Key Definitions Flashcards
a-glucose
glucose in which the hydrogen atom on carbon atom number one projects above the plane of the ring,
ab initio protein modelling
a model is built based on the physical and electrical properties of the atoms in each amino acid in the sequence
accuracy
how close a measured or calculated value is to the true value
active immunity
where the immune system is activated and manufactures its own antibodies
active site
an indented area on the surface of an enzyme molecule, with a shape that is complementary to the shape of the substrate molecule
active transport
the movement of substances against their concentration gradient, from low to high concentration of these substances across a cell membrane, using ATP and protein carriers.
adaptation
a characteristic that enhances survival in the habitat
adhesion
the attraction between water molecules and the walls of the xylem vessel
affinity
a strong attraction
agglutination
the clumping of insoluble antigen molecules caused by crosslinking by antibodies that have a number of binding sites
agglutinins
antibodies that cause pathogens to stick togther
allele
a version of a gene, also called genetic variant
alveoli
tiny folds of the lung epithelium to increase the surface area
amino acids
monomers of all proteins, and all amino acids have the same basic structure
amphiphilic
attracted to both water and fat- containing hydrophobic/lipophilic and hydrophilic/lipophobic parts
amylopectin molecule
a molecule of polysaccharide with glycosidic bonds between carbon 1 and 4, and branches formed by glycosidic bonds between carbon 1 and 6. It is a constituent of starch
amylose molecule
a molecule of polysaccharide with long straight chains of between 100 to 1000 a-glucose molecules. It is a constituent of starch. Like maltose, it has glycosidic bonds between carbon 1 and 4
anatomy
the branch of science concerned with studying the bodily structure of living organisms
angina pectoris
a condition marked by severe pain in the chest, resulting from an inadequate blood supply, and therefore the lack of oxygen, to the heart muscle that causes the coronary arteries to spasm (tighten)
anion
a negatively charged ion
anomaly
a result that does not fit the expected trend or pattern
antibiotic
a chemical which prevents the growth of microorganisms. Antibiotics can be antibacterial or antifungal
antibodies
specific proteins released by plasma cells that can attach to pathogenic antigens
antigen-presenting cell
a cell that isolated the antigen from a pathogen and places it one the plasma membrane so that it can be recognized by other cells in the immune system
antigen
a membrane-bound molecules used to recognise pathogens
anti-toxins
antibodies that render toxins harmless
aorta
the main artery of the body in mammals
apoplast pathway
route by which water travels through the cell walls and in spaces between cells of plant tissue when travelling from roots to xylem and from xylem to leaves.
apoptosis
the death of cells which happens as a normal part of an organisms growth and development
archaea
prokaryotic microorganisms of similar size to bacteria but having some differences of metabolism
arithmetic mean
the average value of numbers in a collection, found by dividing the sum of all the values by the number of vale in the collection
arteries
vessels that carry blood away from the heart
arterioles
small blood vessels that distribute the blood from an artery to the capillaries
artificial classification
a classification based on just one or a few characteristics
artificial immunity
immunity that is achieved as a result of medical intervention
artificial insemination
The medical or veterinary procedure of injecting semen, collected from a male animal, into the vagina or uterus of a female of the same species.
asexual reproduction
some multicellular organisms and single-called protoctists such as Ameoba and Paramecium divide by mitosis to produce new individuals. They are genetically identical to the parent.
assimilates
substances that have become part of the plant
asymptomatic
not having symptoms
atria
thin-walled chambers of the heart that receives the blood from the veins and then pass into the ventricles.
atrio-ventricular nose (AVN)
a patch of tissue in the heart at the top of the septum that conducts the excitation wave from the atria to the ventricles
atrio-ventricular valves
valves between the atria and the ventricles, which ensure that blood flows in the correct direction
B-glucose
glucose in which the hydrogen atom on carbon atom number one projects below the plane of the ring.
