Biochemistry Flashcards
1
Q
Carbonic Anhydrase
A
Catalyses CO2 + H2O H+ + HCO3-
Important for acid base balance
High in RBC
2
Q
BPG
A
2,3-biphosphoglycerate
Binds cavity between β-subunits and stabilises deoxy-Hb (8+ve charges)
Converted from 1,3BPG by mutase (activity increases as pH becomes more alkaline)
3
Q
Myasthenia Gravis
A
Anti-AChR prevents Ach binding to nicotinic receptors and activation of skeletal muscle
4
Q
Phenylketonuria
A
Lack of Phenylalanine hydroxylase
Can’t break down Phenylalanine to Tyrosine, ends up being converted to Phenylpyruvate (a ketone)
Mental Retardation
Seizures/Tremors
Behavioural Disorders
5
Q
Cystic Fibrosis
A
Build up of mucous in lungs & blockage of pancreatic duct
Elevated Immunoreactive Trypsin (IRT) Delta F508 (Phe deletion in Cystic Fibrosis Transmembrane Conductance Regulator gene) - pore can no longer secrete chloride.
6
Q
Ehlers Danlos Syndrome
A
Collagen mutant (fibrous proteins and enzymes) Extra flexibility
7
Q
Marfan Syndrome
A
Mutation / decreased production / delayed transport of fibrillin 1 into ECM
8
Q
Sickle Cell Anaemia
Hiroshima
Hammersmith
A
beta 6 Glu -> Val - crystalline structure
beta 146 His -> Asp - disrupts salt bridge in deoxy state, and alters Bohr effect
beta 42 Phe -> Ser - attracts water into haem pocket
9
Q
Porphyria
A
Haem feedback inhibition failure
10
Q
Haem binding site
A
His F8
Oxy between Fe2+ and His E7
11
Q
Osteogenesis Imperfecta
A
Glycine at position 748 in collage mutates to cysteine causing kink in strand and brittle bones.
12
Q
Cholesterol Structure
A
ABCD rings
hydroxy group on 3rd position
hydrophobic section is planar
13
Q
Cholesterol Synthesis
A
NADPH from malate -> pyruvate
AcetylCoA (2 carbons) -> acetoacetylCoA (4 carbons) \+ acetylCoA -> HMG CoA \+ 2 NADPH (& HMG-CoA Reductase) -> Mevalonic acid + CoA
6 x Mevalonic Acid ->
Squalene ->
Cholesterol & inhibition of HMG-CoA Reductase
14
Q
Lipoproteins
ApoA-I
ApoB-100
ApoC-II
A
ApoA-I = HDL (activates LCAT enzyme allowing cholesterol scavenging) ApoB-100 = VLDL, LDL (binds to LDL receptor) ApoC-II = chylomicrons, VLDL, HDL (activates lipoprotein lipase, an enzyme outside of muscle and adipose tissue that uses fat as an energy source)
15
Q
Familial Hypercholesterolemia (FH)
A
Inherited autosomal dominant
mutation of LDL receptor
Homozygous individuals develop waxy plaques (XANTHOMAS) beneath skin, over elbows, knees buttocks and cornea.
Normal cholesterol < 5.5mmol/L
FH > 15mmol/L
Treated with HMG-CoA reductase inhibitors (statins).
