IMS @ Flashcards
Hyperthyroidism Symptoms
Hyperactive, sweating, lose weight, heat intolerance, palpitations, menstrual problems, hand tremors, goitre,
Periordenadema (swelling around eyes), proptosis (protrusion of the eyes) and paralysis of eye muscles can cause double vision
Diagnosis and treatment of hyperthyroidism
Static Test
Graves disease - thyroid peroxidase enzymes positive in 80% of cases and TSHR antibodies positive in 99% of cases!
Treatment - antithyroid drugs for 6-18months
Radioactive iodine - destroys thyroid gland, but not for pregnant, children, lactating women, urinary incontinent or those with active eye disease
Growth hormone defeciency symptoms
Children - failure of growth
Adults - tiredness, depression, often asymptomatic and requires no treatment
Diagnosis: Glucagon stimulation test - should raise GH as it stimulates its realease and Insulin stress test lowers BGL so should increase it
Treatment: Replace GH injections, but expensive
How do enzymes work?
1) Provide catalytically competent groups
2) Bind substrates in the right orientation
3) Stabilise transition substances
These all lower the activation energy of a reaction!
Active sites bind substrates via multiple weak interactions, e.g. Trypsin
Trypsin His57, Asp 102, Ser 195 (close together when folded)
Km
Describes the enzymes affinity to a substrate. High Km means a low affinity! Km = (k2 + k3 )/ k1
Km is the substrate concentration when Vmax = 1/2
If Km = [S] then V=Vmax/2
V=Vmax x [S]/([S]+Km)
Irreversible Inhibition
Covalent modification of active site
Iadoacetamide –> carboxymethylates cysteine side chains
Nerve agents e.g. Parathion, inhibits Achesterase and modifies serine residues
Competitive Reversible Inhibition
Enzyme binds to inhibitor or substrate but not both
High substrate overcomes inhibition
Vmax unchanged, Km Increased
Methotrexate competitively inhibits dihydrofolate needed for DNA/RNA synthesis
Non-competitive Inhibition
Enzyme binds to inhibitor and substrate as inhibitor doesn’t bind at active site
High substrate won’t overcome inhibition
Max decreased, Km stays the same
Alanine inhibits Pyruvate kinase
What do NADH, coA and Biotin carry
CO2
CoA carries acyl units, used with pantothenic acid (we must consume this acid)
Riboflavin defeciency
Ariboflavinosis
Niacin defeciency
Pellagra
Niacin acts as an electron donor to NADH
Thiamine defeciency
Beriberi
Vit C defeciency
Scurvy
Glucose-6-dehydrogenase defeciency
Commonest mutation, X-linked recessive
Enzyme is needed to produce large amounts of NADPH
Glucose –> Glucose 6 phosphate –> Pentose phophate pathway –> Ribose-5-phosphate which produces lots of NADP in the first step an important metabolic pathway to provide reducing power to erythrocytes
Mutation blocks NADP stops it being responsive to NADP levels
High incidence in malarial regions!
But causes primaquine-induced haemolytic anaemia!
Why do we need NADP?
NADPH refors glutathione (reduced), a scavenger molecule that reacts with free radicals
RBC’s have no mitochondria hence only make NADP via the glucose-6-deyhdrogenase pathway!
Primaquine reduces lots of free radicals (h202), not enough NADPH so the system can’t cope and RBCs can be killed by harmful molecules
Control of enzyme activity
1) Inhibition - often serine proteases
2) Feedback regulation
3) Covalent modification - phosphorylation used, often added to Ser or Thr
4) Proteolytic activation
What odo serpins inhibit
Serine proteases
What does trypsin cleave?
Cleaves the C terminal to lysine and arginine, prefers +ve charges, pancreatic trypsin inhibitors stop it
What does elastase do?
Elastase cleaves the C terminal to glycine and alanine!
