Edexcel GCSE (9-1) Biology - Paper 2
eukaryotic
(of a cell) containing a nucleus - all animal and plant cells
diploid
(of a cell) containing all chromosomes of an organism
haploid
(of a cell) containing half of the normal chromosomes e.g. sperm and egg cells
prokaryotic
(of a cell) not containing a nucleus - bacterial cells
selectively permeable or semi-permeable
(of a membrane) allows water molecules (the solvent) to pass through but not the molecules of dissolved substances (the solutes)
heterotrophic
(of an organism) needing to consume other organisms for nutrition
starch
a carbohydrate polymer storage molecule in plants made of glucose monomers
linear relationship
a correlation between two variables represented on a graph by a straight line
slime coat
a feature that some bacteria have - it is a layer outside the cell wall which provides extra protection from extreme environments
zygote
a fertilised ovum (egg)
chlorophyll
a green pigment found in the chloroplasts of plant cells that absorbs light energy for photosynthesis
tissue
a group of cells with a similar structure and function e.g. muscle tissue, blood tissue or xylem tissue
lipids
a group of compounds that includes fats and oils
organ system
a group of different organs which work together to perform a particular function in a body e.g. the digestive system
organ
a group of more than one type of tissue which work together to perform a particular job
cytoplasm
a jelly-like substance filling a cell where most of the chemical reactions occur
spongy layer
a layer of irregularly shaped cells in a leaf with air spaces to allow gas exchange to take place
eyespot
a light sensitive organelle which some uni-cellular organisms use to find bright light in order to photosynthesise
polymer
a long-chain molecule composed of lots of smaller molecules (monomers) joined together eg. starch
magnification
a measure of how much bigger the image is compared to the actual size - the formula is size of image / actual size
storage organ
a plant organ used to hold energy-rich substances such as starch eg a potato
protein
a polymer made of amino acids
endothermic reaction
a reaction in which the products have more energy than the reagents; when energy is transferred from the surroundings
respiration
a series of enzyme-catalysed reactions occurring in all living cells whereby glucose is broken down to release energy
limiting factor
a single aspect of the conditions of a reaction that limits the rate of that reaction, when in short supply or too high/low
pellicle
a stiff outer layer of some uni-cellular organisms, although it is slightly flexible and can be repeatedly scrunched and unscrunched to move through water
digestive system
a system in mammals to break down food molecules so that they can be absorbed into the blood
nervous system
a system in mammals to control response to environmental changes
skeletomuscular system
a system in mammals to support the body and allow movement
flagellum
a tail that some cells have to allow them to move e.g. sperm cells, some bacteria or euglena
hydrogencarbonate
an indicator that turns from yellow through red to purple as pH increase, and also provides a source of dissolved carbon dioxide in water
organelle
an individual structure within a cell e.g. a mitochondrion
electron microscope
an instrument that uses a beam of electrons to build up an image of a specimen, which a computer then uses to generate an image using visible light - it can achieve magnifications of up to 2 million x
light microscope
an instrument with lenses that refract (bend) visible light to magnify images of specimens, to up to around 1500x magnification
plasmid
an organelle in bacterial cells which contains a small proportion of the bacterium's DNA
contractile vacuole
an organelle which allows cells to expel excess or waste products
movement
animals can move (their whole body or parts of it) in search of shelter, to find food, to avoid danger and harmful stimuli, to find a mate or to reproduce - plants "move" by growing and controlling the volume of water within their cells
cellulose
carbohydrate component of plant cell walls
plasmodesmata
channels that connect the cytoplasm of different cells in roots, allowing the osmosis of water from root hair cell to xylem vessel
connective tissue
connects other tissues together
muscle tissue
contracts and relaxes to cause movement
two routes that water takes from root hair cell to xylem vessel
diffusion through cell walls (apoplast pathway), osmosis through cytoplasm and plasmodesmata (symplast pathway)
wilting
drooping of parts of a plant caused by a lack of water
total magnification
eyepiece lens magnification multiplied by the objective lens magnification
mineral ions