B memory cells
cells that remain in the blood for a long time, providing long-term immunity
bacterium
a member of a large group of unicellular microorganisms that have cell walls made of murein but lack membrane-bound organelles and a nucleus. Their DNA floats free in the cytoplasm
behavioural adaptations
the ways that behaviour is modified for survival
binary fission
a type of division found in prokaryotic cells and organelles such as chloroplasts and mitochondria
binomial system
a system that uses the genus name and the species name to avoid confusion when naming organisms
biodiversity
a measure of the variation found in the living world
blood
the fluid used to transport materials around the body
Bohr effect
the effect that extra carbon dioxide has on the haemoglobin, explaining the release of more oxygen
bordered pits
the part of the plant cell walls which allow the exchange of fluids between tracheids or vessel elements
bradycardia
a slow heart rhythm
breathing rate
the number of breaths per minute
bronchi and bronchioles
smaller airways leading into the lungs
buccal cavity
the mouth
buffer
a solution that resists changes in pH, so keeps the pH stable
callose
a large polysaccharide deposit that blocks old or damaged phloem sieve tubes
canker
a sunken lesion in tree bark caused by necrosis
capillaries
very small vessels with very thin walls
carbaminohemoglobin
a compound of Haemoglobin and carbon dioxide, and is one of the forms in which carbon dioxide exists in the blood, within red blood cells. 10% of carbon dioxide is carried in blood this way
carbohydrates
a group of molecules containing carbon, oxygen and hydrogen
carbonic acid
a very weak acid formed when carbon dioxide reacts with water
carbonic anhydrase
the enzyme that cataylses the combination of carbon dioxide and water
cardiac cycle
the sequence of events in one full beat of the mammalian heart
cardiac muscle
specialised muscle found in the walls of the heart chambers
cartilage
a form of connective tissue
casparian strip
an impermeable, waterproof substance (suberin) in the walls of the endodermal cells of plant roots. It creates a water tight seal between the cells, preventing water entering the xylem via the apoplast pathway
catalyst
a chemical that speeds up the rate of a reaction and remains unchanged and reusable at the end of the reaction
cation
a positively charged ion
chloride shift
the movement of chloride ions into the erythrocytes to balance the charge as hydrogencarbonate ions leave the cell
chromatids
replicate the chromosomes
chromotography
a technique for the separation of a mixture by passing it in solution or suspension through a medium in which the components of the mixture move at different rates
circulatory system
single
one in which the blood flows through the heart once for each circuit of the body
circulatory system
double
one in which the blood flows through the heart twice for each circuit of the body
ciliated epithelium
a layer of cells that have many hair-like extensions called cilia
CITES
Convention on International Trade in Endangered Species
class
a taxonomic group of organisms that all poses the same general traits e.g. the same number of legs
classification
the process of placing living things into groups
climate change
significant, long-lasting changes in weather patterns
clonal expansion
an increase in the number of cells by mitotic cell division
clonal selection
selection of specific B or T cell that is specific to the antigen
closed circulatory system
one in which the blood is held in the vessels
coenzymes
small organic non-protein molecules that bind temporarily to the active site of enzyme molecules, either just before or at the same time that the substrate binds
cofactor
a substance that has to be present to ensure that an enzyme-catalysed reaction takes place at an appropriate rate. Some cofactors (prosthetic groups) are part of the enzyme structure, and others (mineral ion cofactors and organic coenzymes) form temporary associations with the enzyme
cohesion
the attraction between water molecules caused by hydrogen bonds
collenchyma cells
cells that have thick cellulose walls and strengthen vascular bundles and outer parts of the stems, whilst also allowing some flexibility in these regions
colorimeter
an instrument for measuring the absorbance of different wavelengths of the light in a solution
common anscestor
the most recent individual from which a set of organisms in a group are directly descended
companion cells
plant cells that help to load sucrose into the sieve tubes
comparative protein modelling
one approach is protein threading, which scans the amino acid sequence against a database of solved structures and produces a set of possible models which would match that sequence
competitive inhibition
inhibition of an enzyme, where the inhibitor molecule has a similar shape to that of the substrate molecule and competes with the substrate for the enzyme’s active site. It blocks the active site and prevents formation of enzyme-substrate complexes.
