CAIE IGCSE Biology 6.1 Photosynthesis

Practise defining photosynthesis, writing its equations and analysing investigations involving light, chlorophyll, carbon dioxide, oxygen production and limiting factors.

Exam points

state that plants use light energy to synthesise carbohydrates from carbon dioxide and water
write the word equation or balance 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ with correct reactants and products
interpret gas, starch-test or indicator data and identify the factor limiting photosynthesis rate

Covered syllabus points

6.1.1—Photosynthesis as the process by which 6.1.2—Word equation for photosynthesis 6.1.3—Chlorophyll is a green pigment that is 6.1.4—Chlorophyll transfers energy 6.1.10—Photosynthesis equation 6.1.5—Subsequent use and storage 6.1.6—Importance of: (a) nitrate ions 6.1.7—Need for chlorophyll, light and carbon 6.1.8—Effects of varying light intensity 6.1.9—Effect of light and dark conditions on 6.1.11—Explain the limiting factors

[Maximum number: 1]

Which substance is used up in photosynthesis?

chlorophyll

light

oxygen

water

[Maximum number: 4]

Scientists investigated the effect of cuticle thickness on water loss from the leaves of the balsam fir tree, Abies balsamea.

The leaves were divided into three groups:

A - thick cuticle

B - medium cuticle

C - thin cuticle Samples of leaves from each group were weighed. The leaves were placed on a tray in dry air at $20^{\circ} \mathrm{C}$ . The samples of leaves were reweighed, at intervals, over 15 hours. The scientists calculated the mass of each sample of leaves as a percentage of the initial mass. mass of the leaves as a percentage of the initial mass

Fig. 5.1 shows the results.

(a)

Water is one of the raw materials needed for the production of sugars in photosynthesis.

[ 4 ]

(i)

State the name of the other raw material needed for photosynthesis.

[ 1 ]

(ii)

State three ways a plant uses the sugars produced in photosynthesis.

[ 3 ]

[Maximum number: 1]

Which structure contains the pigment that transfers energy from light into chemical energy?

chloroplast

mitochondrion

nucleus

ribosome

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Covered syllabus points

6.1 Photosynthesis question 1

6.1 Photosynthesis question 2

Question (a)

Question (i)

Question (ii)

6.1 Photosynthesis question 3