Biosynthetic Pathways

Question 1

Anabolic Pathways

Answer 1

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)

Question 2

Food Stores in Fed State

Answer 2

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

Question 3

Food Stores in Starvation State

Answer 3

Lack of nutrients, food store broken down. Glycogenolysis, glucogenesis, lipolysis, proteolysis and ketogenesis

Question 4

Glucogenesis Def

Answer 4

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

Question 4

Examples of glucogenesis irreversible steps

Answer 4

PEP to pyruvate by pyruvate kinase and pyruvate to acetyl co A by pyruvate dehydrogenase

Question 5

Substrates of Glucogenesis

Answer 5

Lactate, Glycerol and Amino Acids

Question 6

Glucogenesis from Glycerol Substrate

Answer 6

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

Question 7

Acetyl Co A relation to glucogenesis

Answer 7

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)

Question 8

High AMP relation to glucogenesis

Answer 8

inhibits 1,6-biphosphate (glucogenesis) and activates phosphofructase (glycolysis)

Question 9

Glucogenesis from amino acid substrate

Answer 9

Converts to TCA cycle intermediate and ultimately form oxaloacetate (pyruvate carboxylase converted to Acetyl Co A) converted to PEP (PEP carboxykinase) and then glucose

Question 10

Glucogenesis fructose 1,6-biphosphatase

Answer 10

Inhibited by AMP and by 2,6 biphosphate (which is increased by insulin)

Question 11

Pyruvate kinase (glycolysis) balanced out by what in glucogenesis

Answer 11

pyruvate carboxylase and PEP carboxylase

Question 12

Phosphofructokinase (glycolysis) is balanced out by what in glucogenesis

Answer 12

fructose 2, 6 - biphosphate

Question 13

hexokinase/glucokinase (glycolysis) is balanced out by what in glucogenesis

Answer 13

Glucose 6 phosphate and glucose 6 phosphate translocase (adding phosphate from 6th C from ER)

Question 14

Fatty Acid Oxidation

Answer 14

Forms ATP and NADH for glucogenesis

Question 15

Pentose Phosphate (Hexose Monophosphate) Pathways Outline

Answer 15

Generates NADPH and 5 Carbon sugars for nucleic acids (DNA and RNA). More anabolic and catabolic. 2 Phases oxidative (NADPH) and cyclic (nucleic acids)

Question 16

2 Irreversible Phases of Oxidative Pentose Phosphate Pathways

Answer 16

Glucose-6-P catalysed by glucose-6-phosphate dehydrogenase to ribulose -5-P, CO2 and NADH & 6-phosphogluconolacetone htdrolase

Question 17

3 Reversible, Non-oxidative Phases

Answer 17

Catalyse interconversion of 3,4,5,6,7 carbon sugars, Ribose-5-P for DNA and RNA synthesis

Question 18

NADPH Outline

Answer 18

Electron carrier for pathways. Acts as coenzyme for enzymes in antioxidants - detoxifying

Question 18

Regulation of pentose phosphate pathway

Answer 18

Rate determined by concentration of substrate, rate determining step (glucose-6-P dehydrogenase). NADPH acts as inhibitor, Insulin acts as a stimulant

Question 19

G6PD Deficiency

Answer 19

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

Question 20

Oxidising Factors

Answer 20

Oxidant drugs (eg antibiotics), favism (fava beans), inflammatory response and neonatal jaundice

Question 20

Results of oxidation of RBCs

Answer 20

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

Question 21

Amino Acid Biosynthesis

Answer 21

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

Question 22

Glucogenic Amino Acids

Answer 22

Breakdown yields TCA cycle intermediates to make glucose

Question 23

Ketogenic Amino Acids

Answer 23

Breakdown acetyl Co A

Question 24

Aminotransferase

Answer 24

Move an amine group from alpha keto acid and alpha keto glutamate to alpha amino acids and glutamate

Question 25

Alanine aminotransferase

Answer 25

Alanine + alpha keto glutarate to pyruvate + glutamate

Question 26

Aspartate Aminotransferase

Answer 26

Oxaloacetate + glutamate to aspartate + alpha-ketoglutarate

Question 27

Urea Cycle

Answer 27

Occurs in liver. 3 ATP/urea molecule. Water soluble transported in circulationand excreted in kidney

Question 28

Purine Synthesis

Answer 28

De Novo and salvaging pre-existing molecules

Question 29

Pyrimidine synthesis

Answer 29

De Novo

Question 30

Relationship between ATP and GTP

Answer 30

Of equal energy. Both are needed in equal amounts for some reactions

Question 31

Thymidylate synthase Outline

Answer 31

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

Question 32

Result of excess purine breaksown

Answer 32

Gout - excess of uric acid percipiatates as urate crystals. Causes inflammation of joints in pain