Metabolism and Energy

metabolism

all of the chemical reactions in an organism

potential energy

stored energy

chemical energy

A form of potential energy that is stored in chemical bonds between atoms.

kinetic enrgy

energy of motion

thermodynamics

The study of energy transformations that occur in a collection of matter.

Sadi Carnot

father of thermodynamics

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

when energy is transformed, some energy is lost, typically as heat

entropy

tendency of a system towards disorder and energy is needed to counteract it

food chain

A series of steps in which organisms transfer energy by eating and being eaten; 1-10% of energy is transferred between trophic levels

endergonic reaction

absorbs/stores energy; nonspontaneous; G<0

Gibbs free energy

energy available to do work; high heat = high energy—> unstable

exergonic reaction

releases energy, spontaneous process; G>0

equilibrium

a state in which opposing forces or influences are balanced.

a cell at metabolic equilibrium is -

dead

energy coupling -

an exergonic process is used to power an endergonic one--> release of P from ATP provides the energy for cellular work

what reaction is ATP a product of -

breaking down glucose

ATP hydrolysis -

Inorganic phosphate breaks off, energy is released, and adp is left

Is ATP or ADP more stable? -

adp

phosphorylation -

the addition of a phosphate group to a molecule

energy of activation -

energy needed to start a chemical reaction

catalyst -

substance that speeds up the rate of a chemical reaction by lowering the activation energy

can enzymes be reused -

yes

substrate specificity -

ability of an enzyme to discriminate between very similar molecules

substrate -

chemical reactant an enzyme reacts with

active site -

region of an enzyme where active sites binds

how do enzymes work to lower the activation energy? -

• substrate is held in place by weak bonds

• active site may change shape of substrates

• active site microenvironment has right conditions for this reaction

induced fit -

as the substrate enters the active site, the enzyme changes shape slightly to engulf it

reaction rate depends on -

concentration of substrate & enzyme

point of saturation for enzymes -

where the graph begins to level off

what is the optimal pH for most enzymes? what is the optimal pH for pepsin?

most enzymes: pH of 6-8, pepsin (stomach): pH of 2

cofactors -

a nonprotein substance that helps an enzyme catalyze a metabolic reaction

3 types of enzyme regulation -

1. switching genes that encode for the enzyme on and off

2. allosteric regulation

3. inhibitors

• comp.

• noncomp.

2. feedback

• +

• -

allosteric regulation -

a molecule binds to the enzyme (not at the active site); stimulates or inhibits enzyme activity

competitive inhibitors -

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

how can competitive inhibitors be overcome -

increasing substrate concentration

noncompetitive inhibitors -

bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective

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.

positive feedback -

Feedback that tends to magnify a process or increase its output.