AS Biology definitions

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AS Biology definitions
2015-04-27 18:27:27

AS Biology definitions
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  1. Accurate result
    A result that is really close to the true answer
  2. Activation energy
    The energy required that needs to be supplied before a chemical reaction will start
  3. Active site
    The part of an enzyme where a substrate molecule binds
  4. Active transport
    Movement of molecules and ions across plasma membranes, against a concentration gradient thus requiring energy
  5. Adaptation
    A characteristic that increases and organism's chance of survival
  6. Affinity for oxygen
    The tendency a molecule has to bind with oxygen
  7. Allele
    An alternative form of a gene
  8. Alveolus
    A microscopic air sac in the lungs where gas exchange occurs
  9. Amino acid
    A monomer of proteins
  10. Aneurysm
    A balloon-like swelling of an artery
  11. Anomalous data
    Measurements that fall outside the range of values you'd expect or any pattern you have
  12. Antibiotic
    A chemical used to treat bacterial diseases
  13. Antibiotic resistance
    When bacteria are able to survive in the presence of antibiotics
  14. Antibody
    A protein produced by B-cells in response to the presence of a pathogen
  15. Antigen
    A molecule found on the surface of a cell. A foreign antigen triggers an immune response
  16. Antigenic variation
    Where pathogens change their antigens
  17. Apoplast pathway
    A route that water takes through a plant root to the xylem, through cell walls
  18. Arteriole
    A blood vessel that branches off of an artery
  19. Asthma
    A respiratory condition where the airways become irritated and inflamed, usually because of an allergic reaction to substances such as pollen and dust
  20. Atheroma
    A fibrous plaque caused by the build up and hardening of white blood cells, lipids and connective tissue
  21. Atrioventricular node (AVN)
    A group of cells in the heart wall that are responsible for passing waves of electrical activity from the SAN on to the bundle of His
  22. Atrioventricular valve (AV)
    A valve in the heart linking the atria to the ventricles
  23. B-cell
    A type of white blood cell involved in the immune response by producing antibodies
  24. Base
    A nitrogen-containing molecule that forms part of a DNA nucleotide
  25. Benedict's test
    A biochemical test for the presence of sugars
  26. Biodiversity
    The variety of living organisms and ecosystems on Earth
  27. Biuret test
    A biochemical test for the presence of polypeptides and proteins
  28. Bohr effect
    An effect by which an increase of carbon dioxide in the blood results in a reduction of haemoglobin's affinity for oxygen
  29. Bundle of His
    A group of muscle fibres in the heart, responsible for conducting waves of electrical activity from the AVN to the Purkyne fibres
  30. Cancer
    A tumour that invades surrounding tissue
  31. Capillary bed
    A network of capillaries
  32. Carbohydrase
    An enzyme that catalyses the hydrolysis of carbohydrates
  33. Cardiac cycle
    An ongoing sequence of contraction and relaxation of the atria and ventricles that keeps the blood continuously circulating around the body
  34. Cardiac output
    • The volume of blood pumped by the heart per minute
    • Measured in cm^3 per minute
  35. Cardiovascular disease
    Any disease associated with the heart and blood vessels
  36. Casparian strip
    A waxy strip in the cell wall of an endodermis cell
  37. Catalyst
    A chemical that speeds up a chemical reaction without being used up itself
  38. Causal relationship
    Where a change in one variable causes the change in another
  39. Cell cycle
    The process that all body cells from multicellular organisms use to grow and divide
  40. Cell fractionation
    A method that separates the organelles in a cell
  41. Cell-surface membrane/Plasma membrane
    • The membrane found on the surface of animal cells (and just inside the cell wall of plant and prokaryotic cells
    • Regulates the movement of substances into and out of the cell
  42. Cell wall
    The outermost cell layer found in plant cells
  43. Cellular immune response
    The immune response that involves T-cells
  44. Cellulose
    A polysaccharide made of long unbranched chains of beta-glucose
  45. Centromere
    The point at which two strands of a chromosome are joined together
  46. Chlorophyll
    A green substance found in chloroplasts
  47. Chloroplast
    An organelle present in cells where photosynthesis occurs
  48. Chromatid
    One 'arm' of a double stranded chromosome
  49. Chromosome
    A thread-like structure made up of one long DNA molecule
  50. Classification
    The act of arranging organisms into groups based on their similarities and differences
  51. Common ancestor
    An organism from which all other organisms in a particular taxonomic group have evolved
  52. Competitive inhibitor
    A molecule that has a similar shape to a substrate and blocks an enzyme's active site
  53. Condensation reaction
    A reaction that releases a small molecule (eg water) when it links molecules together