16
Q
Celiacs
A
HLA DQ2 Allele
Tissue Transglutaminase 2 (tTg2) converts glutamine -> glutamate on Gliadin peptides that bind to HLA DQ2 peptide binding cleft
17
Q
Calcium and smooth muscle contraction/relaxation
A
Increase contraction
- Phospholipase C (activated by GPCR, activates IP3)
- Inositol Triphosphate (IP3) (Ca2+ release from SR)
- Rho Kinase (inhibit MLCP)
- Protein Kinase C (inhibit MLCP)
Decrease contraction
- Plasma Ca2+ ATPase
- Sarcoplasmic Ca2+ ATPase (sequester Ca2+ in SR)
- cAMP (increase Protein Kinase A)
- Protein Kinase A (inhibit MLCK, activate MLCP)
Ca2+ & calmodulin phosporylates and activates Myosin Light Chain Kinase = contraction
18
Q
Mediators of airway smooth muscle balance
A
CONTRACTION ACh Histamine LTC LTD
RELAXATION PGE (cAMP) PGI (cAMP) Adrenaline (circulating adrenalin from adrenal glands) b2 agonists (cAMP)
19
Q
Proximal Tubule
A
LUMINAL
Na+, glucose, aa cotransporter (in) [passive]
Na+ / H+ (out) [passive]
BASAL
glucose, aa (out) [passive]
Na+ / K+ (in) ATPase [active]
20
Q
Ascending Loop of Henle
A
LUMINAL
Na+, K+, 2Cl- cotransporter (in) [passive]
BASAL
Na+ / K+ (in) ATPase [active]
21
Q
Familial Cold Urticaria
A
Patients develop systemic signs of ACUTE INFLAMMATION when exposed to COLD
- hive like blisters, fever, myalgia, fatigue, etc.
Due to Single Nucleotide mutations of cyopyrin (NLRP3) gene associated with Interleukin-1-converting enzyme
22
Q
P450 reaction
A
RH + NADPH + H+ + O2
->
ROH + H2O + NADP+
23
Q
P450
A
Oxidized all foreign chemicals with Mw < 5000
Located in ER & mitochondria
Hydrophobic foot anchors P450 into membrane
Transfers 1 electon at a time to O2 -> O22- ROS next to substrate
CYP2A6
2 - Family - share >40% protein sequence
A - Subfamily >55%
6 - Form
24
Q
Ames Test
A
Histadine-requiring salmonella in His-selective agar (no his)
Drug added
Salmonella can mutate back to wild-type and grow if mutagens present
Drugs that fail the Ames test do not progress past Phase I
25
Bilirubin
open chain of tetrapyrrole ring
haem -(haem oxygenase)-> biliverdin -(biliverdin reductase) -> bilirubin
UDP-glucuronyltransferase conjugates bilirubin (twice) and makes it soluble
cMOAT/MRP2 actively pumps into canaliculi
urobilinogen (10% reabsorbed, 1% to kidneys)
stercobilin
26
Haptoglobin (Hp)
plasma protein, binds haemoglobin
high hemolysis decreases free haptoglobin levels
when Hp is depleted free Hb is excreted in urine
27
Hemopexin
carries haem (not Hb) to liver
higher affinity than albumin
low haemopexin is indicator of haemolytic anaemia
28
Alcohol content of 1 std drink
10g
| Cleared in approx 1 hour
29
Alcohol key features
Ethanol - EtOH, C2H5OH
Low melting and boiling point
Almost identical energy amount as fat
Crosses BBB and makes nerve membranes leaky (impairs signal transmission)
Interferes with glutathione through membrane (unable to scavange free radicals from mitochondria)
Inhibits PDH -> reduced H20 retention by kidneys
30% absorbed stomach, 70% intestine
90% metabolised by liver, 2% kidneys, 8% stomach
30
Alcohol Oxidation
Ethanol -> Acetalaldehyde -> Acetate -> Acetyl-CoA (fat synthesis via TCA cycle)
Alcohol Dehydrogenase - produces NADH which represses gluconeogenesis (can lead to hypoglycaemia)
MEOS - induction of CYP 2E1.
