Unit 3 - Cellular Energetics

Enzymes

biological catalysts that speed up reactions in living organisms.

Lock and key method

rejected understanding that an enzyme’s substate has a very specific shape that exactly matches the enzyme’s active site.

Induced fit model

accepted understanding that the substate of an enzyme slightly changes to mold into the active site

Substrate

the molecule that the enzyme acts upon

Active site

where the chemical reaction takes place in an enzyme

Allosteric site

a site on an enzyme where molecules bind to regulate its activity (activate or deactivate)

Activation energy

energy needed to start an reaction.

Positive control

a part of an experiment where all necessary components are intentionally included.

Negative control

a part of an experiment where certain key components are intentionally left out.

Competitive inhibitors

they bind to the active site directly, blocking substates from binding.

Noncompetitive inhibitors

these bind to the allosteric site and causes the active site to change shape and deactivates it.

Anabolic reactions

building larger molecules from smaller ones.

Catabolic reactions

breaking down larger molecules for energy.

First law of Thermodynamics

energy cannot be created or destroyed, only changed from one form to another.

Second law of thermodynamics

in any energy transfer, entropy increases.

Entropy

measure of disorder / randomness in a system

Metabolism

sum of all chemical reactions in an organism that keeps it alive.

Energy coupling

process of using energy released from exergonic reaction to power endergonic reactions.

Exergonic

releases energy.

Endergonic

requires energy input

Light-Dependent Reactions

occurs in thylakoid membranes; convert light energy into ATP and NADPH.

Light-Independent Reactions (Calvin Cycle)

occurs in the stroma; use ATP and NADPH to make glucose from CO₂.

Chloroplast

organelle where photosynthesis takes place.

Thylakoid

flattened sacs containing chlorophyll.

Grana

stacks of thylakoids, beneficial in increasing surface area.

Stroma

fluid-filled space surrounding the grana(s).

The electron transfer chain (ETC)

a series of proteins that transfer electrons, creating a proton gradient to drive ATP production (products:- ATP and NADPH, water as waste product).

Photosystem

the reaction center and the light harvesting protein complexes and pigments in the thylakoid membrane.

Cellular Respiration

process that makes ATP by breaking down glucose with oxygen.

Photosynthesis

process that makes glucose and oxygen using sunlight, water, and CO₂.

Glycolysis

occurs in the cytoplasm, glucose is broken down into pyruvate, releasing energy.

Krebs Cycle

breaks down acetyl-CoA to produce ATP, NADH, and FADH₂ in mitochondria.

ATP (Adenosine Triphosphate)

the main energy currency of the cell.

Phosphorylation

the process of adding a phosphate group to a molecule.

Aerobic Respiration

requires oxygen to produce ATP.

Anaerobic Respiration

occurs without oxygen, producing less ATP