MEH: Carbohydrates, Glycolysis, Pentose Phosphate Pathway

Question 1

What is the general formula of carbohydrates?

Answer 1

(CH2O)n

Question 2

What can carbohydrates contain?

Answer 2

Aldehyde groups, keto groups, multiple hydroxyl groups

Question 3

What are dextrins?

Answer 3

Oligosaccharides

Question 4

What is starch?

Answer 4

Storage molecule in plants which is a polymer of glucose

Question 5

What is glycogen?

Answer 5

Storage molecule in animals which is a polymer of glucose

Question 6

What 2 monosaccharides is sucrose composed of?

Answer 6

Glucose and fructose

Question 7

What 2 monosaccharides is lactose composed of?

Answer 7

Glucose and galactose

Question 8

What 2 monosaccharides is maltose composed of?

Answer 8

Glucose and glucose

Question 9

What enzyme is present in saliva that breaks down carbohydrates?

Answer 9

Amylase

Question 10

What does amylase in saliva break carbohydrates down into?

Answer 10

Dextrins

Question 11

What does amylase released from the pancreas break carbohydrates down into?

Answer 11

Monosaccharides

Question 12

Where are disaccharidases found?

Answer 12

Attached the brush boarder membrane of epithelial.

Question 13

What is primary lactase deficiency?

Answer 13

• Absence of lactase persistence allele

- Only occurs in adults

Question 14

What is secondary lactase deficiency?

Answer 14

• Caused by injury to the small intestine
• Occurs in children and adults
• Generally reversible

Question 15

What is congenital lactase deficiency?

Answer 15

Autosomal recessive defect in lactase gene

Question 16

Name some symptoms of lactose intolerance.

Answer 16

• Boating
• Cramps
• Flatulence
• Diarrhoea
• Vomiting
• Rumbling Stomach

Question 17

How are monosaccharides absorbed at the apical membrane?

Answer 17

Active transport by sodium dependant glucose transporter 1 (SGLT1)

Question 18

How are monosaccharides absorbed at the basal membrane?

Answer 18

Facilitated diffusion using transport proteins GLUT1- GLUT5

Question 19

Where are GLUT2 basal membrane receptors found?

Answer 19

• kidney
• liver
• pancreatic beta cells
• small intestine

Question 20

Where are GLUT4 basal membrane receptors found?

Answer 20

• adipose tissue
• striated muscle
• insulin regulated

Question 21

What is the normal concentration of glucose in blood plasma?

Answer 21

~5mM

Question 22

What is absolute requirement?

Answer 22

When cells can only metabolise energy from glucose, no other source.

Question 23

Name 4 places that have an absolute requirement.

Answer 23

• Red blood cells
• Neutrophils
• Kidney medulla
• Lens of eye

Question 24

What is different about the brain in regards to its metabolism preferences?

Answer 24

It prefers glucose as a fuel but can use ketone bodies for some energy requirements in times of starvation but needs time to adapt.

Question 25

Name the 2 phases of glycolysis.

Answer 25

1. Investment | 2. Payback

Question 26

What is the net gain of ATP from one glucose during glycolysis?

Answer 26

2 molecules

Question 27

What enzyme is required to convert glucose into glucose-6-phosphate?

Answer 27

Hexokinase (glucokinase in liver)

Question 28

What enzyme is required to convert fructose-6-phosphate to fructose 1,6-bisphosphate?

Answer 28

Phosphfructokinase-1

Question 29

What enzyme is required to convert phosphoenolpyruvate into pyruvate?

Answer 29

Pyruvate kinase

Question 30

What is the key control enzyme in glycolysis?

Answer 30

Phosphofructokinase-1

Question 31

In the first stage of glycolysis, glucose is phosphorylated. Why is this necessary?

Answer 31

- Makes glucose negatively charged preventing passage back across the plasma membrane - Increases reactivity

Question 32

Reactions 1 and 3 of glycolysis have a large -deltaG. What does this tell you about the reaction?

Answer 32

It's irreversible

Question 33

True or false: rate of glycolysis is up to 200x greater in cancer?

Answer 33

True, the uptake of a radioactive modified hexokinase substrate can be measured and imaged using positron emission tomography

Question 34

Name the 2 different ways phosphfructokinase can be regulated.

Answer 34

1. Allosteric (muscle) Inhibited by High ATP, Stimulated by high AMP 2. Hormonal (liver) Inhibited by glucagon, Stimulated by insulin

Question 35

Name 2 important intermediates of glycolysis and state their importance.

Answer 35

1. Glycerol phosphate (fat synthesis) | 2. 2,3-bisphosphoglycerate (modulates affinity of haemoglobin for oxygen)

Question 36

Is a tissue has no stage 3 or 4 metabolism (I.e. No ECT), what enzyme is required to regenerate NADH?

Answer 36

Lactate Dehydrogenase (LDH)

Question 37

Above what concentration is a patient diagnosed as having lactic acidosis?

Answer 37

About 5mM

Question 38

What is the purpose of the penthouse phosphate pathway?

Answer 38

Used to produce NADPH and ribose sugars

Question 39

Name the rate limiting enzyme in the pentode phosphate pathway.

Answer 39

G6PDH

Question 40

Is any energy required during the pentose phosphate pathway?

Answer 40

Nope:)