- CYP 2E1 consumes NADPH so less energy is produced
- prevents drug clearance when alcohol is present
- promotes drug clearance when alcohol is not present
- produces lots of free radicals
Catalase - uses H2O2 as oxidant
31
GI Digestive Secretions
MOUTH:
Amylase
STOMACH:
Pepsinogen
HCL
```
SMALL INTESTINE:
HCO3-
Enteropeptidase
Disaccharidases
Peptidases
Phosphotases
```
```
LIVER:
Bile acids (detergents)
```
```
PANCREAS (EXOCRINE):
NaHCO3
NaCl
peptidases
amylase
prolipases
```
LARGE INTESTINE:
Mucous
32
Gallstones
Mostly cholesterol
Stained with bilirubin derivatives
Normal cholesterol crystalisation time is approx 20 days
33
Duodenal Gland secretion Mechanism
- ACh & CCK
- Secretin
ACh & CCK
G protein activates Phospholipase C
PLC increases intracellular Ca2+
Ca2+ stimulates secretion
Secretin
G protein activates Adenylate Cyclase
Adenylate Cyclase converts ATP to cAMP
cAMP stimulates secretion
34
Breakdown of sugars
Lactose -(Lactase)-> Galactose & Glucose (SLGT1)
Sucrose -(Sucrase)-> Fructose (GLUT5) & Glucose
Starch -(Amylase)-> Maltose -(glucosidases)> Glucose
35
Major Causes of Jaundice
PRE-HEPATIC
- Haemolysis
INTRA-HEPATIC
- Drugs (rifampicin - interferes with bilirubin uptake)
- Gilberts (UDP)
- Crigler Najjar (UDP)
- Hepatitis
- Cirrhosis
- Cancer
- Dubin-Johnson (cMOAT)
POST-HEPATIC
- Gallstones
- Biliary stricture
- Carcinoma of Pancreas
- Cholangitis (inflamed bile duct)
36
Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency
RBC depleted before 120 day life
Involved in production of GSH
GSH (reduced glutathione) protects cells from oxidative damage
Confers resistance to malaria
Chloroquine (antimalaria) contraindicated in G6PD
Chloroquine + haem produces ROS which would normally be removed by GSH. In G6PD it leads to RBC breakdown and heinz bodies (oxidized globin)
37
Galactosaemia
Difficiency of any one of 3 enzymes used to convert Galactose to Glucose-6-Phosphate
- galactokinase
- galactose-1-phosphate uridylyl transferase
- UDP galactose-4-epimerase
```
Elevated AST, ALP, conjugated bilirubin
Cataract formation (due to elevated galactitol)
Hepatomegaly
Brain Damage
Jaundice
```
Treatment: Stop giving infant milk
38
Hepatocyte Enzyme Locations & Half Lives
ALP - Membrane (biliary canaliculi) (Bone, Liver, Placenta) (adds phosphate group to molecule)
GGT - Membrane (biliary canaliculi) (Liver, Renal) (glutathione production)
ALT/LD - Cytoplasmic (transport energy to muscle, greater in liver though)
AST - Cytoplasmic & Mitochondrial (liver & muscle)
Half Lives:
AST: 18hrs
ALT: 36hrs
GGT: 5-7 days
39
Liver Enzymes
| Hepatocellular Damage
AST (mostly), LD, ALT
AST > ALT
- acute, affecting mitochondria: acute virus, EtOH
ALT > AST
- chronic, drugs, viral, metabolic
```
ALT = 50 = NORMAL
ALT = 250 = MILD
ALT = 1000 = MODERATE
ALT = 5000 = SEVERE
(with chronic infections ALT is usually mild/normal)
```
Hepatocellular death can lead to Bilary disease (obstruction)
40
Liver Enzymes
| Biliary Disease
ALP, GGT
Extrahepatic biliary obstruction (intrahepatic may have slightly raised levels)
- colon/pancreatic cancer, cholestasis
Biliary Disease can lead to hepatocellular death
41
Liver Enzymes
| Inducing Drugs
GGT, ALP
Antibiotics, Statins (rhabdomyopathy), EtOH, Paracetamol
GGT involved in glutathione production, important in removing ROS
42
Henderson-Hasselbalch for HCO3- and CO2
