What enzyme is involved in the synthesis of ATP to ADP and P?

ATP synthase

Why is the energy stored in sugar gradually released?

Because of a series of chemical transformations, each catalyzed by a different enzyme.

How is the speed at which a reaction occurs determined?

By its activation energy

How do catalysts speed up reactions?

By reducing the reaction's activation energy.

What is ATP synthase responsible for?

Capturing some of the energy released during the series of reactions that break down glucose and then storing it in ATP.

3rd important property of catalysts:

Catalysts are not consumed or permanently changed by the reactions they promote.

2nd important property of catalysts:

Catalysts can speed up both exergonic and endergonic reactions, but they cannot make an endergonic reaction occur spontaneously. An endergonic reaction will still need a net input of energy, with or without an assist from a catalyst.

1st important property of catalysts:

Catalysts speed up reactions by lowering the activation energy required for the reaction to begin.

How do the amino acids within the active site bond to the substrates?

Certain amino acids within the enzyme's active site may temporarily bond with atoms of the substrates, or electrical interactions between the amino acids in the active site and substrates may distort chemical bonds within the substrates. The combination of substrate selectivity, substrate orientation, temporary chemical bonds, and the distortion of existing bonds promotes the specific chemical reaction catalyzes by a particular enzyme.

What controls the rate of energy release and captures some energy in ATP?

Enzymes

Is the reaction of sugar with oxygen to hurl carbon dioxide and water exer or endergonic and does it have a high or low activation energy?

Exergonic, high

How does an enzyme catalyze a reaction? (first step)

First, both the shape and the charge of the active site allow substances to enter the enzyme only in specific orientations.

What does the heat of a match flame do?

Increases the rate of movement of sugar and nearby oxygen molecules, causing them to collide with sufficient force to overcome their activation energy and react; the sugar burns.

What does luciferase do in the presence of oxygen?

It catalyzed a reaction that modified luciferin and used the energy from ATP to boost electrons briefly into a higher-energy electron shell. As they fall back into their original shell, the electrons emit their excess energy as light.

Do enzymes lower or higher activation energy?

Lower

Catalysts

Molecules that speed up the rate of a reaction without themselves being used up or permanently altered.

Do the structure of enzymes change while reconfiguring other molecules?

No

Can all molecules enter the active site?

No, only certain molecules.

What does a given enzyme catalyze?

Only a few types of chemical reactions, at most.

What is the job of catalysts?

Promoting reactions with high activation energies.

How does an enzyme catalyze a reaction? (second step)

Second, when substrates enter the active site, both the substrate and active site change shape.

How many reactions can enzymes catalyze per second?

Several million

Coenzymes

Small nonprotein helper molecules that some enzymes require in order to function.

What happens with the energy released by sugar?

Some is lost as heat, while some is harnessed to power endergonic reactions that lead to ATP synthesis.

Where does the glow of a firefly come from?

Specialized cells in their abdomens that are bioluminescent, meaning they produce "biological light."

Do inorganic catalysts speed up or slow down chemical reactions?

Speed up

What does amylase break down?

Starch molecules by hydrolysis, but leaves cellulose molecules intact, even though both consist of chains of glucose molecules.

What is an example of a reaction that requires a low activation energy?

Table salt dissolving in water.

Substrate

The atoms or molecules that are the reactants for an enzyme-catalyzed chemical reaction.

How do enzymes speed up the rate of chemical reactions?

The breakdown or synthesis of a molecule within a cell usually occurs in many small, discrete steps, each catalyzed by a different enzyme. Aw ah of these enzymes lowers the activation energy for its particular reaction, allowing the reaction to occur readily at body temperature.

How is sugar able to burn on its own?

The energy released by this exergonic reaction speeds up the movement of more sugar and oxygen molecules.

What creates the distinctive shape of the active site and a specific distribution of electrical charges within the site?

The order of amino acids and the precise way in which the amino acid chains of a protein are twisted and folded.

Why are these beetles often described as emitting "cold light?"

The process produces so little heat.

Active site

The region of an enzyme molecule that binds substances and performs the catalytic function of the enzyme.

Why are water soluble vitamins essential to humans?

They are used by the body to synthesize coenzymes.

What is the purpose of ATP and Luciferin?

They serve as substrates for the enzyme luciferase.

How does an enzyme catalyze a reaction? (third step)

When the reaction between the substrates is finished, the product(s) no longer fit properly into the active site and drift away. The enzyme reverts to its original configuration, and it is ready to accept another set of substrates.