The bacterial cell is a typical prokaryotic cell.
Bacterial cell types on the basis of shape:
- Coccus: spherical. E.g., Monococcus, Diplococcus, Streptococcus (chain like), Staphylococcus (in bunches) & Sarcina (cube).
- Bacillus: rod shape.
- Vibrio: comma shaped.
Gram staining of bacteria:
- Bacterial cells are stained with Gram stain (crystal violet & 5% iodine).
- Cells become blue/purple.
- Washed with 95% alcohol/acetone.
-Bacteria that retains color is Gram +ve.
-Bacteria that loses color is Gram -ve.
Prokaryotic cell structure:
- Primitive nucleus. A single circular DNA associated with polyamines is present at the center. Also, referred as genophore or incipient nucleus.
- Outer protective covering that includes cell wall, cell membrane & Glycocalyx.
- Cell wall: made of peptidoglycan (murein). It is made of alternating units of N-acetyl glucosamine & N-acetyl muramic acid. Provide rigidity to the cell & provides shape.
- Cell membrane: made of phospholipid bilayer & proteins. They act as permeability barriers. Sterol like Hopanoids present.
- Glycocalyx: made of polysaccharides.
- Capsule is thick & tough. It is impermeable & prevents bacteria from drying and phagocytosis.
- Slime layer occurs as a loose sheath. It helps in attachment of bacteria to other cells.
Evolution: The geological time scale
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Precambrian (the era of early life).
Paleozoic (the era of ancient life).
Mesozoic (age of reptiles & gymnosperms).
Cenozoic: (age of mammals & angiosperms).
Dark reaction – Photosynthesis
- Also, known as the C3 cycle as the 1st stable compound produced is a 3C compound Phosphoglyceric acid (PGA).
- Occurs in the chloroplast of mesophyll cells.
- Initial acceptor of CO2 is a 5C compound Ribulose bisphosphate (RuBP).
- Carboxylation occurs with the help of Rubisco enzyme.
6RuBP + 6CO2 →12 3-PGA.
- Reduction: ATP & NADPH produced during light reaction are used to convert PGA to Glyceraldehyde-3-phosphate (G3P).
12 3-PGA + 12 ATP + 12NADPH → 12G3P + 12ADP + 12iP + 12NADP+.
- Formation of glucose: by using 2 molecules of G3P.
- Regeneration of 6RuBP: by using10 molecules of G3P & 6ATP