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Bioenergetics

The field of biology that concerns energy flow through living systems, including the study of enzymatic processes, metabolic pathways, cellular respiration, and photosynthesis.

Producers

Organisms, such as plants and algae, that acquire matter from carbon dioxide, water, and minerals, and energy from sunlight.

Heterotrophs

Organisms that obtain both matter and energy from food.

Catabolism

Chemical reactions that break down molecules and release potential energy.

Anabolism

Chemical reactions that combine monomers to build polymers and require an input of kinetic energy.

Metabolism

The sum of all the chemical reactions occurring in an organism.

Exergonic reactions

Reactions that release energy and have a negative change in free energy (ΔG

Endergonic reactions

Reactions that absorb energy and have a positive change in free energy (ΔG>0).

Energy

The ability to do work or make things move.

Kinetic Energy

The energy of movement.

Potential Energy

Energy in its stored form, usually referring to the energy stored in the bonds of chemicals.

Thermal Energy

A form of kinetic energy, often released as heat during chemical reactions.

Metabolic pathways

Enzyme-regulated sets of biochemical reactions that lead to either biosynthesis (anabolic pathways) or breakdown (catabolic pathways).

Thermodynamics

The study of heat energy and its properties.

First Law of Thermodynamics

Energy cannot be created nor destroyed but can be transformed from one type of energy to another and transferred from one location to another.

Second Law of Thermodynamics

Every energy transfer increases the entropy of the universe.

Entropy

A thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work; often interpreted as the degree of disorder or randomness in the system.

Second Law of Thermodynamics

States that during every energy transfer, some of the system's energy is converted to heat, which is then unavailable to do useful work.

ATP

Adenosine triphosphate, a small molecule that serves as the main energy currency of cells. It is composed of a single nucleotide that bears a chain of three phosphates and is used to power many energy-requiring cellular reactions.

Hydrolysis

The breakdown of ATP into ADP and inorganic phosphate (Pi), releasing energy that can be used to power metabolic processes.

ADP

Adenosine diphosphate, the uncharged form of ATP that must be recharged before it can be used as a power source for cellular reactions.

Reaction Coupling

The process of linking an energetically favorable (spontaneous) reaction, such as ATP hydrolysis, with an energetically unfavorable (endergonic) reaction, allowing the release of energy from one reaction to power the other.

Phosphorylation

The addition of a phosphate group to a molecule, often involving ATP, which can provide the energy needed for an energetically unfavorable reaction to occur.

Protein Kinases

Enzymes responsible for carrying out phosphorylation reactions in cells, regulating protein function in response to extracellular stimuli.

Enzymes

Proteins that catalyze chemical reactions by lowering the activation energy required for the reaction to occur. They bind to specific substrates at their active sites and undergo a slight change in shape (induced fit) to facilitate the reaction.

Enzyme

A protein that catalyzes (speeds up) chemical reactions in the body without being changed or used up in the process.

Anabolic reactions

Reactions that build larger molecules from smaller ones, requiring energy.

Catabolic reactions

Reactions that break down larger molecules into smaller ones, releasing energy.

Denature

The process of changing the shape and losing function of an enzyme due to changes in temperature or pH.

pH

A measure of the hydrogen ion concentration in a solution, with values below 7 being acidic and values above 7 being basic.

Optimal temperature

The temperature at which an enzyme works best.

Optimal pH

The pH at which an enzyme works best.

Concentration of enzymes and substrates

The amount of enzymes and substrates present, which can affect the rate of reaction.

Competitive inhibitors

Molecules that compete with the substrate for the active site of an enzyme, slowing down the reaction rate.

Non-competitive inhibitors

Molecules that attach to a site other than the active site of an enzyme, changing its shape and preventing substrate binding.

Feedback inhibition

Temporary deactivation of an enzyme or metabolic pathway caused by an increase in the end product of the pathway.

Allosteric activators

Molecules or ions that enhance an enzyme's ability to work.

Coenzymes

Organic molecules, often vitamins, that attach to and activate specific enzymes.

Cofactors

Inorganic metal minerals, such as Mg, Fe, and Zn, that attach to and activate specific enzymes.

Cellular respiration

The process of releasing energy from organic molecules to make ATP, the energy source for most of the body's reactions.

Redox Reactions

Chemical reactions in which there is a transfer of electrons and energy between molecules or atoms.

Oxidation

The process in which electrons and energy are removed from a molecule or atom.

Reduction

The process in which electrons and energy are added to a molecule or atom.

Oxidizing Agent

The atom or molecule that takes electrons away from another atom or molecule.

Reducing Agent

The atom or molecule that donates electrons to another atom or molecule.

OIL RIG

Acronym to remember the difference between oxidation and reduction - "Oxidation is loss (of electron), Reduction is Gain (of electrons)."

Aerobic Cellular Respiration

The process of breaking down glucose in the presence of oxygen to produce ATP.

Glycolysis

The first step of aerobic cellular respiration, where glucose is broken down into pyruvate.

Krebs Cycle

The second step of aerobic cellular respiration, where pyruvate is further oxidized to produce energy carriers.

Electron Transport Chain

The third step of aerobic cellular respiration, where energy carriers are used to produce ATP.

ATP

Adenosine triphosphate, the energy currency of cells.

Matrix

The innermost compartment of a mitochondrion where the Krebs Cycle takes place.

Cristae

Folds in the inner mitochondrial membrane where the electron transport chain occurs.

Endosymbiotic Hypothesis

The theory that mitochondria originated from aerobic bacteria that entered into a symbiotic relationship with larger prokaryotic cells.

