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Topic 5: Plants and photosynthesis
Topic 5: Plants and photosynthesis
The photosynthesis reaction
The photosynthesis reaction
Objectives
Objectives
Write the word equation for photosynthesis.
Identify where photosynthesis occurs within the cell (chloroplasts) and explain the role of the pigment chlorophyll in capturing light energy.
Describe how plants obtain the reactants for photosynthesis and what happens to the glucose and oxygen products produced.
Photosynthesis
Photosynthesis
Photosynthesis is a vital chemical reaction that happens in plants and algae.
Reactants (What goes in): Carbon dioxide gas (from the air) and water (from the soil).
Energy Source: Light energy (usually from the sun).
Products (What comes out): Glucose (the sugar used as food by the plant) and oxygen gas (released as a waste product).
We can summarise this in a word equation:
Carbon dioxide + Water → Glucose + Oxygen
Location of photosynthesis
Location of photosynthesis
This reaction takes place inside tiny structures called chloroplasts, which are found mainly in the cells of leaves (and sometimes stems).
Chloroplasts contain a green pigment called chlorophyll.
Chlorophyll's Job:
It absorbs the light energy from the sun, providing the power needed to convert carbon dioxide and water into glucose.
This is why plants are green.
Reactants and products
Reactants and products
How do plants get the carbon dioxide and water they need?
Water:
Enters the plant through the root hair cells in the soil.
It's then transported upwards through tiny tubes called xylem in the roots, stem, and into the leaves.
Carbon Dioxide:
This gas enters the leaves from the atmosphere through tiny pores called stomata (mostly found on the underside of the leaf).
What Happens to the Products?
Glucose:
The plant uses this sugar for energy (through respiration), or it can be converted into other substances for growth or stored (like starch) for later use.
Oxygen:
Some oxygen might be used by the plant for its own respiration, but most of it is released back into the air through the stomata.
This is the oxygen that animals need to breathe.
Key words
Key words
Photosynthesis: The chemical process by which plants and algae use light energy to convert carbon dioxide and water into glucose (food) and oxygen.
Reactants: The substances that go into a chemical reaction.
Products: The substances that are produced by a chemical reaction.
Carbon dioxide: A gas from the air that is a reactant in photosynthesis.
Water: Absorbed from the soil and transported to the leaves, a reactant in photosynthesis.
Glucose: A sugar produced during photosynthesis, used by the plant for energy and growth.
Oxygen: A gas produced as a waste product of photosynthesis, released into the air.
Chloroplasts: Organelles in plant cells where photosynthesis takes place.
Chlorophyll: The green pigment inside chloroplasts that absorbs light energy for photosynthesis.
Extension ideas
Extension ideas
Investigate how environmental factors such as light intensity, carbon dioxide concentration, and temperature affect the rate at which photosynthesis occurs and how this can be measured.
Explain the relationship between photosynthesis and respiration in plants, highlighting how they are complementary processes in terms of gas exchange (oxygen and carbon dioxide) and energy transfer.
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