computer modelling
a model of a process which is created on a computer, often used for processes that can need the increased calculation speed
concentration
the abundance of molecules per unit volume
concentration gradient
a measurement of how the concentration of a substrate changes from one place to another, often across a membrane
conformational change
a change in the shape of a macromolecule
conjugated protein
a protein associated with a non-protein component
connective tissue
a widely distributed animal/mammalian tissue consisting of cells in an extracellular matrix of protein and polysaccharide; includes bone, cartilage and blood
conservation ex situ
carrying out active management to maintain the biodiversity in the natural environment
continuous variation
variation where there are two extremes and a full range of values in between
convergent evolution
the process whereby organisms not closely related independently evolve similar traits as a result of being adapted to similar environments or ecological niches
coronary arteries
arteries supplying blood to the heart muscle
correlation coefficent
a measure of how closely two sets of data are correlated. A value of 1 means a perfect correlation.
cotransport
transport across a cell membrane, using a carrier or channel protein, of two substances, both moving in the same direction - for example, both moving into the cell.
countercurrent flow
where two fluids flow in opposite directions
Countryside Stewardship Scheme
a scheme to encourage farmers and other land owners to manage parts of their land in a way that promotes conservation
covalent bonds
formed when electrons are shared between atoms. These bonds are very strong
crenated
a shriveled animal cell that has lost water by osmosis
cytochrome c
a type of cytochrome, an iron-containing protein found within the inner mitochondrial membranes and that forms a part of the electron transport chain
cytokines
hormone-like molecules used in cell signalling to stimulate the immune response
cytokinesis
cytoplasmic division following nuclear division, resulting in two new daughter cells
cytolysis
the process in animal cells where, if a lot of water molecules enter, the cell will swell and burst as the plasma membrane breaks
cytology
the study of cell structures and function
cytoskeletal motor proteins
molecular motors such as myosins, kinesins and dyneins
datalogger
an electronic device that records data over time or in relation to location either with a built-in instrument or sensor or via external instruments and sensors
denaturation
a process in which proteins lose their tertiary structure of proteins; caused by high temperatures or extremes of pH
denatured
the irreversible change of shape/loss of tertiary structure of proteins; caused by high temperatures or extremes of pH
deoxyribose
a five-carbon sugar derived from the five-carbon sugar ribose by replacement of a hydroxyl group by hydrogen, at carbon 2 atom.
diaphragm
a layer of muscle beneath the lungs
dicotyledonous plants
plants with two seed leaves and a branching pattern of veins in the leaf
diastole
the relaxing phase of the cardiac (heartbeat) cycle
differential staining
stains that bind to specific cell structures, staining each structure differently so the structures can be easily identified within a single preparation
differentiation
process by which stem cells become specialised into different types of cells
diffusion
movement of molecules from an area of high concentration of that molecule to an area of low concentration, it may or not be across a membrane; it does not involve metabolic energy (ATP)
digestive system
the organs and glands in the body that are responsible for digestion beginning at the mouth and extending through the oesophagus, stomach, small intestine and large intestine, ending with the rectum and anus
dilate
to make or become wider, larger, or more open
diploid
cell in which the nucleus has two complete sets of chromosomes
direct transmission
passing a pathogen from host to new host, with no intermediary
disaccharides
any of a class of sugars whose molecules contain two monosaccharide residues joined by a condensation reaction
discontinuous variation
where there are distinct categories and nothing in between
dissection
to cut apart tissues, organs or organisms for visual or microscopic study of their structure
dissociation
releasing the oxygen from oxyhaemoglobin
disulfide links
also called disulfide bridges or disulfide bonds, strong covalent bonds (where electrons are shared) between two sulfur atoms, within a (protein) molecule. These bonds are not broken by heat but can be broken by reducing agents
DNA polymerase
enzyme that catalyzes formation of DNA from activated deoxyribose nucleotides, using single-stranded DNA as a template
domain
the highest taxonomic rank. There are three domains: Archaea, Eubacteria and Eukaryotae
double helix
shape of DNA molecule, due to coiling of the two sugar-phosphate backbone strands into a right-handed spiral configuration
ecosystem
a community of interacting organisms and their physical environment
ectopic heartbeat
an extra or early beat of the ventricles
elastic fibres
protein fibres that can deform and then recoil to their original size
elastin
a type of protein made by cross-linking a polypeptide called tropoelastin. Tropoelastin has a coiled structure. The cross-linking and coiling make elastin a strong and extensible protein. It is found in structures in living organisms, such as elastic cartilage and ligaments , where they need to stretch or adapt their shape as part of life processes.
