Cellular Energetics

1st law thermodynamics

• All matter never disappears; matter moves through cycles

• stays in one state for some time and then cycles into another state, but never disappears

2nd law thermodynamics

• heat flows from hot to cold

• Energy naturally spreads out, increasing towards entropy.

• It takes extra energy to keep energy tightly stored in the bonds of matter instead of letting it disperse.

3rd law thermodynamics

As a substance gets closer to absolute zero, its particles lose energy and move less, so entropy goes down and approaches zero, reaching equilibrium state.

kilocalories

1000 calories

calorie

heat input needed to raise 1g of water 1 degree

a joule of energy = __ calories

0.239

potential energy

stored energy due to an object's state/position

kinetic energy

energy that comes from motion

metabolism

The sum of an organism's chemical reactions determines how cells use energy

catabolic pathways

breaks down complex molecules into simple compounds to release energy

(think: a cat breaks stuff; cat breaks down complex into simple)

anabolic pathways

builds complex molecules from simple compounds by consuming energy

free energy

energy that’s available to do work

exergonic reaction

free energy is released

endergonic reaction

absorbs free energy to proceed reaction

free energy equation

ΔG=ΔH−T(ΔS)

G in free energy equation

Gibbs free energy

H in free energy equation

energy in chemical bonds (enthalpy)

S in free energy equation

energy available because of disorder (entropy)

T in free energy equation

absolute temperature in K (Celcius+273)

when ΔG is positive

• more free energy

• not spontaneous

• endergonic

when ΔG is negative

• less free energy

• spontaneous

• exogenic

oxidation

• loss of electrons, hydrogen atoms, or gain oxygen atom

• eg: combustion, rusting, and cellular respiration

  
  

reduction/redux reaction

• gains electrons

• decreases its oxidation state

• or loses oxygen.

redox reaction

chemical reaction where one substance is oxidized and another is reduced

energy coupling

• exergonic process to drive endergonic process.

• primary source is ATP

ATP (Adenosine Triphosphate)

• made up of: adenine (nitrogenous bases), ribose (5-carbon sugar), and a chain of 3 phosphate molecules.

  • Function: used by cells to do work; stores/transfers energy within a cell

activation energy

The amount of energy needed to start a reaction and also break the bonds of reactant molecules

catalyst

substance that speeds up a chemical reaction without being used up or changed.

enzyme

macromolecules that act as catalyst (speed up reaction) by lowering activation energy  of the reaction.

• it doesn't change the overall energy released/absorbed in the reaction

substrate

The reactant that the enzyme acts on

activation sites

where enzyme binds to substrate

enzyme substrate complex

temporary structure formed by enzyme and substrate.

The substrate converted into products

the products are released from the enzyme

catalysis

 activation energy is decreased due to enzymatic activity 

cofactor

• non-protein helper that some enzymes need to work properly

• eg: metal ions like zinc and iron

NAD (nicotinamide adenine dinucleotide)

essential cofactor in all living cells

• It helps enzymes carry out redox reactions (transferring electrons).

• It cycles between NAD⁺ (oxidized form) and NADH (reduced form).

• NAD is crucial for cellular respiration and energy production.

coenzyme

organic cofactor

 Multi-enzyme complex

enzymes joined together that pass products directly to the next enzyme, making reactions faster and more efficient

cooperativity

• Enzyme has multiple active sites.

• Binding one substrate makes it easier for others to bind.

• Multiple reactions can happen at once.

competitive inhibitors

reversible inhibitors that compete w/substrate for the active site on the enzyme.

 Non-Competitive Inhibitors

• doesn't compete with substrate

  • prevents enzyme activity by binding to diff part of the enzyme

penecillin

blocks the active site of DD-transpeptidase, stopping bacteria from building cell walls, which leads to bacterial death.

Methotrexate

• similar to folic acid.

• Competitively inhibits the enzyme dihydrofolate reductase (DHFR).

• Prevents nucleic acid synthesis, slowing cancer cell growth.

allosteric site

specific site on an enzyme (not the active site) where regulators bind

Feedback inhibition

process where a product of metabolic pathway slows down its own production by binding to and inhibiting an enzyme that acts earlier in the pathway

activators

 bind to Allosteric sites on enzymes to to keep the enzymes in active form