Energy, metabolism, and enzymes

energy

the capacity to cause change or do work

Kinetic energy

energy of motion

thermal energy

kinetic energy of randomly moving molecules; heat is thermal energy being transferred

potential energy

energy from location or structure

chemical energy

potential energy released in a chemical reaction

first law of thermodynamics

energy is conserved it can be transferred or transformed but not created or destroyed

second law of thermodynamics

every energy transfer increases entropy of the universe some energy is always lost as heat

metabolism

all of an organisms chemical reactions

metabolic pathway

changes a molecule step by step each step catalyzed by a specific enzyme

catabolic pathway

breaks apart complex molecule down and release energy

anabolic pathway

build complex molecules and consumes energy

free energy

is the part of a system’s energy that can do work at uniform temperature and pressure (higher G = less stable)

equilibrium

forward and reverse reaction rates are equal

Cellular respiration & ATP hydrolysis exergonic or endergonic?

exergonic and is spontaneous

Building polymers and photosynthesis ender or exer?

Endergonic and non-spontaneous because requires energy input

What are the 3 kinds of work a cell does?

chemical, mechanical, and transport

chemical work

drives endergonic reactions

transport work

pumping across membranes

mechanical work

cilia or muscle

energy coupling

using an exergonic process to drive an endergonic one (ATP mediates most coupling)

ATP structure

adenine + ribose + three phosphate groups

ATP function

transfers a phosphate to another molecule (b/c its high energy) making it more reactive

ATP cycle

ATP is released from ADP =Pi using energy from catabolism

Catalyst

speeds up a reaction without being used up

enzymes

catalytic macromolecule

activation energy

the energy needed to break reactants bonds and reach the unstable transition state

Do enzymes lower or increase activation energy?

lower activation energy; they don’t change delta G they only speed up reactants that would happen anyways

substrate

the reactant an enzyme acts on binding to an active site forming the enzyme substrate complex

specificity

comes from the complementary shape of active site and substrate

induced fit

the enzyme changes shape slightly to grip the substrate; weak bonds hold it together

How does the active site lower activation energy

orienting substrates, stretching bonds, providing a favorable microenvironment

substrate concentration

more substrates = faster until the enzyme is saturated then only more enzymes can help

what temperature do human enzymes work best at?

30-40 degrees celsius

what pH does pepsin (stomach) work best at?

pH 2

cofactors

non protein helpers

Inorganic cofactors

metal ions (zinc, copper, iron)

organic cofactors

coenzymes most vitamins are coenzymes or raw materials

irreversible

covalent bonds to enzyme & permanently disables it & cannot be overcome by more substrate

competitive (reversible)

active site; resembles substrate and blocks substrate entry and can be overcome by more substrate

noncompetitive (reversible)

elsewhere on enzyme and changes enzyme shape so active site works poorly; cannot be overcome by more substrate

How do cells regulate pathways?

by switching genes for enzymes on or off or by regulating existing enzymes

allosteric regulation

molecule binds at one site and changes the proteins function at another site (can inhibit or activate)

feedback inhibition

the pathways end product inhibits an earlier enzyme so the cell doesn’t make more than it needs