Inhibited by alpha-1-antitrypsin
Secreted by neutrophils during inflammation to destroy bacteria
Tryspinogen
An enteropeptidase in the duodenum activates it by removing amino acids 1-6, causes a conformational shape change, can then cut itself into 3 chains held together by disulphide bonds
Thrombin
Prothrombin carried by platelets to site of injury
N-terminal of thrombin has carboxyglutamates, which bind to calcium on the platelet surface
However if no Vit K, prothrombin not in close contact with Xa & Va, thrombin isn’t released, fibrin isn’t released and blood can;t clot
Fibrinopeptides
These prevent fibrinogen reactions, normally removed by thrombin
Plasmin
Plasminogen converted to Plasmin by TPA (Tissue Type Plasminogen Activator)
Plasmin digests fibrin clot to small peptides
Fibrinogen
3 linked globular domains, middle domain contains 4 regions known as fibrinopeptides A&B which contain lots of negatively charged residues to prevent fibrinogen sticking together and clotting
Thrombin removes these fibrinopeptides!
Alzheimers
Fragments of the amyloid beta protein accumulate and aggregate in the brain causing insoluble plaques
CJD
Prione protein has identical primary sequence to normal proteins but a higher number of pleated sheets.
Prion causes normal protein to change structure
Insoluble aggregates accumulate causing a loss of neurological function
Haem Prosthetic group
Fe2+, and protoporphyrin IX held together by coordination bonds. Fe2+ is non-covalently bound into a hydrophobic crevice and it can coordinate with 6 ligands!
Haem keeps Fe2+ as Fe2+ not 3+ and prevents other molecules than oxygen binding!
Haemoglboin
2 alpha and beta chains, joined by non-covalent bonds, act as a tetramer of 2 pairs
Allosteric protein - binding of oxygen changes its shape
E&F helix pulled closetogether, protoporphyrin ring straightenes, proximal His H8 pulled in and salt bridges rupture
Bohr Effect
Low pH, H+ protonates residues (e.g. histidine), +ve charges form salt bridges, stabilise T states causing Hb to release oxygen
BPG
BPG binds in space between beta subunits in the T state, -ve charges on BPG react with +ve residues, stabilizes T state and reduces Hb affinity for O2
Foetal Hb
Binds BPG less, hence has a higher affinity for O2 than mothers blood so efficient transfer across the placenta!
Only 9 invariants in Hb
Proximal and distal His for o2 binding
Phe & Leu for Haem contact
Gly, Pro, Tyr - v. hydrophobic and important to maintain the structure!
Fibril forming collagen
1, 2 & 3
Netwrk forming collagen
IV, VII - forms the basal lamina
Fibril associated collaged
V, IX, XII involved in cross linking
Primary structure of collagen
Glycine every 3rd residue, Pro and lysine usually the other 2 aa
Hydroxyproline - needed for H bond to stabilise triple helix
Hydroxylysine - important for sugar attachment and cross linking and cross linking
Secondary collagen structure
Left hand helix - 3.3 residues per turn so tightly wound
Tertiary/Quartenary Structure
Triple helix tropocollagen in right hand twist!
Gly packed in centre, important as only enough room for H in the middle
Individual strands twisted in opposite directions, important for strength!
What forms in the fibroblasts
The pro collagen tirple helix!
Lysyl oxidase role in collagen
Dominates some of the lysine to allysine - allows cross links
Dupuytrens
A condition where too much collagen is produces, treat with collagenases
Osteogenesis Imperfecta (brittle Bones)
Mutation in type 1 collagen - often spontaneous, increases the risk of bone fracture
Ehlers Danlos Syndrome
Lysyl Oxidase defeciency
Scurvy
Lack of Vit C, lysyl and proudly hydrolyses can’t work, therefore no H bonds and cross linkings
Causes muscle weakness, joint tenderness, petichiae, tiredness, swelling/bleeding of gums!
Liver Damage
Increase in GPT & GOT
Later rise in Bilirubin
Prostatic Carcinoma
High Achid Phosphotases
High prostate specific antigens
Myocardial infarction
12 hours - peak in Creatinine Kinase
24 hours - peak in GOT
36 hours - Peak in Lactate Dehydrogenase
Lactate deydrogenase!§ a tetramer of 2, 35kDa subunits!
