We must be able to make glucose

Transcription

1 Biosynthesis of Carbohydrates Synthesis of glucose (gluconeogenesis) Glycogen Formation of pentoses and NADPH Photosynthesis We must be able to make glucose Compulsory need for glucose (above all the brain) Glycogen stores last about 24 h Glucose is synthesised from glycerol, lactate and amino acids (proteins) Reactions of gluconeogenesis Glucose is synthesised from glycerol, amino acids and lactate in gluconeogenesis Control of glycolysis and gluconeogenesis prevents that both processes are active simultaneously (reciprocal control). For thermodynamical reasons three steps of glycolysis gy y must be different in the corresponding one in gluconeogenesis The step between fructose 6-phosphat and fructose1,6-bisphosphate is the most important for the control 1

2 Three steps must be different in glycolysis and gluconeogenesis for thermodynamic reasons GLYCOLYSIS PEP + ADP Pyruvate + ATP GLUCONEOGENESIS Pyruvate + CO 2 + ATP + H 2 O Oxaloacetate + ADP + P i + 2H + Oxaloacetate + GTP PEP + GDP + CO 2 GLYCOLYSIS Fructose 6-phosphate + ATP Fructose 1,6-bisphosphate + ADP GLUCONEOGENESIS Fructose 1,6-bisphosphate + H 2 O Fructose 6-phosphate + P i GLYCOLYSIS Glucose + ATP Glucose 6-phosphate + ADP GLUCONEOGENESIS Glucose 6-phosphate + H 2 O Glucose + P i 2

3 Glycogen The structure and function of glycogen Degradation and formation of glycogen Hormonal control of glycogen metabolism Branched polymer of glucose Muscle glycogen is used to rapidly provide the muscle cells with glucose 6-phosphate which can give ATP in aerobic or anaerobic glycolysis Liver glycogen is used to keep the blood sugar lever constant between meals 3

4 Hormone (adrenalin) Adenylate cyclase Receptor G-protein GTP GDP ATP GTP camp Protein kinase A R 2 C 2 Protein kinase A 2R + 2C Glycogen synthase-p Phosphorylase kinase Phosphorylase kinase-p Glycogen synthase Cascade reaction leading to activation of glycogen phosphorylase Glycogen phosphorylase Glycogen phosphorylase-p Underlined forms are active Glycogen n Glycogen n-1 + Glucose-1-phosphate Pentose phosphate pathway leads to NADPH and ribose 5-phosphate NADP NADPH H 2 O H + Glucose 6-phosphate 6-Phosphogluconolactone 6-Phosphogluconate 1 2 NADP 3 1: Glucose 6-phosphate dehydrogenase NADPH 2: Lactonase 3: 6-Phosphogluconate dehydrogenase Ribulose 5-phosphate + CO 2 Ribulose 5-phosphate Ribose 5-phosphate Glycolysis molecules 3 Ribose 5-phosphate 2 fructose 6-phosphate + glyceraldehyde 3-phosphate 4

5 Photosynthesis 5

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7 Electron transport and phosphorylation are driven by sun-light 4. Return of protons give ATP Thylakoid membrane 2. Electron transport chain 3. Proton gradient established 1. Water is split into protons, electrons and oxygen 7

8 Light and dark reactions of photosynthesis H 2 O O 2 SOLAR ENERGY Light reaction ADP ATP NADP + NADPH Dark reaction Carbohydrates CO 2 + H 2 O 8

9 Calvin cycle (Dark reaction) 9

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11 Summary Glucose is synthesised from glycerol, amino acids and lactate in gluconeogenesis The pentose phosphate pathway leads to NADPH and ribose 5-phosphate Photosynthetic organisms absorb and direct solar energy through electron transport chains to synthesize ATP and NADPH. These high-energy h products are used for making carbohydrates from CO 2 and H 2 O. 11