cell energetics and enzyme

Metabolism

the totality of an organisms chemical reactions that result from interactions between
molecules within the cell

metabolic pathway

a sequence of chemical reactions undergone by a compound in a living
organism, start with substrate end with product

catabolic pathway

breaking a complex molecule down into its simpler parts, releasing energy. i.e.
cellular respiration

anabolic pathway

using energy to build complex molecules from simpler molecules. i.e. protein
synthesis

Bioenergetics

the study of how organisms manage their energy resources

Energy

capacity to cause change, do work

kinetic energy

energy of motion

heat(thermal energy)

kinetic energy associated with random movement of molecules

potential energy

energy of position

chemical energy

potential energy available for release in a chemical reaction, energy within bonds

thermodynamics

study of energy transformations

closed system

isolated from surroundings, no energy transfer, can’t work at equilibrium because its
exhausted its ability to do work. free energy at a min

open system

not isolated, energy and matter can be transferred between system and surroundings,
ie. Cells

1st law of thermodynamics

energy of the universe is constant, cannot be created or destroyed, can
only be transferred or transformed, conservation of energy

2nd law of thermodynamics

during every energy transfer, some energy is unusable and often lost,
every energy transfer or transformation increases the total entropy of the universe

Entropy

disorder, randomness

free energy

delta G, energy that can do work when temperature and pressure are constant, related
to change in enthalpy(delta H), change in entropy(delta S) and temperature in Kelvin(T). delta G =
delta H

exergonic reaction

a reaction with a net release of free energy, negative free energy, spontaneous

endergonic reaction

a reaction that absorbs free energy from its surroundings, non

coupled reactions

the use of exergonic processes to drive endergonic ones, the energy given off
from the exergonic is absorbed by the endergonic

ATP

adenosine triphosphate, composed of ribose (5 carbon sugar), adenine (nitrogenous base),
and 3 phosphate groups. Phosphate tail can be broken through hydrolysis to produce energy, ADP,
and an inorganic phosphate

Phosphorylation

how ATP drives endergonic reactions, covalently bonding a phosphate with another
molecule, such as as reactant

Catalyst

a chemical agent that speeds up chemical reactions without being consumed by the
reaction

Enzymes

a catalytic protein, speeds up metabolic reactions by lowering activation energy, very
specific, reusable, unchanged by reaction

activation energy

initial energy needed to start a chemical reaction, free energy for activating
reaction, given off by heat

induced fit

brings the chemical groups of the active site into positions that enhance their ability to
catalyze the reaction, makes the enzyme more effective

cooperativity

another type of allosteric activation, binds to one active site but locks ALL active sites
open, allowing products to be constantly produced

Substrate

the REACTANT that an enzyme acts on

Enzyme

Substrate Complex

Active Site

region on the enzyme where substrate binds

Hydrogen and Ionic Bonds

substrate held in active site by WEAK interactions

Lock and Key

active site on enzyme fits substrate exactly
Ways enzymes lower activation energy

Hydrolysis

happens when phosphate leaves ATP to give energy to something else. This causes
ATP to become ADP, produces water

Cofactors

non

Coenzymes

organic enzyme helpers ex. Vitamins

Denature

above a certain temperature, activity declines, protein changes shape

Gene Regulation

cell switches on or off the genes that code for specific enzymes

negative feedback inhibition

accumulation of end product slows the reaction to stop production

positive feedback

end product speeds up production (less common)

Allosteric Regulation

can accelerate or inhibit production and enzyme activity by attaching to
another part of the protein. this changes the shape of the active site which inhibits substrates from
bonding and producing more products

Activator

one of the allosteric regulators, stabilizes and keeps active site open for production

Inhibitor

one of the allosteric regulators, changes shape of the active site so the substrate can't bind

Competitive Inhibitor

inhibitor that mimics original substrate and blocks the active site

Non

competitive Inhibitor

exergonic

reaction is spontaneous (

endergonic

reaction is not spontaneous (positive G), absorbs energy