electrocardiogram
a trace that records the electrical activity of the heart
electron micrograph
a trace that records the electrical activity of the heart
elliptocytosis
cells being more elliptical in shape than they usually are
electrophoresis
the movement of charged particles/molecules in a fluid or gel under the influence of an elastic field
embryo-transfer
a step in the process of assisted reproduction in which embryos are placed into the uterus of a female with the intent to establish a pregnancy
endemicity
refers to the degree of a condition being endemic- always present in an area/community
endocytosis
bulk transport of molecules, too large to pass through a cell membrane even via channel or carrier proteins, into the cell
endothelium
the inner layer or lining of blood vessels, made of a single layer of cells
environmental variation
variation caused by a response to environmental factors such as light intensity
endodermis
a layer of cells surrounding the vascular tissue in the root of a plant
enzyme cascade
a sequence of successive activation reactions involving enzymes, which is characterized by a series of amplifications stemming from an initial stimulus. The product of each preceding reaction cataylses the next reaction
enzyme-product complex
enzyme molecule with product molecules in its active site. The two are joined temporarily by non-covalent forces
enzyme-substrate complex
enzyme molecule with substrate molecules in its active site. The two are joined temporarily by non-covalent forces
epidemic
a rapid spread of disease through a high proportion of the population
epidermal tissue
tissue consisting of epidermal cells- cells that form the outer layer of cells of a multicellular organism. Usually has a protective function
epithelial cells
cells that constitute lining tissue in animals
epithelial tissue
lining or covering tissue, consisting of epithelial cells
erythrocyte
a red blood cell
ester bond
a bond formed by a condensation reaction between the -OH group of a carboxylic acid and the -OH group of an alcohol, to produce an ester
eubacteria
taxonomic domain consisting of organisms that have eukaryotic cells
eukaryotae
taxonomic domain consisting of organisms that have eukaryotic cells
eukaryotic
cells having a true nucleus/organism with eukaryotic cells
eukaryotic cell cycle
series of events in a eukaryotic cell leading to its replication to produce two daughter cells; consists of interphase, mitosis and cytokinesis
evaporation
the change of state of a liquid into a vapour at a temperature below the liquids boiling point. Evaporation occurs at the surface of a liquid where some molecules of liquid with high kinetic energy escape
evolution
the gradual process by which the present diversity of living organisms has developed from earlier forms during the last 3000 million years of the history of the earth
exocytosis
the bulk transport of molecules, too large to pass through a cell membrane even via channel or carrier proteins, out of a cell
extant
still in existence; surviving
extinction
when the last living member of a species dies and the species ceases to exist
extracellular
outside the cell
eyepiece graticule
a measuring device. It is placed in the eyepiece of a microscope and acts as a ruler when you view an object under the microscope
facilitated diffusion
movement of molecules from an area of high concentration of that molecule to an area of low concentration, across a partially permeable membrane via protein channels or carriers; it does not involve metabolic energy (ATP)
family
a group of closely related genera e.g. within the order Carnivora we might recognise the ‘dog’ family and the ‘cat’ family
fatty acids
have a carboxyl group (-COOH) at one end, attached to a hydrocarbon tail, made of only carbon and hydrogen atoms. This may be anything from 2 to 20 carbons long
fertilisation
the fusion of male and female gamete nuclei
fetal haemoglobin
the type of haemoglobin usually found only in the fetus
fibrillation
uncoordinated contraction of the atria and ventricles
fibrous proteins
has a relatively long, thin structure, is insoluble in water and metabolically inactive, often having a structural role within an organism
filaments
slender branches of tissue that make up the gill. They are often called the primary lamellae
flaccid
plant tissue where there is no turgor- the tissue is soft
fluid mosaic model
theory of cell membrane structure with proteins embedded in a sea of phospholipids
gamete
sex cell e.g. ovum/ spermatozoon
gene
a length of DNA, that codes for a polypeptide or for a length of RNA that is involved in regulating gene expression
genetic erosion
a process whereby an already limited gene pool of an endangered species of plant or animal diminishes even more when individuals from the surviving population die off without getting a chance to meet and breed with others in their endangered low population
genetic variation
variation caused by possessing a different combination of alleles
genome
the total DNA content of a cell or an individual
genus
a group of closely related species
gill filaments
slender branches of tissue that make up the gill of a fish. They are often called the primary lamellae
glucose
a 6-carbon monosaccharide sugar
glycerol
has three carbon atoms. It is an alcohol, which means it has free -OH groups
globular proteins
has molecules of a relatively spherical shape, which are soluble in water, and often have metabolic roles within the organism
glycocalyx
all the carbohydrates molecules on the exterior of a cell surface membrane
glycogen molecule
the energy store in humans; large polysaccharide molecule made of many glucose residues joined by condensation reactions and like amylopectin, has glycosidic bonds between carbons 1 and 4, and branches formed by glycosidic bonds between carbon atoms 1 and 6.
