Cells, Plants, Definitions

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Active transport
Movement of substances across membranes against their concentration gradient, requiring the use of energy in the form of ATP. Active transport usually involves the use of transport proteins.
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Allele
A version of a gene.
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Alveoli
Small air sacs in the lungs.
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Amino acid
An organic compound that contains both an amino group (–NH2) and a carboxyl group (–COOH). Amino acids are the monomers of protein molecules.
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Anaphase
In mitosis, the stage when the newly separated chromatids are pulled towards opposite poles of the nuclear spindle.
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Anomalous
Describes a result/data point that does not appear to fit the pattern of the other results. It may be assumed to be anomalous if the experimenter has made an error or if the
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Apoplast pathway
The route taken by water between the cells or through the cell walls in a plant.
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Arteriosclerosis
Hardening of the artery walls and loss of elasticity caused by atherosclerosis or by deposition of calcium.
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Asexual reproduction
The production of genetically identical new organisms by a single ‘parent’ organism.
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Artificial selection
Also called selective breeding – the process of improving a variety of crop plant or domesticated animal by breeding from selected individuals with desired characteristics.
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ATP
Adenosine triphosphate – a molecule used to store energy temporarily in organisms. The molecule is broken down to adenosine diphosphate + phosphate to release energy to drive metabolic processes.
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Atrioventricular node (AVN)
A patch of tissue in the septum of the heart that conducts the electrical stimulus from the atria in the heart through to the Purkyne fibres.
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Atrioventricular valves
Valves between the atria and ventricles that prevent backflow of blood.
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Atrium
One of the upper chambers in the heart.
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Binary fission
Method of cell division in bacteria. The DNA replicates and the cell divides into two, each having the same DNA as the parent cell. It does not involve mitosis.
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Bohr shift / Bohr effect
The effect of carbon dioxide concentration on the affinity of haemoglobin for oxygen
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Bronchi
Airways in the lungs that lead from the trachea to the bronchioles.
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Bronchioles
Airways in the lungs that lead from the bronchi to the alveoli.
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Buffer
A chemical system that resists changes in pH by maintaining a constant level of hydrogen ions in solution. Certain chemicals dissolved in the solution are responsible for this.
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Cambium
Plant tissue in the stem and root that contains dividing cells.
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Carbaminohaemoglobin
The molecule resulting from combination of carbon dioxide and haemoglobin.
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Cardiac cycle
The sequence of events making up one heartbeat
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Cardiac muscle
The muscle found in the heart. It has its own intrinsic heartbeat (it is myogenic).
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Carrier protein
A protein found in membranes, which is capable of carrying a specific molecule or ion through the membrane by active transport.
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Cartilage
A flexible, slightly elastic connective tissue.
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Cartilage ring
A flexible ring of cartilage that holds the airways open
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Casparian *****
A ***** of waterproof material (suberin) in the cell walls of root endodermis cells. It blocks the apoplast pathway
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Cell signalling
Processes that lead to communication and coordination between cells. Hormones binding to their receptors on the cell surface membrane are an example.
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Cellulose
A carbohydrate polymer (of β-glucose) that forms plant cell walls.
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Centriole
An organelle from which the spindle fibres develop during cell division in animal cells.
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Centromere
The region of a chromosome where two sister chromatids are joined together, and where the spindle fibre attaches during cell division.
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Channel protein
A protein pore that spans a membrane, through which very small ions and water soluble molecules may pass.
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Chloride shift
The movement of chloride ions into red blood cells to balance the loss of hydrogencarbonate ions.
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Chlorophyll
Pigments found in chloroplasts of plant (and some protoctist) cells. Each molecule consists of a hydrocarbon tail and a porphyrin ring head with a magnesium atom. Chlorophyll absorbs red and blue light, trapping the energy, and reflects green light.
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Chloroplast
An organelle found in plants, which contains chlorophyll and is responsible for photosynthetic activity in the plant.
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Chromatid
A replicated chromosome appears as two strands in early stages of cell division. Each strand is a chromatid.
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Chromatin
Material staining dark red in the nucleus during interphase of mitosis and meiosis. It consists of nucleic acids and proteins. Chromatin condenses into chromosomes during prophase of nuclear division.
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Chromosome A linear DNA molecule wrapped around histone proteins found in the nucleus. Chromosomes become visible in prophase of cell division.
A linear DNA molecule wrapped around histone proteins found in the nucleus. Chromosomes become visible in prophase of cell division.
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Cilia
Short extensions of eukaryotic cells, typically 2–10 µm long and 0.03 µm in diameter. They may be used for locomotion or to move fluids or mucus over a surface, for example in the mammalian respiratory tract.
