Photosynthesis 19/11/17

Question 1

What is photosynthesis?

Answer 1

• the process that produces glucose in plants
• happens in the leaves of green plants, in the chloroplasts which contain chlorophyll which absorbs sunlight and uses the energy from light to convert carbon dioxide and water into glucose, oxygen is also produced

Question 2

What is the word equation for photosynthesis?

Answer 2

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

Question 3

What’s the chemical equation for photosynthesis?

Answer 3

Sunlight
6CO₂ + 6H₂O———->C₆H₁₂O₆ + 6O₂
Chlorophyll

Question 4

Why is photosynthesis an important process?

Answer 4

It converts light energy into chemical energy, which is stored in the glucose the chemical energy is released during respiration

Question 5

What are the parts of a leaf?

Answer 5

• waxy cuticle
• upper epidermis
• palisade mesophyll layer(lots of chloroplast)
• spongy mesophyll layer
  
  • vascular bundle, air space, stoma, guard cell
• lower epidermis
• waxy cuticle

Question 6

How are leaves adapted for efficient photosynthesis?

Answer 6

• leaves are broad, large surface area exposed to light
• most chloroplasts are in palisade layer so they’re near the top to get the most light
• upper epidermis is transparent to let light through
• network of vascular bundles, transport vessels(xylem and phloem) deliver water and nutrients, take away glucose and support structure
• waxy cuticle reduces water loss by evaporation
• lower surface full of stomata which let CO₂ diffuse directly in the leaf

Question 7

How does the limiting factor of photosynthesis depend on the conditions?

Answer 7

-limiting factor depends on the environmental conditions

E.g. Winter-temperature limiting factor, night-light limiting factor

Question 8

What is a limiting factor?

Answer 8

Something which stops photosynthesis from happening any faster. E.g. Light intensity, CO₂ concentration and temperature can all be the limiting factor

Question 9

How can light be a limiting factor to photosynthesis?

Answer 9

-if light intensity is increase the rate of photosynthesis will increase steadily but only up to a certain point(after that temperature or CO₂ will be the limiting factor)

Question 10

How can CO₂ be a limiting factor to photosynthesis?

Answer 10

-increasing the concentration of CO₂ will increase the rate of photosynthesis up to a point after that point the graph will flatten out and light is no longer the limiting factor

Question 11

How can the temperature be a limiting factor for photosynthesis?

Answer 11

• temperature affects the rate of photosynthesis because it affects the enzymes involved
• as the temperature increases so does the rate of photosynthesis up to a point after that the enzymes will become denatured so the rate of photosynthesis rapidly decreases

Question 12

How do you test a leaf for starch? Describe an experiment:

Answer 12

• hold a leaf with tweezers and dump it into boiling water(this stops any chemical reactions happening in the leaf)
• put the leaf in a boiling tube with ethanol in and heat it in a water bath(70°C)[this gets rid of any chlorophyll and makes the leaf a white ish colour]
• rinse the leaf in cold water and add a few drops of iodine-if starch is present it’ll turn blue-black

Question 13

What does the starch test show?

Answer 13

Whether photosynthesis is taking place

Question 14

Describe an experiment to show that chlorophyll is needed for photosynthesis:

Answer 14

Using a variegated leaf(green and white),the green parts contain chlorophyll

• take a variegated leaf from a plant that has had light for 24hours and record which bits are green and which bits are white
• test the leaf for starch using the experiment previous and you’ll see only the green areas turn blue-black
• this suggests that leaves need chlorophyll to photosynthesise and produce starch

Question 15

Describe an experiment to show how carbon dioxide is needed for photosynthesis:

Answer 15

• place a plant and soda lime in a sealed bell jar with a light shining in
• the soda lime will absorb the carbon dioxide out of the air in the jar
• leave the plant in the jar for 24hours and then test a leaf for starch and it won’t turn blue black
• this shows no starch has been made in the leaf which means carbon dioxide is needed for photosynthesis

Question 16

Describe an experiment to show that light is needed for photosynthesis:

Answer 16

• leave a plant in a place without any light for 48 hours(this means it uses up its starch stores)
• cut a leaf from the plant and test it for starch using iodine solution and the leaf won’t turn blue black
• this shows that light is needed for photosynthesis, as no starch has been made

Question 17

What does the oxygen production from a plant show?

Answer 17

It shows the rate of photosynthesis

The faster the oxygen production, the faster the rate of photosynthesis

Question 18

Describe an experiment to show the effect of light intensity on photosynthesis:

Answer 18

Set up a light source with a ruler measuring the distance from test tube with Canadian pondweed in and water+sodium hydrogen carbonate(to make sure the plant has enough CO2) with a clamp on the top and bung connected with a capillary tube and a ruler next to it attached to an empty gas syringe

1) The white light source is at a specific distance from the pondweed
2) The pondweed is left for 1min, the oxygen released collects in the capillary tube
3) at the end of the experiment the syringe is used to draw up the gas bubbles and the length of gas bubbles collected is measured
4) the experiment is then repeated with different distances from the light source

Question 19

How could the experiment showing the effect of light intensity on photosynthesis be adjusted to measure the effect of temperature on the rate of photosynthesis?

Answer 19

Use different set temperatures instead of the light source moving and measure the oxygen production

Question 20

What are the control variables for the experiment to show the effect of light intensity on the rate of photosynthesis?

Answer 20

Temperature and time

Question 21

What are the three main mineral ions plants need and where do they get them from?

Answer 21

Nitrates, phosphates, potassium

They get these elements from mineral ions in the soil

Question 22

Why do they need nitrates and what are the deficiency symptoms?

Answer 22

Needed for:
Nitrates contain nitrogen for making amino acids and proteins, these are needed for cell growth
Deficiency symptom:
The plant will be stunted and older leaves will turn yellow

Question 23

Why do they need phosphates and what are the deficiency symptoms?

Answer 23

Needed for:
To make DNA and cell membranes and they’re needed for respiration and growth
Deficiency:
Poor root growth and there older leaves are purple

Question 24

Why do they need potassium and what are the deficiency symptoms?

Answer 24

Needed for:
Help enzymes needed for photosynthesis and respiration
Deficiency symptom:
Poor flower and fruit growth and discoloured leaves

Question 25

What’s magnesium required for, in what amounts and what are the deficiency symptoms?

Answer 25

Needed for:
Making chlorophyll
Amount:
Small
Deficiency symptom:
Yellow leaves