Combined Flashcards
Iodine is an element commonly found in high abundance in which areas?
in the sea
What is the RDI for iodine
150ug
What is TRH? where is it released from?
Thyrotropin releasing hormone - released from the hypothalamus
What is cretinism? what is it caused by?
A congenital condition caused by maternal iodine deficiency, worlds most common form of mental retardation and growth retardation
Radiation from I (-131) can be used to what?
destroy the thyroid
What kind of receptors do thyroid hormones operate via?
membrane receptors and cause direct activation of genes in DNA
What is the atomic number of iodine?
53
Where is cholesterol found in the body?
free in membranes and as esters in storage
Where are human steroids derived from?
dietary steroids or are made from acetyl-coA in the liver
Corticosteroids refers to which two groups of steroids?
Glucocorticoids (eg cortisol) and mineralocorticoids (aldosterone)
Where are oestrogen and progesterone made primarily
ovary and also placenta during pregnancy
Where is testosterone primarily produced?
testes
Tamoxifen blocks what steroid action?
blocks oestrogen receptors and is used in the treatment of breast cancer
What is the effect of leuprolide?
lowers testosterone - used in treatment of prostate cancers
What are the actions of anabolic steroids?
interact with androgen receptors to increase muscle and bone synthesis
Where does the name cholesterol originate from?
greek chole- (bile) and stereos (solid)
What is cholesterol?
a waxy steroid metabolites
What is cholesterols role in cell membranes?
required for proper membrane permeability and fluidity (makes membrane LESS fluid)
What is a lipoprotein? What is their function?
biochemical assembly that contains proteins and lipids. Carry cholesterol in the blood
What are some examples of lipoproteins?
chylomicrons, low density lipoprotein (LDL), very low density lipoprotein (VLDL) and high density lipoprotein (HDL)
Arteriolosclerosis is promoted by excess levels of which lipoprotein?
LDL
What did Goldstein and Brown win a nobel prize for?
Identifying the LDL receptor on the liver which carries LDL and VLDL into the liver via receptor mediated endocytosis - this process is essential for feedback inhibition of HMG-CoA Reductase, muatations in this receptor lead to familial hypercholesterolaemia
Apart from its role in cell membranes what other roles (3) does cholesterol have?
- precursor to steroid hormones such as testosterone, cortisol, aldosterone, 2. component of bile salts 3. Vit D production
how many carbons does cholesterol have?
27
How many more times energy does NADPH have compared to ATP
7 times more
Where are human steroids derived from?
Cholesterol -> dietary or made in the liver from Acetyl-CoA
What is the most abundant steroid in the body?
cholesterol
Where is oestrogen and progesterone made?
Ovary and placenta
How are steroids eliminated?
by CYP3A4 in the liver endoplasmic reticulum which adds a OH group
What is Cyproterone acetate? what is it used for?
Inhibitor of the andreogen receptor. Used to treat Hirsuitism in females, male-to female gender change, prostate cancer, benign prostatic hyperplasia, priapism and hypersexuality (chemical castration)
What protein does cortisol bind in the blood?
transcortin
Hb makes up what percentage of RBC dry content?
97%
carbon dioxide can bind to Hb and form what? what proportion of the total respiratory CO2 is in this form?
forms carbaminohaemoglobin15% of total
Hb carries nitric oxide bound to what molecule on globin?
thiol group of globin
Why does Hb carry nitric oxide?
releases it at the same time as oxygen to relax vascular walls and enhance gas diffusion
Kendrew and Perutz one a nobel price for doing what regarding Hb?
solving its protein structure (the first protein structure solved)
What is the structural difference between adult and foetal Hb?
Foetal: alpha2-gamma2Adult:alpha2-beta2
Mutations in amino acid sequences cause hundred of whats (in relation to Hb)?
haemaglobinopathies
What was Christian Bohrs contributed to our knowledge about Hb?
described the sigmoid binding character of Hb-O2
What is the structure of haemaglobin?
Tetramer of globin subunits (proteins) with 4 haem groups inserted into each
What colour is Hb-CO?
bright red
What colour is De-oxy Hb?
dark red
What colour is HbO2?
scarlet red
What binds better to Hb O2 of CO?
