Carbohydrates 1 Flashcards
Important Monosaccharides
- Glucose
- Galactose
- Fructose
Important Disaccharides
- Maltose
- Lactose
- Sucrose
Maltose characteristics
- Break down from starch
- Has anomeric C-1, can oxidise
Lactose characteristics
- Formed from glycosidic bond between galactose and glucose
- Anomeric carbon on glucose, can oxidise
Sucrose characteristics
- Only made by plants
- No free anomeric C-1, cannot oxidise
Starch characteristics
-Contain 2 types of glucose polymer: Amylose + Amylopectin
Synthesis of Glycogen
- Glycogenin makes glucose bind to uracil-diphosphate (UDP) -glucose to form chains of around 8 glucose residues
- Glycogen synthase extends glucose chains
- Chains formed are broken by glycogen-branching enzyme and re-attached via (alpha1 -> 6) bonds to give branch points
Degradation of Glycogen
- Glucose monomers are removed one at a time from non-reducing ends as Glucose-1-Phosphate
- After final glucose residue removal, by glycogen phosphorylase, glucose near the branch is removed by 2-step process by debranching enzyme
- Transferase activity of de-branching enzyme removes a set of 3 glucose residue and attaches them to nearest non-reducing end via (alpha 1 -> 4) bond
- Glucosidase activity removes final glucose, breaking (alpha 1-> 6) linkage
- Unbranched chain can be degraded or built upon
Glucokinase Function
Adds phosphate to glucose making Glucose-6-Phosphate in liver
Hexokinase function
Adds phosphate to glucose making Glucose-6-Phosphate in other tissues (not liver)
Fate of Glucose-6-Phosphate
- Can convert to pentose
- Glycolysis to produce ATP
- Glycogen in skeletal muscle
Glycogen in Skeletal muscle
Glycogen converted into Glucose-6-Phosphate then glycolysis into lactate
Glycogen in Liver
Glycogen converted into Glucose-6-Phosphate, Glucose-6-Phosphatase converts G-6-P into glucose in the blood
Irreversible steps of Glycolysis
Steps: 1, 3, 10
Glycolysis definition
Cellular degradation of simple sugar, glucose, to yield ATP as an energy source
Requirement for Glycolysis
NAD+ needed
Fate of Pyruvate
- Ethanol (Yeast & Micro-organisms)
- Lactate (exercising muscles) [Can partake in Cori Cycle to glucose]
- Acetyl CoA (oxygen present, NADH formed)
Process of step 1 & 2 of gluconeogenesis
Pyruvate -> Oxaloacetate -> Malate [in mitochondria]
Malate -> Oxaloacetate -> PEP (phosphoenolpyruvate) [in cytoplasm]
Process of step 3 of gluconeogenesis
Fructose 1,6-biphosphate + H2O -> Fructose 6-phosphate
Process of step 3 of gluconeogenesis
Fructose 1,6-biphosphate + H2O -> Fructose 6-phosphate
Process of step 4 of gluconeogenesis
Glucose 6-Phosphate + H2O -> Glucose
Sugars that can enter glycolysis
Fructose, Galactose
