MCBG S17 Catabolism And Glycolysis

Question 1

Where does stage 1 of metabolism occur?
What does it involve?
Are the pathways long or short?
What bonds are broken?
Is energy released?

Answer 1

GI tract - extracellularly 
Breakdown of macromolecules to smaller building block molecules for absorption. 
Short
C-O and C-N - no C-C bonds
No

Question 2

Where does stage 2 of metabolism occur?
What does it involve?
What is made?
Oxidative or reductive?

Answer 2

• Cytosol or mitochondria
• Breakdown of building blocks to smaller primary metabolites
• NADH and ATP
• Oxidative

Question 3

Where does stage 3 of metabolism occur?
What is it called?
Oxidative or reductive?
Overall reaction?
What does it make?

Answer 3

In the mitochondrial matrix
TCA cycle
Oxidative
AcetylCoA to 2CO2
GTP, FADH2, NADH, precursors for biosynthesis.

Question 4

Where does stage 4 of metabolism occur?
What is it called?
What does it involve?

Answer 4

Mitochondria
Oxidative phosphorylation
Reducing power (NADH,FADH2) to ATP.

Question 5

What is the general formula for a carbohydrate?

Answer 5

(CH2O)n

Question 6

What are carbohydrates that contain aldehyde or ketones called?

Answer 6

Aldoses

Ketoses

Question 7

How many carbons can a monosaccharide have?

Answer 7

3-9

Question 8

What is glucose concentration in the blood?

Answer 8

5mM

Question 9

What cells have an absolute requirement for glucose?

Answer 9

RBCs
Neutrophils
Inner most cells of the kidney medulla
Lens of eye

Question 10

What does salivary amylase break down?

Answer 10

Starch, glycogen to dextrins

Question 11

What do pancreatic amylase breakdown?

Answer 11

Dextrins to monosaccharides

Question 12

What type of bond can pancreatic amylase breakdown?

Answer 12

Alpha 1,4-glycosidic bonds

Question 13

What bond does isomaltase break?

Answer 13

Alpha 1,6 glycosidic bond

Question 14

What are the 3 main causes of lactose intolerance?

Answer 14

Primary lactase deficiency
Secondary ^
Congenital ^

Question 15

What is primary lactase deficiency?

Does it occur in younger children?

Which areas have highest prevalence?

Answer 15

A sense of lactase persistence allele.

Only adults

Northwest Europe

Question 16

What is secondary lactase deficiency caused by?

Answer 16

Injury to small intestine

• Gastroenteritis
• Coeliac disease
• Crohn’s disease
• Ulcerative colitis

Question 17

What is Crohn’s disease?

Answer 17

Type of IBD can affect any part of GI tract from mouth to anus.

Question 18

What is ulcerative colitis?

Answer 18

Inflammation of the colon and rectum

Small ulcers develop in the colon lining, bleed and produce pus.

Question 19

What causes congenital lactase deficiency?

Answer 19

Autosomal recessive defect in lactase gene.

Question 20

What are 5 symptoms of lactase intolerance?

Answer 20

• Bloating
• Cramps
• Flatulence
• Diarrhoea
• Rumbling stomach

Question 21

WHere are GLUT 1, GLUT2, GLUT3, GLUT 4 and GLUT 5 found?

Answer 21

GLUT1= foetal tissues, RBCs, BBB
GLUT2= panc B cells, SI, liver, kidney 
GLUT3=neurones and placenta
GLUT4= adipose,striated muscle
GLUT5= sperm and intestine.

Question 22

What are the functions of glycolysis?

Answer 22

Oxidation of glucose to pyruvate
NADH production 2/ glucose
ATP - 2 net
6 and 3 C intermediates produced.

Question 23

Decarboxylation occurs in glycolysis true or false?

Answer 23

False

Question 24

What step commits glucose to glycolysis?

Answer 24

Step 3 PFK1

Question 25

How many irreversible steps are there in glycolysis and what are they?

Answer 25

3

Hexokinase - reaction 1

PFK - reaction 3

Pyruvate kinase - reaction 10

Question 26

Why are there so many steps?

Answer 26

Chemistry easier in small steps
To allow for interconnections
To produce useful intermediates
To allow for control at different levels.

Question 27

Give a clinical application of glycolysis.

Answer 27

Glycolysis rate 200x faster in cancer cells

Give radioactively labelled hexokinase substrate and image with positron emission tomography.