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Module 4 Respiration. 1.4.3. Glycolysis. Learning Objectives . Success Criteria. To understand Glycolysis. State that Glycolysis takes place in the cytoplasm (Grade D) State that during aerobi c respiration in animals pyruvate is actively pumped into mitochondria (Grade C)
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Module 4Respiration 1.4.3. Glycolysis
Learning Objectives Success Criteria • To understand Glycolysis • State that Glycolysis takes place in the cytoplasm (Grade D) • State that during aerobi c respiration in animals pyruvate is actively pumped into mitochondria (Grade C) • Outline the process of Glycolysis (Grade B/A)
Evolutionary perspective Prokaryotes • first cells had no organelles Anaerobic atmosphere • life on Earth first evolved withoutfree oxygen (O2) in atmosphere • energy had to be captured from organic molecules in absence of O2 Prokaryotes that evolved glycolysis are ancestors of all modern life • ALL cells still utilize glycolysis
glucose pyruvate 6C 3C 2x Glycolysis - occurs in cytoplasm Breaking down glucose “Glyco – lysis” (splitting sugar) Ancient pathway which harvests energy • where energy transfer first evolved • transfer energy from organic molecules to ATP • still is starting point for ALL cellular respiration but it’s inefficient • generate only2 ATP for every 1 glucose That’s not enoughATP for me!
GLYCOLYSIS (carbohydrate splitting) • First stage of aerobic respiration & anaerobic respiration. • Doesn’t need O2 – so this stage is anaerobic! • Occurs in the cytoplasm of all living cells
Glycolysis - phosphorylation • The first stage actually begins by phosphorylating glucose to hexose 1,6-bisphosphate. • Each glucose uses 2 molecules of ATP
Glycolysis - phosphorylation Glucose ATP ADP Glucose 6 phosphate Fructose 6 phosphate ATP ADP Fructose 1,6-bisphospahte
Glycolysis - lysis • This stage involves the breaking of the hexose bisphosphate into two triose phosphate molecules. • The triose phosphate is an intermediate in many biochemical reactions. • The phosphate group allows the sugar to form stronger interaction with the next enzyme in the pathway.
Glycolysis – oxidation/ATP formation • Each Triose phosphate is oxidised to a 3 carbon molecule called Pyruvate • Each Triose Phosphate has hydrogen removed (oxidation) to reduce one NAD+ to NADH + H+ • Each Triose Phosphate adds a phosphate to ADP reducing this to ATP (substrate level phosphorylation) Note that each Triose phosphate releases enough energy for the formation of two ATP
Summary of glycolysis • Glycolysis takes place in the cytoplasm of the cell. • It does not require oxygen. • The hexose sugar (glucose) is converted into two 3C atoms compounds called pyruvate. • Two ATP are consumed but four are produced making a net gain of 2 ATP • Two NADH + H+ are produced which will yield more ATP when they are transferred to the mitochondria and oxidative phosphorylation. • Yield: 2 Pyruvate + 2 ATP + 2NADH + 2H+
NAD+ + 2H NADH + H+(oxidised form ) (reduced form) NB Rather then write NADH, examiners often simply refer to it as reduced NAD or reduced coenzyme Glycolysis Glycogen You start with glycogen. 2 ATP 4 ATP 4 ADP + 4Pi Triose -phosphate (3C x 2) Pyruvate (3C x2) Glucose (6C) 2H x 2 NAD Reduced NAD 2 ADP Nicotinamide adenine dinucleotide = So it gains electrons You finish with Pyruvate Why is Glycolysis termed anaerobic? What is the NET production of ATP?
The sums • The end products of glycolysis are pyruvate and reduced NAD • Energy is released during this reaction. • 4 molecules of ADP + Pi converted to 4 molecules of ATP. • So net gain of 2 molecules of ATP • 2 pairs of hydrogen atoms produced • 2 Molecules of pyruvate.
Products of Glycolysis • 2 reduced NAD (NADH + H+) • 2 Pyruvate • 2 ATP
The Fate of Pyruvate! THIS DEPENDS ON THE AVAILABILITY OF OXYGEN!!!
Task • Complete exam questions (SA)
Plenary Make list of what is needed for glycolysis and what is produced Explain where oxidation occurs and substrate level phosphorylation
Learning Objectives Success Criteria • To understand Glycolysis • State that Glycolysis takes place in the cytoplasm (Grade D) • State that during aerobi c respiration in animals pyruvate is actively pumped into mitochondria (Grade C) • Outline the process of Glycolysis (Grade B/A)