Basic Principles Flashcards
what is ACTH?
adrenocorticotrophic hormone
what gland produces adrenocorticotrophic hormone (ACTH)?
anterior pituitary
what is the function of adrenocorticotrophic hormone (ACTH)?
stimulates the adrenal cortex to synthesise and release cortisol
what does anti-diuretic hormone (ADH) do to the concentration of urine?
increases the concentration
what type of target cells are involved in endocrine signalling?
distant target cell
what type of target cells are involved in autocrine signalling?
acting on itself
what type of target cells are involved in paracrine signalling?
surrounding (local) cells
what are the 3 main classes of hormones?
- (glyco)proteins and peptides
- steroids
- tyrosine and tryptophan derivatives
what molecule are steroids derived from?
cholesterol
what type of hormone is oxytocin?
protein/peptide
what type of hormone is cortisol?
steroid
what type of hormone is aldosterone?
steroid
what type of hormone is adrenaline or epinephrine?
tyrosine/tryptophan derivatives
what type of hormones are the thyroid hormones?
tyrosine derivatives
what type of hormone is insulin?
protein/peptide
what type of hormone is testosterone?
steroid
are amines pre-synthesised and stored or synthesised on demand?
pre-synthesised and stored
where are amines stored?
intracellular vesicles
what is the exocytosis of vesicles concentrated with amine hormones dependent on?
Ca2+ influx caused by a stimuli
calcium dependent exocytosis
are peptide/protein hormones pre-synthesised and stored or synthesised on demand?
pre-synthesised and stored
where are proteinpeptide hormones stored?
intracellular vesicles
what is the exocytosis of vesicles concentrated with protein/peptide hormones dependent on?
Ca2+ influx caused by a stimuli
calcium dependent exocytosis
are peptide hormones hydrophilic or hydrophobic?
hydrophilic
are amine hormones hydrophilic or hydrophobic?
hydrophilic
how are amine hormones transported in the plasma?
free
how are protein/peptide hormones transported in the plasma?
free
in the first stage of production of a steroid hormone, what is cholesterol converted into?
pregnenolone
what is the rate limiting step in the production of a steroid hormone from cholesterol?
conversion of cholesterol to pregnenolone
where does the conversion of cholesterol to pregnenolone occur?
mitochondrial membrane
where are steroid hormones stored?
they aren’t stored within the cell, as soon as they are made they are released directly into the blood stream
why is there a slow time frame of steroid hormone action?
because it depends on synthesis and release of a new hormone and not just release of a pre-existing hormone
how are steroid hormones transported in the plasma?
bound to a carrier protein
what are the 2 functions of a carrier protein in the transportation of hormone?
- increase amount transported in blood
2. prevent rapid excretion by preventing filtration at the kidney
what amine hormones needs to be transported in the bloodstream bound to a carrier protein because it is relatively insoluble in plasma?
thyroid hormones
what is the important carrier protein specific to cortisol?
cortisol-binding globulin
apart from cortisol, what hormone does cortisol-binding globulin also transport?
some aldosterone
what is the important carrier protein specific to thyroxine (T4)?
thyroxine-binding globuline
apart from thyroxine, what hormone does thyroxine-binding globulin also transport?
some triiodothyronine (T3)
what is the important carrier protein specific to testosterone and estradiol?
sex steroid-binding globulin
when are the levels of cortisol in the body highest and when are they lowest?
highest- 9/10am
lowest- 12am
(diurnal rhythm)
when are the levels of testosterone in the body highest?
first thing in the morning
what are the 3 main types of hormone receptor?
- g-protein coupled
- receptor kinases
- nuclear receptors
what type of hormones activate g-protein coupled receptors?
amines and some proteins/peptides
what type of hormones activate receptor kinases?
proteins/peptides
what are the 3 subclasses of nuclear receptors?
class 1 class 2 hybrid class
what is the difference between class 1 and class 2 nuclear receptor?
class 1- in the absence of hormone, located within the cytoplasm, move to nucleus once activated by hormone class 2- always present in the nucleus, hormone has to diffuse into nucleus to have it's effect
what are class 1 nuclear receptors bound to when in the cytoplasm?
inhibitory heat shock proteins
what type of hormones activate class 1 nuclear receptors?
mainly steroids
what type of substance activate class 2 nuclear receptors?
lipids
what type of receptor does insulin signal via?
tyrosine kinase receptor
once the receptor steroid complex (class 1 nuclear receptor) moves to the nucleus, it forms a dimer. what does this dimer bind to within the DNA?
hormone response elements
what endogenous substance might make urine red or red/brown?
haemoglobin
myoglobin
what endogenous substance might make urine smokey red?
intact RBC
what endogenous substance might make urine yellow and frothy when shaken?
bilirubin
what inborn error of metabolism makes urine brown-black on standing?
alkaptonuria
due to homogentisic acid
what does leucocyte presence in urine indicate?
UTI
what does urobilinogen presence in urine indicate?
a normal finding
increased urobilinogen might indicate liver abnormalities or excessive destruction of RBCs (eg haemolytic anaemia)
what is the normal pH of urine?
5-6
5.5 average
when are pH values for urine at their lowest?
after overnight fast
when are pH values of urine at their highest?
after meals
what may a strongly acidic urine pH indicate?
uncontrolled diabetes
starvation
dehydration
what may an alkaline urine pH of >8 indicate?
stale sample
UTI
what does specific gravity of urine assess?
the concentration and diluting power of the kidneys
what does the presence of bilirubin in urine indicate?
hepatic or biliary disease
what does the presence of nitrites in urine suggest?
