Chemical Reactions and Enzymes

Flashcards covering chemical reactions, catabolism, anabolism, enzyme mechanisms, kinetics, cofactors, inhibitors, and feedback inhibition.

What light-emitting molecule produces bioluminescence when catalyzed by luciferase?

Luciferin

What physical requirement must be met for reactants to collide and form products in a chemical reaction?

Reactants must collide in the appropriate position.

What two conditions can be increased to speed up reactant collisions and increase the reaction rate?

Increasing temperature and increasing reactant concentration.

Why is an enzyme written above the reaction arrow rather than listed as a reactant or product?

An enzyme is neither a reactant nor a product; it is not consumed during the reaction and acts as a reusable tool to accelerate a specific chemical reaction.

How is metabolism defined, and why is it considered genetic?

Metabolism includes all the controlled chemical reactions in an organism. It is genetic because a cell reads the instructions in its genes to build enzymes (proteins), which in turn dictate which chemical reactions occur.

What are anabolic reactions, and what is their energy requirement?

Anabolic reactions are building reactions that synthesize larger molecules from smaller ones ($A + B \rightarrow AB$); they require a net input of energy.

What is the chemical equation for photosynthesis provided as an example of an anabolic reaction?

$$6CO_2 + 6H_2O + \text{light} \rightarrow C_6H_{12}O_6 + 6O_2$$

What are catabolic reactions, and what happens to energy during these reactions?

Catabolic reactions are breakdown reactions ($AB \rightarrow A + B$) that result in a net release of energy.

What is the chemical equation for cellular respiration given as an example of a catabolic reaction?

$$C_6H_{12}O_6 + 6O_2 \rightarrow ATP + 6CO_2 + 6H_2O$$

What type of reaction is represented in this diagram, where monomers join by removing a molecule of $H_2O$?

Dehydration reaction (or dehydration synthesis)

What type of reaction is shown in this diagram, where the addition of $H_2O$ breaks a polymer into monomers?

Hydrolysis reaction

What reaction scheme represents the "Lock & Key" mechanism of enzyme action?

$$S + E \rightarrow SE \text{ Complex} \rightarrow P + E$$

What products are formed when lactase breaks down lactose, and what gas do bacteria produce in lactose intolerance?

Lactase breaks down lactose into galactose and glucose; in lactose intolerance, bacteria ferment the unabsorbed lactose and produce $H_2$ gas.

What occurs during the "induced fit" process when a substrate enters an enzyme's active site?

Substrate binding induces the enzyme to close more tightly around the substrate, increasing strain on covalent bonds so that they break more easily and allow new bonds to form.

How does increasing substrate concentration influence the rate of an enzyme-catalyzed reaction?

It increases the number of collisions and the reaction rate until all enzyme active sites become saturated.

What is the effect of increasing enzyme concentration on reaction rate, and why does the cell limit enzyme production?

It increases collisions and the reaction rate until all substrate is used up; making excess enzyme is costly for the cell, so it is more efficient to produce a limited amount and reuse it.

What happens when an enzyme is heated significantly beyond its optimal temperature?

The enzyme denatures, loses its active site shape, and the reaction rate drops back to the uncatalyzed rate.

Why does a deviation from optimal pH reduce the catalytic activity of an enzyme?

Altering the $[H^+]$ changes the charge of the amino acids, altering the shape and charge of the active site so that the substrate cannot bind effectively.

What is activation energy ($E_A$), and how do enzymes affect it?

Activation energy is the initial energy barrier reactants must absorb before a chemical reaction can start; enzymes speed up reactions by lowering this activation energy.

What is the distinction between a cofactor and a coenzyme?

A cofactor is any nonprotein helper required by an enzyme (such as metal ions or minerals), whereas a coenzyme is specifically a large organic cofactor, typically a vitamin or vitamin component like the Vitamin B complex.

How does cyanide function as an irreversible enzyme inhibitor?

Cyanide permanently disables a crucial enzyme required for the synthesis of $ATP$.

How do competitive inhibitors differ from non-competitive inhibitors in their mechanism of binding?

Competitive inhibitors compete directly with the substrate to bind to the active site, whereas non-competitive inhibitors bind to another site on the enzyme, changing the shape of the active site so the substrate can no longer fit.

What is feedback inhibition in a cellular metabolic pathway?

A regulatory mechanism where the final product of a metabolic pathway acts as an inhibitor of the first enzyme in that pathway when produced in excess, temporarily shutting down production.