Smartbook Chapter 6

Exergonic reactions

Spontaneous, have a positive change in free energy

Entropy increases when energy is transferred from one form to another and some is lost as heat

Second law of thermodynamics

Energy of a system that is available to do work

Usable energy

Free energy in exergonic reactions

Negative

Free energy in endergonic reactions

Positive

Endergonic reactions

1. Products have a higher free energy than reactants

2. Not spontaneous

3. Require the addition of free energy

4. Have a positive change in free energy

ATP

carries and releases energy cyclically

Hydrolysis of ATP

when a water molecule is used to remove a phosphate group from ATP

Reactions with a positive change in free energy favor the formation of

reactants

Hydrolysis of ATP is equal to

negative delta G

Hydrolysis of ATP

A water molecule is added to ATP resulting in its breakdown to ADP and inorganic phosphate.

Regarding the hydrolysis of ATP

• Water is a reactant.

• ΔG = -7.3 kcal/mole.

• One phosphate is released.

• ADP is a product.

Catalyst

An agent that speeds up the rate of a chemical reaction

Enzymes are composed of

Proteins

Hydrolysis of which covalent bonds in ATP releases a considerable amount of energy?

phosphate-phosphate bonds

Hydrolysis of which covalent bonds in ATP releases a considerable amount of energy?

bringing the reactants close to one another in the correct orientation, reducing the activation energy of the reaction

Enzymes are composed of which type of macromolecule

protein

Where enzyme mediated chemical reactions take place when the substrate binds to

active site

An enzyme accelerates the rate of a chemical reaction by

lowering the activation energy

Almost all enzymes bind their substrates with a high degree of

specificity

Allosteric Site

Molecule can bind noncovalently and influence enzyme’s activity

Prosthetic Groups

Small molecules permanently attached to the surface of an enzyme that aid in enzyme function

cofactors

Small chemicals that temporarily attach to the surface of an anzyme and promotes a chemical reaction

Coenzyme

Organic molecules that temporarily attach to an enzyme and promote a chemical reaction without being changed during the reaction

Prosthetic groups

Small molecules that are permanently attached to the surface of an enzyme and aid in its function

Why do most enzymes function maximally in a narrow range of temperature and pH?

Exposing enzymes to temperatures and pH outside the optimal range can change the conformation of the active site or denature the protein

Enzymes are sensitive to pH and is therefore prefers a _ range

narrow

Catabolic Reactions

Endergonic

Anabolic Reactions

Endergonic

Organic molecules

Used as building blocks to construct new molecules and macromolecules

substrate-level phosphorylation

The transfer of a high-energy phosphate group from a phosphorylated organic molecule to ADP

Chemiosmosis

Ion electrochemical gradient used to make ATP from ADP and Pi

Organic molecules provide

chemical bonds to store energy and building blocks

Feedback Inhibition

Gene regulation

Cell signaling pathways

Biochemical regulation

During feedback inhibition, how does binding of the product inhibit enzyme function?

When excess product binds to the allosteric site, it causes a conformational change that prevents further binding of reactants to the active site.