Photosynthesis and Respiration

Photosynthesis vs. Respiration

• Photosynthesis occurs in chloroplasts within plant cells, while respiration takes place in mitochondria in all cells.
• Sunlight is the energy source for photosynthesis, whereas chemical energy in glucose fuels respiration.
• Photosynthesis uses carbon dioxide and water as raw materials, producing glucose and oxygen.
• Respiration uses glucose and oxygen as raw materials, producing carbon dioxide, water, and energy (ATP).
• Photosynthesis happens during the day when light is available, while respiration occurs constantly.
• Photosynthesis is an energy-storing (endothermic) process, while respiration is an energy-releasing (exothermic) process.
• Plants, algae, and some bacteria perform photosynthesis.
• All living organisms perform respiration.

Leaf Structure and Function

• The upper epidermis is the top layer of the leaf.
• Palisade mesophyll is the primary site of photosynthesis.
• Spongy mesophyll contains air spaces for gas exchange.
• Veins contain xylem and phloem for transport.
• The lower epidermis is the bottom layer of the leaf
• Stomata are pores for gas exchange and are located on the lower epidermis
• Guard cells regulate the opening and closing of stomata.
• Chloroplasts in palisade cells contain chlorophyll.
• Leaves appear green due to chlorophyll, which absorbs sunlight for photosynthesis and reflects green light.

Word Equations

• Photosynthesis: Carbon dioxide + Water → Glucose + Oxygen
• Respiration: Glucose + Oxygen → Carbon dioxide + Water + Energy

Chemical Reactions in Plants

• Plants use photosynthesis to convert carbon dioxide and water into glucose, using sunlight as energy.
• Photosynthesis happens in the chloroplasts of leaf cells.
• Oxygen is produced as a byproduct of photosynthesis.

Starch and Food Chains

• Plants convert glucose into starch for storage.
• Starch is stored in leaves, roots, or tubers.
• Starch provides energy to herbivores, which are then consumed by carnivores, making it a crucial energy source in food chains.

Iodine Starch Test

• Boil a leaf in water to soften it.
• Place the leaf in ethanol in a hot water bath to remove chlorophyll.
• Rinse the leaf in warm water.
• Add iodine solution to the leaf.
• If starch is present, the leaf will turn blue-black.

Energy Source

• The sun is the primary energy source for processes on Earth.
• The sun powers the water cycle, supports photosynthesis, and provides heat and light.

Oxygen Cycle

• Plants take in carbon dioxide and release oxygen during photosynthesis.
• Animals take in oxygen and release carbon dioxide during respiration.

Carbon Cycle

• Plants absorb carbon dioxide from the atmosphere during photosynthesis.
• Animals consume plants, obtaining carbon.
• Decomposers return carbon to the soil when plants and animals die.
• Burning fossil fuels releases carbon dioxide into the atmosphere.

Nitrogen Cycle

• Nitrogen is essential for proteins and DNA.
• Bacteria convert nitrogen gas into forms that plants can use.
• Animals obtain nitrogen by consuming plants.
• Decomposers return nitrogen to the soil.
• Other bacteria convert nitrogen compounds back into nitrogen gas.

Fertilizers

• Fertilizers add nutrients (nitrogen, phosphorus, and potassium) to the soil.
• Fertilizers enhance crop growth and increase food production.

Environmental Impacts

• Eutrophication occurs when excess fertilizers enter water bodies.
• Algae grow quickly, blocking sunlight and reducing oxygen, harming aquatic life.
• Increased crop growth leads to biodiversity loss, pollution from pesticides and fertilizers, and soil degradation.

Crop Growth Factors

• Light is needed for photosynthesis.
• Water transports nutrients and supports chemical reactions.
• Temperature affects enzyme activity and growth rate.
• Soil nutrients are essential for healthy plant development.
• Increased carbon dioxide levels can increase photosynthesis.

Biofuels

• Biofuels are fuels made from organic matter.
• Biofuels are considered renewable.
• Biofuels are viewed as more sustainable than fossil fuels.
• Biofuels may reduce greenhouse gas emissions.
• Biofuels Can support rural economies
• Biofuels may compete with land for food crops.
• Biofuels can cause deforestation.
• The production of biofuels may require a lot of water and energy.

Revision Quiz - True or False

• True
• False
• True

Revision Quiz - Multiple Choice

• The sun
• Nitrogen

Revision Quiz - Short Answer

• Biofuels come from sugarcane or corn which is fermented to produce ethanol.
• Oils from plants can be processed into biodiesel.
• Can be used as alternatives to petrol or diesel.