AP Biology

What is an endergonic reaction?

A chemical reaction in which the standard change in free energy is positive, and energy is absorbed.

What is hydrolysis?

A reaction involving the breaking of a bond in a molecule using water

What is a spontaneous reaction?

A reaction that occurs with little to no activation energy (i.e. sugar dissolving into water only requires the activation energy of putting the sugar into water)

What is an exergonic reaction?

A reaction where energy is released.

What are the two different types of metabolism?

Anabolism and Catabolism

What is metabolism?

Chemical reactions take place in cells and are responsible for all the actions of organisms.

What do cofactors and coenzymes have in common?

Coenzymes and cofactors are molecules or ions that are used by enzymes to help catalyse reactions.

How do cofactors and coenzymes work?

Cofactors are molecules that increase the rate of reaction or are required for enzyme function. Cofactors are not proteins but rather help proteins, such as enzymes, although they can also help non-enzyme proteins as well. Coenzymes A specific type of cofactor, coenzymes, are organic molecules that bind to enzymes and help them function. Organic means that they contain carbon.

What are four methods of inhabition?

Competitive inhabition: the substrate and inhibitor cannot bind to the enzyme at the same time. This usually results from the inhibitor having an affinity for the active site of an enzyme where the substrate also binds; the substrate and inhibitor compete for access to the enzyme's active site. In uncompetitive inhibition, the inhibitor binds only to the substrate-enzyme complex, it should not be confused with non-competitive inhibitors. In non-competitive inhibition, the binding of the inhibitor to the enzyme reduces its activity but does not affect the binding of substrate. As a result, the extent of inhibition depends only on the concentration of the inhibitor. In mixed inhibition, the inhibitor can bind to the enzyme at the same time as the enzyme's substrate. However, the binding of the inhibitor affects the binding of the substrate, and vice versa. This type of inhibition can be reduced, but not overcome by increasing concentrations of substrate. Although it is possible for mixed-type inhibitors to bind in the active site, this type of inhibition generally results from an allosteric effect where the inhibitor binds to a different site on an enzyme. Inhibitor binding to this allosteric site changes the conformation (i.e., tertiary structure or three-dimensional shape) of the enzyme so that the affinity of the substrate for the active site is reduced.

What does "coupling" mean?

Coupling can be described as a transfer of energy from catabolism to anabolism, or a transfer of energy from an exergonic process to an endergonic process. (2) Free energy (from ATP hydrolysis) is coupled (or functionally linked) to the energy needs of another chemical reaction.

What is catabolism?

Destructive metabolism; the breaking down in living organisms of more complex substances into simpler ones, with the release of energy

How do synthesis and digestion differ in terms of how the enzyme affects the substrates?

Digestion is the separation, breakdown and extraction of the nutrients from more complex chemicals in food. Synthesis is a process of converting the absorbed nutrients to useful form, after they have entered the blood.

What are enzymes?

Enzymes are biological catalysts - substances that increase the rate of chemical reactions without being used up. Enzymes are proteins folded into complex shapes that allow smaller molecules to fit into them. The place where these substrate molecules fit is called the active site.

What are most enzymes made of? (structure and function)

Enzymes are made up of proteins. All enzymes contain an alleosteric site, which is where a molecule that is NOT a substrate will bind, thus changing the function of a reaction.

How do enzymes work at a structural level?

Enzymes work by connecting to a certain substrate.

What is the difference between an Induced Fit model and a "Lock and Key" model?

In the lock-and-key model, the active site of an enzyme is precisely shaped to hold specific substrates. In the induced-fit model, the active site and substrate don't fit perfectly together; instead, they both alter their shape to connect.

Why don't "spontaneous" and "instantaneous" mean the same thing?

Instantaneous means that the reaction happens immediately. Spontaneous reactions can happen slowly over time, but spontaneity is not defined by how quickly the reaction itself occurs. Instantaneous reactions can require a lot of energy in order to happen, whereas spontaneous ones need very little.

What factors affect enzyme action?

PH, temperature, salinitiy (ion concentration), substrait concentration, and enzyme concentration.

How can certain inhibitors and activators be used to regulate enzyme activity (in terms of metabolic pathways and feedback inibition?)

Substrate inhibition will sometimes occur when excessive amounts of substrate are present. The reaction velocity will decrease after the maximum velocity has been reached. Additional amounts of substrate added to the reaction mixture after this point actually decrease the reaction rate. This is thought to be due to the fact that there are so many substrate molecules competing for the active sites on the enzyme surfaces that they block the sites and prevent any other substrate molecules from occupying them.

How is it that a single enzyme can catalyze an incredible number of reactions?

The enzyme has a special site, called the active site, which is a unique binding site that only a particular substrate will recognize and be able to fit inside. The active site is not changed after an enzyme catalyzes a reaction, so a new substrate can still fit in the site when the old substrate has gone away. Therefore, there are specific enzymes for specific biological reactions. Most biological reactions are also connected, meaning that the product from one enzyme-catalyzed (say, enzyme A) reaction is often used as a reactant in another reaction catalyzed by a different enzyme (say, enzyme B). The result is a complicated network of biochemical reactions.

What is dehydration synthesis?

The process of joining two molecules (or compounds) together following the removal of water.

What are substrates?

The substance acted upon by an enzyme.

What is anabolism?

The synthesis in living organisms of more complex substances from simpler ones

What is the difference between cofactors and coenzymes?

To summarize, here are the differences between a cofactor and a coenzyme: A coenzyme is a type of cofactor. It is the loosely bound cofactor to an enzyme. Cofactors are chemical compounds that are bound to proteins. A cofactor is a non-protein chemical compound, while a coenzyme is a non-protein molecule.

How does coupling relate to entropy?

Two or more reactions in a cell sometimes can be coupled so that thermodynamically unfavorable reactions (a decrease in entropy) and favorable reactions (an increase in entropy) are combined to drive the overall process in the favorable direction (an increase in entropy) In this circumstance the overall free energy is the sum of individual free energies of each reaction.

What is coopertivity?

cooperativity has to do with the effect the binding of one substrate has on the binding of the second. If the first binds and increases the affinity of the second, this is called positive cooperativity. If the first inhibits the binding of the second, it is called negative cooperativity.

How does each factor affect the activity of the enzyme?

http://alevelnotes.com/Factors-affecting-Enzyme-Activity/146?tree=

What are the names and functions of some familiar enzymes?

lipase - breaks down fats. protease - breaks down proteins. carbohydrase - breaks down carbohydrates. Amylase - breaks down carbohydrates in to simple single molecule sugars Pepsin - breaks down proteins in to smaller peptides Sucrase - breaks down sucrose to monosaccharides Maltase - converts maltose to glucose Lactase - converts lactose to glucose and galactose