Unit 3: Cellular Energetics

Metabolism

The sum of all chemical reactions occuring in a cell or organism

Metabolic pathway

Series of connected chemical reactions in a cell beginning with a specific molecule and ends with a product; Each step catalyzed by a specific enzyme

Catabolic pathway

Series of metabolic reactions that breaks down complex molecules into simpler ones, releasing stored chemical energy in the process; ex. Cellular respiration breaksdown glucose in the presence of oxygen

Anabolic pathway

Series of chemical reactions that consume energy to build complex, larger molecules from simpler starting materials; ex. Synthesis of a protein from amino acids

Bioenergetics

Study of how organisms manage their energy resources

Enzymes

A biological catalyst, usually a protein, (catalytic protein) that speeds up metabolic reactions by lowering energy barriers without being consumed or altered by the reaction (Can be altered elsewhere)

Hydrolysis of sucrose by the enzyme sucrase is an example of…

an enzyme-catalyzed reaction

Every chemical reaction between molecules involves…

bond breaking and bond forming

Substrate

Reactant that an enzyme acts on

Enzyme-substrate complex

Temporary molecule formed when a substrate binds to the specific active site of an enzyme during a biochemical reaction

Active site

Region on the enzyme where the substrate binds

Induced fit of a substrate brings chemical groups of the active site into positions that…

enhance their ability to catalyze the reaction

The substrate must have a ___________ shape/conformation and _________ to its respective enzyme for the reaction to be facilitated

complementary; charge

Activation Energy (E_A)

The initial energy needed to start a chemical reaction; AKA Free Energy of Activation

Activation energy is often supplied in the form of _________ energy that the reactant molecules absorb from their surroundings

thermal

Endergonic

Chemical reactions that require a net input of energy (unfavorable)

Exergonic

Chemical reactions that have a net loss of energy (favorable)

Enzymes catalyze reactions by…

lowering the E_A barrier

Enzymes do not affect the change in free energy (ΔG); Instead, they…

hasten reactions that would occur eventially

Thermodynamically favorable reactions have a negative ΔG, meaning they are…

exergonic reactions

Thermodynamically unfavorable reactions have a positive ΔG, meaning they are…

endergonic reactions

Enzymes can lose their shape/conformation based on…

local conditions

Denaturation

Loss of a protein’s native structure; (Sometimes reversible)

Denatured proteins are biologically inactive. For enzymes, this means…

they will not catalyze chemical reactions

Enzymes can function better in optimal ______ and ____ that favors the most active shape for the enzyme molecule

temperature; pH; Also concentration of substrate and enzymes as well

pH affects enzyme structure due to increased number of protons in a solution that alters ______ in protein structure, causing…

H-bonds; loss of secondary and tertiary structures (more favorable, complementary shape for substrate)

Temperature increases the _________ of the enzymes and substrates which increases…

kinetic energy; collisions and therefore reaction rate UP TO A CERTAIN POINT

Cells produce molecules as needed but cease to produce them when demand is met and homeostasis is restored. This is determined by…

Negative feedback where the product of the pathway inhibits the process responsible for its production and allows the cell to avoid wasting energy and resources

Competitive inhibitors

Binds to the active site of an enzyme, competing with the substrate

Noncompetitive inhibitors

Binds to the active site of an enzyme, causing the enzyme to change shape and making the active site less effective

Allosteric regulation

Either inhibits or stimulates an enzyme’s activity that occurs when a regulatory molecule binds to a protein at one site and affect the protein’s function at another site; Includes allosteric inhibition