LDH1/H4 - Heart - allows aerobic respiration
H3M - monocytes/macrophages
H2M2- lungs
H1M3 - kidneys/pancreas
LDH5/M4 - liver/skeletal muscle - allows anaerobic respiration
LDH1:LDH2 measured, above 1 if heart attack occurs
Asparaginase
Converts asparagine to aspartate
Treats Childhood acute lymphoblastic leukaemia
Phenylketonuria
Give phenylalanine hydroxylase enzyme
Acatalassemia
Give catalase enzyme
Lesch-Nyhan syndrome (also a target for gene therapy)
Give HGPRT
Smooth muscle disorder - leimyoma/fibroids
Benign growths in the female reproductive tract
Can cause heavy uterine bleeding and pain
More common in Afro-Caribbean
Tubocurarine
Non-depolarising: Blocks ACh receptor, higher doses block the Na channels
Succinycholine
Bonds to ACh receptor and depolarises
Causes paralysis as not metabolised as quickly as ACh
Myasthenia Gravis
Antibodies produced against ACh receptors
Lambert Eaton Sybdrom
Antibodies produced against Calcium channels, less ACh therefore released
Amifamipradine
K+ channel blockers to prolong AP, treats lambert eaton syndrome!
Wolf Parkinson White Syndrome
Extra conductive tissue from atria to ventricle causes supra ventricular tachycardia
How does noradrenaline increase heart rate?
Increases cAMP, activates PKA, phosphorylates L type calcium channel so more Ca2+ released causing faster heart rate
Digoxin
Blocks Na/K pump. Causes stronger contraction of heart
Class I Arrythmia
Ventricular ectopics, Give Na blockers
Arrhythmia class II
Beta blockers - treats low SA and AVN conduction and decreases the sympathetic effect
Class III -
Potassium Blockers. treats ventricular tachycardia and AF
Class IV
Calcium channel blockers, slows SA AND AV contraction. Reduces contractility of heart hence not appropriate for heart failure
Duchenne Muscular Dystrophy
x linked recessive, mutation in dystrophin gene! causes muscle weakness etc.
Tay Sachs Disease
Lysosome enzyme is lacking so sugar head on lipids isn’t cut back causing neurological problems
Ganglioside a are a member of which family
The sphingolipids, they have very hydrophilic sugar groups so are exposed on the outer face of the membrane!
rafts
Rich in cholesterol and sphingolipids (e.g. sphingomyelin) as they can pack closely with chilesterol!
Linolic acid
essential for the Synthesis of some fatty acids
Sphingolipids
ONLY IN THE OUTER LEAFLET
do triacylyglycerols and cholesterol esters from membranes
NO they pack inside structures with one layer of phospholipids
Alzheimer’s treatment
Cholinesterase inhibitors (Aricept, Exelon, Reminyl) and NMDA receptor antagonists (Ebixa) aim to increase stinulation across neurones to prevent neutron death
Glyphorin A
In erythrocytes!
`Bacteriorhodopsin
Pumps H ions across the membrane, 7TM alpha helixes with 20-30 amino acids in each helix
Lipid linked membrane proteins
covalently attached to fatty acids in the membrane (e.g. glycosyl-phosphatidylinositol)
Also used for insulin receptor where palmetto locks insulin close to the membrane
Peripheral membrane proteins
Don’t interact with hydrophobic core of bilayer, only interact with head groups or other membrane proteins through ionic attractions!
O-linked sugars
Attached to hydroxyl groups in serine or threonine proteins residues
N-linked sugards
Attached to side chain of asparagine residues but only in sequence Asn-X-Ser/Thr and X cannot be proline! Have large branded structure (30-40 residues)
Blood antigens
N-acetyl-galactosamine in A
Galactose in B antigen
Vancomycin
Transportsv vitamin K across the cell membrane as a carrier ionophore
Gramicidin A
a permanent channel forming ionophore for the transfer of ions across the membrane
Glucose transport into erythrocytes
Integral transporter with 12 TM helixes, brings glucose in then hexokinase adds phosphate to make glucose-6-phosphate hence conc. gradients aren’t wrecked
Aquaporins
28kDa proteins with 6 TM sections for water reabsorption particularly in the kidneys
Na/K ATPase enzyme
Has two alpha and two beta chains
Cardiac Glycosides e.g. Digitalis
Inhibit Na/K pump, means less gradient for Ca/Na pump (usually 2 Ca out for 3Na in) so less calcium leaves the cell hence stronger heart contraction
ORT
Contains salt and glucose! glucose lowers the water potential in the intestinal cells as it is absorbed hence treats diarrhoea!
Which ions are directly coupled to ATP hydrolysis for membrane transport
Na, K, Ca, H.
