Cellular Energetics EC

Free Energy

energy that is available to do work

First Law of Thermodynamics

Energy can be transferred and transformed, but it cannot be created or destroyed.

Second Law of Thermodynamics

Every energy transfer or transformation increases the entropy of the universe.

Entropy

A measure of disorder or randomness.

Metabolism

All of the chemical reactions that occur within an organism

Exergonic Reaction

A chemical reaction that releases energy

Endergonic Reaction

A reaction that absorbs free energy from its surroundings.

Activation Energy

Energy needed to get a reaction started

Enzyme

A type of protein that speeds up a chemical reaction in a living organism

Active Site

The part of an enzyme or antibody where the chemical reaction occurs.

Substrate

reactant of an enzyme-catalyzed reaction

Lock and Key Model

Enzymes and substrates fit together based on their specific shapes like a key fits a lock

Induced Fit Model

Change in the shape of an enzyme's active site that enhances the fit between the active site and its substrate(s)

Conformation

The particular three-dimensional shape of a protein molecule

Cofactor

Non-protein helpers that may be bound tightly to the enzyme as a permanent resident, or may bind loosely and reversibly along with the substrate.

Coenzyme

If the cofactor is an organic molecule.

Denaturation

loss of normal shape of a protein due to heat or other factor

Renaturation

Regaining the correct tertiary structure after denaturation of a protein

Enzyme Saturation

A point of substrate concentration at which all enzymes are engaged

Inhibitor

A substance that slows down or stops a chemical reaction

Reversible Inhibition

inhibitor bonds noncovalently to the active site and prevents substrate from binding

Irreversible Inhibition

inhibitor permanently deactivates an enzyme, often by forming a covalent bond with the active site

Competitive Inhibition

Inhibitor competes with substrate for active site.

Non-competitive Inhibition

a molecule that binds to an enzyme at a location outside the active site and inhibits the enzyme's function.

Allosteric Inhibition

inhibition by a binding event at a site different from the active site, which induces a conformational change and reduces the affinity of the enzyme for its substrate

Allosteric Site

A specific receptor site on some part of an enzyme molecule remote from the active site.

Photosynthesis

Conversion of light energy from the sun into chemical energy.

Cyanobacteria

Photosynthetic, oxygen-producing bacteria

Light-Dependent Reactions

reactions of photosynthesis that use energy from light to produce ATP and NADPH

Light-Independent Reactions

set of reactions in photosynthesis that do not require light

Calvin Cycle

light-independent reactions of photosynthesis in which energy from ATP and NADPH is used to build high-energy compounds such as sugar

Chloroplast

An organelle found in plant and algae cells where photosynthesis occurs

Chlorophyll

A green pigment found in the chloroplasts of plants, algae, and some bacteria

Stroma

fluid portion of the chloroplast; outside of the thylakoids

Thylakoid

A flattened membrane sac inside the chloroplast, used to convert light energy into chemical energy.

Granum/Grana

stacks of thylakoids

Photosystem I

One of two light-harvesting units of a chloroplast's thylakoid membrane

Photosystem II

One of two light-capturing units in a chloroplast's thylakoid membrane or in the membrane of some prokaryotes

Electron Transport Chain

A sequence of electron carrier molecules that shuttle electrons during the redox reactions that release energy used to make ATP.

Electrochemical Gradient

The combined difference in concentration and electrical charge across a membrane that influences the movement of ions

Photophosphorylation

The production of ATP by chemiosmosis during the light reactions of photosynthesis.

Oxidation

loss of electrons

Reduction

gain of electrons

Proton

positively charged particle

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

ADP

(Adenosine Diphosphate) The compound that remains when a phosphate group is removed from ATP, releasing energy

ATP Synthase

Large protein that uses energy from H+ ions to bind ADP and a phosphate group together to produce ATP

NADPH

electron carrier that provides high-energy electrons for photosynthesis

NADP+

carrier molecule that transfers high-energy electrons from chlorophyll to other molecules

G3P

molecule that is made in the Calvin cycle; glucose is formed when two of these molecules combine

Aerobic Cellular Respiration

the process by which cells use oxygen to obtain usable energy from an energy source

Anaerobic Cellular Respiration

the process by which cells obtain energy from an energy source without using oxygen

Mitochondria

An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur.

Cristae

Infoldings of the inner membrane of a mitochondrion that houses the electon transport chain and the enzyme catalyzing the synthesis of ATP.

Matrix

Innermost compartment of the mitochondrion

Intermembrane Space

the fluid-filled space between the inner and outer mitochondrial membranes

Glycolysis

the breakdown of glucose by enzymes, releasing energy and pyruvic acid.

Glucose

A simple sugar that is an important source of energy.

NADH

the reduced form of NAD+; an electron-carrying molecule that functions in cellular respiration

NAD+

electron carrier involved in glycolysis

Pyruvate

Organic compound with a backbone of three carbon atoms. Two molecules form as end products of glycolysis

Krebs Cycle

second stage of cellular respiration, in which pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions

FADH2

A molecule that stores energy for harvest by the electron transport chain.

Oxidative Phosphorylation

The production of ATP using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration.

Chemiosmosis

A process for synthesizing ATP using the energy of an electrochemical gradient and the ATP synthase enzyme.

Fermentation

Process by which cells release energy in the absence of oxygen

Lactic Acid Fermentation

the chemical breakdown of carbohydrates that produces lactic acid as the main end product

Alcoholic Fermentation

the anaerobic process by which yeasts and other microorganisms break down sugars to form carbon dioxide and ethanol