Biology Module 3 Test Review

An enzyme is considered _ because of its ability to recognize the shape of a particular molecule.

specific

In a catalyzed reaction a reactant is often called a _

substrate

When is an

An enzyme is denatured when it loses its native conformation and its biological activity.

What factors can denature an enzyme?

When enzymes denature, they are no longer active and cannot function. Extreme temperature and the wrong levels of pH -- a measure of a substance's acidity or alkalinity -- can cause enzymes to become denatured.

A substrate binds to an enzyme at the _, where the reaction occurs.

active site

A cofactor, such as iron or a vitamin, binds to an enzyme and plays a role in

catalysis; the acceleration of a chemical reaction by a catalyst

When properly aligned, the enzyme and substrate form an _

enzyme-substrate (ES)complex

What is ATPase?

ATPase is another important enzyme. ATP is referred to as the "universal energy currency" since it is used in every living cell to drive every facet of cellular activity. ATPase works by facilitating the removal of one of ATP's phosphate groups, in the process, releasing a significant amount of energy.

You have an enzymatic reaction proceeding at the optimum pH and optimum temperature. You add a competitive inhibitor to the reaction and notice that the reaction slows down. What can you do to speed the reaction up again?

Add more substrate; it will outcompete the inhibitor and increase the reaction rate. Competitive inhibition can be overcome by adding more substrate to outcompete the inhibitor. Many drugs used to treat different medical conditions, including hypertension, are competitive inhibitors. It is fairly easy to make a molecule that is similar in structure to a particular substrate because the known enzyme's shape can be used as a model of what the molecule needs to look like. It is more difficult to make a noncompetitive inhibitor because it is less obvious what the noncompetitive inhibitor's shape and structure should be.

What ways can enzymatic activity be inhibited?

Competitive inhibitors - a molecule blocks the active site so that the substrate has to compete with the inhibitor to attach to the enzyme. Non-competitive inhibitors - a molecule binds to an enzyme somewhere other than the active site and reduces how effectively it works. Uncompetitive inhibitors - the inhibitor binds to the enzyme and substrate after they have bound to each other. The products leave the active site less easily, and the reaction is slowed down. Irreversible inhibitors - an irreversible inhibitor binds to an enzyme and permanently inactivates it.

What will happen to the rates of the forward and reverse reactions when a catalyst is added?

Both forward and reverse rates increase. For example, the Haber process can be cheaply catalyzed using porous iron. A much more effective catalyst for the Haber process is osmium; however, it is very expensive and toxic.

What's the difference between competitive and noncompetitive inhibitors?

Competitive inhibitors compete physically and structurally with the substrate for an enzyme's active site; they can be outcompeted by adding extra substrate. Noncompetitive inhibitors do not compete for the active site, but inhibit the enzyme by binding elsewhere and changing the enzyme's shape.

What do digestive enzymes do?

Digestive enzymes are present throughout our digestive tract, in our mouth, stomach, and small intestine. They are responsible for breaking down food molecules.

Describe the properties of enzymes.

Enzymes are macromolecules that act as catalysts to speed up reactions without being consumed by the reaction. Enzymes are usually proteins and regulate the pathways of metabolism. The active site of an enzyme is the specific region where substrate molecules will bind. For an enzyme-mediated chemical reaction to occur, the substrate must be compatible with the active site of the enzyme. Specificity is a property of the enzyme and describes how restrictive the enzyme is in its choice of substrate; a completely specific enzyme would have only one substrate. Enzymes are sensitive to temperature and pH like other proteins, so they can only speed up reactions when the conditions are right. If an environment changes out of an enzyme's ideal pH or temperature range, then the enzyme becomes denatured (distorted -it can no longer bind to its substrate/work correctly).

Explain how enzymes affect the rate of biological reactions.

Enzymes are special proteins that increase the rate of a reaction by decreasing the amount of energy needed to get a reaction started. Enzymes are biological catalysts, molecules that increase the speed of a reaction without being used up in the reaction. Enzymes speed up metabolic reactions by lowering energy barriers.

Enzymes are highly specific both in the reactions that they catalyze and in their choice of reactants, which are called substrates. Why are enzymes considered highly specific?

Enzymes are specific because different enzymes have differently shaped active sites. An enzyme usually catalyzes a single chemical reaction or a set of closely related reactions. The shape of the active site of an enzyme is complementary to the shape of its specific substrate.

What are enzymes made of and what do they do?

Enzymes come in all shapes and sizes. Since they are proteins, they are made from a combination of 20 different amino acids. This means there is a large variety of enzymes in our body that work daily to catalyze all types of chemical reactions. Although enzymes are produced inside cells, they are able to catalyze reactions inside and outside the cell.

Do enzymes increase/decrease reaction rate? How do they affect the activation energy of a chemical reaction?

Enzymes increases reaction rate (faster speed) and lowers the activation energy of a chemical reaction. This means that a catalyzed reaction is more likely to proceed than an uncatalyzed reaction, and it forms products more rapidly than an uncatalyzed reaction.

give an example of enzyme specificity

Enzymes showing substrate specificity are specific only to one substrate and one reaction. Example: Enzyme lactase can only hydrolyze the β-1-4 glycosidic bond of lactose to yield galactose and glucose. Similarly, Maltase can only act on the α-1-4 glycosidic linkage of two glucose molecules in maltose

Consider a situation in which the enzyme is operating at optimum temperature and pH, and has been saturated with substrate. What is your best option for increasing the rate of the reaction?

