What is the photosynthesis reaction?
Carbon dioxide + water (+light energy) —> glucose + oxygen.
What happens during photosynthesis?
Light energy is absorbed by chlorophyll in the chloroplasts of the green parts of the plant. It is then used to convert carbon dioxide and water into sugar (glucose). Oxygen is released as a by-product.
Leaf adaptations for photosynthesis:
Most leaves are broad, giving them a big surface area for light to fall on. They contain chlorophyll in the chloroplasts to absorb light energy. They have air spaces which allow CO2 to get to the cells and oxygen to leave them by diffusion (called stomata). They have veins, this can bring plenty of water to the cells of the leaves.
How are algae adapted to photosynthesis?
Algae are aquatic so they absorb CO2 dissolved in the water around them.
How can the rate of photosynthesis be limited?
The rate of photosynthesis may be limited by: A shortage of light A low temperature A shortage of carbon dioxide.
Light and photosynthesis
For most plants, the brighter the light, the faster the rate of photosynthesis.
Temperature and photosynthesis
Temperature can affect all chemical reactions. As the temperature rises, the rate of photosynthesis rises too. However, photosynthesis is controlled by enzymes so once temperatures reach around 40-50 degrees C- the active site can denature.
Carbon dioxide and photosynthesis
Increasing carbon dioxide levels will increase the rate of photosynthesis. On a sunny day carbon dioxide is one of the most common limiting factors in photosynthesis. The CO2 levels tend to rise at night because in the dark, a plant respires instead of photosynthesises. Then, as the light and temperature levels increase in the morning, the CO2 gets used up again.
How to control limiting factors?
Limiting factors can be controlled by artificially manipulating the limiting factors, for example- CO2 levels can be manipulated in order to increase the rate of photosynthesis.
How do plants and algal cells use the soluble glucose produced in photosynthesis?
They use it for: Respiration To convert into insoluble starch for storage To produce fats or oils for storage To produce fats, proteins or cellulose for use in cells and cell walls. They also cause anabolic reactions by building up larger molecules from smaller molecules.
Plants also use some of the glucose produced in photosynthesis to make amino acids. They do this by combining sugars with nitrate ions and other mineral ions from the soil. The amino acids then make proteins to be used in cells.
Why is starch used for storage?
Starch is used for storage as starch is insoluble. Glucose is soluble in water, so if it were stored in plant cells- it could affect the way water moves into and out of the cell (osmosis). Starch doesn't affect the osmotic balance.
So why is starch stored?
Starch is stored so that it can provide and energy store for when it is dark or when light levels are low. Many plants also produce tubers and bulbs. These help them to survive during winter as they are full of stored starch.
What happens the more a plant photosynthesises?
The plant grows quicker and it makes more biomass.
How does a greenhouse affect the rate of photosynthesis?
The glass/ plastic structure is more controllable than outside. The atmosphere is also much more warmer which means the plants can grow quicker.
Control through technology
Companies using big and commercial greenhouses can take advantage of the limiting factors. The factors can be manipulated so the plant grows quicker and in the right conditions.
What is hydroponics?
Hydroponics is growing crops without the use of soil.
Advantages and disadvantages of hydroponics:
Advantages: • Quickly produced; profits are high. • The crops are clean and unspoilt. • There is no ploughing or preparation of land needed. • Limiting factors are controlled Disadvantages: • Costs a lot of money. • Takes a lot of energy to keep conditions in greenhouses just right. • Lots of maintenance needed.
Why is magnesium needed in plants?
Why is phosphorus needed in plants?
What physical factors can affect the distribution of organisms?
Temperature Nutrients The amount of light The availability of water The availability of oxygen and carbon dioxide
Temperature and organisms:
Temperature can be a limiting factor for photosynthesis, so therefore growth in plants can be affected
Nutrients and organisms:
Nutrient levels can also affect the distribution of organisms. For example, Venus Flytraps thrive where nitrate levels are low as the nitrates they need are provided when they break down animal protein
Light and organisms:
Light is also a limiting factor for photosynthesis. Some plants live in low light levels and they tend to have more chlorophyll or bigger leaves. Plants only live in regions where the light intensity are right for them
Water, Carbon dioxide, oxygen and organisms:
If there is no water, there will be little or no life. The distribution of land organisms is not affected by oxygen levels due to plenty of oxygen being available in air Carbon dioxide is a limiting factor for photosynthesis so this can also affect the distribution of organisms
How can we get quantitative data on the distribution of organisms?
We can: Use random sampling with quadrats Sample along a transect
What is a quadrat?
A quadrat is usually a square frame made of wood or metal that you lay on ground
What is a transect?
A transect involves stretching tape between two points. You sample the organisms along that line at regular intervals using a quadrat. This shows how the distribution of organisms changes along that line. Physical factors such as soil pH and light levels can also be measured along a transect
What is a reproducible experiment?
A reproducible experiment is where other people can do the same investigation that you're doing and get the same results as you
What is a valid experiment?
A valid experiment answers the question