C1.3 - photosynthesis process (4a)

Question 1

what is photosythesis?

Answer 1

an endothermic reaction in which energy is transferred from the environment to chloroplasts by light

Question 2

what is the equation for photosynthesis?

Answer 2

carbon dioxide + water – light –> oxygen + glucose

6CO2 + 6H2O –> O2 + C6H12O6

Question 3

what is the photosynthesis process?

Answer 3

the production of carbon compounds in chloroplasts within cells, using light energy

Question 4

what group or organisms carries out photosynthesis?

Answer 4

plants, algae and cyanobacteria carry out photosynthesis

Question 5

where do plants obtain carbon dioxide from?

Answer 5

• absorbed from the air
• from water (for aquatic plants)

Question 6

what transfer of energy occurs during photosynthesis?

Answer 6

light energy –> chemical energy

Question 7

why is energy transformation needed from photosynthesis?

Answer 7

supplies most of the chemical energy needed for life processes in ecosystems

Question 8

what is an example of an energy transformation during photosynthesis?
where is this energy stored?

Answer 8

e.g) glucose is respired to release ATP to support metabolic reactions in living organisms
- this chemical energy is stored in covalent bonds

Question 9

how is glucose used by plants?

Answer 9

glucose forms carbohydrates or other carbon compounds

Question 10

how are nitrates used by plants?

Answer 10

nitrates are used to produce nitrogen-containing compounds such as amino acids, nucleotides and ATP

Question 11

how are phosphates used by plants?

Answer 11

phosphates are used to produce phosphate-containing compounds such as phospholipids, nucleotides and ATP

Question 12

what is the process of photosynthesis?

Answer 12

1. the splitting of water and the production of oxygen requires light:
   - this process is called photolysis
   - oxygen is the by product of photosynthesis and is released into the atmosphere
2. hydrogen ions are released, which reduce carbon dioxide
3. carbon dioxide is ‘fixed’ when it is converted to glucose
4. the glucose is converted to a wide range of organic compounds

Question 13

what happens when a pigment molecule absorbs light?

Answer 13

• when a pigment molecule absorbs light some of its electrons become excited
• the excited electrons can be used to make chemical bonds, thus transforming the light energy to chemical energy
• thus there is transformation of light energy to chemical energy

Question 14

what does the exciting an electron require?

Answer 14

exciting an electron requires a specific amount of energy to raise it to a higher energy level
- the amount of energy differs depending on the pigment molecule, and so different wavelengths of light are required to provide each of these

Question 15

what is an absorption spectra?

Answer 15

the absorption spectrum shows the wavelengths of light that are absorbed by each pigment
- different pigments absorb different wavelengths of light and have different peaks, allowing for a wider action spectrum

Question 16

what is an action spectrum?

Answer 16

an action spectrum is a graph that shows the rate of photosynthesis at different wavelengths of light

Question 17

what are similarities between action and absorption spectra?

Answer 17

• they both have a similar shaped graph for chlorophyll
• both have wavelength or colour of light in the x-axis

Question 18

how can we determine rates of photosynthesis for varying wavelengths?

Answer 18

recording the rate of oxygen production or carbon dioxide intake allows direct measurement of photosynthesis rate

Question 19

what must be corrected for these methods?

Answer 19

the rate of cell respiration must be corrected, and this is possible as the plant has a fairly consistent rate of cell respiration as long as this is corrected for cell respiration

Question 20

what type of spectrum would be produced?

Answer 20

if the independent variable is wavelength of light, plotting the rate of photosynthesis against this produces an action spectrum

Question 21

what wavelengths of light are absorbed the most and least by chlorophyll?

Answer 21

most - red and blue

least - green (it is reflected)