Chapter 3- Enzymes, Photosynthesis, and Cellular Respiration

Photosynthesis

The process by which organisms capture energy from the sun to produce sugars.

Prokaryotic photosynthesis

Photosynthesis that first evolved in prokaryotic organisms, particularly cyanobacteria, which contributed to an oxygenated atmosphere.

Light-Dependent Reactions

A series of reactions in eukaryotic photosynthesis that capture light energy to produce ATP and NADPH.

Chlorophylls

Pigments that absorb light energy and boost electrons to a higher energy level during photosynthesis.

Photosystems I and II

Complexes of proteins and chlorophyll that are involved in the light-dependent reactions.

Electron Transport Chain (ETC)

A sequence of reactions where higher energy electrons are transferred between molecules, creating an electrochemical gradient.

Proton Gradient

An increase in hydrogen ions (H+) across a membrane, linked to ATP synthesis.

ATP Synthase

An enzyme that synthesizes ATP from ADP and inorganic phosphate using the energy from the proton gradient.

Calvin Cycle

The process where ATP and NADPH are used to produce carbohydrates from carbon dioxide.

Stroma

The fluid-filled space in chloroplasts where the Calvin cycle occurs.

Molecular Variation

Variation at the molecular level that allows organisms to respond to environmental stimuli.

Thylakoid Membrane

The location of light-dependent reactions in chloroplasts.

Photon

A particle of light energy that is captured in the light-dependent reactions.

Photolysis

The process of splitting water molecules in light-dependent reactions.

RuBisCo

An enzyme that catalyzes the first step of the Calvin cycle, making CO2 usable.

3-PGA

A 3-carbon molecule produced during the first phase of the Calvin cycle after carbon fixation.

G3P

A 3-carbon molecule that is produced from 3-PGA and used to regenerate RuBP.

RuBP

A 5-carbon molecule that combines with CO2 in the Calvin cycle to initiate the formation of carbohydrates.

NADP+

A molecule that serves as an electron acceptor in the light-dependent reactions, being reduced to NADPH.

Oxidation

The loss of electrons during a chemical reaction.

Reduction

The gain of electrons during a chemical reaction.

Cyclic Electron Flow

A process where electrons from PSI are recycled back into the electron transport chain in the absence of NADP+.

Oxygen Production

O2 is produced as a byproduct during the light-dependent reactions from the splitting of water.

ATP

A high-energy molecule produced during the light-dependent reactions, used in the Calvin cycle.

NADPH

A reduced electron carrier produced during the light-dependent reactions, used in the Calvin cycle.

Light Energy

Energy from sunlight that is captured by chlorophyll and used in photosynthesis.

Electrochemical Gradient

A gradient formed when protons are pumped across the thylakoid membrane, driving ATP synthesis.

Hydrogen Ions (H+)

Ions released during the photolysis of water that contribute to the proton gradient.

PSI (Photosystem I)

The second photosystem in the light-dependent reactions that absorbs light to energize electrons.

PSII (Photosystem II)

The first photosystem in the light-dependent reactions that captures light energy and initiates electron flow.

Phosphorylation

The process of adding a phosphate group to ADP to form ATP.

Calvin Cycle Phase 1

The carbon fixation phase where RuBisCo combines CO2 with RuBP.

Calvin Cycle Phase 2

The reduction phase where ATP and NADPH convert 3-PGA to G3P.

Calvin Cycle Phase 3

The regeneration phase where G3P is used to regenerate RuBP, consuming ATP.

Photosynthetic Pigments

Molecules in plants that absorb specific wavelengths of light necessary for photosynthesis.

Environmental Stimuli

Changes in the environment that organisms respond to through molecular variation.

Eukaryotic Photosynthesis

Photosynthesis that occurs in eukaryotic organisms, utilizing chloroplasts.

Cyanobacterial Photosynthesis

Photosynthesis conducted by cyanobacteria that contributed to the development of an oxygen atmosphere.

ATP Production

The synthesis of ATP during light-dependent reactions as a result of proton flow.

Respiration

The process by which cells convert sugars into energy, complementary to photosynthesis.

Glucose

A simple sugar produced by the Calvin cycle that serves as an energy source for organisms.

Biological Processes

Processes necessary for the survival of organisms, including energy capture and storage.

Photosynthetic Pathways

The series of biochemical processes that different organisms use to capture light and convert it to energy.

Enzymes

Biological catalysts that speed up reactions without being consumed.

