Resources from Plants (Edexcel A Level Biology (A) SNAB): Flashcards

The green pigment found in chloroplasts, needed for photosynthesis, is chlorophyll.

True.

Chloroplasts carry out photosynthesis and amyloplasts store starch — both are plant organelles.

Transport of water and dissolved minerals up the plant.

Structural support.

They are made of dead cells with no cytoplasm or organelles.

This forms hollow tubes so water can flow freely.

It strengthens the cell walls.

This lets the vessels withstand the pressure of the moving water column and gives support.

Translocation is the transport of organic compounds such as sucrose through the phloem, from sources to sinks.

To transport organic compounds (assimilates), mainly sucrose.

It moves them from sources (e.g. leaves) to sinks (e.g. roots), up or down the plant.

Sieve tube elements and companion cells.

They control the metabolism of their sieve tube element.

They help load and unload sugars into the phloem.

To provide support to the plant.

They are dead cells with lignified walls and extra cellulose, but are not involved in transport.

Xylem is towards the middle of the stem.

Phloem is nearer the outside.

Mature xylem is made of dead cells with lignified walls.

Phloem contains living cells with sieve plates and companion cells.

Xylem and phloem are grouped together in a stem to form a vascular bundle.

False.

Phloem transports organic compounds both up and down the plant, from sources to sinks.

It is a reactant in photosynthesis and a transport medium for minerals.

It also keeps cells turgid and helps regulate temperature.

For the production of chlorophyll.

Chlorophyll gives the green colour and is essential for photosynthesis.

To synthesise DNA, proteins (including enzymes) and chlorophyll.

These are essential for growth and for making fruit and seeds.

They are an important cell wall component.

They are needed for proper plant growth.

Yellow leaves (chlorosis).

Without magnesium, chlorophyll cannot be made.

They are absorbed through the root hairs.

They then travel up the stem in the xylem vessels.

To control variables.

This ensures any difference in growth is due to the mineral concentration, not the plants themselves.

To keep light away from the broth.

This prevents the growth of algae, which could use up the minerals.

By recording each seedling's mass before and after.

The mean change in mass is compared between the different mineral concentrations.

A plant lacking nitrate ions cannot make proteins, chlorophyll or DNA.

True.

Mineral deficiencies commonly cause symptoms such as stunted growth and yellowing leaves.

One broth containing all the minerals.

One broth containing no minerals.

Amylose and amylopectin.

An unbranched, helix-shaped chain of alpha glucose.

It contains only 1,4 glycosidic bonds.

A branched chain of alpha glucose.

It has 1,4 glycosidic bonds along the chains and 1,6 glycosidic bonds at the branch points.

It is compact, so large amounts can be stored.

It is insoluble, so it has no osmotic effect on the cell.

Beta glucose, joined by 1,4 glycosidic bonds.

Beta glucose is an isomer of alpha glucose.

Rotating alternate molecules allows the 1,4 glycosidic bonds to form.

The inverted beta glucose chains lie parallel.

Many hydrogen bonds form between the chains, grouping them into strong microfibrils.

It is the main structural component of the cell wall.

Its high tensile strength lets cell walls withstand turgor pressure.

It can be stretched without breaking.

This lets the cell wall resist the internal turgor pressure of the cell.

Starch is made of alpha glucose, whereas cellulose is made of beta glucose.

False.

Cellulose is a structural molecule in the cell wall; starch is the energy store.

It is a large polymer of thousands of glucose monomers.

These bonds must be hydrolysed before the glucose can be used.

Sclerenchyma fibres and xylem vessels.

Their cell contents have died.

Lignification of the wall makes it almost impossible for substances to enter or leave.

Making rope.

Making fabrics such as cotton and hemp.

The mesh-like arrangement of microfibrils.

Secondary thickening of the wall, often with lignin.

Secondary thickening is the development of a thick secondary cell wall, often containing lignin, that adds strength to a plant fibre.

They are arranged in a mesh-like pattern.

This makes the cell wall strong in all directions.

Lignin makes the wall rigid and strong.

But it also makes the wall impermeable, so the cell contents die.

The strength of plant fibres comes partly from the mesh-like arrangement of cellulose microfibrils.

False.

Mature sclerenchyma fibres are dead, hollow cells with lignified walls.

Cellulose.

Their great strength allows them to be used for products that must bear loads.

Examples are rope and durable fabrics.

True.

Both xylem vessels and sclerenchyma fibres are long, strong, hollow cells used as plant fibres.

So that light can pass through it under the microscope.

This allows the tissues to be seen clearly.

To make the different tissues visible and distinguishable.

Different tissues take up the stain to different degrees.

Xylem and sclerenchyma fibres appear blue-green.

Phloem appears pinkish-purple.

