Biology: Energy, Enzymes, Biological Reactions, Cellular Respiration, and Photosynthesis

Vocabulary flashcards related to energy, enzymes, biological reactions, cellular respiration, and photosynthesis.

The ultimate source of energy for most organisms.

Sun

Kinetic energy of light

Plants capture this and convert it to chemical potential energy.

Chemical potential energy

Energy stored in sugars and other organic molecules.

Heat energy

The type of energy that most solar energy absorbed by green plants is converted into.

Exergonic reaction

Reaction that releases free energy.

ΔG

The symbol that represents the change in free energy.

Endergonic reaction

Reaction that requires reactants to gain free energy from the surroundings.

Metabolic pathway

A series of reactions in which the products of one reaction are used as the reactants for the next.

Catabolic pathway

A pathway in which energy is released by the breakdown of complex molecules.

Anabolic pathway

A pathway in which energy is used to build complicated molecules from simpler ones.

Biosynthetic reaction

Another name for an anabolic reaction.

Adenosine Triphosphate (ATP)

A nucleotide consisting of ribose, adenine, and three phosphate groups.

Hydrolysis of ATP

The process of breaking down ATP, resulting in ADP and inorganic phosphate.

Adenosine Diphosphate (ADP)

The product of ATP hydrolysis.

Inorganic phosphate (Pi)

The product of ATP hydrolysis.

ATP/ADP cycle

The continual hydrolysis and resynthesis of ATP.

Activation energy (Ea)

The energy required to start a spontaneous reaction.

Catalyst

A chemical agent that accelerates a reaction without being changed by the reaction.

Enzymes

Proteins that act as biological catalysts.

Conformation

The 3D structure of a protein that determines its function.

Substrate

The reactant that an enzyme acts on.

Active site

The small pocket or groove in the enzyme molecule where the substrate interacts.

Cofactor

A nonprotein group that binds to an enzyme for catalytic activity.

Coenzymes

Small organic molecule cofactors, often derived from vitamins.

Enzyme inhibitors

Nonsubstrate molecules that bind to an enzyme and decrease its activity.

Competitive inhibition

Inhibitors that bind to the active site, blocking access for the normal substrate.

Noncompetitive inhibition

Inhibitors that bind at a location other than the active site, reducing the ability of the active site to bind substrate.

Optimal pH

The pH at which an enzyme operates at peak efficiency.

Mitochondria

Organelles that animals, plants, fungi, and most protists depend on for energy.

Cellular respiration

Collection of metabolic reactions that breaks down food molecules to produce energy in the form of ATP.

Aerobic respiration

Form of cellular respiration in eukaryotes and many prokaryotes where oxygen is a reactant.

Anaerobic respiration

Form of cellular respiration in some prokaryotes using a molecule other than oxygen.

Photosynthesis

The process that produces most food molecules broken down in cellular respiration and the oxygen used in aerobic respiration.

Oxidation

The removal of electrons from a substance.

Reduction

The addition of electrons to a substance.

Redox reactions

Reactions that remove electrons from a donor molecule and simultaneously add them to an acceptor molecule.

Dehydrogenase enzymes

Enzymes that facilitate transfer of electrons from a fuel molecule to an electron carrier.

Nicotinamide adenine dinucleotide (NAD+)

The most common electron carrier.

Glycolysis

The process where enzymes break down glucose into pyruvate.

Substrate-level phosphorylation

An enzyme-catalyzed reaction that transfers a phosphate group from a substrate to ADP.

Pyruvate oxidation

The process where enzymes convert pyruvate into an acetyl group which enters the citric acid cycle.

Electron transfer system

A sequence of electron carriers that deliver high-energy electrons to oxygen.

Chemiosmosis

The use of an H+ gradient to generate ATP.

ATP synthase

Enzyme that uses the H+ gradient as the energy source to make ATP.

Cytosol

The location in a cell where glycolysis take place.

Mitochondrial matrix

The location in a cell where pyruvate oxidation and citric acid cycle take place.

Inner mitochondrial membrane

The location in a cell where the electron transfer system and ATP synthase enzymes are located.

Glycolysis (Embden–Meyerhof pathway)

Breaks glucose into pyruvate.

CO2, acetyl-coenzyme A (acetyl-CoA), and NADH

The products of pyruvate oxidation.

Citric acid cycle

Oxidizes carbon products of pyruvate oxidation to CO2.

Pyruvate oxidation (pyruvic acid oxidation)

Removes CO2 from pyruvate and oxidizes the remaining fragment to an acetyl group.

