VCE Biology Unit 3 AOS 2

Enzyme

A type of protein, also referred to as a biological catalyst, that speeds up reactions within an organism by lowering activation energy.

Substrate

A molecule that binds to the active site of an enzyme and then takes part in a reaction; also referred to as a reactant.

Catalyst

A substance that increases the rate of a reaction by lowering the activation energy and providing an alternative reaction pathway.

Activation energy

The minimum amount of energy required for a reaction to proceed.

Active site

The region of an enzyme where the substrate binds for a chemical reaction to take place.

Catabolic

Describes a type of chemical reaction that releases energy and involves breaking down molecules into simpler components.

Anabolic

Describes a type of chemical reaction that requires energy and involves constructing molecules from simpler components.

Allosteric site

A binding site on an enzyme, where molecules other than the substrate may bind.

Coenzyme

An organic molecule that contains carbon and binds to enzymes to help them to function; examples are NADP, NAD and FAD.

Denaturation

The process by which a protein loses its 3D conformational structure through breaking of hydrogen bonds, caused by an external stress such as temperature or pH.

Enzyme saturation

The point at which the rate of reaction reaches a maximum, with no further increase at a specific enzyme concentration.

Competitive inhibition

The process of disrupting the function of an enzyme by blocking its active site with a molecule other than the substrate.

Non-competitive inhibition

The process of disrupting the function of an enzyme through a molecule binding to another site on the enzyme, which alters the shape of the active site in such a way that the substrate cannot bind.

Inhibitor

A molecule that is involved in disrupting the function of an enzyme, either directly (competitive) or indirectly (noncompetitive).

Autotroph

An organism that synthesises its own organic materials (food), by capturing light energy and taking in inorganic compounds from its physical environment, to meet its energy needs (auto = self, troph = food).

Photosynthesis

A chemical reaction in which light energy is used to convert the inorganic compounds carbon dioxide (CO2) and water (H2O) into the organic compound glucose; occurs in the chloroplast (photo = light, synthesis = build or put together).

Heterotroph

An organism that ingests organic materials by feeding on autotrophs or on other organisms and their products, in order to convert energy into the form of energy stored in ATP (heteros = other, trophe = food).

ATP (adenosine triphosphate)

The main immediate source of chemical energy in a cell, powering most cellular processes; when a phosphate group is removed, energy is released, and ADP is formed.

Cellular respiration

A series of chemical reactions in which the organic compound glucose is broken down, producing various products (depending on presence or absence of oxygen) and energy stored in ATP.

Chlorophyll

The green pigment on the thylakoid membranes of the chloroplasts of green plants; absorbs light energy for photosynthesis.

Granum (plural grana)

A stack of thylakoid membranes inside the chloroplast of plant and algae cells.

Thylakoid membrane

Disc-shaped interconnected membrane-bound compartments inside a chloroplast that make up the grana and are the location of the pigment chlorophyll, and therefore the site of the light dependent stage of photosynthesis.

Stroma

The gel-like fluid inside a chloroplast which surrounds the grana, site of the light independent stage of photosynthesis.

Light dependent stage

The first stage of photosynthesis; occurs in the thylakoid membranes and involves the splitting of water using light energy.

Light independent stage

The second stage of photosynthesis; occurs in the stroma of the chloroplast and involves the use of carbon dioxide to create glucose; also called the Calvin Cycle or carbon fixation.

Photolysis

The splitting of water using the light energy from the Sun.

ADP (adenosine diphosphate)

A compound composed of adenosine and two phosphate groups that can store energy when another inorganic phosphate group is added, forming ATP.

NADP+

A coenzyme that accepts and transfers hydrogen ions from one place to another during photosynthesis.

Coenzyme

An organic molecule that contains carbon and bind to enzymes to help them to function; examples are NADP, NAD and FAD.

Rubisco

An enzyme that catalyses the formation of PGA by fixing carbon dioxide to RuBP during the Calvin Cycle of photosynthesis to eventually produce glucose

Rate

The speed at which a process occurs, or how quickly the reactants are used up and the products are created.

Limiting factor

Any factor that slows down the rate of photosynthesis when there is not enough of it, for example, carbon dioxide, water, chlorophyll and light energy.

C3 plants

Plants that fix CO2 from the atmosphere to form 3-phosphoglycerate or PGA, which contains three carbon atoms; are better suited to cooler and temperate climates; examples are rice, wheat, soybeans and cotton.

Photorespiration

The series of reactions that occur as a consequence of Rubisco using O2 as a substrate instead of CO2; an inefficient process that cannot produce glucose.

C4 plants

Plants that fix CO2 to form malate, which contains four carbon atoms; better suited to grasslands; examples are maize and sugar cane.

CAM plants

Plants that fix CO2 to form malate, which contains four carbon atoms; better suited to deserts; examples are cacti and pineapples.

Energy shuttle

The cycling between the formation of ATP when energy is stored and the formation of ADP and Pi when energy is released; also known as the ATP-ADP cycle.

Glycolysis

The first stage of cellular respiration, where glucose is broken down into two pyruvate molecules in the cytosol, producing 2 ATP and 2 NADH; does not require oxygen.

Aerobic cellular respiration

Cellular respiration that occurs in the presence of oxygen and involves the transformation of the chemical energy stored in glucose into ATP; includes the Krebs Cycle and the electron transport chain, which occur in the mitochondria.

Anaerobic cellular respiration

Cellular respiration that occurs in the absence of oxygen and involves the transformation of the chemical energy stored in glucose into 2 ATP; the products depend on the type of organism carrying out the process.

NAD+

A coenzyme that accepts hydrogen ions and transfers them from one place to another during cellular respiration.

Crista

A fold in the inner membrane of a mitochondrion and site of the third stage of aerobic cellular respiration, the electron transport chain.

Matrix

The fluid component of a mitochondrion and site of the second stage of aerobic cellular respiration, the Krebs Cycle.

ATP synthase

An enzyme responsible for catalysing the formation of ATP from ADP and Pi.

Fermentation

The process by which glucose is broken down in the absence of oxygen to produce 2 ATP; also called anaerobic cellular respiration.

CRISPR-Cas9

An immune system in bacteria that uses CRISPR nucleotide sequences and the Cas9 DNA cutting enzyme, also modified for use as a genome editing tool.

Cas9

An endonuclease (enzyme) that cuts DNA at a specific point determined by guide RNA (gRNA).

Gene editing

The insertion, removal or replacement of DNA within the genome of a living organism.

Biofuel

Fuel produced from biomass; usually liquid.

Biomass

Organic material, including plant material, animal by-products, microbes and waste material; produced by many different industries.