Metabolism

Question 1

What is catabolism?

Answer 1

Breakdown of large molecules into smaller ones to release energy in the form of ATP

Question 2

What is the general formula for Carbohydrates?

Answer 2

(CH2O)n

Question 3

Define an oligosaccharide.

Answer 3

A carbohydrate containing 3-12 sugar units

Question 4

The disaccharide Sucrose is formed from which monosaccharides?

Answer 4

Glucose and Fructose

Question 5

What is the disaccharide found in milk and what are it’s constituent monosaccharides?

Answer 5

Lactose

Galactose and Glucose

Question 6

Starch and glycogen are both storage molecules; which molecule is found where?

Answer 6

Starch - Plants

Glycogen - Animals

Question 7

Which enzyme is found in saliva and what is it’s function at this point?

Answer 7

Amylase - Starch/Glycogen breakdown into dextrins

Question 8

Other than the salivary glands, which organ secretes amylase? What is it’s role?

Answer 8

The pancreas

Breakdown of dextrins into monosaccharides

Question 9

Why can’t humans digest cellulose?

Answer 9

Humans are unable to perform significant hydrolysis on the beta 1-4 linkage

Question 10

Lactose intolerance can present in three different ways. These are …

Answer 10

Primary lactase deficiency
Secondary lactase deficiency
Congenital lactase deficiency

Question 11

What are some symptoms of lactose intolerance?

Answer 11

Bloating/cramps
Flatulence
Diarrhoea
Vomiting
Rumbling stomach

Question 12

What is primary lactase deficiency?

Answer 12

Absence of lactase persistence allele and it only occurs in adults

Question 13

What causes secondary lactase deficiency?

Answer 13

Caused by injury to small intestine, as a result of Coeliac disease, Crohn’s, UC etc., and is generally reversible

Question 14

What is congenital lactase deficiency and why is it more dangerous?

Answer 14

It is as a result of an autosomal recessive defect in lactase genes and means that children are unable to digest breast milk

Question 15

How are monosaccharides, such as glucose, absorbed from the gut into the blood?

Answer 15

Active transport by SGLT1 into intestinal epithelial cells and then by GLUT2 into blood

Question 16

What transport proteins are responsible for the facilitated diffusion of monosaccharides into Ella from the blood?

Answer 16

GLUT1 - GLUT5

Question 17

Where are GLUT2 found?

Answer 17

Kidney, Liver, Pancreatic beta cells, Small intestine

Question 18

Where are GLUT4 found?

Answer 18

Adipose tissue, striated muscle

Question 19

Briefly outline glycolysis.

Answer 19

An intracellular cytosolic pathway in which monosaccharides are converted into pyruvate/lactate

Question 20

What is the net ATP produced from the glycolysis of one glucose molecule?

Answer 20

Spend 2, Make 4, Net 2

Question 21

Name the coenzyme which is reduced in gcolysis.

Answer 21

NAD+ -> NADH

Question 22

Name the one additional enzyme which allows for glycolysis to operate anaerobically.

Answer 22

PDH

Question 23

Name the three key enzymes involved in glycolysis and state their pathways.

Answer 23

Hexokinase
Glucose -> Glucose-6-P

Phosphofructokinase-1
Fructose-6-P ->Fructose-1,6-bis-P

Pyruvate kinase
Phosphoenolpyruvate -> Pyruvate

Question 24

What is the alternate name for Hexokinase when found in the liver?

Answer 24

Glucokinase

Question 25

Which molecule inhibits the action of Hexokinase?

Answer 25

Glucose-6-P

Question 26

Outline the first phase of glycolysis.

Answer 26

Phosphorylation of glucose to G-6-P and makes glucose negatively charged. Increases reactivity of glucose. Glucose -> Glucose-6-P -> Fructose-6-P -> Fructose 1,6-bis-P

Question 27

Outline phase 2 of glycolysis.

Answer 27

Cleavage of C6 -> 2x C3 Reducing power captured (NADH) Fructose 1,6-bis-P -> Glyceraldehyde 3-P -> 1,3-bis phosphoglycerate -> 3-phosphoglycerate + ATP -> 2-phosphogycerate -> phosphoenolpyruvate ->Pyruvate + ATP

Question 28

Relative to healthy tissue, what is the rate of glycolysis like in cancer?

Answer 28

Up to 200 times greater