glycolipid
lipid/phospholipid with a chain of carbohydrate molecule attached
glycoprotein
protein with a chain of carbohydrate molecules attached
glycosidic bonds
a bond formed between two monosaccharides by a hydrolysis reaction
growth factors
a substance, such as a vitamin, hormone or cytokinin, which is required for the stimulation of growth in living cells
goblet cells
cells that secrete mucus
guard cell
in leaf epidermis, two of these cells surround stomata
habitat
where an organism lives
haemoglobin
the red pigment used to transport oxygen in the blood
haemoglobinic acid
the compound formed by the buffering action of haemoglobin as it combines with excess hydrogen ions
haemolysis
lysis of animal cells, in this case it is referring to lysis of red blood cells
haemolytic anemia
anemia with chronic premature destruction of red blood cells
haploid
having only one set of chromosomes; represented by the symbol ‘n’
helicase
enzyme that cataylses the breaking of hydrogen bonds between the nitrogenous base pairs of bases in a DNA molecule
hazard
a factor that has the potential to cause harm
herd vaccination
using a vaccine to provide immunity to all or almost all of the population at risk
heterotopic ossification
overgrowth of bone, often in the wrong place e.g. muscle tissue
high-power drawing
a drawing showing detail of some individual cells
histamine
a compound which is released by mast cells in response to injury and in allergic and inflammatory reactions, causing contraction of smooth muscle and dilation of capillaries
homologous chromosomes
matching chromosomes, containing the same genes at the same place (loci). They may contain different alleles for some or all of the genes
homozygosity
in a diploid cells or organism the state where both copies of a given gene are the same allele
hormone
a chemical produced in glands and that travels to its target cells via the blood. Later broken down in the liver. Involved with communication and control
hydathodes
structures in plants that can release water droplets which may then evaporate from the leaf surface
hydrocarbon
a compound consisting of only hydrogen and carbon
hydrogen bond
a weak interaction that can occur wherever molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen
Hydrogencarbonate ion
HCO3-
Hydrolysis reaction
reaction that occurs when a molecule is split into two smaller molecules with the addition of water
hydrophilic
attracted to water
hydrophobic
repelled by water
hydrophyte
a plant adapted to living in water or where the ground is very wet
hydrostatic pressure
the pressure that a fluid exerts when pushing against the side of the vessel or the container
hypertension
long term high blood pressure
hyphae
each of the branching filaments that make up the mycelium of a fungus
immune response
the reaction of the cells and fluids of the body to the presence of a substance which is not recognised as a constituent of the body itself
immune system
the organs and processes of the body that provide resistance to infection and toxins. Organs include the thymus, bone marrow and lymph nodes
in vitro fertilisation
a process where an egg is surgically removed from the ovaries and fertilised with sperm in a laboratory
indirect transmission
passing a pathogen from host to new host, via a vector
inflammation
swelling and redness of tissue caused by infection
inhibitor
a substance that reduces or stops a reaction
inorganic ions
charged particles of inorganic (not carbon-based) substances e.g. Mg2+ and Ca2+
integumentary system
the organ system that protects the body from various kinds of damage, such as loss of water or abrasion from outside. The system comprises the skin and its appendages (including hair, scales, feathers, hooves and nails)
intercalated discs
gap junctions between muscle cells in the heart muscle. They enable the heart muscle cells to fit tightly together and help to facilitate synchronized contraction of the heart muscle
intercostal muscles
muscles between the ribs. Contraction of the external intercostal muscles raises the rib cage
interleukins