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Ciliated epithelium
Epithelial cells that have cilia on their cell surface.
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Clonal expansion
The division of selected cells by mitosis to increase their numbers.
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Clones
Genetically identical cells or individuals.
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Companion cell
A cell in the phloem involved in actively loading sucrose into the sieve tube elements. The companion cell is closely associated with a phloem sieve element, to which it is linked by many plasmodesmata
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Concentration gradient
The difference in concentration of a substance between two regions.
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Coronary arteries
Arteries that carry blood to the heart muscle.
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Cortex
Tissue in plant roots and stems between epidermis and vascular tissue
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Cotransporter protein
A protein in a cell membrane that allows movement of one molecule when linked to the movement of another molecule in the same direction by active transport.
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Crenation
State of animal cells when they have been immersed in a solution of lower water potential and have lost water by osmosis. They become shrivelled.
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Cristae
The folds found in the inner membrane of a mitochondrion. Stalked particles containing ATP synthase are found on cristae.
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Cytokinesis
The division of the cell, following nuclear division, to form two new cells.
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Cytoskeleton
The network of protein fibres and microtubules found within the cell that gives structure to the cell and is responsible for the movement of many materials within it.
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Deoxygenated
Blood with haemoglobin that carries no or little oxygen.
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Diaphragm
A sheet of muscular and fibrous tissue separating the chest cavity from the abdominal cavity.
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Diastole
The period when the heart muscle in the ventricles is relaxing and blood pressure is at its lowest.
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Diffusion
The net movement of molecules or ions in a gas or liquid from an area of high concentration to an area where they are less concentrated.
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Diffusion gradient
The gradient in molecular concentration (the difference in concentrations) that allows diffusion to occur.
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Dilate
To make wider. For example, vasodilation is when the lumens of blood vessels become wider.
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Diploid
Cells or organisms that have two copies of each chromosome in their nuclei.
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Dissociation
The breakdown of a molecule into two molecules, atoms or ions. For example, the release of oxygen from oxyhaemoglobin.
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Dissociation curve (oxyhaemoglobin)
The curve on a graph showing the proportion of haemoglobin that is saturated with oxygen at different oxygen tensions.
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DNA
Deoxyribonucleic acid – a polymer of nucleotide molecules that form the instructions for the synthesis of proteins found within organisms. These nucleotides contain the 5-carbon sugar deoxyribose.
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Double circulatory system
A transport system in which blood travels twice through the heart for each complete circulation of the body.
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Double helix
Describes the structure of DNA, a twisted helix of two strands with bases joining the strands.
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Electrocardiogram
Trace (graph) showing the electrical activity of the heart muscle (atria and ventricles) during a cycle.
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Endocytosis
The process of taking materials into a cell by surrounding them with part of the plasma membrane, which then pinches off to form a vesicle inside the cell. This is an active process requiring ATP.
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Endodermis
A ring of cells between the cortex of a root and the area housing the xylem and phloem.
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Endoplasmic reticulum (ER)
A series of membrane-bound, flattened sacs extending from the outer nuclear membrane through the cytoplasm. It may appear rough (rough ER) when ribosomes are attached to the outer surface, and it is involved with synthes
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Endothelium
A tissue that lines the inside of a structure, such as a blood vessel.
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Epidermis
Outer layer(s) of cells of a multicellular organism. Plants have a single layer surrounding the tissues of roots, stems and leaves. Invertebrates have an epidermis made of a single layer of cells that secrete a cuticle. Vertebrate (includi
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Epithelium
A tissue that covers the outside of a structure.
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Erythrocytes
Red blood cells.
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Eukaryote
An organism having cells with a nucleus and membrane-bound organelles.
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Eukaryotic cell
Cells that have a nucleus inside a nuclear envelope, and other membrane-bound organelles.
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Exchange surface
A specialised area adapted to make it easier for molecules to cross from one side of the surface to the other
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Exocytosis
The process of removing materials from the cell by fusing vesicles containing the material with the plasma membrane (cell surface membrane).
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Facilitated diffusion
The passive movement of molecules across membranes down their concentration gradient, which is aided by transport (carrier) protein molecules. No metabolic energy is required.
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Fibrillation
A state in which the chambers in the heart contract out of rhythm.
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Flaccid
A term used to describe plant tissue where the cells have lost turgor and are not firm.
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Fluid mosaic (model)