Citric acid cycle (tricarboxylic acid cycle or Krebs cycle)

Oxidize acetyl groups completely to CO2, generate NADH and FADH2, and synthesize ATP.

CoA

Carries products of many oxidative pathways into the citric acid cycle.

Mitochondrial electron transfer system (ETS)

Series of electron carriers that alternately pick up and release electrons and ultimately transfer them to their final acceptor – oxygen.

Cytochromes

Proteins with a heme prosthetic group that contains an iron atom that accepts and donates electrons.

Proton-motive force

Stored energy produced by proton and voltage gradient.

ATP synthase

In the mitochondrion, this enzyme synthesizes ATP.

Chemiosmosis

The hypothesis that H+ gradient powers ATP synthesis.

Photophosphorylation

Synthesis of ATP coupled to the transfer of electrons energized by photons of light.

Cyclic electron flow

A circular process where photosystem I works independently of photosystem II.

CO2 fixation (Calvin cycle)

Takes place in the light-independent reactions of photosynthesis.

Ribulose 1,5-bisphosphate (RuBP)

CO2 is added to this in the first phase of the Calvin Cycle.

C3 plants

Plants that initially fix carbon by adding CO2 to RuBP.

Photorespiration

An enzyme in plants that can use O2 as the first step in a pathway to generate CO2.

Autotrophs

Organisms that make required organic molecules from inorganic sources such as CO2 and water.

Photoautotrophs

Autotrophs that use light as the energy source to make organic molecules by photosynthesis.

Heterotrophs

Consumers and decomposers, which need a source of organic molecules to survive.

Light-dependent reactions

Energy of sunlight is absorbed and converted into chemical energy (ATP and NADPH).

Light-independent reactions (Calvin cycle)

Electrons in NADPH are used as a source of energy to convert inorganic CO2 to an organic form (CO2 fixation).

Thylakoid membranes and stromal lamellae

The location in a cell where light-dependent reactions are carried out.

Stroma

The location in a cell where light-independent reactions take place.

Chlorophylls

Green pigments used in photosythesis.

Carotenoids

Yellow-orange pigments used in photosythesis.

Chlorophylls and Carotenoids

In photosynthesis, light is absorbed by these two types of pigments.

Chlorophylls a and b

Light-absorbing electrons are distributed among the bonds in a carbon ring structure.

Carotenoids

Light- absorbing electrons are distributed along the carbon backbone in a series of alternating double and single carbon bonds.

Photophosphorylation

Synthesis of ATP coupled to the transfer of electrons energized by photons of light.

Cyclic electron flow

A circular process where photosystem I works independently of photosystem II.

CO2 fixation (Calvin cycle)

Takes place in the light-independent reactions of photosynthesis.

Ribulose 1,5-bisphosphate (RuBP)

CO2 is added to this in the first phase of the Calvin Cycle.

Photorespiration

Enzyme in plants that can use O2 as the first step in a pathway to generate CO2.

Photosynthesis

The conversion of light energy to chemical energy in the form of sugar and other organic molecules.

Theodor Engelmann

Used a glass prism to break light into a spectrum of colors to see the effects of each color on photosynthesis.

Photosynthesis

The process of converting energy of sunlight into chemical energy, used to assemble simple inorganic raw materials into complex organic molecules.

Autotrophs

Organisms that make required organic molecules from inorganic sources such as CO2 and water.

Photoautotrophs

Autotrophs that use light as the energy source to make organic molecules by photosynthesis.

Heterotrophs

Consumers and decomposers, which need a source of organic molecules to survive.

Light-dependent reactions and Light-independent reactions (Calvin cycle)

The two stages of photosynthesis.

Electrons and protons (H+)

CO2 fixation is a reduction reaction in which these are added to CO2.

Water (H2O)

In plants, algae, and cyanobacteria, the source of electrons and protons for CO2 fixation.

Chloroplast

The eukaryotic organelle in which photosynthesis takes place.

Stroma

The inner compartment of a chloroplast that is filled with a fluid.

Thylakoids

Flattened, closed sacs within the stroma of chloroplasts.

Grana

Stacks of thylakoids.

Stomata

Small pores in the surface of leaves and stems where CO2 enters the plant.

Light-dependent reactions (light reactions)

Convert light energy to chemical energy.

Photosynthetic pigments

Absorb photons and transfer excited electrons to primary acceptor molecules.

Chlorophylls

Major photosynthetic pigments in plants, green algae, and cyanobacteria.

Carotenoids

Accessory pigments that absorb light energy at a different wavelength than chlorophylls.

Photophosphorylation

Synthesis of ATP coupled to the transfer of electrons energized by photons of light.