Science Unit 1 Photosynthesis STAGE 9 S2A

Unit Test 1 U1 Photosynthesis, the Carbon Cycle, and Climate Change

Photosynthesis is the chemical reaction by which plants create their own food when carbon dioxide and water is made to react in the presence of light and chlorophyll to produce oxygen and glucose.

What is photosynthesis?

Carbon dioxide and water.

What are the reactants in photosynthesis?

Oxygen and glucose.

What are the products in photosynthesis?

Photosynthesis is essential because:

1. Energy flow in ecosystems:
   - We need photosynthesis as it is the starting point for producing energy in food chains. Plants produce energy in photosynthesis, and animals eat plants to obtain this energy. All of this energy is passed around until it eventually reaches us.

2. Food source:
   - Photosynthesis produces glucose, which plants use to grow.
   - All the food we eat (fruits, vegetables, grains and even MEAT) comes DIRECTLY or INDIRECTLY from photosynthesis.

3. Carbon dioxide balance:
   - Plants absorb CO2 during photosynthesis, which helps maintain the balance of carbon dioxide concentration in the atmosphere.
   - It regulates the Earth’s atmosphere.

4. Oxygen production:
   - Photosynthesis releases oxygen as a by-product.
   - Without plants, photosynthesizing, humans and other animals would not have oxygen to breathe.
   - The oxygen on Earth was mainly produced by plants photosynthesizing, and it first came form bacteria photosynthesizing, as Earth’s atmosphere barely had any oxygen millions of years ago.

Why is photosynthesis important?

Chlorophyll is the green pigment found in structures in some plant cells that absorbs light energy and converts it to chemical energy.

Define chlorophyll.

Chlorophyll are found in the chloroplasts of plant cells. (Particularly in cells such as palisade cells found on the surface of leaves.)

Where are chlorophyll found?

Light + 6H2O + 6CO2 (in the presence of chlorophyll) → C6H12O6 + 6O2

State the balanced chemical equation of photosynthesis:

The stomata (singular: stoma) are tiny holes in leaves that facilitate gas exchange.

What are the stomata in leaves?

In the oceans. This is because 75% of the Earth is comprised of oceans, only a mere 25% is the land. So there will be a higher proportion of oxygen production done in the oceans as the mass is greater and the proportion is larger compared to land.

Mortals aren’t that amazing compared to the bodies of water we live near.

Is oxygen production higher in the oceans or on land?

False. Photosynthesis needs light energy to convert carbon dioxide and water into glucose and oxygen. At night, there is no light, so photosynthesis cannot occur. However, respiration happens all the time, day and night.

TRUE/FALSE: Photosynthesis happens at night.

False. Although leaves are the main site of photosynthesis, (because they have many chloroplasts), other green parts of the plants like green stems and sometimes even unripe green fruits can photosynthesize, just as long as they have chlorophyll.

TRUE/FALSE: Photosynthesis only occurs in the leaves of a plant.

It lacks water. This is because water is needed to keep a plant UPRIGHT and prevent its cells from GOING FLACID. It is needed for turgidity, which keeps a plants cells stiff, firm and in its characteristic rectangular/block shape.

If a plant’s leaves are floppy, what deficiency does it have?

The xylem is the part of the plant that transports water and mineral salts from the roots to all parts of the plant. It only goes in one direction, and that is upwards. It initiates the transport system that sustains the plant’s life.

What is the xylem in a plant?

• Roots: The roots have tiny hairs. These increase the surface area of the roots for absorbing water from the soil.

• Leaves: Leaves have a large surface area in order to capture sunlight. They are also thin in order to provide a short diffusion pathway for gases to move in and out.

What adaptations do plants have for photosynthesis?

Minerals are the natural elements found in the soil. Plants need them in tiny amount to grow well.

Define minerals.

Mineral salts are the usable form of minerals that plants can absorb through their roots, usually dissolved in water. They are compounds made of minerals combined with other elements. (eg. Nitrates, magnesium sulfate and potassium nitrate.)

Define mineral salts.

Minerals provide the raw elements. Mineral salts are the usable forms of minerals. Mineral salts are the exact chemical compounds that plants absorb.

What is the difference between minerals and mineral salts?

