05 Photosynthesis

Question 1

Photosynthesis

Answer 1

The process that converts energy in sunlight to chemical forms of energy that can be used by biological systems

Question 2

Gas Exchange in Leaves

Answer 2

Stomata: openings in the leaf that allow movement of gases and water vapour into and out of the leaf

Guard cell: these cells change shape and by doing so, open and close the stomata.

These cells contain chloroplasts unlike other epidermal cells, therefore must perform photosynthesis.

It is the occurrence of photosynthesis that causes a stoma to open in the morning and close at night.

Question 3

An Open Stoma

Answer 3

In daylight, the guard cells produce glucose via photosynthesis
The presence of sugar inside the guard cells causes water to enter by osmosis from neighbouring epidermal cells

The increase in turgor pressure causes the guard cells to swell opening the stoma between them
The open stoma allow O2 and CO2 to leave and enter the leaf

Question 4

A Closed Stoma

Answer 4

When the sun sets, photosynthesis stops and the guard cells stop producing glucose.
Water no longer enters the cells by osmosis and the turgor pressure decreases

The stoma then close