Photosynthesis and Leaf Structure

Question 1

What is the word equation for photosynthesis

Answer 1

Carbon dioxide + water —> glucose + oxygen

Question 2

What is the balanced equation for photosynthesis

Answer 2

6️⃣CO2 + 6️⃣H2O —> C6H12O6 + 6️⃣O2

Question 3

What do plants do to the glucose

Answer 3

Convert it into starch and use for respiration

Question 4

An experiment to show that CO2 is needed for photosynthesis to occur and result

Answer 4

Destarch leaf (place in darkness)
Place in CO2 free air
Expose to light for 24 hours
Iodine test for starch 
Result: no starch

Question 5

An experiment to show that light is needed for photosynthesis to occur and result

Answer 5

Destarch plant (leave in darkness so that all starch is converted to glucose due to aerobic respiration)

Expose part of plant to light for 24 hours, part covered in black paper

Iodine test for starch
Exposed: starch present
Covered: no starch

Question 6

What chemical is used to test for starch and what is the result

Answer 6

Iodine

Positive —> blue/ black

Question 7

Why will the green parts of a leaf being able to photosynthesise and not the white bits

Answer 7

The green parts of the leaf contain chlorophyll so are able to photosynthesise whereas the white bits don’t

Question 8

How are leaves adapted to their function (5)

Answer 8

Broad, flat, large surface area to trap light

Palisade cells contain chlorophyll in chloroplasts

Air spaces in spongy mesophyll layer allow gaseous exchange

Transparent epidermis allows light to pass through

Leaf is thin so there is a short diffusion pathway

Question 9

What is the structure of a leaf (order from top to bottom)

Answer 9

Waxy cuticle
Upper epidermis
Palisade mesophyll
Spongy mesophyll
Lower epidermis + guard cells
Waxy cuticle

Question 10

What is the function of the waxy cuticle

Answer 10

Controls loss of water (evaporation)

Protects epidermis

Question 11

What is the function of the upper epidermis

Answer 11

Let’s light thought to the palisade layer

Question 12

What is the function of the palisade cells

Answer 12

Contains chloroplasts with chlorophyll so can absorb sunlight for photosynthesis

Question 13

What is the function of the spongy mesophyll layer

Answer 13

Contains air spaces for gaseous exchange via stomata

Question 14

What is the function of the guard cells

Answer 14

Opens/ closes stomata so it controls gas exchange and water loss

Question 15

What is the function of the stomata

Answer 15

Where gaseous exchange takes place

Question 16

Which two features of the leaf control water loss

Answer 16

Guard cells

Waxy cuticle

Question 17

How do we test a leaf for starch and results

Answer 17

Boil leaf in boiling water bath to kill it

Put leaf in a test tube of ethanol to remove chlorophyll

Rinse leaf with cold water to get ride of the rest of the chlorophyll

Iodine - blue/black if starch is present

Question 18

What are the uses of glucose in a plant (4)

Answer 18

Stored as starch
Respiration to release energy
Converted to proteins for growth
Cellulose for cell walls

Question 19

What factors affect the rate of photosynthesis

Answer 19

Concentration of CO2
Temperature
Light intensity

Question 20

What is the useful product from photosynthesis and what is it use for

Answer 20

Glucose is used as a source of energy

Question 21

Which long chain molecules can glucose convert into and. What are their uses

Answer 21

Starch - stores energy

Cellulose - cell walls

Question 22

Which element is needed to make protein and not to make carbohydrates

Answer 22

Nitrogen

Question 23

Which gases enter and leave plants during photosynthesis

Answer 23

Carbon dioxide enters

Oxygen leaves

Question 24

Which gases enter and leave during respiration in plants

Answer 24

Oxygen enters

Carbon dioxide leaves

Question 25

What affects the rate of photosynthesis

Answer 25

Light intensity
Amount of CO2
Varying temperature

Question 26

How does light intensity affect photosynthesis

Answer 26

Increasing light intensity increases photosynthesis as plants need light to photosynthesise. After a certain point the rate will reach its maximum as there will be another limiting factor

Question 27

How does increasing the concentration of Co2 increase the rate of photosynthesis

Answer 27

Increasing the concentration will increase the rate of photosynthesis as plants need CO2 to photosynthesise. After a certain point the rate will reach its maximum as there will be another limiting factor

Question 28

How does increasing the temperature increase the rate of photosynthesis

Answer 28

Rate of photosynthesis has an optimum temperature so too hot and photosynthesis will decrease, too cold and photosynthesis will also decrease. At a certain point the rate will reach its maximum as there will be another limiting factor

Question 29

Which 4 minerals do plants need to thrive

Answer 29

Nitrate
Potassium
Phosphate
Magnesium

Question 30

Why do plants need nitrates and what will happen if there is a deficiency

Answer 30

Makes amino acids, proteins, DNA, chlorophyll

Stunted growth
Older leaves turn yellow

Question 31

Why do plants need potassium and what happens if there is a deficiency

Answer 31

For enzymes for respiration
Needed for photosynthesis to work

Leaves turn yellow with dead spots

Question 32

Why do plants need phosphate and what will happen if there is a deficiency

Answer 32

Makes DNA and compounds in cell membrane

Younger leaves turn purple
Poor root growth

Question 33

Why do plants need magnesium and what happens if there is a deficiency

Answer 33

Part of the chlorophyll molecule

Leaves turn yellow

Question 34

What are the advantages of hydroponic cultivation of vegetables (3)

Answer 34

Clean
Disease/ pest control
Efficient/ controlled

Question 35

What are the disadvantages of hydroponic cultivation of vegetables (3)

Answer 35

Expensive to set up
High maintenance
Diseases can spread easily