Glycolysis stage one.
Glycolysis - A metabolic pathway where each glucose molecule is broken down to two molecules of pyruvate. It occurs in the cytoplasm of all living cells and is common to anaerobic & aerobic respiration
Hydrolysis - the breaking down of large molecules to smaller ones by the addition of water
GLYCOLYSIS STAGE 1 - Phosphorylation
- 1 ATP molecule is hydrolysed and the phosphate group released
- Glucose 6-phosphate is changed to fructose 6-phosphate
- Another ATP is hydrolysed and the phosphate grouup released is attached to fructose 6-phosphate at carbon 1. This hexose sugar is now called fructose 1,6-bisphosphate
- The energy from the hydrolysed ATP molecules activates the hexose sugar and stops it from being transported out of the cell. Hexose 1,6-bisphosphate is a hexose sugar with two phosphates attached, one at carbon 1 and 6
- This stage has used two molecules of ATP for each molecule of glucose
Glycolysis stage two & three.
GLYCOLYSIS STAGE 2 - Splitting of hexose 1,6-bisphosphate
- Each molecule of hexose bisphosphate is split into two molecules of triose phosphate - 3-carbon sugar molecules each with one phosphate group attached
GLYCOLYSIS STAGE 3 - Oxidation of triose phosphate
- This process is ANAEROBIC. However, it does include oxidation.
- 2 hydrogen atoms (with their electrons) are removed from each triose phosphate molecule. This involves dehydrogenase enzymes
- Theses are aided by the coenzyme NAD (nicotinamide adenine dinucleotide) which is a hydrogen acceptor. NAD combines with hydrogen atoms, becoming reduced NAD
- At this stage, 2 molecules of NAD are reduced per mol of glucose
- And two molecules of ATP are formed. This is called substrate-level phosphorylation
Glycolysis stage four.
GLYCOLYSIS STAGE 4 - Conversion of triose phosphate to pyruvate
- 4 enzyme-catalysed reactions convert each triose phosphate molecule to a molecule of pyruvate. Pyruvate is also a 3-carbon compound
- In the process another 2 molecules of ADP are phosphorylated (inorganic phosphate group, Pi is added) to 2 molecules of ATP (by substrate-level phosphorylation)
PRODUCTS OF GLYCOLYSIS?
- 2 molecules of ATP. 4 have been made, but 2 had to be used to kick start the process, so net gain is 2 molecules of ATP
- 2 molecules of reduced NAD. These will carry hydrogen atoms, indirectly via a shunt mechanism, to the inner mitochondrial membranes and be used to produce more ATP during oxidative phosphorylation
- have an inner and outer phospholipid membrane. These make up the envelope
- The outer membrane is smooth, and the inner membrane is folded into cristae that give the inner membrane a large surface area
- The two membranes enclose and seperate the two compartments within the mitochondrion. Between the two membranes is the inter membranal space
- The matrix is enclosed by the inner membrane. It is semi-rigid and gel-like, consisting of a mixture of proteins and lipids. It also contains looped mitochondrial DNA, mitchondrial ribosomes, and enzymes.
Mitochondria - how does their structure enable the
The matrix - where the link reaction and Krebs cycle takes place. It contains:
- the enzymes that catalyse the stages of these reactions
- molecules of coenzyme NAD
- oxaloacetate - the 4-carbon compound that accepts acetate from the link reaction
- mitochondrial DNA, some of which codes for mitochondrial enzymes and other proteins
- mitochondrial ribosomes (structurally the same as prokaryote ribosomes) where these proteins are assembled.
The inner membrane:
- Has a different lipid composition from the outer membrane and is impermeable to most small ions, including hydrogen ions (protons)
- is folded into cristae and has electron carriers and ATP synthase enzymes
The electron carriers are arranged in electron transport chains.
- Each carrier is an enzyme, and is associated with a cofactor, which are non protein groups. They are haem groups and contain an iron group.
- cofactors can accept and donate electrons because the iron atoms can be reduced by accepting an electron and oxidised by donating an electron to the next electron carrier.
- they are oxidoreductase enzymes because they are involved in reduction and oxidation
- Some of the electro