UTI
what type of bacteria causing UTIs cause the presence of nitrites in urine and why?
gram negatives
convert dietary nitrates into nitries
what main 5 diagnoses does the persistent presence of protein in urine suggest?
renal disease UTI hypertension pre-eclampsia congestive heart failure
what does the presence of blood in urine suggest?
serious renal or urological disease
UTI
what does the presence of ketones in urine suggest?
starvation
uncontrolled diabetes
what are the 5 main causes of glucose in urine?
uncontrolled diabetes stress cushings syndrome post-general anaesthetic acute pancreatitis
(because of either increased blood glucose levels or reduced renal glucose absorption)
if not tested within one hour of collection, where should urine be stored?
refrigerator
where should the urine reagent strips be stored?
a cool, dry place
do not put in refrigerator
are acinar cells the exocrine or endocrine part of the pancreas?
exocrine
what cells secrete insulin?
pancreatic beta cells
found in pancreatic islets
what cells secrete glucagon?
pancreatic alpha cells
found in pancreatic islets
compare glucagon and insulin in terms of effect on hepatic glucose output? (gluconeogenesis)
insulin decreases gluconeogenesis
glucagon increases gluconeogenesis
what secretes somatostatin?
pancreatic delta cells
found in pancreatic islets
what organelle synthesise preproinsulin? (the larger single chain preprohormone of insulin)
rough endoplasmic reticulum
what type of insulin was used before human insulin?
bovine insuline
what transporter does glucose enter pancreatic B cells via?
GLUT 2
once inside a pancreatic B cell, what enzyme phosphorylates the glucose?
glucokinase
once inside a pancreatic B cell, what does glucokinase convert glucose into?
glucose-6-phosphate
what happens to the pancreatic beta cell intracellular ATP concetration as the metabolism of glucose increases?
ATP concentration increases
how many molecules of ATP are produced after oxidative phosphorylation of one glucose molecule?
36
what does ATP within the pancreatic beta cell do to the ATP-sensitive K+ channels? and what does this cause?
ATP inhibits the ATP-sensitive K+ channels
prevents K+ efflux
therefore cause depolarisation of the beta cell membrane
inhibition of K+ efflux within the pancreatic beta cell cause depolarisation of the beta cell membrane, what does this result in?
opening of voltage-gated Ca2+ channels
what does an increase of intracellular calcium within the pancreatic beta cell cause?
fusion of the secretory vesicles with the cell membrane (exocytosis)
–> release of insulin into the bloodstream
how many stages of insulin release are there after glucose is administered orally?
2 stages
biphasic
compare the 2 stages of insulin release?
1st stage: insulin granules immediately available for release from readily releasable pool
2nd stage: reserve pool must undergo preparation reactions to become mobilised and then release
what is the target for sulphonylurea drugs? (in diabetes)
and how does it work?
the sulphonylurea subunit of the ATP-sensitive K channel
inhibits the ATP-sensitive K channel to cause depolarisation
how many proteins make up the ATP-sensitive K channel?
2
what cells must be functioning in order for sulphonylureas to be useful in the treatment of diabetes?
pancreatic B cells
working beta cells, but defective ATP-sensitive K channels
what is the function of diazoxide on ATP-sensitive K channels within pancreatic B cells?
stimulates the ATP-sensitive K channels causing repolarisation and inhibits insulin secretion
what is MODY?
maturity-onset diabetes of the young
familial form of early-onset type 2 diabetes
what enzyme do mutations causing MODY affect?
glucokinase
what do MODY mutations do to the blood glucose threshold for insulin secretion?
increase the blood glucose threshold for insulin secretion
glucose sensing defect
why can MODYs be treated with sulphonylurea?
because they have working beta cells
what is the primary problem in type 2 diabetes?
reduced insulin sensitivity in tissues
what are the 3 amino acids that can be phosphorylated and why?
serine
threonine
tyrosine
because they have an OH group
what charge is introduce into the protein structure when serine, threonine or tyrosine are phosphorylated?
a large negative charge
what are the subunits of an insulin receptor?
2 extracellular alpha subunits
2 transmembrane beta subunits
what are the insulin-binding domains on the insulin receptor?
the 2 extracellular alpha subunits
what are the subunits of the insulin receptor linked by?
disulfide bonds
what does binding of insulin to the alpha subunits cause?
autophosphorylation of the beta subunits thus activating the catalytic activity of the receptor
glucose enters cells via what transporter?
GLUT 4
in which type of diabetes can ketoacidosis occur?
type 1 diabetes
where are ketone bodies formed?
liver mitochondria
what type of oxidation converts acetyl Co-A into ketone bodies?
beta-oxidation
when is acetyl coA converted to ketone bodies?
when there is no oxaolacetate to allow acetyl CoA to enter the TCA
why might oxaloacetate be unavailable for the TCA cycle?
during times of starving oxaloacetate is used for gluconeogenesis and is not generated through glycolysis
what is broken down into acetyl CoA?
fatty acids
why does ketoacidosis occur in type 1 diabetes?
when insulin isn’t injected, cells fail to receive enough glucose and therefore switch to fat breakdown.
fatty acids are broken down into acetyl CoA which can’t go through the TCA cycle so form ketone bodies
–> ketoacidosis
why is there no ketoacidosis normally in type 2 diabetes?
the high concentrations of insulin in inhibit lipase (the enzyme which breaks down triglycerides into glycerol and free fatty acids)
–> no excessive breakdown of fat resources
what does insulin do to the activity of hexokinase?
increases the activity of hexokinase
what does glucagon do to the activity of phosphofructokinase?
decreases the activity of phosphofructokinase
what are the 3 ketone bodies?
acetone
acetoacetic acid
beta-hydroxybutyric acid
compare the half lives of steroid hormones to tyrosine derivative hormones?
steroid hormones have a longer half life
how many transmembrane domains are there in a G-protein coupled receptor?
7 transmembrane domains