Starter For some light relief..although biologically correct!! Remember???? Remind yourself!

Glycolysis: True or False Glycolysis produces a net gain of 4 ATP molecules The co-enzyme NADH is oxidised during glycolysis When coenzymes become reduced, they carry hydrogen molecules Glycolysis takes place in the matrix of the mitochondrion In glycolysis, glucose is converted in this order: glucose, triose phosphate, hexose bisphosphate then pyruvate If you think they are false, you must write the correct version- and there are false ones!!!

Glycolysis produces a net gain of 4 ATP molecules- False: the net gain is 2 ATPs as 2 are used up The co-enzyme NADH is oxidised during glycolysis- False: NAD is reduced during glycolysis to form NADH When coenzymes become reduced, they carry hydrogen molecules- False: they carry hydrogen atoms, not molecules or ions Glycolysis takes place in the matrix of the mitochondrion- False: it takes place in the cytoplasm In glycolysis, glucose is converted in this order: glucose, triose phosphate, hexose bisphosphate then pyruvate- False: the correct order is glucose, hexose bisphosphate, triose phosphate, pyruvate

Cellular Respiration

The Start of the Krebs Cycle Some History first… The Krebs Cycle (also known as the Tricarboxylic Acid cycle – TCA cycle for short) is named after Sir Hans Krebs, a German – British scientist who pieced together the 8 series of reactions.

Glycolysis releases less than a quarter of the chemical energy stored in glucose, most of the energy remains stocked in the two molecules of pyruvate. Pyruvate is the starting block for the Krebs Cycle........

The Start of the Krebs Cycle If oxygen is present, the pyruvate enters the mitochondrial matrix (via a transport protein), where the enzymes of the Krebs cycle complete the oxidation of the organic fuel Cytosol Mitochondria O- C O Pyruvate Transport Protein C O CH3 What type of respiration will be occurring in this example? AEROBIC RESPIRATION

The Link Reaction learning outcomes State that the link reaction takes place in the mitochondrial matrix; Outline the link reaction, with reference to decarboxylation of pyruvate to acetate and the reduction of NAD; Explain that acetate is combined with coenzyme A to be carried to the next stage;

The Link Reaction The link reaction happens when oxygen is available… For each glucose molecule used in glycolysis, two pyruvate molecules are made But the link reaction uses only one pyruvate molecule, so the link reaction and the Krebs cycle happen twice for every glucose molecule which goes through glycolysis The link reaction happens in the matrix of the mitochondrion

The function is to carry the acetate into the Krebs cycle Pyruvate 3C Decarboxylation- removal of a carboxyl group (which becomes CO2) by the enzyme pyruvate decarboxylase 1C CO2 Dehydrogenation- the enzyme pyruvate dehydrogenase removes hydrogen atoms from pyruvate and NAD accepts it 2C acetate NAD Coenzyme A (CoA) Accepts the 2C acetate NADH 2C Acetyl CoA The function is to carry the acetate into the Krebs cycle

Tasks Summarise the link reaction State the products of the link reaction for each glucose molecule

The Products of the Link Reaction go to the Krebs Cycle So for each glucose molecule: Two molecules of acetyl co enzyme A go into the Krebs cycle Two carbon dioxide molecules are released as a waste product of respiration (decarboxylation) Two molecules of reduced NAD are formed and go into the electron transport chain (dehydrogenation)

Exam Questions Describe what happens in the link reaction (4)

Answers The 3-carbon pyruvate is combined with coenzyme A (1) to form a 2-carbon molecule, acetyl coenzyme A (1). The extra carbon is released as carbon dioxide (decarboxylation of pyruvate) (1). The coenzyme NAD is converted into reduced NAD in this reaction by accepting hydrogen ions (dehydrogenation of pyruvate)

The Challenge: Whiteboards Can you draw glycolysis and the link reaction….?