pH = pKa + log{[base] / [acid]}
= 6.1 + log ([HCO3-] / 0.03*pCO2}
= 6.1 + log (24mM / 1.2mM)
= 7.4
NB: Kidneys control HCO3-
Lungs control CO2
43
Gastric acid secretion (internal biochemistry)
H2O & CO2 diffuse into cell
Become H+ and HCO3-
HCO3- exchanged with Cl- on basolateral
H+/K+ exchange apical
K+ & Cl- diffusion out apical side
44
Gastric acid secretion (stimulation)
Gastrin causes ECLcells to release histamine
Histamine acts on H2
triggers converstion of ATP to CAMP
-> broken down to AMP by phosphodiesterase
-> acts on PKA and opens Cl- channels
ACh from vagus acts on M3
causes opening of Ca2+ channels
Ca2+ activates CAM which stimulates H+/K+ATPase
45
Alcohol Cytochrome
2E1
46
TRPV1
Noiceceptive transducer
Receptor for capsaicin
Capsaicin lowers heat threshold so that essentially the channel is always open (i.e. pain)
47
Unstable Repeat Expansions
repeating units of three or more nucleotides in tandem
expansion of DNA segment within specific gene above a THRESHOLD
```
ANTICIPATION:
# repeats increases -> age of onset decreases & severity increases
```
Testing: PCR, fragment analysis on capillary electrophoresis
48
Iodine & Thyroxine
Atomic number 53
Antiseptic (I2 oxidizes respiratory chain enzymes)
High abundance in sea (kelp), low on land
I-131 destroy thyroid gland
RDI 150ug
Goitrogens (soy, cabbage, broccoli) inhibit iodine uptake
Iodine deficient mothers give berth to CRETINS (mental retardation, deaf-mute)
Energy from TSH binding to TSHR (cAMP) causes uptake into Thyroid by NIS (Na+/I- symport), balanced by 3Na+/2K+ATPase
Oxidised to chemically reactive form by THYROPEROXIDASE (TPO)
reacts with tyrosines in THYROGLOBULIN protein
peptide links hydrolised and T3, T4 released
70-80% bound to Thyroid Binding Globulin (TBG)
T4 more abundant, T3 more potent
Deiodinase converts T4 to T3
bind DNA receptors & cause transcriptional activation (upregulate oxidative phosphorylation -> more ATP)
49
Steroid Elimination Cytochrome
CYP3A4
Most abundant CYP in entire body
Introduces -OH into steroid ring then other enzymes form bile acids
50
Where do steroids bind?
At Hormone Response Elements (HRE's) in DNA
Sex steroids enter nucleus and activate DNA binding recepotrs that bind to HREs and cause gene transcription
Mineralocorticoids and glucocorticoids bind cytoplasmic receptors and displace heat shock proteins to expose active site
51
What is tested for in a pregnancy test
hCG
Human Chorionic Gonadotropin
Produced by trophoblast and placenta
52
Energy in ATP
30. 5kj/mol
| * Adenosine Triphosphate Phospate backbone stabilised by Mg2+ forming Mg-ATP as substrate
53
Energy in NADH
220kj/mol
Nicotinamide Adenine Dinucleotide (from vitamin B3)
Storage molecule for electrons from Glycolosis/Krebs to ETC
54
ATP production of Aerobic vs Anerobic Metabolism
Aerobic: 30-32ATP
Anaerobic: 2ATP
*106 ATP is generated from palmitate (fatty acid)
55
Glucose
- structure
- dangers
All D except 3! (OH point down)
Highly reactive adehyde, prone to glycation of amino acids and amino groups on proteins. Glycated blood vessels become brittle and prone to clots.
Esp if damage occurs faster than turnover (i.e. 3 days for vessels, 120days for RBCs)
56
Aldose vs Ketose sugars
ALDOSE:
Glucose & Galactose
Aldehydes O=CR-H
KETOSE:
Fructose
Ketones O=CR-R'
57
Cell Glucose Transporters
```
GLUT1 = universal