If an enzyme is saturated with substrate, and it is operating at optimum pHpH and optimum temperature, there is very little that can be done except to increase the enzyme concentration. Some enzymes can be activated further by allosteric activators, in which case one might add some activator to the reaction. But otherwise, increasing the enzyme concentration is the only option.

reaction rate increases with substrate concentration until a certain point (where the active site is saturated with substrate) at which the rate of the reaction will not increase with the concentration of substrates. Look at the graph of reaction rate versus substrate concentration for an enzyme. In which region does the reaction rate remain constant? In which region is the enzyme saturated with substrate?

In region C of the graph, the reaction rate is independent of substrate concentration because this is the point where the slope of the graph (reaction rate v substrate concentration) levels out and reaches maximum activity. C is also the region where the enzyme is saturated with substrate since reaction rate stop increasing at the point when the active site is saturated with substrate.

What are the two types of enzyme reactions?

The reactions are: Oxidation and reduction. Enzymes that carry out these reactions are called oxidoreductases.

What is the difference between intracellular enzymes and extracellular enzymes?

Intracellular enzymes function inside cells. They speed up metabolic reactions, while extracellular enzymes, function outside cells. (e.g. extracellular digestive enzymes break down complex macromolecules into smaller units to be taken up by the cell for growth and assimilation)

Irreversible inhibitors do not bind to a different location than the substrate. Because they compete directly with the binding of the substrate to the enzyme, where do they bind to the enzyme? Irreversible inhibitors do not resemble the substrate. If they did, their effect could be reversed by adding more substrate. Where do irreversible inhibitors bind to an enzyme?

Irreversible inhibitors bind directly to the active site by covalent bonds, which change the structure of the enzyme and inactivate it permanently.

Why does an enzyme remain intact after being used in a reaction?

Just as the shape of the wrench determines the types of bolts it can tighten, the shape of an enzyme determines what reaction it can speed up within a cell. A wrench is not changed or destroyed after its use, just as an enzyme remains intact after its use in a reaction. In essence, an enzyme is a tool in a reaction, not the reactant or product.

What is the difference between lock and key model and induced fit?

Lock and Key states that there is no change needed and that only a certain type will fit. However induced fit says the active site will change to help to substrate fit. In lock and key the active site has one single entry however in induced fit the active site is made of two components.

What do metabolic enzymes do?

Metabolic enzymes are found in every cell in our body. They control all aspects of metabolism, from energy production to the growth of new tissue. DNA polymerases are a crucial group of enzymes, responsible for various stages of DNA replication, including generating complementary strands using the original strands as templates and, finally, proofreading the new strands for any errors.

Ammonia, NH3NH3, is used in numerous industrial processes, including the production of pharmaceuticals such as sulfonamide and antimalarials and vitamins such as the B vitamins. The equilibrium equation for the synthesis of ammonia (sometimes known as the Haber process) is N2(g)+3H2(g)⇌2NH3(g) The Haber process is typically carried out at a temperature of approximately 500∘C∘C. What would happen to the rate of the forward reaction if the temperature were lowered to 100∘C? What would happen to the rate of the forward reaction if the concentration of nitrogen were decreased?

Most reactions double in rate for each 10∘C increase in temperature. When you lower the temperature, the molecules are slower and collide less. When temperature drops, the reaction rate decreases. A decrease in concentration of a reactant will cause the reactant molecules to collide less frequently. A decrease in concentration of a reactant will change the rate of the reaction because the molecules will collide less frequently. As the concentration of nitrogen decreases, collisions between nitrogen and hydrogen are less likely to occur, therefore, the reaction rate would decrease.

Describe the factors that affect enzymatic activity.

Some factors that can affect the functions of enzymes include pH, temperature, and chemical inhibitors. When enzymes reach a certain temperature range or pH, they become denatured due to disruptions in chemical bonds and weak interactions that stabilize the shape of the enzymes. There are also chemicals that can inhibit the enzymatic activity by binding to an enzyme. A competitive inhibitor binds to the active site of the enzyme and blocks substrates from binding. A noncompetitive inhibitor binds to another part of the enzyme, which causes the enzyme's shape to change. The substrate will no longer be able to bind effectively. Examples of enzyme inhibitors include toxins, poisons, and antibiotics.

You have added an irreversible inhibitor to a sample of enzyme and substrate. At this point, the reaction has stopped completely. What can you do to regain the activity of the enzyme?

The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity. Because they bind directly to the active site by covalent bonds, irreversible inhibitors permanently render an enzyme inactive. Some drugs are irreversible inhibitors, including the antibiotic penicillin (which inhibits an enzyme involved in bacterial cell-wall synthesis) and aspirin (which inhibits cyclooxygenase-2, the enzyme involved in the inflammatory reaction).

Which of the following would increase the rate of the reverse reaction?

The product concentration would affect the reaction rate (in a reverse reaction), therefore, increasing ammonia (the synthesized product) would increase the rate of the reverse reaction. The concentration of NH3NH3 affects how quickly N2N2 and H2H2 can be made.

What factors affect reaction rate?

The rate of a reaction is defined as the ratio of the change in concentration of a product to the change in time: rate of reaction = change in concentration over change in time

The highly complex organization of living systems requires

constant input of energy and the exchange of macromolecules.

How does the structure and function of enzymes contribute to the regulation of biological processes?

he structure of enzymes includes the active site that specifically interacts with substrate molecules. For an enzyme-mediated chemical reaction to occur, the shape and charge of the substrate must be compatible with the active site of the enzyme. The structure and function of enzymes contribute to the regulation of biological processes. Enzymes catalyze biological processes by lowering the activation energy needed for chemical reactions to occur.