• Keeps plants upright (stands)

• Needed for the turgidity of plant cells

• Supports the leaves for photosynthesis

• Helps growth

• Opens stomata

• Helps leaves spread out (so there can be more photosynthesis, and photosynthesis is possible, and the leaves are not flacid.)

• Water is needed to regulate the temperature of a plant through transpiration.

• New seeds need water in order to germinate.

Why do plants need water?

• Light intensity: As the intensity of light increases, the rate of photosynthesis increases.

• Carbon dioxide: As the concentration of carbon dioxide increases, the rate of photosynthesis increases.

• Temperature: If the temperature is too low, the rate of photosynthesis is also low. As the temperature increases, the rate of photosynthesis increase. But if the temperature if too high, the rate of photosynthesis will decrease.

What are the factors that affect the rate of photosynthesis?

1. Boil the leaf for 5 minutes

2. Boil the leaf in ethanol for 2 minutes

3. Place the leaf in cold water

4. Place the leaf on a petri disc for better inspection

5. Add a few drops of iodine to the leaf

6. Wait for the leaf to turn blue-black to indicate that there is presence of starch.

In order to test for starch in a leaf, what is the procedure of the experiment in doing so?

To stop all chemical reactions (photosynthesis) and remove any chemicals in the leaf.

Why do we put the leaf in boiling water?

To remove all chlorophyll and get rid of any other chemicals that may interfere with the experiment.

Why do we put the leaf in ethanol?

To make it easier to handle after boiling.

Why do we put the leaf in cold water?

Respiration is the process by which plants, animals and microorganisms/living organisms break down glucose to release energy.

Define respiration.

Respiration occurs both day and night, while photosynthesis can only occur during the day. There is an exchange of gases in photosynthesis all the time, however, there is no gas exchange in respiration during the night, as the stomata is closed during the night. (although the plant may still have gas exchange during the night if the stomata isn’t fully closed; the plant closes the stomata during the night to conserve water.)

Photosynthesis takes place in chloroplasts, while respiration occurs in mitochondria. Photosynthesis requires sunlight, carbon dioxide, and water, while respiration requires glucose and oxygen. Photosynthesis produces glucose and releases oxygen, while respiration produces ATP and releases carbon dioxide and water.

What is the difference between photosynthesis and respiration?

1. Photosynthesis

2. Respiration

3. Decomposition

4. Combustion

5. Feeding

What are the processes in the Carbon Cycle?

Boron, chlorine, copper, zinc, iron, molybdenum, manganese

What are the micronutrients?

PRIMARY: Nitrogen, phosphorus, potassium

SECONDARY: Magnesium, calcium and sulfur.

What are the macronutrients?

Nitrogen, Phosphorus, Potassium, Calcium, Magnesium and iron.

What are the mineral nutrients? (essential minerals)

The carbon cycle is the exchange of carbon cycling through the atmosphere, soil, land, air and biosphere. Carbon is exchanged between organisms and the environment.

What is the carbon cycle?

The processes involved in forming fossil fuels are anaerobic decay (decomposition, but not fully so that the remains can still be subjected to intense heat and pressure to be converted to fossil fuels), intense heat and pressure while being buried under layers of rock and soil.

What are the processes involved in forming fossil fuels?

Carbon sinks are organisms or things that take more carbon out from the atmosphere in the carbon cycle than they add to it.

What are carbon sinks?

Carbon sources are sources of carbon where a lot of carbon is released to the atmosphere through them.

What are carbon sources?

glucose + oxygen → water + carbon dioxide + energy ATP

State the chemical equation for respiration.

Decomposition is the breakdown of carbon compounds in plants and animals and other living organisms when they die by microorganisms called decomposers. Some of the carbon stored in their bodies are released back to the atmosphere as carbon dioxide.

What is decomposition?

Combustion is burning. It is present in the carbon cycle when fossil fuels are burned to be used as fuel for other processes in factories, cars and other places. This process releases carbon dioxide to the atmosphere.

What is combustion?

Feeding is the transfer of energy from plants to animals, animals to other animals or from one living organism to another living organism. It transfers the energy and carbon stored in one organisms body to the other.

What is feeding?

They are non-renewable because they cannot be replenished as fast as we use them, so they will deplete faster than we can restore them, as they form over thousands to millions of years from the remains of organisms. It takes too long to restore them, so they are non-renewable. Eventually, we will run out of fossil fuels.

Why are fossil fuels non-renewable?