Biosynthetic Pathways Flashcards
Anabolic Pathways
forming of precursors (catabolic eg amino acids, fatty acids and sugar molecules), form complex molecules together and joining of complex molecules together (RNA and DNA)
Food Stores in Fed State
Plenty of nutrients, build up of food stores. Increase of insulin secretion and nutrient uptake. Glucose is made into glycogen, fatty acids form triglycerides and amino acids make protein
Food Stores in Starvation State
Lack of nutrients, food store broken down. Glycogenolysis, glucogenesis, lipolysis, proteolysis and ketogenesis
Glucogenesis Def
Formation of glucose from non-carbohydrate (lipid/protein) precursors when glycogen is depleted. Mix of reversible and irreversible steps. Need enzyme to undo irreversible processes, thus path requires energy
Examples of glucogenesis irreversible steps
PEP to pyruvate by pyruvate kinase and pyruvate to acetyl co A by pyruvate dehydrogenase
Substrates of Glucogenesis
Lactate, Glycerol and Amino Acids
Glucogenesis from Glycerol Substrate
Glycerol released from adipose tissues into blood by triglyceride hydrolysis. Glycerol is phosphorylated by glycerol phosphate by glycerol kinase (taken from ATP). Glycerol kinase exists in liver, kidney and intestines. Glycerol phosphate oxidised to DHAP
Acetyl Co A relation to glucogenesis
Acetyl Co A created in lipolysis and not used in glucogenesis (and can’t reform a lipid as pyruvate dehydrogenase is irreversible). High Acetyl Co A stimulates glucogenesis. Inhibits pyruvate dehydrogenase (inhibiting glycolysis)
High AMP relation to glucogenesis
inhibits 1,6-biphosphate (glucogenesis) and activates phosphofructase (glycolysis)
Glucogenesis from amino acid substrate
Converts to TCA cycle intermediate and ultimately form oxaloacetate (pyruvate carboxylase converted to Acetyl Co A) converted to PEP (PEP carboxykinase) and then glucose
Glucogenesis fructose 1,6-biphosphatase
Inhibited by AMP and by 2,6 biphosphate (which is increased by insulin)
Pyruvate kinase (glycolysis) balanced out by what in glucogenesis
pyruvate carboxylase and PEP carboxylase
Phosphofructokinase (glycolysis) is balanced out by what in glucogenesis
fructose 2, 6 - biphosphate
hexokinase/glucokinase (glycolysis) is balanced out by what in glucogenesis
Glucose 6 phosphate and glucose 6 phosphate translocase (adding phosphate from 6th C from ER)
Fatty Acid Oxidation
Forms ATP and NADH for glucogenesis
Pentose Phosphate (Hexose Monophosphate) Pathways Outline
Generates NADPH and 5 Carbon sugars for nucleic acids (DNA and RNA). More anabolic and catabolic. 2 Phases oxidative (NADPH) and cyclic (nucleic acids)
2 Irreversible Phases of Oxidative Pentose Phosphate Pathways
Glucose-6-P catalysed by glucose-6-phosphate dehydrogenase to ribulose -5-P, CO2 and NADH & 6-phosphogluconolacetone htdrolase
3 Reversible, Non-oxidative Phases
Catalyse interconversion of 3,4,5,6,7 carbon sugars, Ribose-5-P for DNA and RNA synthesis
NADPH Outline
Electron carrier for pathways. Acts as coenzyme for enzymes in antioxidants - detoxifying
Regulation of pentose phosphate pathway
Rate determined by concentration of substrate, rate determining step (glucose-6-P dehydrogenase). NADPH acts as inhibitor, Insulin acts as a stimulant
G6PD Deficiency
Caused by inheriting mutated G6PD (presents aminly in RBC). Results in insufficient production of NADPH causing Glutathione to not be regenerated resulting in oxadative damage
Oxidising Factors
Oxidant drugs (eg antibiotics), favism (fava beans), inflammatory response and neonatal jaundice
Results of oxidation of RBCs
Proteins are denatures (forming Heinz body’s). Happens most commonly in erythrocytes due to pentose phosphate pathway being only source of NADPH. Results in haemolytic anaemia
Amino Acid Biosynthesis
Amino acids aren’t stored and essential amino acids can’t be made in body. essential amino acids can be broken down into alpha-keto acids and rejoined to differnt ones to form non-essential amino acids. Excess is used as TCA cycle intermediates. excreted as urea
Glucogenic Amino Acids
Breakdown yields TCA cycle intermediates to make glucose
Ketogenic Amino Acids
Breakdown acetyl Co A
Aminotransferase
Move an amine group from alpha keto acid and alpha keto glutamate to alpha amino acids and glutamate
Alanine aminotransferase
Alanine + alpha keto glutarate to pyruvate + glutamate
Aspartate Aminotransferase
Oxaloacetate + glutamate to aspartate + alpha-ketoglutarate
Urea Cycle
Occurs in liver. 3 ATP/urea molecule. Water soluble transported in circulationand excreted in kidney
Purine Synthesis
De Novo and salvaging pre-existing molecules
Pyrimidine synthesis
De Novo
Relationship between ATP and GTP
Of equal energy. Both are needed in equal amounts for some reactions
Thymidylate synthase Outline
dUridine Diphosphate to dTMP by enzyme thymidylate synthase with cofactor tetrahydrofolate. Chemotherapy drugs target thymidylate synthase as it inhibits DNA production. Inhibited by 5- FU. Dihydrofolate reductase damages cofactors which also inhibits thmidylate synthase
Result of excess purine breaksown
Gout - excess of uric acid percipiatates as urate crystals. Causes inflammation of joints in pain
