Carbohydrates Flashcards
What are the functions of carbohydrates?
Energy storage
Structural and protective
Cell- cell recognition
What are the three main monosaccharides in human biochemistry?
Glucose
Galactose
Fructose
What are the three main disaccharides in human biochemistry?
Sucrose
Maltose
Lactose
What are the two glucose polymers contained in starch?
Amylose and Amylopectin
What is the difference between Amylose and Amylopectin?
Amylose is a straight chain molecule, containing only alpha 1-4 glycosidic bonds
Amylopectin is a branched molecule, containing alpha 1-4 and 1-6 glycosidic bonds
What is the structure of glycogen?
Glycogen is an extensively branched polymer of glucose, containing alpha 1-4 and 1-6 glycosidic bonds.
Does Starch have more reducing ends or non- reducing ends? Why?
It has more non- reducing ends which can be reacted with.
This allows it to be hydrolysed rapidly into monomers to be utilised by the body,
Why is Glucose stored as Starch in the body?
Compactness
Will not affect osmotic pressure, as insoluble starch is not in solution
What is the difference between glycoproteins and proteoglycans
Proteoglycans have a greater quantity of carbohydrate than protein.
Glycoproteins have greater quantity of protein than carbohydrate.
What is the role of cellulose and hemicellulose?
Increase faecal bulk and reduce transit time
How is glycogen degraded?
Glucose residues broken off glycogen one by one using Glycogen phosophorylase to yield G-1-P.
Transferase activity of enzyme near branching point breaks off 3 glucose residues and reattaches them to the nearest non-reducing end via alpha 1-4 glyosidic bonds.
What is the end product of glycolysis?
Pyruvate
How is ATP yielded in Glycolysis?
Substrate level phosphorylation
What are the substrate level phosphorylation reactions of glycolysis?
1,3- Bisphosphoglycerate +ADP -> ATP + 3- Phosphoglycerate
Phosphophenolpyruvte + ADP -> ATP + pyruvate
In what reaction is the catalyst glyceraldehyde-3-phoshpate dehydrogenase used?
Conversion of glyceraldehyde-3-phosphate into 1,3-bisphosphoglycerate
What two products is fructose-1,6- bisphosphate cleaved into using fructose-1,6-bisphosphate aldolase?
Dihydroxycetone phosphate and glyceraldehyde-3-phosphate
In what reaction is the catalyst phosphoglycerate mutase used?
Conversion of 3- Phosphoglycerate to 2- Phosphoglycerate
What catalyst is used to convert glucose-6- Phosphate to fructose- 6- phosphate?
Phosphohexose Isomerase
What enzyme is used to cleave fructose-1,6-bisphosphate in step 4 of glycolysis?
Fructose-1,6-bisphosphate aldolase
What catalyst is used in the conversion of 2- Phosphoglycerate to phosphophenol pyruvate?
Enolase
What is the product when fructose- 6- phosphate is reacted with enzyme phosphofructokinase?
Fructose-1,6-bisphosphate
What happens to lactate produced from anaerobic respiration?
Converted to Glucose in gluconeogenesis in liver
If conditions are anaerobic, what happens to pyruvate produced from glycolysis?
Reduced to lactate
This is driven by oxidation of NADH- so also replenishing NAD+ stores for continued glycolysis
What catalyst is used to convert dihydroxyacetone phosphate to glyceraldehyde-3-phosphate?
Triose phosphate isomerase
What happens to pyruvate produced from glycolysis in aerobic conditions?
Oxidised to Acetyl CoA in the mitochondria using pyruvate dehydrogenase- reducing NAD+ to NADH in the process.
In what part of the cell does the citric acid cycle occur?
Mitochondrial matrix
Which 3 Glycolysis pathways are irreversible?
Glucose + ATP -> Glucose-6-phosp. + ADP
Fructose-6-Phosphate + ATP -> Fructose-1,6-bisphosphate + ADP
Phosphoenolpyruvate + ADP -> Pyruvate + ATP
Where does the final step of gluconeogenesis to create free glucose occur?
Lumen of the ER
What are the functions of the pentose phosphate pathway?
Produce NADPH
Produce pentose (5C) sugars
Metabolises the small amount of pentose sugars in the diet.