Pyruvate Conversion

The process in which pyruvate, a 3 carbon molecule created during glycolysis, is converted to a 2 carbon molecule known as an acetyl group in the mitochondria. This process is also referred to as the Preparatory Step, the Transition Step, or the Pyruvate Conversion.

Krebs Cycle

A series of chemical reactions that occur in the matrix of the mitochondria (in eukaryotic cells) or in the cytoplasm of aerobic prokaryotic cells. During the Krebs Cycle, the 2 Acetyl CoA molecules (the remains of the original glucose molecule from glycolysis) are oxidized, producing electron carriers/coenzymes NADH or FADH2 and ATP through substrate level phosphorylation.

Acetyl Coenzyme A

The 2 carbon molecule formed during the Pyruvate Conversion that serves as the starting point for the Krebs Cycle.

NADH

A molecule that carries electrons to the electron transport system during cellular respiration. It is produced during both the Pyruvate Conversion and the Krebs Cycle.

FADH2

A molecule that carries electrons to the electron transport system during cellular respiration. It is produced during the Krebs Cycle.

Substrate Level Phosphorylation

The process in which ATP is produced by transferring phosphate groups directly from a substrate molecule to ADP. This process occurs during the Krebs Cycle.

Carbon Dioxide

A waste product released during cellular respiration. In the Krebs Cycle, all of the carbon atoms from the original sugar are released as carbon dioxide gas.

Electron Transport Chain

A series of proteins and molecules located in the inner mitochondrial membrane that transfers electrons from electron carriers (such as NADH and FADH2) to generate ATP through oxidative phosphorylation.

Electron Transport Chain

A series of coupled reactions that occur on the folds of the inner mitochondrial membrane (in eukaryotic cells) or on the folds of the cell membrane (in aerobic prokaryotic cells), transferring energy from electrons to establish an electrochemical gradient and produce ATP.

ATP

Adenosine triphosphate, a molecule that stores and releases energy for cellular processes.

Electron Carriers

Molecules like NADH and FADH2 that carry electrons during the electron transport chain.

Cytochromes

Proteins that make up the actual electron transport chain and are highly conserved in all organisms.

Proton Pumps

Proteins that move protons (hydrogen ions) across the membranes during the electron transport chain, creating a proton gradient.

ATP Synthase

An enzyme embedded in the inner membrane that allows protons to move through it and uses their kinetic energy to produce ATP.

Chemiosmosis

The process of using energy from a proton gradient to phosphorylate ADP with an inorganic phosphate group, resulting in the production of ATP.

Oxidative Phosphorylation

The collective term for the electron transport chain and chemiosmosis, where electron carriers are oxidized and their energy is used to phosphorylate ADP to make ATP.

Decoupling

The separation of oxidative phosphorylation from electron transport, which generates heat in cellular respiration.

Anaerobic Cellular Respiration

The process of cellular respiration that occurs in the absence of oxygen, involving glycolysis and fermentation.

Glycolysis

The process in which glucose is broken down to produce ATP, pyruvate, and NADH.

ATP

Adenosine triphosphate, a molecule that stores and releases energy for cellular processes.

Pyruvate

A molecule produced during glycolysis that can be further metabolized in aerobic or anaerobic conditions.

NADH

Nicotinamide adenine dinucleotide, a molecule that carries high-energy electrons during cellular respiration.

Fermentation

An anaerobic process that regenerates NAD+ from NADH, allowing glycolysis to continue in the absence of oxygen.

Alcoholic Fermentation

A type of fermentation in which pyruvate is converted to ethanol and carbon dioxide.

Lactic Acid Fermentation

A type of fermentation in which pyruvate is converted to lactic acid.

Anaerobic Cellular Respiration

The process of producing ATP in the absence of oxygen.

Photosynthesis

The process by which plants, algae, and some bacteria convert sunlight into chemical energy stored in glucose.

Autotrophs

Organisms that can produce their own food, usually through photosynthesis.

Heterotrophs

Organisms that obtain energy and nutrients by consuming other organisms.

Chlorophyll

A green pigment found in chloroplasts that absorbs light energy for photosynthesis.

Chloroplast

An organelle found in plants and algae where photosynthesis takes place.

Thylakoid

A sack-like structure in the chloroplast where the pigment molecules for photosynthesis are embedded.

Grana

Stacks of thylakoids that increase the surface area for light-dependent reactions in photosynthesis.

Stroma

The watery space in the chloroplast where the Calvin Cycle takes place.

Electromagnetic Spectrum

The range of all possible frequencies of electromagnetic radiation, including visible light.

Photon

The smallest unit of light energy, which travels in waves with different wavelengths and frequencies.

Wavelength

The distance between two consecutive peaks or troughs of a wave.

Frequency

The number of wave cycles that pass a given point per unit of time.

Absorption Spectrum

The set of wavelengths absorbed by a pigment is its absorption spectrum.

Chlorophyll A

The main pigment found in all plants and algae, best at absorbing blue and red wavelengths of light.

Chlorophyll B

A yellowish-green pigment that acts as an accessory pigment, absorbing some wavelengths of light that chlorophyll A cannot absorb.

Carotenoids

A group of yellow, orange, and red pigments that act as accessory pigments.

Photosystems

Complex arrangements of chlorophyll A molecules with other pigments, embedded within the thylakoid membranes of chloroplasts.

Special Pair

A pair of molecules of chlorophyll A in a photosystem that can lose electrons when excited.

Photosystem II (PSII)

The photosystem that comes first in the path of electron flow, absorbs light best at 680 nm (orange to red color range).

Photosystem I (PSI)

The photosystem that comes second in the path of electron flow, absorbs light best at 700 nm (orange to red color range).