Tuesday WK 6

Catabolism of other organic food molecules include: Proteins & Lipids.

Anabolic Pathways: Photosynthesis

Photosynthesis – synthesis of food molecules such as glucose, using light energy

Photosynthesis in Plants, Algae & Cyanobacteria:

6CO2 + 12H2O + light → C6H12O6 + 6O2 + 6H2O
Main Stages:
  1. Light Reactions – light energy is converted to chemical energy (ATP, NADPH)
  2. Calvin-Benson Cycle – Carbon incorporated into the organic molecules of plants from CO2 in the atmosphere & used to make food such as glucose. (Carbon Fixation)

Photosystem – Collection of pigments such as chlorophyll A, chlorophyll B and others that absorb light energy. 

1. Relationship  between 2 photosystems involved in light RXNs (Light RXN)

  • Light energy is absorbed & transferred from one pigment to another and finally to the reaction center. (Chlorophyll A)
  • Electrons jump from to primary acceptor and go through electron transport chain, extra electrons are added from (H+) water. 
  • NADP is final electron acceptor becoming NADPH
Note: these light reactions take place in photosystems that are embedded in Thylakoid Membrane.
Cyclic Photophosphorlation – in some cases, electrons circle back from photosystem 1 into the ETC again to generate more ATP
Non Cyclic – Electrons do not circle back through electron transport chain from photosystem 1. 

2. Calvin-Benson Cycle

This cycle occurs in Stroma in Eukarya

This cycle occurs in cytosol for Prokarya

  • ATP that is used to conduct this cycle is from first ETC of the light RXN
  • Main product of this cycle is glucose
  • H+ being used comes from the light dependent RXNs of photosynthesis catabolic pathways. (NADPH in, NADP+ out)
  • RuBP – most abundant molecule on earth (Ribulose triphosphate)

Photosynthesis by Purple Sulfur Bacteria & Green Sulfur Bacteria

  • H2S is electron donor (not H2o)
  • Nonoxygenic (does not produce 02)


Microbial Genetics: Terminology

Nucleic Acid – Molecules that store genetic information and are made of nucleotides

Genome – All of an organisms DNA

Chromosome – DNA + protein (protein generally structural)

Gene – sequence of nucleotides that contains instructions for making a specific product such as a protein

Genotype – genetic makeup or instructions

Phenotype – physical outcome (product) of the genetic intructions (genotype) 

Hologenome – all of an organisms DNA + DNA from symbionts (microbes on our bodies) 



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