Cofactor

Inorganic molecules (like metals or ions) that assist enzymes in their function.

Coenzyme

Carbon-based molecules that help enzymes function.

Active Site

The specific region of an enzyme where the substrate binds.

Specificity

Enzymes are specific for their substrate, meaning each enzyme fits a particular substrate.

Lock and Key Model

A model that illustrates the specificity of enzymes and substrates.

Induced Fit Model

A more accurate model than the lock and key, describing a conformational change of the enzyme when the substrate binds to the active site.

Denaturation

The process in which enzymes or proteins lose their functional shape due to changes in pH, temperature, or salinity.

Optimal Conditions

The specific pH, temperature, and salinity that allow enzymes to function most effectively.

Competitive Inhibition

A type of inhibition where a molecule competes with the substrate for the active site.

Non-competitive Inhibition

A type of inhibition where a molecule binds to the enzyme, not at the active site, causing a shape change.

Saturation

The point at which all active sites of an enzyme are occupied, resulting in maximum reaction rate.

Reversible Inhibition

Inhibition where the inhibitor can be removed from the enzyme.

Irreversible Inhibition

Inhibition where the inhibitor cannot be removed from the enzyme, often covalently bound.

Allosteric Site

A site on an enzyme where an inhibitor can bind, causing a change in enzyme shape.

Enzyme Activators

Molecules that bind to enzymes and enhance their activity.

Hydrogen Bonds

Weak bonds that can be disrupted during denaturation, affecting protein structure.

Kinetic Energy

Energy that increases with temperature, leading to more molecular collisions.

Optimal Temperature

The temperature at which enzyme activity is highest before denaturation occurs.

Biological Function

The role that enzymes play in facilitating biological reactions.

R Group Interactions

Interactions between the side chains of amino acids that help maintain protein structure.

Substrate Concentration

The amount of substrate present that can affect the rate of enzyme-catalyzed reactions.

Penicillin

An antibiotic that blocks an enzyme used by bacteria to build their cell wall.

Tamiflu

A drug that blocks an enzyme allowing flu viruses to enter cells.

Cyanide

A molecule that blocks a critical enzyme in cellular respiration by binding outside of the active site.

Molecular Collisions

Interactions between enzyme and substrate that lead to reactions.

pH

A measure of acidity or alkalinity that can affect enzyme activity.

Temperature

A factor that can increase or slow down enzyme reactions based on its optimal conditions.

Salinity

The concentration of salts in the environment that can impact enzyme activity.

Biological Systems

Complex networks of biological components that rely on enzymes for various reactions.

Conformational Change

A structural change in a protein or enzyme that affects its function.

Maximum Rate of Reaction

The highest rate at which a reaction can occur when an enzyme is saturated.

First Law of Thermodynamics

Energy cannot be created or destroyed, only transformed.

Second Law of Thermodynamics

Systems trend from order to disorder.

Free energy (G)

The energy available to do work within a system.

Exergonic reactions

Reactions that release energy and reduce usable free energy (−ΔG).

Endergonic reactions

Reactions that require energy and increase usable free energy (+ΔG).

Activation energy

The minimum amount of energy required to initiate a chemical reaction.

Enzymes

Biological catalysts that decrease the activation energy of a reaction.

Entropy

A measure of disorder in a system.

Energy transformation

The process of changing energy from one form to another.

Metabolism

The sum of all chemical reactions that occur in an organism.

Heat energy

Energy that is not usable (transformable) in a system.

Coupling reactions

A process where endergonic reactions are linked with exergonic reactions to maintain energy balance.

Disorder

A state that represents a lack of order or predictability in a system.

Energy input

The constant supply of energy needed to maintain order in a living system.

Chemical reactions

Processes that convert energy from one type to another and can release energy stored in bonds.

Death in systems

The result of loss of energy flow or too much disorder.

Usable free energy

The energy in a system that can perform work.

Energy conversion

The process through which energy changes forms, such as from chemical to kinetic.

Biological catalysts

Substances that accelerate chemical reactions in biological systems.

Reaction rate

The speed at which reactants are converted into products in a chemical reaction.

Constant energy replacement

The need for living systems to continuously replace energy lost to maintain order.

Chemical bonds

The connections between atoms in a molecule which hold energy.

Reaction equilibrium

The state at which the forward and reverse reaction rates are equal.

Energy efficiency in cells

Cells increase their efficiency in performing metabolic tasks through enzyme activity.

Thermodynamic systems

A system in which energy transfer and transformation take place.