BIOL151 ch 6

metabolism

metabolism

all energy and matter conversions in a cell

emergent property of life

metabolic pathways

energy-driven sequences of enzyme-mediated rxns

concentrate, convert, or dispose of materials in cells

control enzymes for key steps to shift cell activities fast

bioenergetics

study of how organisms manage their energy resources

calorie

used to measure energy

kinetic energy

energy used to do work associated with motion

sound, light

thermal energy

kinetic energy associated with movement of atoms

• heat transferred from one object to another

potential energy

energy that is stored and available, potential to do KE

chemical energy

available for release in chemical rxns

chemical bonds can be broken to release energy

thermodynamics

study of energy transformations

mass transfer

net movement of mass from one place to another

open system

energy and matter can be transferred between system and surroundings

organisms are this

first law of thermodynamics

energy of the universe is constant

can be transferred or transformed, but not created or destroyed

kinetic and radiant come from potential values

second law of thermodynamics

some energy is unusable during a transfer/transformation

normally lost as heat

every transfer/transformation increases entropy in the universe

entropy

amount of disorder within a system

need energy to overcome, the higher the energy the higher the order

organisms need energy input to overcome this and function properly

spontaneous process

occurs without energy input, thus increasing the entropy in the universe

can be harnessed to perform work if only moving toward equilibrium

free energy decreases, and stability of system increases

impossible to occur when at equilibrium

-🔺G

free energy

portion of a system’s energy that can do work when temp and pressure are constant

measure of a system’s instability and tendency to change to a more stable state

catabolic pathways

breakdown

release energy by breaking down complex molecules into simple compounds

cellular respiration is this because it breaks down glucose into CO2 and H2O

anabolic pathways

build

consume energy to build complex molecules from simple compounds

synthesis of proteins from amino acids is this

free energy change

tells us if reaction occurs spontaneously or not

(aka Gibb’s free energy)

🔺G = G final state - G initial state

cofactor

assists enzymes in chemical rxns, other than proteins

may carry e-, H, or functional groups to rxn sites to help break bonds

energy carrier

couples rxns that release energy with rxns that require energy

mainly ATP

chemical reactions

release and store energy

activation energy

necessary amount of energy to begin a reaction

enzymes lower the amount needed

often occurs in heat that reactant molecules can absorb from the surroundings and then move quickly and collide with eachother

endergonic reactions

absorb energy to build complex molecules

does not occur spontaneously b/c requires input of energy

aka anabolic reactions (b/c building)

exergonic reactions

release energy by breaking apart molecules

proceed spontaneously once started

have high activation energy

aka catabolic reactions (b/c breaking down)

chemical equilibrium

most reactions can proceed in both directions

reactants accumulate, rxn goes forward (& vice versa)

rxn goes in both directions at same rate at equilibrium

cells must remain far from equilibrium

ATP

temporary energy storage in covalent bonds

too unstable for long term storage

energy “currency” in cells

drive reactions in cells

ATP hydrolysis

ATP process that is exergonic (releases energy)

ATP synthesis

ATP process that is endergonic (stores energy)

phosphorylation

cell uses ATP as energy source by transferring its phosphate group to another molecule

• may cause protein to change shape of molecule

• may energize target molecule, making it more likely to bond, fueling endergonic rxn

coupled reactions

exergonic and endergonic go together as a pair

energy released in exergonic is used in endergonic

excess energy stored for later use

helps cells to manage energy resources

mediated by ATP within cells

regeneration

ATP does this by having a phosphate group added to ADP

energy to do so comes from catabolic rxns in cell

enzyme

catalyst for reactions (almost always a protein)

lowers activation energy barrier or speeds up the reaction

do not affect 🔺G

specific - only work for a few chemical reactions

substrate

reactant molecule on which an enzyme acts

forms enzyme-substrate complex

active site

region on enzyme where substrate binds and rxn is catalyzed

specifically shaped to fit the substrate molecule, have to lock in perfectly in order to work properly

coenzyme

organic cofactor

synthesized with vitamins

important for cellular respiration and protein metabolism

competitive inhinitors

bind to the active site of an enzyme

compete with substrate

noncompetitive inhibitors

bind to another part of an enzyme

enzyme changes shape and makes active site less effective

allosteric regulation

either inhibits or stimulates an enzyme’s activity

occurs when regulatory molecule binds to a protein at one site and affects the protein’s function at another site

allosteric activator

turns an enzyme active site back on

allosteric inhibitor

turns an enzyme active site off

cooperativity

form of allosteric regulation that can amplify enzyme activity

binding substrate to one active site affects catalysis in a different active site

feedback inhibition

end product of a metabolic pathway shuts down the pathway

prevents cell from wasting chemical resources by synthesizing more product than is needed