B2 2 Photosynthesis

Question 0

What happens during photosynthesis?

Answer 0

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.

Question 1

What is the photosynthesis reaction?

Answer 1

Carbon dioxide + water (+light energy) —> glucose + oxygen.

Question 2

Leaf adaptations for photosynthesis:

Answer 2

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.

Question 3

How are algae adapted to photosynthesis?

Answer 3

Algae are aquatic so they absorb CO2 dissolved in the water around them.

Question 4

How can the rate of photosynthesis be limited?

Answer 4

The rate of photosynthesis may be limited by: A shortage of light A low temperature A shortage of carbon dioxide.

Question 5

Light and photosynthesis

Answer 5

For most plants, the brighter the light, the faster the rate of photosynthesis.

Question 6

Temperature and photosynthesis

Answer 6

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.

Question 7

Carbon dioxide and photosynthesis

Answer 7

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.

Question 8

How to control limiting factors?

Answer 8

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.

Question 9

How do plants and algal cells use the soluble glucose produced in photosynthesis?

Answer 9

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.

Question 10

Amino acids

Answer 10

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.

Question 11

Why is starch used for storage?

Answer 11

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.

Question 12

So why is starch stored?

Answer 12

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.

Question 13

What happens the more a plant photosynthesises?

Answer 13

The plant grows quicker and it makes more biomass.

Question 14

How does a greenhouse affect the rate of photosynthesis?

Answer 14

The glass/ plastic structure is more controllable than outside. The atmosphere is also much more warmer which means the plants can grow quicker.

Question 15

Control through technology

Answer 15

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.

Question 16

What is hydroponics?

Answer 16

Hydroponics is growing crops without the use of soil.

Question 17

Advantages and disadvantages of hydroponics:

Answer 17

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.

Question 18

Why is magnesium needed in plants?

Answer 18

For chlorophyll.

Question 19

Why is phosphorus needed in plants?

Answer 19

For DNA.

Question 20

What physical factors can affect the distribution of organisms?

Answer 20

Temperature Nutrients The amount of light The availability of water The availability of oxygen and carbon dioxide

Question 21

Temperature and organisms:

Answer 21

Temperature can be a limiting factor for photosynthesis, so therefore growth in plants can be affected

Question 22

Nutrients and organisms:

Answer 22

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

Question 23

Light and organisms:

Answer 23

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

Question 24

Water, Carbon dioxide, oxygen and organisms:

Answer 24

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

Question 25

How can we get quantitative data on the distribution of organisms?

Answer 25

We can: Use random sampling with quadrats Sample along a transect

Question 26

What is a quadrat?

Answer 26

A quadrat is usually a square frame made of wood or metal that you lay on ground

Question 27

What is a transect?

Answer 27

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

Question 28

What is a reproducible experiment?

Answer 28

A reproducible experiment is where other people can do the same investigation that you’re doing and get the same results as you

Question 29

What is a valid experiment?

Answer 29

A valid experiment answers the question

Question 30

Quadrat image:

Answer 30