GLUT2 = liver and pancreas (respond to rising glucose)
GLUT4 = muscle and adipose (insulin responsive)
SGLT1 = Na+ cotransporter in intestinal epithelium and kidney tubules
```
58
Beta-oxidation
Fatty Acids -> Acetyl-CoA
If NADH is high TCA cycle is inhibited and Acetyl-CoA goes off to form ketone bodies for other cells (brain, muscle, heart, kidney). Carnitine helps transport acetyl-CoA in/out of mitochondria
Occurs in mitochondria
59
Glycolysis
Occurs in Cytosol
Produces ATP anaerobically
glucose + 2NAD+ + 2ADP + 2Pi -> 2pyruvate + 2NADH + 2ATP + 2H2O
```
PATHWAY:
Glucose
Glucose-6-phosphate
Fructose-6-phosphate
Fructose-1,6-bisphosphate
Glyceraldehyde 3-phosphate & Dihydroxyacetone phosphate
Glyceraldehyde 3-phosphate (2)
1,3-Bisphosphoglycerate (BPG) (2)
3-Phosphoglycerate (2)
2-Phosphoglycerate (2)
Phosphoenolpyruvate (PEP) (2)
Pyruvate (2)
```
60
Glycogenesis
Creation of glycogen
61
Glycogenolysis
Breakdown of glycogen
62
Gluconeogenesis
Generation of glucose from glycerol of amino acids, NOT fatty acids (they undergo beta-oxidation)
Carbon sources:
Lactate
Amino Acids
Glycerol (from TAGs) -
63
Anaerobic Glycolysis
Produces 2ATP
Occurs in cell cytosol
Produces Lactate
*Only pathway for RBCs, lens, retina, as they have no mitochondria
64
Normal Blood Glucose Levels
- Fasting
- Fed (100g glucose)
Fasting: 4-5mM
Fed: <10mM (the renal threshold)
65
Hb A1C
Haemoglobin A1C
Diagnostic indicator of uncontrolled high glucose levels
β-subunits prone to glycation of N-termini
Normally 3-5% of Hb, rises to 15%+ in uncontrolled diabetes
66
Glycogen
Fasting reserve of glucose
| Chemically intert, low osmotic profile
67
Hexokinase
Catalyses Glucose -> Glucose 6-phosphate reaction in glycolysis
Transfers phosphate from ATP to glucosee
68
Phosphohexose Isomerase
Catalyses Glucose 6-phosphate -> Fructose 6-phosphate reaction in glycolysis
69
Phosphofructokinase
Catalyses Fructose 6-phosphate -> Fructose 1,6-phosphate reaction in glycolysis
Only active when cells have low [ATP]
Irreversible in glycolysis
In gluconeogenesis fructose 1,6-bisphosphatase reverses this reaction
70
Glucose-6-Phosphotase
Enzyme in liver and kidney cells which allows them to form glucose (final stage of gluconeogenesis) and transport out of cell into the blood.
71
Lactose
β1-4 linked disaccharide of galactose and glucose
| inability to epimerise the galactose to glucose is the cause of galactosaemia
72
Glycerol metabolism
Backbone of TAGs
enters glycolisis (or exits) at GAP / DHAP stage
can also be created from fructose (via GAP / DHAP)
73
Why is fructose bad?
2-3 times sweeter than glucose and cheaper (so used in many foods)
Fails to increase leptin production by adipose cells
Fails to supress ghrelin
Fails to elect insulin release
Gets coverted to glycerol (backbone of TAGs), therefore more fat is created and stored (LDLs)
74
Mitochondria Functions & Disorders
Pyruvate -> Acetyl-CoA -> TCA cycle
Acetyl-CoA -> Ketone bodies
Aging = loss of mitochondria
Electron leak from mitochondria -> ROS
Mitochondria come from mother
Disorders have characteristic Ragged Red Fibres (RRFs)
75
Urea
Produced from protein breakdown
100g excreted per day
Non-toxic
Highly soluble
76
Products of The Citric Acid Cycle
Each turn produces:
3 molecules of NADH
1 molecule of FADH2
1 molecule of GTP or ATP
77
Which ETC complexes are encoded by nDNA and which are encoded by mtDNA?