The model of cell membrane structure proposed by Singer and Nicholson – a phospholipid bilayer with proteins ‘floating’ in it.
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Gamete
Sex cells, usually haploid (one set of chromosomes). Male and female gametes can fuse, during sexual reproduction, to form zygotes (diploid).
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Gaseous exchange
The movement of gases by diffusion across a barrier such as the atreous wall.
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Gated channels
Protein channels found in cell membranes, which can be opened or closed in response to cell signals.
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Gene
A length of DNA that carries the code for the synthesis of one (or more) specific polypeptide.
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Goblet cells
Mucus-secreting cells in epithelial tissue.
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Golgi body
Membrane-bound organelle in eukaryote cells. Its functions are: to modify proteins, made at the rough endoplasmic reticulum, into glycoproteins; to package proteins for secretions outside the cell; to make lysosomes; in plant cells to secrete carbohy
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Guard cells
In pairs, these form the stomatal pore in the epidermis plants. They control the opening and closing of the pore by changes in their turgidity.
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Haem
The iron-containing prosthetic group found in haemoglobin
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Haemoglobin
The protein that carries oxygen in the red blood cells.
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Haemoglobinic acid
The acid produced when haemoglobin takes up hydrogen ions.
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Haemolysis
(First observed in red blood cells.) The rupturing of animal cell surface membranes and subsequent release of their contents, when animal cells are placed in a solution of higher water potential and water enters by osmosis.
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Haploid
A cell or organism that has one set of chromosomes/one copy of each chromosome
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Histone
Type of protein associated with DNA in eukaryotes. DNA is wound around histone proteins to form chromatin.
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Homologous
Chromosomes that have the same genes at the same loci. Members of an homologous pair of chromosomes pair up during meiosis. Diploid organisms, produced by sexual reproduction, have homologous pairs of chromosomes – one member of each pair from the ma
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Hormone
Chemicals made in endocrine glands that are carried in the blood to target cells/tissues/organs. They act as chemical messengers and are associated with developmental changes of the organism. Most are polypeptides but some are steroids.
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Hydrophilic
Associating with water molecules easily (water-loving).
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Hydrophobic
Water-repelling (water-hating).
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Hydrostatic pressure
Pressure created by a fluid pushing against the sides of a container.
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Interphase
The phase of the cell cycle where synthesis of new DNA and organelles takes place.
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Leucocytes
White blood cells.
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Lignin
A waterproofing substance that impregnates the walls of xylem tissue. Lignin gives wood its strength.
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Limiting factor
A variable that limits the rate of a process. If it is increased, then the rate of the process will increase.
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Lumen
A cavity surrounded by a cell wall in cells, such as xylem vessels, which have lost their cell contents. Also used for the central cavities of blood vessels.
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Lymphatic system
A system of lymph nodes and lacteals with lymph fluid.
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Lymphocyte
A type of white blood cell activated as part of the immune response.
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Lysosomes
Membrane-bound vesicles made by pinching off from the Golgi body. They usually contain digestive enzymes.
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Macromolecule
A very large molecule.
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Magnification
The number of time greater an image is than the object.
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Meiosis
Nuclear division that results in the formation of cells containing half the number of chromosomes of the adult cell.
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Meristem cells
Undifferentiated plant cells capable of rapid cell division
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Messenger RNA (mRNA)
A type of RNA polynucleotide involved in protein synthesis. Carries the information coding for a polypeptide from the nucleus to the ribosomes in the cytoplasm.
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Metaphase
The phase of mitosis where the chromosomes line up at the equator of the spindle.
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Microtubule motors
Proteins associated with microtubules. The proteins can move along microtubules. Kinesin moves towards the (+) end of the microtubules and dynein moves towards the (–) end.
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Microtubules
Components of the cell cytoskeleton. They have a diameter of about 24 nm and length varying from several micrometres in most cells to possibly several millimetres in some nerve cells. Microtubules are involved in mitosis, cytokinesis and movement of
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Microvilli
Folds in the membrane of a cell that increase its surface area.
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Mitochondrion (pl: mitochondria)
The organelle found in cells in which most of the ATP synthesis occurs. It is the site of aerobic respiration.
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Mitosis
The organelle found in cells in which most of the ATP synthesis occurs. It is the site of aerobic respiration.
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Mucus
A slimy substance secreted by goblet cells in animal epithelial tissues. It is made up mostly of glycoproteins (proteins bonded to carbohydrates) and is used to protect and/or lubricate the surface on to which it is secreted.
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Myogenic
Describes muscle tissue (heart muscle) that generates its own contractions.
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Nuclear envelope
The double membrane structure surrounding the nucleus in eukaryotic cells.
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Nucleic acid
