Category: Week 6

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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Monday WK 6

Aerobic Cellular Respiration

2nd Stage: Formation of Acetyl Coenzyme A (COA)

Reactants:

  • 2 Pyruvic acid
  • 2 coenzyme A

Products

  • 2 CO2
  • 2 NADH
  • 2 Acetyl COA

3rd Stage: Krebs Cycle

Reactants

  • 2 Acetyl COA

Products

(Goes through Krebs cycle twice)

  • 3 NADH    x2 = 6 NADH
  • 2 CO2        x2 = 4 CO2
  • 1 ATP         x2 = 2 ATP
  • 1 FADH2   x2 = 2 FADH2

ATP is made by substrate-level phosphorylation during Krebs cycle.

NAD+ (oxidized) can take on H+ and carry them becoming NADH (reduced)

4th Stage: Electron Transport Chain & Chemiosmosis

Reactants

  • 10 NADH
  • 2 FADH2
  • 6O2

Products

  • 34 ATP
  • 6 H2O
  • 10 NAD+
  • 2 FAD

Chemiosmosis – Chemical osmosis. Flow of electrons back down their gradient through ATP synthase. 

(ETC) – Electron Transport Chain – Series of molecules (embedded in cell membranes) that transport/carry electrons through redox RXNs, releasing energy for making ATP. Final electron acceptor is Oxygen. (O, not O2)

Process: the electron transport chain is embedded in the cytoplasmic membrane of bacterial cells or the inner membrane of mitochandria in eukaryotes. The electrons are passes through molecules in Redox RXNs, being pulled towards the oxygen that has the highest electronegativity, where is will finally be accepted. During this process H+ (which are taken from the FADH2 & NADH) are pushed through the membrane and began to buildup against their gradient, the H+ are filtered out through ATP synthase “portals” through the membrane creating ATP (this process is the Chemiosmosis)  in this RXN:          

ADP + P → ATP

3 Types of Electron Carriers in ETC:

  1. Flavoproteins – ex. flavin mononucleotides (FMN)
  2. Cytochromes (contain iron) – ex. Cytochrome C
  3. Ubiquinones – Coenzyme Q (COQ)

Summary table:

Glycolysis:                    4 ATP – 2 ATP used = 2 ATP          2 NADH

COA & KREBS:           2 ATP – 2 ATP used for eukaryotes only = 0 ATP             8 NADH            2 FADH

ETC:                              34 ATP

Net For Prokaryotes = 38 ATP

Net For Eukaryotes = 36 ATP. Note: Eukaryotes glycolysis process (stage 1) takes place in the cytosol, 2 ATP are expended to move the RXN through the membrane.

 

Alternate Pathways for Glycolysis

Pentose Phosphate Pathway

  • produces pentose sugars (for nucleotide synthesis)

Entner-Dourodoff Pathway

  • Glucose catabolized to pyruvate but w/ different enzymes
  • Occurs in a few prokaryotes (but not eukaryotes)
  • ex. Pseudomonas aeruginosa & Enterococcus faecalis

Carbohydrate Catabolism: Fermentation

  • Uses an organic molecule as final electron acceptor (NAD+ → NADH)
  • Does not require O2
  • Produces 2 ATP per glucose molecule
  • Other Products: Various acids such as lactic acid; gases such as CO2; alcohols