ApoA Lipoprotein
In HDL
ApoB
In LDL, facilitates LDL uptake
ApoC
Activates lipoprotein lipase
ApoE
Stabilises VLDL
FPP & GGPP
They are isoprenoids, add a small lipid tail to G proteins allowing them to attach to the cell membrane
Rho effects
Crenelated by GGPP, increases adhesion molecules, thrombosis, cytokines and decreases vasodilation.
Hence statins also decrease endothelial dysfunction as they prevent the inflammatory responses that are also from Rho!q
GPCR’s
7TM helixes, NH2 extracellular, COOH intracellularly, binding allows interaction of loop 3 with the G protein - leads to effect of G protein
Renin-angiotensin system
Renin released by kidneys in low blood pressure or low Na+
AT1 receptor effects
Vasoconstriction, increased Na secretion and reabsorption, aldosterone secretion. AT1 antagonists can treat heart failure!
AT2 receptor effects
Opposes AT1, anti-hypertension, anti-hypertrophic
Arginine + eNOS enzymes
Forms L-citrulline and NO
Heme plus HO-1&2 enzymes
forms CO and Fe2+ + bilirubin
Homecysteine + CBS, CSE, 3MST
H2S
G protein mechanism
Binding of ligand - causes conformational shape change
Loop 3 can interact with G protein, GDP exchanged for GTP and it becomes activated
Alpha subunit dissosciates and moves downstream to activate the effector protein
Intrinsic GTPase activity of the G protein hydrolyses GTP to GDP and subunit deactivated
Gs
Stimulates adenylate cyclase - raises cAMP - activates PKA
Gi
Inhibits adenylate cyclase - lowers cAMP - less PKA activated
Gq
Stimulates phospholipase C - PIP2 is converted into DAG & IP3 - IP2 diffuses through the endoplasmic reticulum causing increased Ca2+ release
DAG stays in the membrane and activates PKC
Cholera
Inhibits GTPase activity of Gs, remains activated, increased cAMP, chloride channels stay open
Whooping Cough
Pertussis toxin prevents GDP/GTP exchange in Hi, hence increased cAMP increases histamine and insulin secretion
Caffeine and viagra are both…
PDE Inhibitors
Angiotensin II binds to AT1R receptor and activates…
Gq protein activated
Protein kinases only phosphorylate which residues
Serine, Threonine and Tyrosine
Serine & Threonine - by PKA, PKC, PKG
Tyrosine kinases - Insulin or Src
Map Kinase Kinases - phopsohrylate all 3
Gleevex (Imatmib)
Tyrosine kinase used in treating chronic myeloid leukaemia,
Neuropeptide or NO stimulates what
Activates gauntlet cyclase - produces cGMP - activates PKG
ACh binds to muscarinic M2 receptor…
Gi activated, adenylate cyclase inhibited, lowers cAMP, less PKA activated
Adrenaline binds to Beta1-AR…
Gs activated, adenylate cyclase stimulated, raises cAMP, more PKA activated
What will make a membrane more fluid?
Decrease cholesterol, decreases length of fatty acid chain, increase number of saturated D bonds
Why is D-glucose taken up much more readily than L-glucose in erythrocytes
As the glucose transporter has a much higher affinity for D glucose
NFkB is a transcription factor, what happens when it binds to a gene promoter?
Transcription of that gene increases!
Sphingolipids are only in the outer membrane of lipids true or false?
True
What causes kinks in fatty acids
cis double bonds!
Dyslipidaemias
mutations that affect the LDL receptor
Throid blocking hormones
Cabrimazole and propylthiouracil!
Epigenetics
Control of gene expression by means other than genetic variation
Polymerase has 3 to 5’ proof reading activity, reduces errors to…
1 in 100 (10^5 to 10^7)
Aspirin
Competitive irreversible, covalent modification of serine residue in COX-1
Ibuprofen
Competitive reversible, binds to COX-1 active site but not covalently
Mucin staining
Use Periodic Acid Schiff - stains mucin but also glycogen, hence apply diastase enzyme to remove glycogen before PAS added
Marfans Syndrome
A lack of fibrillin
Pyruvate –> Acetaldehyge
Pyruvate Carboxylase catalyses this (needs biotin)
Acetaldehyde –> ethanol
Alcohol dehydrogenase catalyses this (uses NADH)
Seligline
Treats Parkinsons