signalling molecules that are used to communicate between different white blood cells
interphase
phase of cell cycle where the cell is not dividing, it is subdivided into growth and synthesis phases
interspecific variation
the differences between species
intracellular
inside the cell
intraspecific variation
the variation between members of the same species
ionic bond
a type of chemical bond that involves the electrostatic attraction between oppositely charged ions
karyotype
a photomicrograph of chromosomes in a cell
keratin
a fibrous protein forming the main structural constituent of hair, feathers, hooves, nails, claws and horns
keratinocytes
an epidermal cell that produces keratin
keystone species
one that has a disproportionate effect upon its environment relative to its abundance
kinetic energy
the energy of motion
kingdom
taxonomic group; traditionally there are five main kingdoms: Plantae, Animalia, Fungi and Protoctista are all Eukarya whose cells posses a nucleus. All those single celled organisms that do not posses a nucleus are grouped into the kingdom Prokaryota.
lamellae
folds of the filament to increase the surface area. They are also called secondary lamellae or gill plates
leucocyte
a white blood cell
lignification
the deposition of lignin in the walls of xylem vessels
lignin
the waterproof substance that impregnates the walls of xylem vessels. When plant xylem vessels are lignified they are woody
limiting factor
an environmental factor that limits the rate of a biological process. When a process is controlled by a number of factors, the factor that is in least supply will limit the process. If this factor is increased then the process with proceed at a faster rate. If it is decreased the process will proceed at a slower rate.
lipids
a group of substances that are soluble in alcohol rather than water. They include triglycerides, phospholipids, glycolipids and cholesterol
lipophilic
attracted to fat
lipophobic
repelled by fat
locus
the position of a gene on a chromosome
longitudinal section
a section cut lengthways
low-power plan
a drawing showing distribution of cells but no individual cells shown
lymph
the fluid held in the lymphatic system, which is a system of tubes that return excess tissue fluid to the blood system
lymphatic system
a network of vessels and organs that help maintain the internal fluid environment of the body; also transports fat and proteins and makes some blood cells. Receives tissue fluid that has passed out of blood capillaries and bathed cells. Lymph drains into blood vessels in the neck region. Lymph organs include the tonsils, thymus, spleen and lymph nodes.
macromolecule
a very large, organic molecule
macrophages
large phagocytic cells that ingest and digest pathogens and present the pathogens antigens to other ells of the immune system
magnification
the number of times larger an image appears, compared to the size of the object
marine conservation zones
areas of the sea set aside to conserve the diversity of species and habitats
median
the number that separates a data set into two halves; half the set is above the median value and the other half is blow the median value. In a sample there may be no specimen that actually has the median value
meiosis
type of nuclear division that results in the formation of cells containing half the number of chromosomes of the parent cell
meristem
an area of unspecialised cells, in plants, that can divide and differentiate into other cell types
mesenchyme
connective tissue
mesoderm
the middle of the three layers in the early embryo; gives rises to connective tissue, muscles and part of the gonads (ovaries and testes)
mesophyll
a type of cell found in plant leaves
metabolic/metabolism
the chemical reactions that take place inside living cells or organisms
micrometer
a precise measuring device and not a unit of measurement. It is a small scale on a microscope slide that can be viewed under a microscope and used to calibrate the value of eyepiece divisions at different magnifications
micrometre
equal to one millionth (10-6) of a metre. It is the standard unit for measuring cell dimensions.