ions from naturally-occurring compounds dissolved in water that are used by plants for their vital processes
km
kilometre
adaptations of a leaf
large surface area, thin, chloroplasts, stomata, waxy cuticle, veins
epithelial tissue
lines tubes in the body
m
metre
μm
micrometre (10 to the -6 equivalent in metres)
mm
millimitre (10 to the -3 equivalent in metres)
8 characteristics of living organisms
movement respiration sensitivity to stimuli control reproduction excretion nutrition growth & development
plant
multicellular organism that can trap energy from light to produce its own biomass
nm
nanometre (10 to the -9 equivalent in metres)
nucleus
organelle which controls the whole of a cell
autotroph
organism able to live entirely of its own food i.e. it can make organic molecules from inorganic molecules
pm
picometre (10 to the -12 equivalent in metres)
villi
projections from the intestinal lining to maximise surface area for absorption of food molecules
skeletal tissue
supports and protects the body's delicate organs, and allows movement
palisade cell
tall column-shaped cells tightly packed in a layer near the upper surface of plant
limiting factors of photosynthesis
temperature, carbon dioxide concentration, light intensity
cell membrane
the "skin" around a cell - it holds the cell together and controls which substances enter and leave the cell
control
the ability of an organism to influence its internal conditions
sensitivity to stimuli
the ability to detect changes in the environment and respond to them
guard cell pairs
the cells surrounding stomata, which can become turgid or flaccid to open or close the stomata
nucleolus
the centre of the nucleus
osmosis
the diffusion of a solvent (almost always water) across a selectively permeable membrane
reproduction
the generation of offspring / new individuals
growth and development
the increase in mass, and often number, of cells in an organism
lower epidermis
the layer of cells forming the underside of a leaf, containing stomata with guard cells on either side
objective lens
the lens closest to the specimen in a light microscope
eyepiece lens
the lens closest to your eye when you look down a light microscope
chloroplast
the organelle in plant cells which contains chlorophyll for producing glucose by carrying out photosynthesis
ribosome
the organelle responsible for protein synthesis
mitochondrion
the organelle responsible for respiration
nuclear envelope
the outside of the nucleus
net movement
the overall movement of a substance - the movement in one direction minus the movement in the other direction
stage
the platform on which the slide is placed in a light microscope
stoma (pl. stomata)
the pores on the underside of leaves, through which gas exchange can occur; they can be opened and closed in response to environmental stimuli
mitosis
the process by which all animal and plant cells, except the gametes, are produced - the daughter cells are genetically identical to the parent cells
gas exchange (plant)
the process by which one gas diffuses into a space and another gas diffuses in the opposite direction
nutrition
the process by which the body takes in and uses food - plants make their own whereas animals need to consume other organisms
diffusion
the random movement, collision and spreading of particles which causes a net movement of particles down their concentration gradient
excretion
the removal of toxic waste products from a body e.g. carbon dioxide
cell wall
the rigid outer layer of plant and bacterial cells, but made of very different materials
photosynthesis
the series of enzyme-catalysed chemical reactions by which plants absorb energy from the sun and produce glucose from carbon dioxide and water
slide
the small rectangular glass sheet on which a specimen is placed for viewing in a light microscope.
cell
the smallest living unit of a living organism
sucrose
the type of sugar found in phloem in plants
upper epidermis
the uppermost layer of cells in a leaf; secretes the waxy cuticle
waxy cuticle
the waterproof layer on the surface of leaves; prevents water evaporating out of the upside of leaves
suberin
the waterproof substance found in the casparian strip
casparian strip
the waterproofed strip in a root that forces any water diffusing through cell walls to change their path, and diffuse through the plasmodesmata
biomass
total mass in living organisms, usually measured after drying
nerve tissue
transmits electrical impulses and co-ordinates messages
permanent vacuole
void filled with cell sap to help keep the cell turgid
inverse square law
when the abundance of a quantity is in inverse proportion to the square of the distance from the source of that quantity
DNA loop
where bacterial chromosomal DNA is stored, loose in the cytoplasm
