CELL1010 Ch 6: An introduction to energy, enzymes, and metabolism

kinetic energy

energy associated with movement

potential energy

energy that a substance/object possesses due to its structure or location

types of kinetic energy

chemical, nucelar, electrochemical, elastic

types of potential energy

thermal, sonic, radiant/electromagnetic

things that store energy for long term use

reduced carbon: lipids, carbohydrates

things that store energy for immediate use

transmembrane electrochemical gradients, high-energy phosphates, and electron carriers

0th law of thermodynamics

defining temperature law: if two thermodynamic systems are each in thermal equilibrium with a third system, then they are also in thermal equilibrium with each other

1st law of thermodynamics

law of conservation of energy: energy cannot be created or destroyed, only transformed

2nd law of thermodynamics

entropy law: for an isolated and closed system, entropy cannot be decreased

entropy

measure of randomness of molecules in a system

3rd law of thermodynamics

absolute zero law: the entropy of a pure, perfectly crystalline substance approaches zero as its temperature approaches absolute 0 (0 K)

enthalpy

H, total energy

free energy

G, usable energy

lost energy

TS, unusable energy, temperature x entropy

total energy equation

H = G + TS

ΔH = ΔG + TΔS

endergonic reaction

chemical reactions that require an addition of free energy and do not proceed simultaneously, ΔG>0 (cells can use ATP to drive these reactions)

exergonic reactions

chemical reactions that release free energy and occur spontaneously, ΔG<0 (ex: removal of phosphate from ATP)

anabolism

synthesizes molecules/stuff

catabolism

breaks down molecules/stuff

enzymes

protein catalyst

catalyst

speeds something up without being permanently changed or consumed by it; stabilizes intermediate (forward and reverse reactions)

activation energy

allows molecules to collide with enough force to break chemical bonds

protein turnover

protein turnover → proteolysis → amino acids → translation → protein turnover

proteolysis

a breakdown of proteins into smaller peptides or individual amino acids through the hydrolysis of peptide bonds; can be done by lysosomes and proteasomes

lysosomes in proteolysis

newly evolved; digestive organelle; not inherited

proteasomes in proteolysis

proteins in cytosol and nucleus; inherited from archaea

ubiquitin

small, globular protein; in every eukaryote, in almost all archaea; marks structures for them to be broken down; autophagy (in lysosomes) - marked by chains of ubiquitin hanging of vesicle

competitive inhibitor

type of reversible inhibitor; bind non-covalently to the active site of an enzyme and inhibit the ability of the substrate to bind

noncompetitive inhibitor

type of reversible inhibitor; binds to another site on the enzyme and causes the enzyme to change its shape, which makes the enzyme less effective at carrying out the reaction

do all reactions need catalysts?

no!

rate-limiting step

the slowest step in a sequence of chemical reactions or a metabolic pathway that dictates the overall speed of the entire process

ways to regulate rate of reactions

1) expression of enzymes (changing amount of enzymes); more enzymes → faster reactions; controlled through synthesis and degradation

2) covalent changes to proteins make it a better enzyme or stop it from being an enzyme; adding or removing a chemical group can change a protein’s activity

3) non-covalent regulation; another molecule can temporarily bind to an enzyme and inhibit the enzyme (decrease its activity) or activate the enzyme (increase its activity); competitive and non competitive inhibitors

chemiosmosis

another way to make ATP; energy stored in an ion electrochemical gradient is used to make ATP from ADP and Pi

energy intermediates

molecules such as ATP where released energy is stored

substrate-level phosphorylation

a method of synthesizing ATP that occurs when an enzyme directly transfers a phosphate from an organic molecule to ADP

ways to break down molecules to obtain energy

energy intermediates, substrate-level phosphorylation, and chemiosmosis

feed-forward regulation

“I see something so I’ll prepare for it”; when the body anticipates a change before it actually happens; ex: you smell chocolate and your stomach might start preparing for digestion before the food even enters your stomach, fight or flight

negative feedback

type of feedback regulation; “stop/return to normal”; purpose to maintain homeostasis; ex: when you get hot, your body sweats to cool you down

positive feedback

type of feedback regulation; “more”; response amplifies the original change; ex: childbirth, contractions → hormone release → stronger contraction → more hormone release → even stronger contractions → etc

redox reactions

involve transfer of electrons

oxidation

the loss of electrons

reduction

the gain of electrons

protein degradation

1) string of ubiquitins is attached to target protein

2) protein with attached ubiquitins is directed to the proteasome

3) protein is unfolded by enzymes in the cap and injected into proteasome core; ubiquitins are released back into cytosol

4) protein is degraded into small peptides and amino acids

5) small peptides and amino acids are recycled back to the cytosol

autophagy

1) membrane tubule begins to enclose an organelle

2) double membrane completely encloses an organelle to form an autophagosome

3) autophagosome fuses with a lysosome; contents are degraded and recycled back to the cytosol