3.2. Energy And Photosynthetic Bacteria

Question 1

Describe the two part process whereby photoautotrophs convert light into energy resulting in the reduction of CO2 to meet carbohydrate demands

Answer 1

Photosynthesis is the process in which light energy is converted to chemical energy in the form of sugars. In a process driven by light energy, glucose molecules are constructed from water and carbon dioxide and oxygen is released as a byproduct
- obtain cellular energy via carbon dioxide assimilate from light.

Question 2

Why is it important that chlorophylls can absorb light at different wavelengths

Answer 2

• pigment molecules, just like any other molecule, have electrons that can occupy different energy levels.
• actually absorbs red and blue light and reflects green light and the reason it absorbs certain colour of light and reflect other colours is because of its chemical structure.

Question 3

What are carotenoids and what is their role in photosynthesis?

Answer 3

Carotenoids are long hydrocarbon chains consisting of a conjugated double bond system that absorbs light at the blue end of the spectrum so they confer hues of red, yellow and orange on the cell. They may trap light energy and pass it onto the chlorophyll pigments.
- They quench toxic forms of oxygen such as singular oxygen so act as a protective molecule.

Question 4

What is the role of Phycobilins and where might they be beneficial to microorganisms?

Answer 4

Phycobilins are light capturing bikinis found in Cyanobacteria and in the chloroplasts of red algae.

They are important as they are able to supplement the light capturing ability of Chl by absorbing energy where Chl is not a very efficient absorber. They pass the light energy to chlorophylls for photosynthesis. Green to red wavelength.

Question 5

Describe the properties of Purple S bacteria and state why the intracytoplasmic membrane is important to survival

Answer 5

Properties:

• strict anaerobes
• photolithoautotrophs
• intracellular S deposits
• Grow in deeper, anaerobic, S2- rich zones

The intracytoplasmic membrane harvests light for photosynthesis

Question 6

What are meromictic lakes and why do shallow ponds have such diversity of microbial life?

Answer 6

Meromictic lakes: deep, permanent stratification, upper layer is warm and aerobic whereas the deep layer is cold and anaerobic.
- purple and green S bacteria grow at anaerobic interface, rich in carotenoids to absorb 450-550 micrometers of light

Shallow ponds: rich in organic matter, sediment is anaerobic and there is a layer of algae and cyanobacteria that can absorb light (long wavelengths transmitted through these layers)