Membrane transport:
- 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
- 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