```
nDNA = II
mtDNA = I, III, IV, V
```
78
Malate-aspartate shuttle
Transfers reducing power of NADH from cytosol to mitochondria for oxidative phosphorylation (ETC)
79
Glycerol-3-phosphate shuttle
Rapid ENERGY DEPENDANT shuttle for transferring reducing power of NADH from cytosol to mitochondria for oxidative phosphorylation (ETC)
-> results in ATP production of 30
80
Typical adult dietary energy need per day
10MJ
| All of which is radiated as heat regardless of work performed
81
Calcium
- sources
- functions
- deficiency
- toxicity
- intake
- control
Best sources: Diary, nuts, seaweed
Primary functions: bones/teeth, muscle contraction, nerve function, blood clotting, BP, tight junctions (bone)
Deficiency: rickets, poor clotting, OSTEOPOROSIS, stunted growth
Toxicity: constipation, malabsoprtion, impaired kidney function (stones), malignant hyperthermia
approx 1.2kg stored in bone
kidneys pass 1g per day
Calcitonin (from thyroid) lower blood [Ca2+] by depositing in bone (stimulate osteoblasts)
VitD and PTH increases [Ca2+] via kidney reabsorption, GI absorption, bone breakdown
82
Phosphorous
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Meats, eggs, milk
Primary functions: Mineralisation of bone/teeth, cell integrity, phospholipids, DNA, ATP, acid-base buffers
Deficiency: weakness, bone pain, growth retardation
Toxicity: diarrhoea, calcification of non-skeletal tissue (particularly kidney)
1000mg/day
83
Potassium
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Bananas, tomatoes, meat, milk, fruit, vegies, grains, legumes
Primary functions: fluid & electrolyte balance, nerves, muscles, cell integrity
Deficiency: irregular heartbeat, weakness, glucose intolerance
Toxicity: weakness, vomiting (if IV), cardiac arrest
2800-3800mg/day
84
Sulphur
- sources
- functions
Best sources: Proteins (methionine, cysteine)
| Primary functions: Keratin in hair and nails
85
Sodium
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Table salt, soy, milk, meat
Primary functions: fluid & electrolyte balance, nerves, muscles
Deficiency: cramps, apathy, loss of appetite
Toxicity: oedema, acute hypertension
460-920mg/day
86
Chloride
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Table salt, soy, milk, meat
Primary functions: fluid & electrolyte balance, stomach acid & digestion
Deficiency: N/A
Toxicity: vomiting (NaCl is an emetic)
intake - N/A
87
Magnesium
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Nuts, legumes, grains, vegies
Primary functions: Bone mineralization, protein, enzymes, nerve impulse, immunity
Deficiency: weakness, immunity, convulsions, growth failure, hallucinations
Toxicity: diarrhoea, dehydration, alkalosis
310-400mg/day
88
Iron
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Meat, eggs, legumes
Primary functions: haemoglobin/myoglobin
Deficiency: Anaemia, fatigue, headache, impaired immunity, pallor, inability to regulate body temperature, pica (dirt)
Toxicity: Gi distress, infections, fatigue, joint pain, pigmentation, organ damage, haemochromatosis
8-18mg/day
Absorption increased by Vitamin C
89
Zinc
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Protein-containing foods, oysters
Primary functions: Enzymes, insulin, proteins, vitA transport, wound healing, foetal development, spermatogenesis
Deficiency: Growth retardation, delayed sexual maturity, impaired immune system, hair loss, eye/skin lesions
Toxicity: loss of appetite, low HDL, copper and iron deficiency
8-14mg/day
90
Copper
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Seafood, nuts, grains, seeds
Primary functions: Iron absorption, electron transport chain
Deficiency: Anaemia, bone abnormality
Toxicity: liver damage, wilson's disease, menke's disease
1.2-1.7mg/day
91
Manganese
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Nuts, grains, vegetables
Primary functions: enzyme cofactor, bone formation
Deficiency: Rare
Toxicity: nervous system disorders
5-5.5mg/day
92
Iodine
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Seafood, iodised foods
Primary functions: T3/T4
Deficiency: goitre, cretanism
Toxicity: elevated TSH, goitre
150ug/day
93
Selenium
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Seafood, meat, grains, fruit, vegies
Primary functions: defence against oxidisation, T3/T4
Deficiency: heart disease - fibrous cardiac tissue
Toxicity: hair and nail brittleness, skin rash, fatigue, irritability, CNS disorders, garlic breath
60-70ug/day
94
Chromium
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Meats, whole grains, brewers yeast
Primary functions: enhance action of insulin
Deficiency: diabetes-like condition (impaired glucose tolerance)
Toxicity: N/A
25-35ug/day
95
Molybdenum
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Legumes, cereals, nuts
Primary functions: enzyme cofactor
Deficiency: N/A
Toxicity: N/A - reproductive effect?
