These notes cover the first half of the content taught by Dr. Khan and include potential questions for each section. The notes are clear and comprehensive as well as provide an excellent summary of the work. Study well from these, and you're guaranteed a distinction!
- The aim of the cell is reproduction
- The first step in nutrient use is the
uptake of nutrients needed by the
cell
- The uptake mechanisms must be
specific – necessary substances
must be acquired
- A microbe must be able to incorporate large amounts of nitrogen, phosphorous and sulphur
in order to grow
- Nitrogen is needed to synthesise amino acids, purines/pyrimidines, some carbohydrates,
lipids and co-factors etc.
- Phosphorous is present in nucleic acids, phospholipids, nucleotides like ATP, proteins, etc.
- Sulphur is needed for the synthesis of amino acids (cysteine and methionine),
carbohydrates, biotin etc.
- If the cell cannot use membrane transport then it cannot bring nutrients into the cell or
reproduce
- Metabolism is a crucial process in cells and without it, the essential components cannot be
made
- Catabolic reactions: break down
- Anabolic reactons: build up
- Class 1:
o Degradative reactions (Catabolic)
o Sugars, proteins etc. broken into
smaller carbon compounds.
o Net process is exergonic i.e. energy
released
o Reactions also be considered as
Amphibolic as carbon skeletons are
produced which are used in
biosynthetic reactions
- Class 2:
o Biosynthetic reactions (anabolic)
o Small molecules synthesised e.g. amino acids, nucleotides, hexosamines etc.
o Monomers which are incorporated into macromolecules
o Included in this category is synthesis of vitamins and co-factors which are not
incorporated into macromolecules.
o Energy requiring reactions
- Class 3:
o Polymerisation of monomers
o DNA, protein, peptidoglycans etc.
o When enough have been synthesised, cell divides
o Anabolic, energy-requiring reactions
- Class 1, 2 and 3 reactions apply to heterotrophs only
- Microbes often live in nutrient poor habitats thus must be able to transport nutrients from
dilute solutions into cell against concentration gradient
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