Plant Resources Flashcards
role of cell wall
offers structural support to the cell
This structural support is provided by the polysaccharide cellulose
What is middle lamella
outermost layer of the plant stickingplant cells together
It provides stability to the plant
What is plasmodesmata
Narrow threads of cytoplasm called plasmodesmata connect the cytoplasm of neighbouring plant cells
This allows substances to be transported between plant cells and facilitates cell to cell communication
cytoplasmic connection (between cells) (1)
which allows { transport / communication} (between cells) (1)
What are pits
very thin regions of the cell wall
The pits in adjacent plant cells are lined up in pairs
This facilitates transport of substances between cells
What are chloroplasts
membrane
membrane bound compartments
site of…
DNA
surrounded by a double-membrane
Membrane-bound compartments called thylakoids containing chlorophyll stack to form structures called grana. Grana are joined together by lamellae.
Chloroplasts are the site of photosynthesis. Certain parts of photosynthesis occur in thylakoid membranes, while other parts happen in the stroma
Chloroplasts also contain small circular pieces of DNA and ribosomes used to synthesise proteins needed in chloroplast replication and photosynthesis
what are amyloplasts
Small, membrane bound organelle containing starch granules
They are responsible for storing starch in plants and converting it back to glucose when the plant needs it
vacuole and tonoplasts
roles of vacuole and tono
The vacuole is a sac in plant cells surrounded by the tonoplast
Contains cell sap, which is a mixture of different substances such as water, minerals, waste and enzymes
They keep cells turgid, which stops the plant from wilting
They can break down and isolate unwanted chemicals in plant cells
The tonoplast controls what can enter and leave
what is the xylem tissue
tissue that transports dissolved minerals and water around the plant and provides structural support
what do the cell walls of xylem tissue contain
lignin, which enables the vessels to withstand the pressure created by the moving column of water
what does the structure of xylem tissues look like
long, hollow straw-like structures that are formed by dead cells (due to lignification of cell walls)
do xylem tissues contain cytoplasm or organelles
they do not contain any cytoplasm or organelles that could slow down the flow of water
what are the not lignified parts of wall called
pits, which allows for movement of water and minerals between xylem vessels
since xylem tissues have no end walls what does this mean
allows mass flow of water and dissolved solutes as cohesive and adhesive between walls and water
what is sclerenchyma involved in
not involved in transport of substances, they provide support
what do sclerenchyma consist bundles of
dead cells
structure of sclerenchyma
long, hollow tubes, but they do have end walls present
Lignification of cell walls occur, but they do not have pits like xylem vessels
They have more cellulose in their walls compared to other plant cells
function of phloem tissue
Transport organic compounds particularly sucrose.
how do the compounds transport in phloem
up and down the plant
This is known as translocation
structural support in phloem?
Phloem has no support function in a plant
what do the organic compounds dissolve into in phloem
in water to form sap
structure of phloem
contains living cells, unlike xylem tissue.
bulk is made up of sieve tube elements which are the main conducting cells and companion cells
what do sieve tube elements do
line up end to end to form a continuous tube
what are companion cells
Each sieve tube element has a companion cell associated with it as companion cells control the metabolism of their associated sieve tube member
loading and unloading of sugars into the phloem sieve tube elements
why do companion cells have mitochondria
to provide ATP for active transport of organic compounds
what symptom does plant show when stunted growth
yellow leaves
four reasons why plants need water
important component required for
photosynthesis
transport medium for minerals
Maintains turgidity in plant cells
Regulates temperature - to ensure that enzymes can function at their optimum rate
why do plants require magnesium ions
production of chlorophyll, This provides the green colour of stems and leaves and is essential for photosynthesis
why do plants need nitrate ions
Without nitrate ions, the plant would be unable to synthesise DNA, proteins and chlorophyll
produces proteins needed for growth
what is starch for plants
storage polysaccharide of plants
how is starch stored
granules in plastids (e.g. chloroplasts) and amyloplasts
why does starch take longer to digest than glucose
Due to starch molecules being large polymers consisting of thousands of glucose monomers, starch takes longer to digest than glucose
what is starch made up of
amylose and amylopectin
what is amylose made of
Unbranched helix-shaped chain with 1,4 glycosidic bonds between α-glucose molecules
what does the helix shape of amylose allow
The helix shape enables it to be more compact and thus it is more resistant to digestion
what is amylopectin made of
1,4 glycosidic bonds between α-glucose molecules (as found in amylose) but also 1,6 glycosidic bonds form between glucose molecules creating a branched molecule
what does branching in amylopectin do
glucose molecules that can be easily hydrolysed for use during cellular respiration or added to for storage
how is starch a good storage polysaccharide
- starch is insoluble so does not affect the water potential
- starch is a branched molecule which makes it compact
describe structure of cellulose
polysaccharide consisting of long chains of β-glucose joined together by 1,4 glycosidic bonds with inverted glucose at 180 degrees arranged as microfibrils by hydrogen bonds
why are the b glucose isomers rotated at 180 degrees
in order to form the 1,4 glycosidic bonds
how does cellulose get its strength
Due to the inversion of the β-glucose molecules many hydrogen bonds form between the long chains, giving cellulose it’s great strength
where are the hydrogen bonds found in cellulose
micrfibrils
what does high tensile strength allow of cellulose
stretched without breaking which makes it possible for cell walls to withstand turgor pressure
