Carbohydrates 1

Question 1

Important Monosaccharides

Answer 1

• Glucose
• Galactose
• Fructose

Question 2

Important Disaccharides

Answer 2

• Maltose
• Lactose
• Sucrose

Question 3

Maltose characteristics

Answer 3

• Break down from starch

- Has anomeric C-1, can oxidise

Question 4

Lactose characteristics

Answer 4

• Formed from glycosidic bond between galactose and glucose

- Anomeric carbon on glucose, can oxidise

Question 5

Sucrose characteristics

Answer 5

• Only made by plants

- No free anomeric C-1, cannot oxidise

Question 6

Starch characteristics

Answer 6

-Contain 2 types of glucose polymer: Amylose + Amylopectin

Question 7

Synthesis of Glycogen

Answer 7

• 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

Question 8

Degradation of Glycogen

Answer 8

• 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

Question 9

Glucokinase Function

Answer 9

Adds phosphate to glucose making Glucose-6-Phosphate in liver

Question 10

Hexokinase function

Answer 10

Adds phosphate to glucose making Glucose-6-Phosphate in other tissues (not liver)

Question 11

Fate of Glucose-6-Phosphate

Answer 11

• Can convert to pentose
• Glycolysis to produce ATP
• Glycogen in skeletal muscle

Question 12

Glycogen in Skeletal muscle

Answer 12

Glycogen converted into Glucose-6-Phosphate then glycolysis into lactate

Question 13

Glycogen in Liver

Answer 13

Glycogen converted into Glucose-6-Phosphate, Glucose-6-Phosphatase converts G-6-P into glucose in the blood

Question 14

Irreversible steps of Glycolysis

Answer 14

Steps: 1, 3, 10

Question 15

Glycolysis definition

Answer 15

Cellular degradation of simple sugar, glucose, to yield ATP as an energy source

Question 16

Requirement for Glycolysis

Answer 16

NAD+ needed

Question 17

Fate of Pyruvate

Answer 17

• Ethanol (Yeast & Micro-organisms)
• Lactate (exercising muscles) [Can partake in Cori Cycle to glucose]
• Acetyl CoA (oxygen present, NADH formed)

Question 18

Process of step 1 & 2 of gluconeogenesis

Answer 18

Pyruvate -> Oxaloacetate -> Malate [in mitochondria]

Malate -> Oxaloacetate -> PEP (phosphoenolpyruvate) [in cytoplasm]

Question 19

Process of step 3 of gluconeogenesis

Answer 19

Fructose 1,6-biphosphate + H2O -> Fructose 6-phosphate

Question 19

Process of step 3 of gluconeogenesis

Answer 19

Fructose 1,6-biphosphate + H2O -> Fructose 6-phosphate

Question 20

Process of step 4 of gluconeogenesis

Answer 20

Glucose 6-Phosphate + H2O -> Glucose

Question 21

Sugars that can enter glycolysis

Answer 21

Fructose, Galactose