Page 31 - Ranger SPM 2022 Biology

Biology SPM Chapter 2 Leaf Structure and Function
3. Chlorophyll absorbs blue, red, and 2. At the compensation point,
purple lights. (i) Rate of carbon dioxide uptake
4. Photosynthesis rate is highest in blue is equal to the rate of carbon
light, followed by red light. dioxide release.
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5. Green light is not absorbed by plants, (ii) Rate of production of sugar is
therefore green light is not used in equal to rate of sugar being
photosynthesis. used. All sugar that is produced
during photosynthesis is oxidised
during respiration.
2.5 Compensation

Point
SPM TIP
1. The compensation point is the level Compensation point of plant in the
of light intensity at which the rate shade is lower than compensation
of photosynthesis is equal to the point of plant exposed to sunlight.
rate of respiration.

Compensation point
(Photosynthesis rate = Respiration rate)
Form 5
Photosynthesis rate (Sugar
production) exceeds repiration
rate (sugar used)
Increase CO2
uptake
Reduce CO2
released Respiration rate (sugar used)
exceeds photosynthesis rate
(sugar produced)

Low High
Increase in light intensity
Figure 2.11 Compensation point
Table 2.3 Comparison between photosynthesis and respiration
Aspect Photosynthesis Respiration
Organism involved Green plant All living organism
Occurence time In the presence of light All the time
Substance needed Water and carbon dioxide Glucose and oxygen
Product Glucose and oxygen Carbon dioxide, water and energy
Site of process Chloroplast Mitochondrion
Energy conversation Light energy to chemical energy Chemical energy is converted to ATP
and heat is released
Aim To synthesise glucose and organic To generate energy for metabolic
compound in plants activities
Type of metabolism Anabolism Catabolism

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F5 Chapter 2.indd 226 3/29/22 4:35 PM