  54. Conjugation
    When two bacteria come together and exchange genetic material
  55. Control experiment
    An extra experiment set up to eliminate the effect of some variables that can't be controlled
  56. Control group
    A group in a study that is treated in exactly the same way as the experimental group, apart from the factor you're investigating
  57. Control variable
    A variable that is kept constant throughout an experiment
  58. Coronary artery
    An artery that supplies the heart muscle with blood
  59. Coronary heart disease (CHD)
    When the coronary arteries have lots of atheromas in them, which restricts blood flow to the heart
  60. Correlation
    A relationship between two variables
  61. Cortex (plants)
    The outer layer of cells in a plant root
  62. Counter-current system
    The system in which blood flows in the opposite direction to water in the gills of a fish
  63. Courtship behaviour
    Behaviour carried out by organisms to attract a mate of the right species
  64. Crossing over
    When chromatids twist around each other and bits of them swap over during meiosis
  65. Cytoplasm
    A gel-like substance where most of the chemical reactions in a cell take place
  66. Denatured
    The point at which an enzyme no longer functions as a catalyst
  67. Deoxyribose
    The pentose sugar in DNA
  68. Dependant variable
    The variable you measure in an experiment
  69. Dicotyledonous plant
    A type of flowering plant
  70. Differentiation
    The process of a cell becoming specialised
  71. Diffusion (simple)
    Net movement of particles from an area of higher concentration to an area of lower concentration
  72. Digestion
    The process of breaking down food into substances that can be used by the body
  73. Dipeptide
    A molecule formed from two amino acids
  74. Diploid
    When a cell contains two copies of each chromosome
  75. Disaccharide
    A molecule formed from two monosaccharides
  76. DNA (deoxyribonucleic acid)
    The molecule in cells that stores genetic information
  77. DNA helicase
    An enzyme that breaks the hydrogen bonds between two polynucleotide DNA strands during DNA replication
  78. DNA sequencing
    The process of determining the base order of a section of DNA
  79. DNA polymerase
    An enzyme that joins together the nucleotides on a new strand of DNA during DNA replication
  80. Double-blind trial
    A study involving a control group and an experimental group where neither the scientists involved nor the participants know which group the participants are in
  81. Double helix
    • The structure of a DNA molecule
    • - Two separate strands wound together in a spiral
  82. Emphysema
    A lung disease caused by smoking or long-term exposure to air pollution, where foreign particles in the smoke or air become trapped in the alveoli
  83. Endodermis
    A single layer of cells between the cortex and the xylem
  84. Endoplasmic reticulum
    • A system of membranes enclosing a fluid-filled space
    • Involved with lipid and protein processing
  85. Endothelium
    The inner lining of a blood vessel
  86. Enzyme
    A protein that speeds up the rate of chemical reactions
  87. Enzyme-substrate complex
    The intermediate formed when a substrate molecule binds to the active site of an enzyme
  88. Epidermis (plants)
    The outermost layer of cells on a leaf
  89. Eukaryote
    Organism made up of a cell (or cells) containing a nucleus
  90. Exchange organ
    An organ specialised to exchange substances
  91. Exon
    A section of DNA within a gene that codes for amino acids
  92. Facilitated diffusion
    The diffusion of particles through carrier proteins or channel proteins in the plasma membrane
  93. Fair test
    A test in which only the independent variable has been allowed to affect the dependant variable
  94. Fertilisation
    When a haploid sperm fuses with a haploid egg to generate a diploid zygote
  95. Fibrosis
    The formation of scar tissue in the lungs' which can be the result of an infection or exposure to substances such as asbestos or dust
  96. Fluid mosaic model
    Model describing the arrangement of molecules in a cell membrane
  97. Founder effect
    The reduction in genetic diversity that occurs when just a few organisms from a population start a new colony
  98. Gamete
    A sex cell
  99. Gas exchange
    The process of taking in gases that are needed for life processes and getting rid of waste gases
  100. Gas exchange surface
    A boundary between the outside environment and the internal environment of an organism, over which gas exchange occurs
  101. Gene
    A section of DNA which codes for a protein
  102. Gene flow
    Different alleles being moved between populations when individuals migrate from one population into another
  103. Gene pool
    The complete range of alleles in a population
  104. Genetic bottleneck
    An event that causes a big reduction in a population and reduces genetic diversity
  105. Genetic diversity
    Differences in DNA
  106. Genotype
    The alleles an organism has
  107. Gill
    The respiratory organ of a fish
  108. Gill filament
    A thin plate in a fish's gill
  109. Glycogen