CO binds 200x better than O2
What is Met Hb?
Hb with Fe3+ in the haem due to oxidation = found in aged RBCs
Haem inserts into the globin via a locking mechanism involving binding of histidine residues F8 and E7. One is always bound whilst the other can be displaced - which is which?
F8 is always locked (think its FATE for globin and haem to be together)E7 can be displaced by O2, CO and cyanide
What is the role of Bisphosphoglycerate (BPG)
stabilises Deoxy-Hb via 8 salt bonds which makes this form rigid (tense) and stops Oxygen binding back to Hb in the tissues. It is displaced when O2 levels are high (in the lungs)
Oxygen binding to Hb shows cooperativity - what does this mean?
When the first Oxygen binds to Hb it induces a change in the quaternary structure of Hb which changes the affinity of the other Oxygen binding sites - this means with only small increases in the concentration of O2 it is much easier to saturate the rest of the Hb molecule
What happens to the Hb-Oxygen binding curve in the presence of acid (bohr effect)? What functionally is the relevance of this?
graph is shifted to the right- meaning Hb has LESS affinity for O2, the relevance of this is that working tissues produce lactic acid and they require more O2 so we want the DeOxy-Hb form to be more stabilized so more oxygen is given up in the tissues - this is achieved via bonding to histidine residues
How does altitude alter the Oxygen-Hb binding curve? how is this achieved?
shifts it to the right -> giving more O2 to the tissues compensates for less O2 being picked up in the lungs. At altitude RBCs produce more BPG
Why does foetal Hb have higher affinity for O2 than adult hb?
gamma subunits have 6 positive charges (not 8) so BPG is bound less avidly so deoxy-form is stabilised less
What was Archibald Garrods field of study?
inborn errors of metabolism
The major burden of pathology in australia from genetic diseases is due to what disease?
Cystic Fibrosis
________was the first disease to be routinely tested for at birth and treated as required
phenylketonuria (PKU)
Genetic testing is usually carried out using what technique?
PCR
What is the most common x-linked recessive disorder? give some other examples
red-green colour blindess is the most common, others are haemophilia Am duchenne muscular dystrophy, Lesch-Nyhan syndrome
What happens in children affected by PKU?
they lack phenylalanine hydroxylase leading to a build up of Phe which gets converted to phenylpyruvate (a ketone) which damages the brain and affects melanin synthesis
What is the incidence of CF in australia?
in in 2500 births
What is the carrier rate of the CF gene in Australia?
1 in 25
What is the most common CF mutation?
Delta F506 in the CFTR protein (chloride channel)
What is Ehlers Danlos syndrome?
Inherited connective tissue disoder - mostly autosomal dominant condition due to mutations in genes that encode the structure, production or processing of COLLAGEN or proteins that interact with collagen -> those affected have hypermobile joints, hyper-elasticity of the skin but also affects arteries.
What is Marfan Syndrome?
mutation in fibrillin gene leading to bone overgrowth and joint laxity, with disproportionately long extremities compared to the size of the trunk
What enzyme is important in melanin formation?
tyrosinase
Is the inheritance of skin colour mono or polygenetic?
polygenetic -> 40 genes influence skin colour
If you lack tyrosinase what colour is your skin?
NO melanin = albinism
How do dietary toxins get to the liver?
Directly, via the hepatic portal vein
Which molecules are oxidised by P450 system?
ALL foreign chemicals with MW < 5,000
Where in the cell are the P450 cytochromes located?
Endoplasmic reticulumMitochondria
What are microsomes?
Pink spherical vesicles with embedded cytochrome P450. They don’t exist in cells - they’re an artefact of centrifuging.
What sort of enzymes are the P450s?
Monoxygenases
What reaction do the P450s typically catalyse?
RH + NADPH + H+ + O2 —>ROH + H2O + NADP+(The key point is that RH becomes ROH)
What initiates the P450 cycle of reactions?
Binding of a substrate to the P450
What P450 is deficient in people who can’t convert codeine to morphine?
CYP 2D6
What’s the structure of bilirubin?
It’s a a tetrapyrrole - an open chain of 4 pyrrole rings
Where is bilirubin usually produced?
In the spleen