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Flashcards in 2: Photosynthesis Deck (22)
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1
Q

Define ‘photosynthesis’.

A

the production of carbon compounds in cells using light energy

2
Q

State the substrates for photosynthesis.

A

simple inorganic substances:

  • carbon dioxide
  • water
3
Q

Give synthesis of glucose through photosynthesis equation.

A

CO2 + H2O + light energy –> glucose + oxygen

4
Q

Name some organisms who produce their carbon compounds by photosynthesis.

A

plants, algae, some bacteria

5
Q

State the stages of photosynthesis.

A
  1. carbon dioxide converted into carbohydrates and other carbon compounds. high energy electrons needed for this.
  2. electrons obtained by photolysis, which is splitting of water molecules. oxygen is a waste product from the photolysis of water. energy is needed for this.
  3. energy obtained in form of light. light is absorbed by photosynthetic pigments.
6
Q

Name a waste product of photosynthesis.

A

oxygen

7
Q

How is oxygen produced in photosynthesis?

A

oxygen produced as waste product when water is split by photolysis

8
Q

What were the first organisms to release oxygen into the atmosphere? When?

A

bacteria, about 3.5 billion years ago

9
Q

What happened to atmospheric oxygen levels 2.4-2.2 billion years ago? What caused this event? What was the effect of this?

A
  • rose from very low concentration to 2%
  • due to photosynthesis in bacteria
  • rise caused dissolved iron in oceans to precipitate as iron oxide, where it sank to the ocean bed, forming deposits of rock called banded iron formations
10
Q

What happened to atmospheric oxygen levels 750 million years ago? What caused this event?

A
  • oxygen levels rose from 2% to 30%, before dropping back down to todays level of 20%
  • probably due to evolution of multicellular algae and land plants, which raised global photosynthesis rates
11
Q

What is a spectrum?

A

the range of wavelengths of electromagnetic radiation

12
Q

What is the spectrum of visible light?

A

range of wavelengths from 400nm to 700nm that are used in human vision

13
Q

What is colour has the shortest wavelength? What has the longest?

A
  • shortest = violet

- longest = red

14
Q

What spectrum - range of wavelengths of electromagnetic radiation - are is used in photosynthesis? Why?

A
  • same as visible light (400nm-700nm)

- because photosynthetic pigments do not absorb other wavelengths

15
Q

What does the ‘absorption spectrum’ graph show?

A

the range of wavelengths absorbed by a pigment

16
Q

Draw the absorption spectrum. (p34)

A

it’s a gaph:

  • chlorophyll a
  • chlorophyll b
17
Q

What is the main photosynthetic pigment?

A

chlorphyll

18
Q

What does the absorption spectrum show?

A
  • that chlorophyll absorbs red and blue light most effectively
  • small amounts of green light are absorbed but most is reflected, making structures containing chlorophyll appear green to us
19
Q

Comment on the efficiency of photosynthesis for different wavelengths of light.

A
  • efficiency here = percentage of light of a wavelength that is used in photosynthesis
  • not the same in all wavelengths
  • maximum photosynthesis rates are in blue light, and (slightly less efficient) in red light. green light is used less efficiently
20
Q

Name the graph showing the efficiency of photosynthesis for different wavelengths of light.

A

action spectrum of photosynthesis

21
Q

Draw the action spectrum of photosynthesis. (p.34)

A

2 peaks:

  • first at 450
  • second at 670
22
Q

Why does the action spectrum show some use of green light in photosynthesis, even though chlorophyll absorbs little of it?

A

accessory photosynthetic pigments are present, which absorb some green light that can be used in photosynthesis

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