    A polysaccharide made from a long, very branched chain of alpha-glucose
  110. Glycosidic bond
    A bond formed between monosaccharides
  111. Golgi apparatus
    • A group of fluid-filled flattened sacs
    • Involved with processing and packaging lipids and proteins, and making lysosomes
  112. Granum
    A structure in chloroplasts formed from the stacking of thylakoid membranes
  113. Guard cell
    A cell that controls the opening and closing of stomata
  114. Haemoglobin
    An oxygen-carrying protein found in red blood cells
  115. Haploid
    When a cell contains one copy of each chromosome
  116. Heart rate
    The number of heartbeats per minute
  117. Herd immunity
    When unvaccinated people are protected because the occurrence of the disease is reduced by the number of people who are vaccinated
  118. Histone
    Protein the DNA is wound around in order to fit into the nucleus
  119. Homologous pair
    A pair of matching chromosomes- each chromosome contains the same gene but may contain different alleles
  120. Horizontal gene transmission
    When genes are passed on horizontally to other members of the same or different species, without reproduction occurring
  121. Humoral immune response
    The immune response that involves B-cells and the production of antibodies
  122. Hydrolysis
    A chemical reaction that uses a water molecule when it breaks bonds between molecules
  123. Hydrophilic
    Attracts water
  124. Hydrophobic
    Repels water
  125. Hypothesis
    A specific testable statement, based on a theory, about what will happen in a test situation
  126. Immunity
    The ability to respond quickly to an infecrion
  127. Immunological comparison
    Using antibodies to determine how similar proteins are
  128. Incidence of disease
    How many people suffer from a disease
  129. Independent segregation
    The random division of maternal and paternal chromosomes into gametes during meiosis
  130. Independent variable
    The variable you change in an experiment
  131. Index of diversity
    A measure of species diversity that takes into account the number of species present and the number individuals of each species
  132. Infectious disease
    A disease caused by an infection with a pathogen
  133. Intraspecific variation
    Variation between members of the same species
  134. Interphase
    A period of the cell cycle in which the cell grows and DNA is replicated
  135. Interspecific variation
    Variation between different species
  136. Intron
    A section of DNA within a gene that does not code for amino acids
  137. Iodine test
    A biochemical test for the presence of starch
  138. Isotonic solution
    A solution with the same water potential as another solution or cell
  139. Lactose-intolerant
    The inability to digest lactose due to an insufficient amount of the enzyme lactase
  140. Lamella (chloroplasts)
    A thin, flat piece of thylakoid found in the chloroplasts
  141. Lamella (fish)
    A tiny structure found on the gill filament in a fish
  142. Lipase
    An enzyme that catalyses the hydrolysis of lipids
  143. Loading of oxygen (onto haemoglobin)
    The action of an oxygen molecule binding with a haemoglobin molecule
  144. Locus
    The position on a chromosome where a particular allele is found
  145. Lymphatic system
    A network of tubes which transports excess tissue fluid back into the circulatory system
  146. Lysosomes
    A round organelle that contains digestive enzymes
  147. Magnification
    How much bigger an image from a microscope is compared to the specimen
  148. Mass transport system
    A system that carries substances to and from individual cells
  149. Mean
    The average of the values collected in a sample
  150. Meiosis
    A type of cell division where a parent cell divides to create four genetically different haploid cells
  151. Memory cell
    A white blood cell that remains in the body and remembers how to respond to infections
  152. Mesophyll cell
    A type of plant cell present in a leaf and the main gas exchange surface in a plant
  153. Metabolic rate
    The rate at which energy is used by an organism
  154. Microfibril
    A strong fibre formed by chains of cellulose linked together by hydrogen bonds
  155. Microvillus
    A fold in the plasma membrane that increases the surface area
  156. Mitochondrion
    • An oval-shaped organelle with a double membrane
    • The site of anaerobic respiration
  157. Mitosis
    A type of cell division where the parent cell divides to produce two genetically identical daughter cells
  158. Monoclonal antibody
    An antibody produced from a single group of genetically identical B-cells
  159. Monomer
    A small, basic molecular unit
  160. Monosaccharide
    A monomer of carbohydrates
  161. MRSA (methicillin-resistant Staphylococcus aureus)
    Staphylococcus aureus bacteria that are resistant to the antibiotic methicillin
  162. Multicellular organism
    An organism that has more than one cell
  163. Multiple repeat
    A section of repetitive DNA found outside of genes- does not code for amino acids
  164. Mutation
    A change in the base sequence of an organism's DNA
  165. Myocardial infarction
    Heart attack