4A plant structure and function Flashcards
cell wall
a freely permeable wall around plant cells, made mainly of cellulose
suberin
a waterproof chemical that impregnates cellulose cell walls in cork tissues and makes them impermeable
lignin
a chemical that impregnates cellulose cell walls in wood and makes them impermeable
pectin
a polysaccharide that holds cell walls of neighbouring plant cells together and is part of the structure of the primary cell wall
primary cell walls
the first very flexible plant cell walls to form, with all the cellulose microfibrils orientated in a similar direction
secondary cell wall
the older plant cell wall in which the cellulose microfibrils have build up at different angles to each other making the cell wall more rigid
hemicelluloses
polysaccharides containing many different sugar monomers
composite material
a material made of two or more materials which combined together make a composite with different properties form either of the constituent materials
plant fibres
long cells with cellulose cell walls that have been heavily lignified so the y are rigid and very strong
turgid
swollen
flaccid
floppy, soft
plasmodesmata
cytoplasmic bridges between plant cells that allow communication between the cells
cell sap
the aqueous solution that fills the permanent vacuole
pits
thin areas of cell wall in plant cells with secondary thickening, where plasmodesmata maintain contact with adjacent cells; in xylem vessels, where the cells are dead, they become simple holes through which water moves out into the surrounding cells
tonoplast
the specialised membrane that surrounds the permanent vacuole in plant cells and controls movements of substances into and out of the cell sap
osmosis
a specialised form of diffusion that involves the movement of solvent molecules down their water potential gradient
chloroplasts
organelles adapted to carry out photosynthesis, containing the green pigment chlorophyll
chlorophyll
the green pigment that is largely responsible for trapping the eneregy form light, making it available for the plant to use in photosynthesis
amyloplasts
plant organelles that store starch
collenchyma
plant cells with areas of cellulose thickening that give mechanical strength and support to the tissues
sclerenchyma
plant cells that have very thick lignified cell walls and an empty lumen with no living contents
sclereids
sclerenchyma cells that are completely impregnated with lignin
xylem
the main tissue transporting water and minerals around a plant
phloem
the main tissue transporting dissolved food around the plant
vascular bundle
part of the transport system of a plant, with phloem on the outside and xylem on the inside - often with strengthening sclerenchyma
cambium
the layer of unspecialised plant cells that divide to form both the xylem and the phloem
protoxylem
the first xylem the plant makes; it can stretch and grow because the walls are not fully lignified
metaxylem
consists of mature xylem vessels made of lignified tissue
transpiration stream
the movement of water up from the soil through the root hair cells, across the root to the xylem, then up the xylem, across the leaf until it is lost by evaporation from the leaf cells and diffuses out of the stomata down a concentration gradient
translocation
the active movement of substances around a plant in the phloem
sieve plates
the perforated walls between phloem cells that allow the phloem sap to flow
companion cells
very active cells closely associated with the sieve tube elements that supply the phloem vessels with everything they need and actively load sucrose into the phloem
tensile strength
the resistance of a material to breaking under tension
carbon neutral
a process where no net carbon is released into the atmosphere
carbon neutral
a process where no net carbon is released into the atmosphere
bioplastics
plastics based on biological polymers
binary fission
asexual reproduction in bacteria in which the bacteria split in half
culture
growing microorganisms in the laboratory, providing them with the nutrients, oxygen, pH and temperature they need to produce large numbers so they can be observed and measured
aseptic technique
method of carrying out a procedure to prevent contamination by unwanted microorganisms
sterile
something free from living microorganisms and their spores
aspirin
a widely used drug which relieves pain and reduces blood clotting and inflammation
digitalis
a chemical found in foxgloves that affects the beating of the heart
oedema
swelling of the tissues due to fluid retention
digoxin
a drug based on the chemical found in foxgloves that improves heart function
placebo
an inactive substance resembling a drug being trialled which is used as an experimental control
double-blind trial
a clinical drug trial where neither the doctor nor the patient knows whether the patient is receiving the new medicine, a control medicine or a placebo
placebo effect
when patients appear to respond to a drug simply because they think it is doing them good
parenchyma
relatively unspecialised plant cells that act as packing in stems and roots to give support
symplast
all of the material contained within the surface membrane of a plant cell
middle lamella
the first layer of the plant cell wall to be formed when a plant cell divides, made mainly of calcium pectate (pectin) that binds the layers of cellulose together
structural layer made of cellulose microfibrils embedded in pectin which provide the cell with strength and support
cell wall
Disc-shaped structure, about 1um wide and up to 7um long. They consist of stacks of thylakoids called grana where the light-dependent reaction occurs.
chloroplast
pectin layer which cements two adjoining plant cells together
middle lamella
a type of colourless plastid called a leucoplast that produces and stores starch within internal membrane compartments
amyloplast
membrane which separates the vacuole from the surrounding cytoplasm and helps to maintain turgor pressure
tonoplast
junction where the cytoplasm of one cell is connected to that of another through a gap in the cell wall
pits
filled with water and solutes (cell sap) which push against the cell wall when full
vacuole
