AS Definitions Flashcards
Abiotic factors.
Non-living conditions in a habitat.
Activation energy.
The energy required to initiate a reaction.
Active site
Area of an enzyme with a shape complimentary to a specific substrate, allowing the enzyme to bind a substrate with specificity.
Adenosine diphosphate (ADP)
A nucleotide composed of a nitrogenous base (adenine), a pentode sugar and two phosphate groups. Formed by the hydrolysis of ATP, releasing a phosphate ion and energy.
Adenosine triphosphate (ATP)
A nucleotide composed of a nitrogenous base (adenine), a pentose sugar and three phosphate groups. The universal energy currency for cells.
Agglutinins
Chemicals (antibodies) that cause pathogens to clump together so they are easier for phagocytes to engulf and digest.
Alleles.
Different versions of the same gene.
Amino acids.
Monomer used to build polypeptides and thus proteins.
Anabolism (anabolic)
Reactions of metabolism that construct molecules from smaller units. These reactions require energy from the hydrolysis of ATP.
Analogous structures.
Structures that have adapted to perform the same function but have a different origin.
Anaphase.
Third stage of mitosis when chromatids are separated to opposite poles of the cell.
Antibiotic-resistant bacteria
Bacteria that undergo mutation to become resistant to an antibiotic and then survive to increase in number
Antibiotics
A chemical or compound that kills or inhibits the growth of bacteria.
Antibodies
Y-shaped glycoproteins made by B cells of the immune system in response to the presence of an antigen.
Antigen
Identifying chemical on the surface of a cell that triggers an immune response.
Antigen-antibody complex.
The complex formed when an antibody binds to an antigen.
Antigen-presenting cell.
A cell that displays foreign antigens complexed with major histocompatibility complexes on their surfaces.
Antisense strand.
The strand of DNA that runs 3’ to 5’ and is complementary to the sense strand. It acts as a template strand during transcription.
Antibiotic-resistant bacteria
Bacteria that undergo mutation to become resistant to an antibiotic and then survive to increase in number
Antibiotics
A chemical or compound that kills or inhibits the growth of bacteria.
Antibodies
Y-shaped glycoproteins made by B cells of the immune system in response to the presence of an antigen.
Antigen
Identifying chemical on the surface of a cell that triggers an immune response.
Antigen-antibody complex.
The complex formed when an antibody binds to an antigen.
Antigen-presenting cell.
A cell that displays foreign antigens complexed with major histocompatibility complexes on their surfaces.
Antisense strand.
The strand of DNA that runs 3’ to 5’ and is complementary to the sense strand. It acts as a template strand during transcription.
Anti-toxins
Chemicals (antibodies) that bind to toxins produced by pathogens so they no longer have an effect.
Apoplast
The cell walls and intercellular spaces of plant cells.
Apoplast route
Movement of substances through the cell walls and cell spaces by diffusion and into cytoplasm by active transport.
Arrhythmia
The abnormal rhythm of the heart.
Artefacts
Objects or structures seen through a microscope that have been created during the processing of the specimen.
Artificial active immunity.
Immunity which results from exposure to a safe form of a pathogen, for example, by vaccination.
Artificial passive immunity.
Immunity which results from the administration of of antibodies from another animal against a dangerous pathogen.
Asexual reproduction.
The production of genetically identical offspring from a single parent.
Assimilates
The products of photosynthesis that are transported around a plant eg. Sucrose
Atrial fibrillation
An abnormal rhythm of the heart when the atria beat very fast and incompletely.
Atrio-ventricular node (AVN)
Stimulates the ventricles to contract after imposing a slight delay to ensure atrial contraction is complete.
Autoimmune disease
A condition or illness resulting from an autoimmune response.
Autoimmune response.
Response when the immune system acts against its own cells and destroys healthy tissue in the body.
Autotrophic.
Organisms that synthesise complex organic molecules from inorganic molecules via photosynthesis.
B effector cells
B lymphocytes that divide to form plasma cell clones.
B lymphocytes (B cells)
Lymphocytes which mature in the bone marrow and that are involved in the production of antibodies.
B memory cells.
B lymphocytes that live a long time and provide immunological memory of the antibody needed against a specific antigen.
Belt transect.
Two parallel lines are marked along the ground and samples are taken of the area at specified points.
Benedict’s reagent.
An alkaline solution of copper (II) sulfate used in the chemical tests for reducing sugars and non-reducing sugars. A brick-red precipitate indicates a positive result.
Beta pleated sheet.
Sheet-like secondary structure of proteins.
Binomial nomenclature.
The scientific naming of a species with a Latin name made of two parts - the first indicating the genus and the second the species.
Biodiversity.
The variety of living organisms present in an area.
Biuret test.
The chemical test for proteins; peptide bonds form violet coloured complexes with copper ions in alkaline solutions.
Bohr effect.
The effect of carbon dioxide concentration on the uptake and release of oxygen by haemoglobin.
Bradycardia.
A slow heart rhythm of below 60 beats per minute.
Breathing rate.
The number of breaths (inhalation and exhalation) taken per minute.
Bulk transport.
A form of active transport where large molecules or whole bacterial cells are moved into or out of a cell by endocytosis or exocytosis.
Bundle of His.
Conducting tissue composed of purkyne fibres that passes through the septum of the heart.
Callose.
A polysaccharide containing B 1-3 linkages and B 1-6 linkages between the glucose monomers that is important in the plant response to infection.
Carbaminohaemoglobin.
The compound formed when carbon dioxide combined with haemoglobin.
Carbohydrates.
Organic polymers composed of the elements carbon, hydrogen and oxygen, usually in the ratio Cx(H2O)y. Also known as saccharides or sugars.
Carbonic anhydrase.
Enzyme which catalyses the reversible reaction between carbon dioxide and water to form carbonic acid.
Cardiac cycle.
The events of a single heartbeat, composed of diastole and systole.
Cartilage
Strong, flexible connective tissue found in many areas of the bodies of humans and other animals.
Carrier proteins
Membrane proteins that play a part in the transport of substances through a membrane.
Catabolism (catabolic)
Reactions of metabolism that break molecules down into smaller units. These reactions release energy.
Catalase.
An enzyme that catalyses the breakdown of hydrogen peroxide.
Cell cycle.
The highly ordered sequence of events that takes place in a cell, resulting in division of the nucleus and the formation of two genetically identical daughter cells.
Cell signalling.
A complex system of intracellular communication.
Cellulose.
A polysaccharide formed from beta glucose molecules where alternate beta glucose molecules are turned upside down. It is unable to coil or form branches but makes hydrogen bonds with other cellulose molecules to produce strong and insoluble fibres. Major component of plant cell walls.
