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Endocrinology > Biochemistry > Flashcards

Biochemistry Flashcards

(60 cards)

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1
Q

Beta cells are the only cells in the body capable of making insulin true or false

A

True

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2
Q

What do PP cells of the pancreatic islet secrete

A

Pancreatic polypeptide

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3
Q

Describe how insulin is synthesized

A

Made in RER of beta cells as large single chain preproinsulin
Cleaved to form mature insulin

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4
Q

Describe the structure of insulin

A

Two polypeptide chains linked by disulphide bonds

Has a connecting C peptide - no known function

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5
Q

What is the main difference between the different insulin preparations used clinically

A

How long acting they are in the body

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6
Q

Give an example of ultra-short acting insulin

A

Insulin lispro
Position of Lys and Pro are switched in chain
Usually taken when eating

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7
Q

Give an example of ultra-long acting insulin

A

Insulin glargine
Asp at end of A chain is switched to Gly
2 Arg are added to end of B

Given at night to prevent hypoglycemia at night

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8
Q

What effect does increased glucose metabolism have on ATP

A

Leads to an increase in intracellular ATP concentration

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9
Q

How many ATP molecules are produced per glucose

A

36

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10
Q

Which channel does ATP inhibit

A

The ATP-sensitive K+ channel KATP

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11
Q

What does inhibition of the KATP channel cause

A

Depolarisation of cell membrane
Opening of voltage-gated Ca2+ channels
Increase of internal Ca2+ causes insulin release from vesicles

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12
Q

What happens to beta cells in T1DM

A

Mostly lost

Autoimmune process

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13
Q

Insulin release is biphasic - true or false

A

True

2nd phase is dependent on how well the 1st phase has dealt with glucose increase

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14
Q

What forms the 2 phases of insulin release

A

1st phase - immediate release insulin (5% total)

2nd phase - reserve pool that must undergo preparation reactions before release

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15
Q

Which class of drugs directly inhibits the KATP channel

A

Suphonylurea

Second line in T2DM

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16
Q

Which drug stimulates the KATP channel

A

Diazoxide

Inhibits insulin secretion

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17
Q

What can mutations in Kir6.2 r SUR1 lead to

A

neonatal diabetes
usually responds to SURs

Hyperinsulinism
Can be helped by diazoxide

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18
Q

How do you differentiate between MODY and T1DM

A

Robust genetic screening

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19
Q

How does treatment differ between MODY and T1DM

A

MODY - treated with sulphonylurea

T1DM - treated with insulin

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20
Q

What is the effect of insulin on DNA and protein synthesis

A

Switches these processes on

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21
Q

What is the effect of insulin on gluconeogenesis in the liver

A

Switches it off

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22
Q

Which type of receptor is the insulin receptor

A

Receptor tyrosine kinase

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23
Q

Through which pathways can insulin stimulation cell growth

A

PI3K

Ras

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24
Q

What can cause insulin resistance

A

Reduced insulin sensing and/or signalling

Associated with obesity - most common
Also seen in complete lack of adipose tissue

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25
Describe the cause of T2DM
Polygenic with large environmental input | Associated with obesity
26
What is Donohue syndrome
Rare autosomal recessive disorder Mutation is in the gene for insulin receptor Severe insulin resistance Also cause leprechaunism Patients have elfin facial features, growth retardation and absence of fat
27
What is Rabson Mendenhall syndrome
Rare autosomal recessive condition Severe insulin resistance - hyperglycaemic and high insulin Get hypoglycemic attacks and ketoacidosis
28
What are the symptoms of diabetic ketoacidosis
Vomiting Dehydration Increased heart rate Distinctive smell on breath
29
Where are ketone bodies formed
Liver mitochondria
30
What is the physiological use for ketone bodies
Travel through blood to peripheral tissue where the are used for energy metabolism in the heart muscle and renal cortex
31
What happens if there is an excess of ketones in the blood
Leads to acidosis
32
Where is ADH released from
The posterior pituitary
33
What is the function ADH
Control of water balance Makes you pee less by causing water reabsorption in the renal tubules Urine will be more concentrated
34
How is urine concentration measured
Measured in urine osmolality | Concentrated urine has a high osmolality
35
What can cause ADH to stop functioning
Can stop being produced after head trauma etc Kidneys can be resistant Will start peeing out huge volumes
36
What controls sodium balance
Steroids released from adrenals | Their effect is known as mineralocorticoid activity
37
Which steroids have mineralocorticoid activity
Mainly aldosterone | Others such as cortisol also have the effect
38
What does too much mineralocorticoid activity cause
sodium gain | occurs with hormone excess such as Cushing's
39
What does too little mineralocorticoid activity cause
Sodium loss
40
What balance can cause low sodium
too little sodium itself (lost from ECF) OR too much water – dilutes every body compartment
41
What balance can cause high sodium
too much sodium (gained exclusively in ECF) OR too little water (lost from all compartments)
42
Which body compartment has the greatest volume of water
Intracellular | Has twice as much
43
Which compartment is water found in
It's present in all compartments Can move between them all as well Therefore loss/gain of water occurs from the whole body
44
Which compartment is sodium found in
Confined to the extracellular fluid | Loss or gain of sodium occurs solely from ECF
45
How is the movement of water and sodium linked
Water follows solute by osmosis As Na is the most abundant solute it pretty much always follows Na if you lose/gain Na+ from the ECF, you lose/gain water with it.
46
What are the symptoms of sodium loss
Very symptomatic Dehydrated - dryness, low urine output Hypotensive Tachycardia
47
What are the symptoms of sodium gain
Symptoms of fluid overload Swelling of abdomen, legs Pulmonary oedema etc
48
What are the symptoms of water gain/loss
Often mostly asymptomatic | This is because effect on individual compartments is minor
49
What can cause low sodium
Diarrhoea and vomiting Loss of fluid through skin in burn victims Loss of Na through kidneys – due to steroid hormones not working Can be fatal Decreased sodium intake (rare)
50
What can cause high water content (therefore lower sodium)
Decreased water excretion - SIADH (very common) | Increased water intake is rare
51
What can cause increased sodium
``` Increased sodium intake Near drowning in salt-water Malicious Some iV meds Deceased sodium loss All very rare ```
52
What can cause low water levels (therefore high sodium)
Increased water loss - diabetes insipidus etc | Decreased water intake - common
53
How do you treat low sodium levels
If due to too little Na - gove sodium | If due to too much water - fluid restrict
54
How do you treat high sodium
Too much Na- remove sodium | Too little water - give water in form of dextrose
55
What is SIADH
Syndrome of inappropriate ADH Non-osmotic stimuli can cause release when it's not needed E.g. hypovolaemia/hypotension, pain, nausea/vomiting
56
What is the cause of oedema and how do we treat it
Too much water and sodium | Treat with loop diuretics
57
What is pseudohyponatremia
Low sodium result when patient is actually fien Caused by excess protein in blood (sample) as it causes sodium to be lower due to lower volume its distributed in Actual relative conc of Na is fine
58
What is Addison's disease
Adrenal insufficiency - don't make enough steroids Low mineralocorticoid activity Lose Na and water through kidneys Become clinically dehydrated
59
What are the common symptoms of Addison's disease
Dizziness Hypotension Hyperpigmentation - caused by excess ACTH which is broken down to MSH (melanocyte stimulating hormone)
60
What is a T1 weighted MRI
where you see cs fluid as dark | Posterior pituitary will show up as white

Endocrinology (13 decks)

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