IGCSE Chapter 10 Plants & Food (Photosynthesis)

Describe how carbon dioxide gets into the leaf.

By diffusion from the air.

Through stomata.

Into the air spaces in the spongy mesophyll.

Describe two differences between a palisade cell and a root cell.

Palisade cell has many chloroplasts for photosynthesis.

Root cell lacks chloroplasts because it is in the dark.

Explain the effect of temperature on the rate of photosynthesis.

As temperature increases so does the rate of photosynthesis.

As enzymes can catalyse more reactions.

Maximum rate of photosynthesis at the optimum temperature for enzymes.

Above the optimum, enzymes become denatured.

So rate of photosynthesis decreases.

In which cells of a leaf would you expect to find most chlorophyll?

Palisade cells.

Name the mineral ion in soil and in liquid fertiliser that helps plants make chlorophyll.

Magnesium.

Name the part of a plant cell where food is made.

Chloroplast.

Name the process that uses carbon dioxide to make the carbohydrate.

Photosynthesis.

Name two factors that can affect the rate of photosynthesis.

Temperature.

CO₂.

Light intensity.

Wavelength of light.

State the term used for the evaporation of water from the leaves of a plant.

Transpiration.

What do plants use (i) nitrate ions and (ii) phosphate ions for?

(i) To synthesise amino acids/ proteins/ chlorophyll/ DNA.

(ii) To synthesise DNA/ lipids/ ATP.

What is the function of the air spaces in spongy mesophyll?

To allow gases to diffuse to and from the palisade cells (CO₂ in, O₂ out).

What is the function of the spongy mesophyll in a leaf?

To allow gases to diffuse to/from the palisade cells via the air spaces.

What kind of molecule is starch?

A polysaccharide.

What molecules can a plant produce from glucose?

Starch.

Sucrose.

Lipids.

Cellulose.

Proteins.

Chlorophyll.

When do plant cells respire?

All the time.

When testing leaves for starch, what is the purpose of the ethanol?

To remove the chlorophyll & waxy cuticle.

Which ion is found in chlorophyll?

Magnesium.

Why it is an advantage to plants to store starch rather than glucose.

Starch is a large molecule (containing many glucose units) so less space is needed.

Insoluble so water is not taken in by osmosis.

Starch does not react in the cell.