microscopy
the use of the microscope to study small objects or organisms
mitosis
a type of nuclear division that produces daughter cells genetically identical to each other and to the parent cell
mode
the most common value amongst a group or data set
monoculture
a crop consisting of one strain of one species
monocytes
the largest white blood cells, usually have a large kidney-shaped nucleus
monomer
a small molecule which binds to many other identical molecules to form a polymer
monosaccharide
any of the class of sugars (e.g. glucose) that cannot be hydrolysed to give a simpler sugar
mucous membrane
specialised epithelial tissue that is covered by mucus
muscle tissue
highly cellular, well vasculised (has many blood vessels) tissue responsible for most types of body movement. Muscle cells are called fibres, contain the proteins actin and myosin, and can contract. Three types of muscle tissue: smooth, skeletal and cardiac
musculo-skeletal system
the combination of the skeletal muscles and skeleton working together; includes the bones, muscles, tendons and ligaments of the body
mutation
a change to the genetic material of an organism, either to a gene or to a chromosome. The changing of the structure of a gene, resulting in a variant allele that may be transmitted to subsequent generations, caused by the alterations of single base units in DNA, or the deletion, insertion, or rearrangement of larger sections of genes or chromosomes. May involves loss of a portion of a chromosomes, or an abnormal chromosome number.
mycelium
the vegetative part of a fungus, consisting of a network of fine white filaments called hyphae
myocardial infarction
a heart attack
myofibrils
microscopic fibres that make up the larger fibres of skeletal (striated) muscle
myogenic muscle
muscle that can initiate its own contraction
nanometre
one thousandth (10-3) of a micrometre. It is therefore one thousand millionth (10-9) of a metre. It is a useful unit for measuring the sizes of small organelles within cells and for measuring the size of large molecules
natural classification
the term used to explain how features of the environment apply a selective force on the reproduction of individuals in a population
natural immunity
immunity achieved through normal life processes
natural selection
the term used to explain how features of the environment apply a selective force on the reproduction of individuals of a population
necrosis
cell death caused by disease or injury; it may subsequently limit the spread of a pathogen
nervous system
the central nervous system (brain and spinal cord) and the peripheral nervous system- the network of nerve cells (neurons) that transmit nerve impulses between parts of the body and the central nervous system. Fast acting control system to detect stimuli and to bring about responses in muscles and glands
nervous tissue
the main component of the nervous system. Consists of neurones and supporting cells
neutrophil
a type of white blood cell that engulfs foreign matter and traps it in a larger vacuole (phagosome), which fuses with lysosomes to digest the foreign matter
non-competitive inhibition
the inhibition of an enzyme where the competitor molecule attaches to a part of the enzyme molecule but not to the active site. It changes the shape of the active site and prevents ES complexes forming as the enzyme active site is no longer complementary in shape to the substrate molecule
nucleotide
molecule consisting of a five-carbon sugar, a phosphate group and a nitrogenous base
oncotic pressure
the pressure created by the osmotic effects of the solutes in a solution
open circulatory system
one in which the blood is not held in the vessels
operculum
a bony flap that covers and protects the gills
opsonins
proteins that bind to the antigen on a pathogen and then allow the phagocytes to bind
optimum pH
the pH at which an enzyme works best, as its fastest rate
order
taxonomic group; a subdivision of the class using additional information about the organisms e.g. the class Mammalia is divided into meat-eating animals (order Carnivora) and vegetation-eating mammals ( order Herbivora)
organ
collection of tissues working together to perform a function or related functions
organ system
a number of organs working together to carry out an overall life function
organelles
small structures within cells, each of which carries out a specific function
osmosis
passage of water molecules down their water potential gradient, across a partially permeable membrane
ossification
process of changing cartilage to bone by depositing calcium phosphate
ostia
pores in the heart of an insect that allow blood from the body to enter the heart
ovalocytosis
cells being more oval in shape than they usually are
oxygen tension
measured in units of pressure (kPa)
oxygen uptake
the volume of oxygen absorbed by the lungs in one minute
oxyhaemoglobin
a molecule of haemoglobin with oxygen molecules loosely bound to it. When haemoglobin takes up oxygen, it becomes oxyhaemoglobin
palisade cells
closely-packed photosynthetic cells within leaves
pandemic
an infectious disease which spreads rapidly across continents
