Ap Bio Unit 3 (Metabolism, ATP, and Enzymes)

Metabolism

The totality of an organism’s chemical reactions. Manages the materials and energy resources of a cell

Catabolic Pathways

Release energy by breaking down complex molecules into simpler compounds. Ex: digestive enzymes break down food and release energy

Anabolic Pathways

Series of reactions that consume energy to build complicated molecules from simpler ones

Kinetic Energy

Energy associated with motion. Heat (thermal energy) is this and is associated with the random movement of atoms or molecules

Potential Energy

Stored energy as a result to its position or structure. Chemical energy is this and is available for release in a chemical reaction. Energy can be converted from one form to another

Thermodynamics

The study of energy transformations that occur in matter

Closed System

Isolated from its surroundings

Open System

Energy and matter can be transferred between the system and its surroundings (organisms)

1st Law of Thermodynamics

The energy of the universe is constant. Energy can be transferred and transformed but cannot be created or destroyed

2nd Law of Thermodynamics

Every energy transfer or transformation increases the entropy (disorder) or the universe. During every energy transfer/transformation, some energy is unusable, often lost as heat

Cellular Energetics

Autotrophs/producers make food (by photosynthesis). Autotrophs/producers and heterotrophs/consumers break down food to produce ATP. A living cell is not at true equilibrium so there is a constant flow of materials in/out of the cell. Cells manage energy resources to do work by energy coupling

Energy Coupling

Using an exergonic process to drive an endergonic one

Exergonic Reaction

Energy is released, spontaneous (digestion)

Endergonic Reaction

Energy is required, non spontaneous (photosynthesis)

Adenosine Triphosphate

The bond between the second and third phosphate is high-energy. When it is broken, energy is released and ADP forms. The phosphate that has been broken off attaches to another molecule, which transfers the energy to that molecule (called phosphorylation)

Catalyst

A substrate that can change the rate of a reaction without being altered in the process

Enzyme

A biological catalyst that speeds up chemical reactions, lowers activation energy, is not used up in a chemical reaction, and is substrate specific

Enzyme & Substrate Concentrations, Environmental Factors and Activators and Inhibitors 

These are several factors that can affect the rate of reactions

Substrate

The reactant that an enzyme acts on

Enzyme Substrate Complex

This is formed when the enzyme binds to its substrate

Active Site

The region on the enzyme where the substrate binds

Induced Fit

When enzymes fit snuggly around the substrate

Plenty of Substrate

Adding more enzyme to the reaction will increase the rate of reaction. Once most of the substrate has reacted, adding more enzyme will have no effect

Available Enzyme

Adding more substrate will increase the rate of reaction. Once all the enzymes are saturated, adding more substrate will have no effect

Above Optimal Temp

Activity starts to decrease until the enzyme denatures

Optimal Temp

Max Rate (Temp)

Below Optimal Temp

Molecules move slower (fewer collisions between substrate and enzyme) until enzyme is inactive or denatured

Above Optimal pH

Rate decreases; lower [H+] interferes with enzyme shape

Optimal pH

Max Rate (pH)

Below Optimal pH

Rate decreases; higher [H+] interferes with enzyme shape

Activators

Stabilize the active form

Coenzymes

Organic activators

Cofactors

Inorganic activators (vitamins)

Inhibitors

Stabilize the inactive form

Competitive Inhibitors

Attach to the active site so the substrate can’t

Noncompetitive/Allosteric Inhibitors

Attach to the enzyme somewhere other than the active site, causing the active site to change shape

Feedback Inhibition

A product can act as an inhibitor so the reaction doesn’t continue unnecessarily

Allosteric Regulation

Protein’s function at one site is affected by binding of regulatory molecule to a separate site