Photosynthesis and Energy Transfer

Photosynthesis

• Photosynthesis is a process carried out by green plants and some other organisms containing chlorophyll
• It combines carbon dioxide and water to produce glucose and oxygen using light energy absorbed by chlorophyll
• The word equation for photosynthesis is: carbon dioxide + water → glucose + oxygen
• The symbol equation for photosynthesis is: 6CO2 + 6H2O → C6H12O6 + 6O2
• Chlorophyll is the green pigment in plant chloroplasts needed for photosynthesis
• Chlorophyll absorbs light energy needed to drive the reaction
• Photosynthesis converts light energy into chemical energy stored in plant material

Transfer of Energy

• Chlorophyll is not a reactant but needed for photosynthesis
• Chlorophyll absorbs light energy, which converts it to chemical energy in glucose and oxygen
• The products (glucose and oxygen) have more chemical energy than reactants (carbon dioxide and water)

Use and Storage of Carbohydrates

• The first product of photosynthesis is glucose, a simple sugar
• Glucose is used by plants for energy, which is part of cellular respiration
• Glucose can also be stored as starch

Plant Nutrition - Extension Materials

• Photosynthesis involves multiple chemical reactions, not just one step
• Rate of photosynthesis is affected by factors impacting enzyme activity
• Organic substances have carbon, while inorganic ones don't
• Carbon-carbon or carbon-hydrogen bonds define organic compounds
• Starch is a stored carbohydrate in plants that can release glucose for respiration
• Cellulose, another carbohydrate, is a component of plant cell walls
• Carbohydrates, fats, proteins, and DNA are organic molecules containing carbon, hydrogen, and oxygen
• Other elements such as nitrogen and phosphorus are part of some more complex compounds.
• These elements are obtained from mineral ions in the soil

Conditions Needed for Photosynthesis

• Five factors are required for photosynthesis: carbon dioxide, water, light, chlorophyll, and suitable temperature
• Light is needed for photosynthesis
• Temperature affects reactions in photosynthesis
• Chlorophyll captures light energy for photosynthesis
• Carbon dioxide is a reactant in photosynthesis

Practical - Testing a Leaf for Starch

• Allows testing if photosynthesis has occurred
• Iodine solution is used to test for starch
• Leaf is boiled in ethanol to remove chlorophyll and then in iodine solution
• If starch is present, the leaf turns blue-black; otherwise, it remains a pale colour

Factors Necessary for Photosynthesis

• Photosynthesis needs carbon dioxide, water, light, chlorophyll, and optimal temperature.
• Experimentation with these factors, such as depriving a plant of carbon dioxide, can test their necessity.

Investigating the need for Chlorophyll, Light, & Carbon Dioxide

• Plants with variegated leaves (having both green and white areas), allow investigation of chlorophyll's role
• Investigation of light's role involved carefully covering part of a leaf
• Investigation of carbon dioxide's role involved using soda lime to absorb carbon dioxide

Measuring Photosynthesis Rate

• Rate of photosynthesis can be measured by measuring the rate of oxygen production by an aquatic plant, i.e. by counting produced bubbles
• Light intensity can vary a plant's rate of photosynthesis

Explore the fascinating process of photosynthesis, where green plants convert light energy into chemical energy. This quiz covers key concepts including the chemical equations, the role of chlorophyll, and the production and storage of carbohydrates. Test your understanding of how sunlight is transformed into the energy that sustains plant life.