B8.1 - B8.4 Photosynthesis ✔️

Question 1

Photosynthesis equation?

Answer 1

Carbon dioxide + water → (light) →glucose + oxygen

Question 2

What type of reaction is photosynthesis reaction?

Answer 2

Endothermic reaction in which energy (light) is transferred from the environment to the chloroplasts

Question 3

Leaf adaptions for photosynthesis?

Answer 3

• leaves are thin - short diffusion distances
• leaves contain pigment, called chlorophyll to absorb light
• guard cells open and close the stomata to regulate gas exchange

Question 4

Light affect on photosynthesis?

Answer 4

More light increases rate of photosynthesis

Question 5

Temperature affect on photosynthesis?

Answer 5

Temperature rise - photosynthesis increases as reaction speeds up - too high enzymes denature and rate falls

Question 6

Carbon dioxide affect on photosynthesis?

Answer 6

Increased photosynthesis - often most common limiting factor for plants

Question 7

Chlorophyll levels affect on plants?

Answer 7

Less chlorophyll results in less photosynthesis

Question 8

Light intensity and the inverse square law?

Answer 8

Distance of light increases then the light intensity decreases - inverse relationship

Question 9

method for measuring rate of photosynthesis practical?

Answer 9

1) place pondweed in a tube of water - place test tube in water bath - (keep it at same temperature)

2)setup a light at 10cm from test tube - set a 1 min timer - count number of bubbles rising

3)repeat 3 times for an average - then repeat at different distances eg (20,30 ….)

Question 10

Photosynthesis practical variables?

Answer 10

Dependent: rate of photosynthesis at different light intensity’s

Independent variable: light intensity - distance of light from pondweed

Control variable: Temperature and pondweed

Question 11

Uses of glucose?

Answer 11

• converted into insoluble starch for storage
• used for respiration
• used to produce amino acids for protein synthesis

Question 12

Why can glucose bs stored in large amounts?

Answer 12

Starch is in soluble in water - has no effect on the water balance of the plant - can be stored in large amounts

Question 13

Where is starch stored?

Answer 13

• Starch is stored in the cells of the leaves - provides and energy store when it is dark
  -kept in special storage areas of a plant eg tubers and bulbs - full of starch to help them survive through the winter

Question 14

What is the test for starch?

Answer 14

using iodine solution - leaves have to be prepared - turns blue-black if starch is present from brown/orange

Question 15

How do you prepare a leaf for iodine test?

Answer 15

boil the leaf in ethanol - destroys waxy cuticle and then remove the colour - rinse in hot water to soften - now add iodine solution

Question 16

Why does leaf have to be treated before iodine test?

Answer 16

• waterproof cuticle keeps iodine out
• chlorophyll masks any colours changes

Question 17

how do plants produced proteins and why are proteins needed in plants?

Answer 17

glucose + sugars and nitrate ions and other mineral ions from the soil make amino acids - which are then built up into proteins and can then be used for respiration or as enzymes

Question 18

How do plants make lipids?

Answer 18

Use some glucose and energy transferred from respiration to build fats and oils used in the cell as energy stores … ext

Question 19

Pros of enhancing greenhouses for getting maximum rate of photosynthesis?

Answer 19

• more crops produced
• seed to harvest time is much shorter
• less staff needed
• cleaner crops

Question 20

Cons of enhancing greenhouses for getting maximum rate of photosynthesis - Give to drawbacks?

Answer 20

• expensive to set up and expensive equipment
• expensive to maintain conditions inside

Question 21

How is maximum growth achieved in special greenhouses?

Answer 21

by controlling all the factors - light, temperature, carbon levels and amount of mineral ions plant is getting - gives fastest possible rates of photosynthesis

Question 22

Symbol for glucose?

Answer 22

C6H12O6

Question 23

What is the limiting factor?

Answer 23

The factor which is in short supply and limits the amount of photosynthesis that can take place

Question 24

What does glucose provide?

Answer 24

Glucose is broken down using oxygen to provides energy for the cells - carbon dioxide and water are waste products of the reaction

Question 25

What is energy transferred by respiration used for - Give 3 ways?

Answer 25

• converting glucose into starch
• building smaller molecules into bigger molecules (eg making cellulose from carbohydrates)
• making amino acids which are built up into proteins to make enzymes

Question 26

What is starch?

Answer 26

Main energy store in plants - and can be found in cells all over the plant (it is insoluble in water)

Question 27

What are 2 benefits of plants using starch over glucose?

Answer 27

• glucose is soluble in water where as starch is insoluble not affecting water balance
• starch is also a better form of glucose energy wise and is more compact so it can be stored in greater quantity

Question 28

what is the test for starch?

Answer 28

Use iodine solution test

Question 29

How to test for starch using iodine solution test?

Answer 29

1) take two leaves from a plant left in the dark for 24 hours and one left in the light for 24 hours

2) boil the leaf’s in ethanol - to destroy waxy cuticle and remove colour

3) rinse in hot water to soften

4) add iodine solution to both - will turn blue/black from orange/brown if starch is present

Question 30

Why can we not just add iodine solution to leaf’s to test for starch - explain 2 reasons?

Answer 30

• waxy waterproof cuticle keeps the iodine out
• green chlorophyll masks any colour changes

Question 31

How does algae make amino acids?

Answer 31

Algae makes amino acids through taking nitrate ions and other materials from the water they live in

Question 32

How to plants make proteins?

Answer 32

Plants use glucose from photosynthesis to make amino acids by combining sugars and nitrate ions which are built up into proteins

Question 33

Why are limiting factors important?

Answer 33

Limiting factors are important in the economics of enhancing the conditions in greenhouses to gain the maximum rate of photosynthesis while sill maintaining profit

Question 34

effect of decreased magnesium for plants?

Answer 34

lack of magnesium means leaf cant make chlorophyll - so rate of photosynthesis drops

Question 35

issues with plants storing glucose?

Answer 35

if stored in a plant it could affect how water moves in and out of cells - affecting the plants water balance

Question 36

what does starch present on a leave suggest?

Answer 36

Presence of starch on leaf gives evidence that photosynthesis has taken place

Question 37

what is the light intensity and the inverse square law equation ?

Answer 37

Light intensity = 1/distance ^2