Enzymes

Metabolism

All of the chemical reactions that occur within an organism

reactants

substance that goes into a chemical reaction

products

substances that are released by a chemical reaction.

metabolic pathways

series of chemical reactions that either build up or break down complex molecules

anabolic pathways

metabolic pathways that consumes energy to build a complex molecule from simpler compounds.

energy

the ability to do work

kinetic energy

the energy an object has due to its motion

thermal energy

energy associated with the movement of atoms or molecules

potential energy

stored energy (due to location or structure)

Chemical energy

A form of potential energy that is stored in chemical bonds between atoms (available to be released in a chemical reaction)

thermodynamics

the study of energy transformations

1st law of thermodynamics

The principle of conservation of energy. Energy can be transferred and transformed, but it cannot be created or destroyed.

2nd law of thermodynamics

Every energy transfer or transformation increases the entropy of the universe.

free energy

used to determine the likelihood of reactions

exergonic reaction

A spontaneous chemical reaction in which there is a net release of free energy. (negative delta G)

endergonic reaction

A non-spontaneous chemical reaction in which free energy is absorbed from the surroundings. (delta G is positive)

energy coupling

The use of an exergonic process to drive an endergonic one.

examples of mechanical work

beating of cilia, contraction of muscle cells, movement of chromosomes during cellular reproduction

examples of transport work

-pumping substances across membranes against the direction of spontaneous movement
-moving vesicles from ER to Golgi

examples of chemical work

synthesis of complex molecules

ATP (adenosine triphosphate)

main energy source that cells use for most of their work

phosphorlyation

the addition of a phosphate group to a molecule, giving it energy

enzyme

type of protein that catalyzes (speeds up) reactions by lowering the activation energy

activation energy

energy that is needed to get a reaction started

substrate

A specific reactant acted upon by an enzyme

active site

region on an enzyme where the substrate binds

induced fit

The change in shape of the active site of an enzyme so that it binds more snugly to the substrate

Enzyme efficiency is affected by...

temperature, pH, chemicals, and environmental factors (i.e. salinity)

co-factors

non-proteins factors that help the enzyme function properly

holoenzyme

enzyme with its cofactor

Co-enzyme

An organic molecule serving as a cofactor (i.e. vitamins)

enzyme inhibitors

A chemical that interferes with and reduces an enzyme's activity

permanent enzyme inhibitor

inhibitor binds with covalent bonds (ex: toxins/poisons)

reversible enzyme inhibitors

bind to enzymes by weak interactions, usually competitive inhibitors

competitive inhibitors

bind to the active site of an enzyme, competing with the substrate

noncompetitive inhibitor

A substance that reduces the activity of an enzyme by binding to a location remote from the active site (the allosteric site), changing its shape so that it no longer binds to the substrate.

allosteric regulation

when molecules bind to an allosteric site which changes the shape and function of the active site can either lead to activation or inhibition

allosteric activation

substrate binds to allosteric site and stabilizes the shape of the enzyme so that the active sites remain open, increasing their activity

allosteric inhibition

substrate binds to allosteric site and stabilizes the enzyme shape so that the active sites are closed (inactive form)

cooperativity

substrate binds to one active site (on an enzyme with more than one active site) which stabilizes the active form

feedback inhibition

A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.

catabolic pathways

metabolic pathways that release energy by breaking down complex molecules into simpler compounds