OCR RESPIRATION

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  • Created by: Georgia
  • Created on: 19-05-11 16:33

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
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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

 

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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
  • 
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Mitochondrial ultrastructure.

Mitochondria

  • 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.
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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
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Electron carriers.

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
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