To avoid trapping air bubbles.

Air bubbles could be mistaken for plant structures.

The positions of the xylem vessels, phloem sieve tubes and sclerenchyma fibres.

To remove excess stain.

This prevents the image being too dark to see the tissues clearly.

Using a pre-prepared permanent slide of a stem section.

The coverslip should be lowered slowly to avoid trapping air bubbles under it.

True.

This is why the coverslip is lowered slowly from one side to avoid trapping them.

A scalpel.

Xylem is nearer the middle of the stem.

Phloem is nearer the outside.

To ensure the tissues take up a consistent amount of stain.

This gives a clear, comparable image.

Tensile strength is the maximum load a fibre can carry before it breaks.

Attach the fibre to a clamp stand and hang a weight from it.

Add weights one at a time until the fibre breaks, and record the mass at which it broke.

The mass (load) at which the fibre breaks.

To increase the accuracy of the results.

A mean tensile strength can then be calculated.

To control a variable.

This ensures any difference in strength is due to the fibre type, not its length.

It shows how much load a product can bear before breaking.

This matters, for example, when making rope from plant fibres.

To find the exact load at which the fibre breaks.

Adding gradually gives a more precise measurement.

The tensile strength of a fibre is the maximum load it can carry before breaking.

True.

Repeating with several samples and calculating a mean reduces the effect of anomalies.

The type of plant fibre being tested (so only the variable being investigated changes).

A clamp (retort) stand.

Keep all variables the same except the fibre type.

Use the same length, add weights the same way and take repeats for each.

A clinical trial is the testing of a new drug for effectiveness and side effects before it can be sold to the public.

Extracts of foxglove (containing digitalis) at different concentrations.

He used them to find the most effective dose to treat dropsy without poisoning the patient.

Dropsy — swelling caused by heart failure.

Computer modelling of the drug's effects.

Testing on human tissues in the lab, then on animals.

The drug is tested on a small group of healthy people.

This checks the body's reaction, side effects and the correct dosage.

The drug is tested on a larger group of patients who need it.

This checks how effective the drug is.

The new drug is compared with an existing drug.

A large number of patients are split into two groups, each given one of the drugs.

A placebo looks exactly like the drug but contains no active ingredient, used to test whether the drug really works.

A double-blind study is one in which neither the patient nor the doctor knows who is receiving the drug or the placebo.

To remove bias from patients and doctors.

Neither knowing the group prevents their expectations affecting the results.

A patient who improves simply because they believe they are receiving a drug is showing the placebo effect.

False.

Patients are not told which group they are in, so the drug's true effect can be measured.

Antimicrobial describes a substance that kills microbes or prevents their growth.

Nutrients and, for aerobes, oxygen.

A suitable temperature and pH for their enzymes to work.

The plant tissue is dried, ground finely and soaked in ethanol to extract the antimicrobial substances.

The mixture is then filtered.

A clear zone is the area around a disc where bacteria cannot grow, showing the antimicrobial effect of the extract.

That the plant extract has more effective antimicrobial properties.

Ethanol only (no plant extract).

This shows that any effect is due to the plant extract, not the ethanol or the disc.

25 °C allows good bacterial growth.

It avoids the warmer temperatures that would encourage the growth of human pathogens.

Working near a Bunsen flame so rising air carries microbes away.

Using sterile equipment and keeping the plate lid open as little as possible.

To prevent contamination of the culture by other microbes.

Contamination would affect the growth of the bacteria being studied and spoil the results.

By measuring its diameter.

The area can then be calculated using πr².

The area around a disc where bacteria cannot grow is called the clear zone.

True.

This ensures each disc absorbs a similar amount of extract, making the comparison fair.

Sustainability is using resources to meet the needs of the current generation without depleting them for future generations.

A renewable resource can be replaced and used without running out (e.g. solar energy).

A non-renewable resource can run out (e.g. fossil fuels).

Fewer fossil fuels are used and plants can be replanted.

Plant fibres are also biodegradable, reducing pollution.

They can be broken down by microbes.

This reduces environmental pollution compared with most oil-based plastics.

They are typically not as strong as plastic ropes.

Starch can be used to make bioplastics.

These use fewer fossil fuels and come from replantable crops.

Bioethanol, used as a vehicle fuel.

It comes from renewable crop plants rather than finite oil.

Growing and processing plants is easier and cheaper than extracting and processing oil.

Plastics made from starch instead of oil are called bioplastics.

False.

Fossil fuels are non-renewable — they take millions of years to form and can run out.

A sustainable practice is one that minimises damage to the environment and its resources, such as replanting trees after logging.

Sustainable: replanting trees after logging.

Unsustainable: using fossil fuels to make oil-based plastics.