what do cellulose fibres and other molecules (e.g. lignin) form
form a matrix which increases the strength of the cell walls
These strengthened cell walls provide support to plants
why are sclerenchyma fibres and xylem vessels hollow
cell contents died (often due to the lignification of the cell wall, which makes it almost impossible for substances to enter or leave the cell)
what is the strength in fibres due to
The arrangement of microfibrils in a mesh-like pattern
Secondary thickening, which results in a thick secondary cell wall developing which often contains lignin
what is the method for identifying a tissue type
Cut a very thin cross-section of the stem using a scalpel
transfer each section into a dish containing a suitable stain
such as toluidine blue leave for 30mins so it has time to bind to chromatin and stain it and be visible under microscope
Rinse off each section in water and mount onto a microscope slide, before adding a cover slip
View under a microscope and adjust the focus to form a clear image
What colour does toluidine blue make
xylem and sclerenchyma fibres appear blue-green, while phloem will appear pinkish purple
why should you add cover lip slowly
lower the coverslip slowly over the sample from one side to the other to avoid trapping air bubbles, which can then be mistaken for plant tissues/structures)
what is the method for working out the tensile strength of plant fibres
fibre should be attached to a clamp stand. Attach a weight on the other end of the plant fibre.Carefully continue to add one weight at a time until the fibre breaks. Record the mass at which the fibre broke
How can you increase the accuracy of tensile strength practical
repeated with more samples of the same plant fibre
These values can be used to calculate the mean tensile strength for the fibre
It is important to ensure that the fibres are all of the same length and that all other variables are kept constant
definition of sustainability
using resources in such a way that the requirements of the current generation are met without depleting these resources for future generations
why are plant fibres better then using fossil fuels
replanted
biodegradable so broken down by microbes to minimise environmental pollution
fossil fuel extraction is expensive so plant based products are easier and cheaper.
how is starch sustainable
Plants store excess sugars as starch in their cells
Starch can be used to make bioplastics which is more sustainable than making oil-based plastics
It does not require as much fossil fuels to be burned to produce them and the crop plants can be replanted
Describe the structure of the cell wall of a xylem vessel
idea of cellulose (molecules) { in bundles / as
microfibrils / held together by hydrogen bonds } ;
layers of microfibrils (in the primary cell wall) / mesh of
microfibrils (in secondary cell wall) ;
reference to presence of lignin in the cell wall ;
distribution of lignin described ;
presence of (bordered) pits ;
presence of { pectin / hemicellulose } in the cell wall
Three phases in clinical testing
(for phase 1) - to make sure the not harmful (1) side effects of the drug and the correct dosage that should be taken
- (for phase 2) - to see if it is effective in larger group of patients (non-healthy individuals who require the drug)
- (for phase 3) - to gather much data / data for statistical tests / to look for rare side effects (1) comparing the drug to existing drugs to see if it works any better
when is placebo carried out
done during phase 2 of a clinical trial
compare contrast cellulose and amylopectin
both are
{polysaccharides / polymers of glucose}
(1)
both contain (1,4)
glycosidic bonds (1)
- cellulose contains { B /beta } glucose whereas amylopectin contains { a / alpha } glucose (1)
- cellulose { is not branched / does not contain 1-6 glycosidic bonds ? (1)
tensile strength formula
force / cross sectional area
describe the structure of cell wall of a xylem vessel
idea of cellulose (molecules) { in bundles / as microfibrils / held together by hydrogen bonds } ;
layers of microfibrils (in the primary cell wall) / mesh of microfibrils (in secondary cell wall)
reference to presence of lignin in the cell wall;
distribution of lignin described;
presence of (bordered) pits;
presence of { pectin / hemicellulose } in the cell wall;
relationship between structure and function of granum
(granum) is formed from many layers of thylakoid membranes to increase surface area (for absorbing light)
- thylakoid membranes contain chlorophyll to absorb light
electron carrier molecules in thylakoid membrane involved in ATP production
how is nitrate ion transported from root to leaves
via xylem vessels in water
why does companion cell have more mitochondria than sieve tube element
Role of ST is to provide a channel so cellular contents kept to a minimum
ST has no ability to carry out aerobic respiration
ATP is supplied to the sieve tube element from the CC
when labelling structure on plant stem whats the order for flat picture and for shape type picture
outside to inside
picture : schlerenchyma then xylem then phloem
shape : schlerenchyma , phloem , xylem
describe the importance of nitrate ions to plants
nitrates are used to make {amino acids / protein} (1)
- {growth is reduced / plants are stunted } if nitrates are lacking (1)
- (nitrates) needed to make { nucleic acids / DNA / RNA /
ATP / chlorophyll } (1)
what is a double blind trial
a trial using {a placebo / pre-existing medication} (1)
where the patients and the doctors do not know who has been given the drug and who has not (1)
to prevent bias (1)
pre clinical trials when testing for a new drug
{tested on animals / tissue samples} (1)
* to determine {toxicity / safe dosage} (1)
deduce reasons why higher percentage of trials progress from stage 1 to stage 2 than stage 2 to stage 3 of trials
stage I is conducted on healthy volunteers (1)
stage I is to determine {side effects / safety} (1)
stage Il is to determine the effectiveness of the drug / drug may not progress to stage Ill if it is ineffective (1)
(fewer progress from Stage II to Stage III because) { patients / people with the condition} are more likely to have side effects (1)
what is meant by tensile strength
the (pulling) force the fibre can withstand before breaking