A polymer of nucleotide molecules.
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Nucleus
A large, membrane-bound organelle found in eukaryotic cells, which contains the genetic material in the form of chromosomes.
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Organ
A collection of tissues that work together to perform a specific overall function or set of functions within a multicellular organism.
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Organelle
Structure inside a cell. Each organelle has a specific function.
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Osmosis
The movement of water molecules from a region of higher water potential to a region of lower water potential across a
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Oxygen tension
The amount of oxygen in the air expressed as the pressure created by the presence of oxygen, expressed in kilopascals (kPa).
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Oxygenated
Describes blood carrying oxygen in the form of oxyhaemoglobin.
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Oxyhaemoglobin
Haemoglobin with oxygen molecules attached.
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Partially permeable membrane
A membrane that will allow some molecules to pass through but will not allow some others to pass through.
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Pericycle
A layer of cells in the root that lies just inside the endodermis. It usually consists of meristematic cells whose division gives rise to lateral roots.
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pH
Gives measure of acidity/alkalinity of a solution. It is the reciprocal of the logarithmic value of the hydrogen ion concentration. So pH 1–6 are acidic (lots of hydrogen ions), 7 is neutral, and 8–14 are alkaline.
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Phagocyte
A cell that can carry out phagocytosis and ingest bacteria or small particles. Macrophages and neutrophils are phagocytes
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Phloem
A tissue in plants that is used to transport dissolved sugars and other substances.
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Phospholipid
A molecule consisting of a glycerol molecule, two fatty acid molecules and a phosphate group covalently bonded together. Phospholipids form the basis of cell membranes.
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Photosynthesis
Process by which plants, some bacteria and some protoctists make food using carbon dioxide, water and sunlight energy.
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Pits (or bordered pits)
Thin areas in the lignified walls of xylem tissue cells that allow communication between adjacent cells.
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Plasma membrane / cell surface membrane
The membrane that surrounds every cell, forming the selectively permeable boundary between the cell and its environment. It is made up of a double layer of phospholipids with embedded proteins.
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Plasmid
Small, circular piece of DNA present in some bacterial cells. Plasmids may have genes for antibiotic resistance. Plasmids can also be used as vectors in genetic engineering.
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Plasmodesma (pl: plasmodesmata)
A fine strand of cytoplasm that links the protoplasm of adjacent cells through a thin area of cell wall called a pit.
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Plasmolysis
Detachment of the plasma membrane from the cell wall as the cytoplasm shrinks when water is lost from a plant cell.
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Platelets
Fragments of cells in the blood that play a part in blood clotting.
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Potometer
Apparatus used to measure water uptake in a leafy shoot and so to estimate rate of transpiration.
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Prokaryote
An organism with cells that do not contain a true nucleus.
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Prophase
The phase of mitosis where the chromosomes become visible as a pair of sister chromatids joined at the centromere.
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Pulmonary circulation
The circulation of the blood through the lungs.
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Pulmonary vein
The vein carrying oxygenated blood from the lungs to the left atrium of the heart.
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Purkyne tissue (Purkinje tissue)
Specialised tissue (muscle fibres) in the septum of the heart that conducts the electrical stimulus from the sinoatrial node to the ventricles.
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Resolution
The ability to distinguish two separate points as distinct from each other.
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Respiration
The process in which energy is released from complex molecules, such as glucose, within cells and transferred to molecules of ATP.
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Ribosome
The organelle on which proteins are synthesised inside the cell.
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RNA
Ribonucleic acid – a single-stranded polynucleotide molecule that exists in three forms. Each form plays a part in the synthesis of proteins within cells.
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Root hair cells
Cells in the epithelium of roots that have long extensions to increase surface area for the absorption of water and minerals.
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Semilunar valves
Valves between the ventricles and the main arteries leading out of the heart, which prevent backflow of blood.
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Septum
The wall separating the ventricles of the heart.
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Sexual reproduction
The production of a new individual formed by the fusing of gametes from two different parent organisms. The offspring have unique combinations of alleles inherited from both parents.
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Sieve tube element
A cell found in phloem tissue through which sap containing sucrose is transported. It has very little cytoplasm, no nucleus, and non-thickened cellulose cell walls, with the end walls perforated to form sieve plates through which the sap passes from
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Simple diffusion
The movement of molecules from a region of their higher concentration to a region of their lower concentration.
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Single circulatory system
A circulation in which blood flows through the heart once during each circulation of the body.
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Sink
A part of a plant that removes sugars from the phloem.
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Sinoatrial node (SAN)
