Biochemistry

Question 1

Which cells in the Islets of Langerhans secrete insulin?

Answer 1

Beta-cells

Question 2

Which cells in the Islets of Langerhans secrete glucagon?

Answer 2

Alpha-cells

Question 3

Which cells in the Islets of Langerhans secrete somatostatin?

Answer 3

Delta-cells

Question 4

What is the initial structure that is cleaved to form insulin?

Answer 4

Preproinsulin

Question 5

There is great variation in the amino acid sequence of insulin between species. True/False?

Answer 5

False

Very little variation

Question 6

What is the effect of insulin upon amino acids, glucose and lipids?

Answer 6

Increases uptake into respective tissues

amino acid in muscle, glucose in muscle, lipid in adipose

Question 7

Insulin inhibits lipolysis. True/False?

Answer 7

True

Question 8

Through which transporter does glucose enter beta-cells in the pancreas?

Answer 8

GLUT2

Question 9

What happens to glucose once in the beta-cell in the pancreas?

Answer 9

Phosphorylated to glucose-6-phosphate

Question 10

Which enzymes carry out glucose phosphorylation?

Answer 10

Glucokinase

Hexokinase (RBCs)

Question 11

Which two proteins make up a functional Katp channel?

Answer 11

Kir6.1
Sulphonylurea receptor (SUR1)

Question 12

What inhibits the Katp channel? What happens as a result?

Answer 12

Intracellular ATP, causing depolarisation (less K efflux), causing opening of Ca channels to allow insulin exocytosis

Question 13

What is MODY?

Answer 13

Maturity-onset diabetes of the young

Genetic defect in beta-cell function, causing early-onset type II diabetes

Question 14

Which enzyme is impaired in MODY?

Answer 14

Glucokinase

causing defective glucose sensing

Question 15

How are ketone bodies formed?

Answer 15

Derived from acetyl-CoA in B-oxidation

Question 16

Give examples of ketone bodies

Answer 16

Acetone
Acetoacetic acid
B-hydroxybutric acid

Question 17

Ketoacidosis is most associated with which diabetes - type 1 or 2?

Answer 17

Type 1

Question 18

Sodium follows water everywhere. True/False?

Answer 18

False
Water follows sodium!
(WafS)

Question 19

Concentration of Na inside the cell is more than concentration of Na outside the cell. True/False?

Answer 19

False

Concn of Na outside cell is greater than inside

Question 20

What does mineralocorticoid activity refer to?

Answer 20

Sodium retention in exchange for potassium and/or hydrogen ions

Question 21

What is the main steroid in the body with mineralocorticoid activity?

Answer 21

Aldosterone

Question 22

Excess mineralocorticoid activity causes what?

Answer 22

Sodium retention

Question 23

What effect does sodium loss have upon water?

Answer 23

Sodium loss means water loss (water follows sodium!)

Question 24

Outline what happens in terms of sodium and water when blood pressure drops

Answer 24

Decreased blood pressure causes sodium + water retention in order to compensate and bring blood pressure up

Question 25

Which hormone controls water reabsorption?

Answer 25

ADH

Question 26

What effect does ADH have on water reabsorption and thus urine output?

Answer 26

Causes increased water reabsorption (anti-diuresis), producing low-volume concentrated urine

Question 27

Concentrated/small volume urine has a high omolality. True/False?

Answer 27

True

Question 28

What are the main causes of decreased sodium levels?

Answer 28

Too much water

Too little sodium

Question 29

What are the main causes of increased sodium levels?

Answer 29

Too little water

Too much sodium

Question 30

Decreased sodium levels can be due to too much water. How can this arise?

Answer 30

SIAD (inappropriate ADH secretion)

Compulsive water drinking

Question 31

Decreased sodium levels can be due to too little sodium. How can this arise?

Answer 31

Sodium loss (renal insufficiency, gut fistulae)
Decreased sodium intake (rare)

Question 32

Increased sodium levels can be due to too little water. How can this arise?

Answer 32

Water loss (diabetes insipidus)
Decreased water intake

Question 33

Increased sodium levels can be due to too much sodium. How can this arise?

Answer 33

IV medication
Drowning in sea
High-salt feeds

Question 34

Outline pathogenesis of Addison’s disease

Answer 34

Adrenal insufficiency;
can't make enough aldosterone;
can't retain enough sodium;
lose sodium + water;
low ECF volume, so patient is dehydrated + dizzy

Question 35

What is the main osmotic stimulus for ADH release?

Answer 35

High sodium (high osmolality) causes increased ADH

Question 36

Does hypovolaemia cause increased or decreased ADH release?

Answer 36

Increased ADH release (to compensate for loss of fluid)

Question 37

Outline pathogenesis of diabetes insipidus

Answer 37

Disrupted pituitary;
can't secrete ADH;
less water reabsorption;
lots of water lost in urine;
sodium is high to reflect water deficit