Photosynthesis (chpt. 11)

Question 1

Photosynthesis

Answer 1

The process by which plants make food using carbon dioxide and water in the presence of sunlight and chlorophyll

Question 2

Photosynthesis

Answer 2

The process by which plants make food using carbon dioxide and water in the presence of sunlight and chlorophyll

Question 3

Chemical formula for photosynthesis

Answer 3

6CO. + 6H. O. Sunlight. C. H. O. + 6O
2. 2. Chlorophyll 6. 12. 6. 2

Question 4

Word formula for photosynthesis

Answer 4

. .Sunlight
Carbon dioxide + water ——————> glucose + oxygen
Chlorophyll

Question 5

Why is photosynthesis important

Answer 5

Plants use it to make food
Animals get their food from plants
Produces oxygen
Takes in carbon dioxide from the air

Question 6

Factors affecting the rate of photosynthesis

Answer 6

Carbon dioxide → external (taken in from atmosphere) internal (small amount produced during respiration of leaf cells
Light → provides energy needed for photosynthesis
Temperature → optimum temperature for plant enzymes is 25 - 30°C
Water → freely available, absorbed by plant root hairs and is conducted through the xylem by the transpiration stream

Question 7

Light stage - pathway 1

Answer 7

Light is absorbed by chlorophyll and electrons are energised
High energy electrons enter P 1 where they move through electron receptors and lose energy
This energy is trapped by ADP and a phosphate and is used to make ATP and water

Question 8

Light stage - pathway 2

Answer 8

Electrons move from P 1 to P 2 and do not return to chlorophyll
At the same time, water is split into 4 hydrogen ions, oxygen and 4 electrons (photolysis)
These electrons are passed back to the chlorophyll
Hydrogen ions combine with NADP- to form NADPH
Some hydrogen ions are sent to a proton pool for later use
Oxygen is released into atmosphere or used for internal respiration

Question 9

Photolysis

Answer 9

The splitting of water by light

Question 10

Products of the light stage

Answer 10

ATP - supplies energy for dark stage
NADPH - supplies protons and electrons for dark stage
oxygen - used in respiration or released into atmosphere

Question 11

What is the dark stage

Answer 11

Light independent
Occurs in chloroplast
Enzymes used so is affected by temp
Aka Calvin cycle
Requires products from light stage

Question 12

Where does the dark stage of photosynthesis take place

Answer 12

Chloroplast

Question 13

Key stages of dark stage

Answer 13

NADPH releases protons and electrons
Carbon dioxide is reduced to glucose
ATP releases energy and is converted back into ADP
ADP and NADP+ are recycled back to light stage

Question 14

Products of dark stage

Answer 14

Glucose
NADP
ADP

Question 15

How can you increase plant production in a greenhouse

Answer 15

Burn gas
Pump in carbon dioxide
Artificial light

Question 16

When light is absorbed by the chlorophyll, to which specific type of chlorophyll molecule is it passed

Answer 16

Reaction centre

Question 17

Where in the leaf does the dark stage take place

Answer 17

Chlorophyll/ stroma

Question 18

Where does the light stage take place

Answer 18

Chlorophyll / grana

Question 19

What features do pathway 1 and pathway 2 have in common

Answer 19

Formation of ATP
Movement of electrons through carriers

Question 20

Does chlorophyll absorb green light?

Answer 20

No, leaves are green and therefore green light is reflected

Question 21

What is the role of electron acceptors in the production of ATP

Answer 21

Energised electrons picked up by electron acceptor
As electrons pass from one acceptor to the next they lose energy
This energy is then used to add a phosphate group to ADP, forming ATP

Question 22

Importance of photolysis

Answer 22

Produces hydrogen ions, electrons
Used to make NADPH

Question 23

One factor that could alter rate of the dark phase

Answer 23

Temperature

pH

Question 24

Role of ATP in dark stage

Answer 24

Provides energy for conversion of carbon dioxide to glucose