The patch of tissue that initiates the heartbeat by sending waves of excitation over the atria.
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Smooth muscle
A type of muscle (involuntary muscle) found mostly in certain internal organs and involved in involuntary movements such as peristalsis.
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Solute
A solid that dissolves in a liquid.
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Solute potential (φs)
The component of water potential that is due to the presence of solutes – the potential energy of a solution provided by the solutes.
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Solution
Liquid with dissolved solids.
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Solvent
A liquid that dissolves solids.
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Spindle
A structure consisting of protein fibres found in eukaryotic cells during cell division. Chromosomes become attached to the spindle at their centromeres, and spindle fibres guide the movement of chromosomes to opposite end of the cell at telophase.
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Stem cells
Undifferentiated cells that are capable of becoming differentiated to a number of possible cell types (e.g. totipotent, pluripotent).
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Stoma (pl: stomata)
Pore in leaf epidermis, surrounded by two guard cells. Changes in turgidity of the guard cells can open or close the stoma. Stomata allow gaseous exchange in plants and also allow transpiration.
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Surface tension
The ‘skin’ on the surface of water formed as a result of hydrogen bonding in water molecules pulling the surface molecules downwards.
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Symplast pathway
The route taken by water through the cytoplasm of cells in a plant.
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Systemic circulation
The circulation that carries blood around the body, excluding the circulation to the lungs.
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Systole
The stage of the heart cycle in which heart muscle contracts to pump blood.
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Telophase
Final phase of mitosis. Two new nuclear envelopes form around the two new nuclei.
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Tissue
A group of similar cells that perform a particular function.
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Tissue fluid
The fluid, derived from blood plasma, that surrounds the cells in a tissue.
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Totipotent
Undifferentiated cell that is capable of differentiating into any kind of specialised cell. All cells in an embryo are totipotent, as are meristem cells in plants. Embryonic stem cells are totipotent.
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Trachea
The windpipe leading from the back of the mouth to the bronchi.
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Transcription
The assembly of an mRNA molecule that is a copy of the DNA coding strand (and complementary to the template strand).
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Transfer RNA (tRNA)
A type of RNA polynucleotide involved in protein synthesis. It transports amino acids to the ribosomes to be added to the growing polypeptide chain.
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Translocation
The movement of sucrose and other substances up and down a plant.
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Transpiration
The loss of water vapour from the aerial parts of a plant due to evaporation.
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Turgid
Describes a cell that is full of water as a result of entry of water due to osmosis. When the pressure of the cell wall prevents more water entering, the cell is said to be turgid.
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Ultrastructure
The detailed structure of the internal components of cells as revealed by the electron microscope rather than by the light microscope. Sometimes called fine structure.
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Vacuolar pathway
The pathway taken by water in plants as it passes from cell to cell via the cell cytoplasm and vacuole.
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Vascular tissue / bundle
The transport tissue in a plant – usually found as a bundle containing both xylem and phloem.
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Vena cava
Either of two large veins that carry deoxygenated blood from the body back to the heart.
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Ventilation
Breathing – movement of diaphragm and rib cage that bring air into and out of the lungs.
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Ventricles
The lower chambers in the heart.
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Vesicle
A membrane-bound sac found in cells and used to transport materials around the cell.
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Villi
Folds in the wall of an organ or tissue that increase surface area.
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Water potential (Ψ)
A measure of the ability of water molecules to move freely in solution. Measures the potential for a solution to lose water – water moves from a solution with high water potential to one of lower water potential. Water potential is decreased by the p
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Water vapour potential
The potential energy of water vapour in a gas – it is used to indicate how much water vapour is present.
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Xylem
A plant tissue containing xylem vessels (and other cells) that are used to transport water in a plant and provide support.
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Biology Flash Cards
Unit 1 : Module 1 & 2 : Cells and Exchange and Transport
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A version of a gene.

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Allele

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Small air sacs in the lungs.

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Card 4

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An organic compound that contains both an amino group (–NH2) and a carboxyl group (–COOH). Amino acids are the monomers of protein molecules.

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Preview of the back of card 4

Card 5

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In mitosis, the stage when the newly separated chromatids are pulled towards opposite poles of the nuclear spindle.

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Preview of the back of card 5
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bellaciaoxy

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Mitosis answer is incorrect - should be mitochondria/on. Great crossword otherwise though. :)

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