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Photosynthesis is the process by which plants make their own food, using carbon dioxide and water as raw materials, in the presence of sunlight and chlorophyll, to make glucose and oxygen.
Photosynthesis is necessary for life on earth, for this is the means through which energy enters into food chains. Light energy from the sun is converted into chemical energy stored in the bonds between food molecules. |
It is useful to note that respiration is the opposite of photosynthesis, combining glucose and oxygen to yield carbon dioxide, water and energy.
Learning Objectives
The Photosynthesis study Learning Objectives will guide you through self-study and revision.
Photosynthesis
Photosynthesis
- Define photosynthesis
- State word and balanced chemical equations for photosynthesis to include raw materials, conditions and products.
- Distinguish between the light (light-dependent) and dark (light independent) reaction, in terms of sites, reactants and products.
- Describe the fate of the products of photosynthesis.
- Understand the concept of limiting factors (carbon dioxide
concentration, light intensity, wind speed, humidity and water) and
their variation on the rate of photosynthesis.
- Interpret reaction rate graphs in order to identify the limiting factor.
- Explain the importance of photosynthesis (conversion of light energy to chemical energy transmissible to other organisms through food chain, oxygen production and carbon dioxide removal)
Leaf Structure & Function
Mineral Nutrition
- Explain how a leaf is adapted for photosynthesis i.e. arrangement of leaves, relate structure to function
- Differentiate between guard cells and epidermal cells ( shape, presence/absence of chloroplasts, no/control of rate of diffusion, thickness of cell wall)
- Describe how guard cells control the size of the stomata
- Demonstrate the presence of stomata in a leaf
Mineral Nutrition
- Describe the effects of nitrate and magnesium ion deficiency on plant growth
Photosynthesis Experiments
Photosynthesis Experiments investigate whether the raw materials or conditions are necessary for photosynthesis to take place. They also investigate the formation of the products of photosynthesis.
You should be able to explain and/or conduct experiments using appropriate controls and reagents.
You should be able to explain and/or conduct experiments using appropriate controls and reagents.
Most photosynthesis experiments include the Iodine Test for Starch. Ensure that you understand the principle of the Iodine Test for Starch. Take time to understand each step of the Test for Starch in a leaf - destarching, de-colourization, rehydration, etc. Finally, you also need to understand the significance of de-starching a leaf.
Raw materials
Conditions
Products
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Leaf
- Draw the external features of a leaf
- Draw and annotate the internal structure of the lamina ( upper epidermis, palisade mesophyll, spongy mesophyll, lower epidermis, cuticle, chloroplasts, nucleus, vascular bundle, xylem, phloem, inter cellular air space, stoma/stomata, stomatal pore, guard cell)
Process/Practical Skills
Drawing
Observation/Recording and Reporting
- Draw to scale, adhering to drawing and labeling guidelines
- Label/Annotate the external features of a leaf - petiole, lamina, margin, apex, mid-rib, vein network/parallel veins'
- Label/Annotate from a prepared slide the internal structure of the lamina ( upper epidermis, palisade mesophyll, spongy mesophyll, lower epidermis, cuticle, chloroplasts, nucleus, vascular bundle, xylem, phloem, inter cellular air space, stoma/stomata, stomatal pore, guard cel
Observation/Recording and Reporting
- Observe and record colour changes - ethanol used to extract chlorophyll, iodine in the presence of starch
- Observe and record texture changes - leaf boiled in ethanol. leaf rehydrated with water
- Lighting of a Bunsen Burner
- Setting up a water bath - electric or beaker over a Bunsen Burner
- Use of test tube tongs/clamps to hold hot boiling tubes, angling away from face and others
- Collect oxygen bubbles using downward delivery (more dense than air)
- Test for oxygen gas using a glowing splint