BioChem 2.9 Photosynthesis

Question 1

What is photosynthesis?

Answer 1

Photosynthesis is the production of carbon compound cells using LIGHT energy and simple inorganic substances (CO2 and water)

Question 2

What is essential for living organisms to carry out life processes?

Answer 2

Require complex carbon compounds to build structure and perform functions

Question 3

What is photosynthesis an example of?

Answer 3

energy conversion (light energy -> chemical energy stored in carbon compounds like carbohydrates, lipids, proteins)

Question 4

How is the visible light ranged?

Answer 4

Has a range of wavelengths with violet (shortest) to red (longest)

Question 5

Why is sunlight visible to us/plants?

Answer 5

Made up of all wavelengths of electromagnetic radiation our eyes can detect (other wavelengths invisible)

Question 6

What are examples of short wavelengths?

Answer 6

Blue/Violet -> X-rays and ultraviolet radiation -> high energy

Question 7

What are examples of long wavelengths?

Answer 7

Red/Orange -> infrared radiation and radio waves -> low energy

Question 8

How is light absorbed by plants?

Answer 8

Chlorophyll absorbs red and blue light most effectively

Question 9

What is the first stage of photosynthesis?

Answer 9

Absorption of sunlight through chemical substance/photosynthesizing pigment like chlorophyll

Question 10

What are pigments?

Answer 10

Substances that absorb light (appear coloured).

White does not absorb any and has no colour and reflect light while black absorbs all and is black and emits nothing

Some pigments absorb only certain wavelengths of visible light eg. Gentian flower only absorbs all except blue

Question 11

Why is our ecosystem mainly dominated by the colour green?

Answer 11

Because of the pigment chlorophyll, this is not very effective in absorbing green light which are therefore to be reflected

Question 12

What are the products of photosynthesis?

Answer 12

Oxygen is produced in photosynthesis from photolysis

Question 13

What colours are most effectively reflected by chlorophyll?

Answer 13

Green Light

Question 14

Draw absorption spectrum of plant pigments

Answer 14

horizontal axis is labelled wavelengths (nm) and scale extends from 400 to 700 nm,

vertical axis is labelled %absorption with scale of 0 to 100,

chlorophyll a peaks at around 440 and 680,

chlorophyll b peaks at around 500 and 650,

carotenoids peaks at 470 and 510

Question 15

Draw an action spectrum of a plan pigment

Answer 15

horizontal axis is labelled wavelengths (nm) and scale extends from 400 to 700 nm,

vertical axis measures amount of photosynthesis given as % of the max rate,

Question 16

What are the effects of photosynthesis to the atmosphere?

Answer 16

rise in oxygen concentration, as methane and co2 in atmosphere decrease

Question 17

What are the effects of photosynthesis on the ocean?

Answer 17

increased dissolved oxygen in the ocean causes oxidation of iron in water and precipitates onto the sea bed

Question 18

What rock is formed due to the oxidation of dissolved iron in water?

Answer 18

banded iron formation (most important iron ore)

Question 19

What is needed during photosynthesis?

Answer 19

Photosynthesis converts CO2 and H2O into Carbohydrates and O2 using light energy (endothermic)

Question 20

Is a reaction where small molecules like CO2 and H2O combine to form larger compounds like glucose, exothermic or endothermic?

Answer 20

endothermic

Question 21

Why does photosynthesis only occur in the light?

Answer 21

It provides energy that cannot disappear so that it can be converted into chemical energy

Question 22

What are possible limiting factors on rate of photosynthesis?

Answer 22

temperature, light intensity, CO2 concentration

Question 23

In a combination of limiting factors, can there be more than actually limiting photosynthesis rate?

Answer 23

No. There is only ONE LIMITING REACTANT. So the one furthest from optimum

Question 24

If other factors are changed, but not the limiting factor does it have an effect on photosynthesis rate?

Answer 24

No, only the limiting factor has effect on the rate (until it is not longer the limiting factor)