45ug/day
96
Fluoride
- sources
- functions
- deficiency
- toxicity
- intake
Best sources: Water, tea, seafood
Primary functions: bone/teeth
Deficiency: tooth decay
Toxicity: Fluorosis (pitting and discolouration of teeth)
3-4mg/day
97
Cobalt
We actually need vitamin B12 which contains cobalt
98
Fat Soluble Vitamins
A, D, E, K
99
Thiamine (B1)
Coenzyme in decarboxylations (aerobic metabolism)
Carbohydrate, protein, and fat metabolism
Nerve function
Sources: vegemite, breads, cereals
Deficiency: beriberi, wernicke-korsakoff
100
Riboflavin (B2)
```
Electron carrier (FMN, FAD)
Carbohydrate, protein, and fat metabolism
```
Sources: vegemite, dairy, cereals
Deficiency: magenta tongue
101
Niacin (B3) (nicotinamide)
Coencyme
Electron carrier (NADH, NADPH)
Carbohydrate, protein, and fat metabolism
Sources: vegemite, wheat bran, cereals
Deficiency: Pellagra (dermatitis, diarrhoea, dementia, death)
102
Pyridoxine (B6)
Amino acid metabolism
Sources: vegemite, nuts, bananas, cereals
Deficiency: rare
103
Biotin
Glucose, fat, amino acid biosynthesis
Sources: brewers yeast, eggyolk cooked, soy
Deficinecy: dry, shiny, scaly skin of hands
104
Folate
Amino acid, fat, purine (DNA) biosynthesis
Sources: green vegetables, fortified cereals
Deficiency: common in alcoholics & elderly
Concern for pregnant women
macrocytic anaemia, spina bifida
glossitis w/ papillae atrophy
105
Cobalamin (B12)
Coenzyme containing cobalt
folate metabolism, transalkylations (nerves and blood)
Sources: meat, egg, dairy
Deficinecy: neurological disorders and anaemia
Intrinsic factor from parietal cells of stomach requried for B12 absorption in small intestine
106
Ascorbic Acid (VitC)
Cofactor in collagen synthesis
Neurotransmitter metabolism
Iron absoroption
Antioxidant
Sources: citrus fruit, cabbage
Deficiency: scurvy
107
Vitamin A
Derived from β carotine
Stored in liver
Retinal -> night vision
Retinol -> epithelium growth (skin/eyes)
Deficiency: Xeropthalmia (dry eye)
108
Vitamin D
1,25-Dihydroxycholecalciferol
(liver adds OH at 25, kidney adds OH at 1)
Derived from cholesterol
Requires UV for synthesis (from 7-dehydrocholesterol)
Important in Ca2+ regulation and bone development
PTH, [Ca2+], [PO4] alter kidney enzymes for synthesis
Deficiency: rickets, osteomalacia, MS?
(PTH maintains [Ca2+] at expense of bones)
109
Vitamin E
Antioxidant (in membranes, intercepts free radicals)
| Signal molecule for inflammation & cell division
110
Vitamin K
Important in blood clotting (factors II, VII, IX, X)
| Gut flora make significant amounts of Vitamin K
111
BMI
weight (kg) / height squred (m2)
40 = morbidly obese
* increased incidence of cancer, stroke, CVD, diabetes
112
Euchromatin vs Heterochromatin (constitutive and facultative)
Hererochromatin
- light bands with giemsa stain
- A+T rich
- hypermethylation of CpGs
- hypoacetylation of histones
- contains hardly any genes, not opened easily
- chromatin very condensed
Euchromatin
- light bands with giemsa stain
- regions that are actively transcribing genes
- G+C rich
- hypomethylation of CpGs
- hyperacetylation of histones
- located towards centre of nucleus
some chromatin never goes into euchromatic state (constitutive) vs that which can switch (facultative)
113
Which way do we read genes?
5' to 3'
114
Basics of Gene Expression
```
DNA
promotor region (TATA box)
transcription (RNA polymerase)
mRNA (5'cap and poly-A tail)
excision of introns (snRNPs form spliceosome loop)
translation
proteins
```
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Regulation of Gene Expression
- constitutive - 'housekeeping' genes, constant expression
- regulated - time (development), place (cell type), signal
- multiple promotors
- alternative splicing
- non-coding RNAs
- acetylation / methylation
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Non-coding RNAs
lnc
si
mi
long non coding lncRNAs (decoy, scaffold, guide, enhance)
short interfering siRNAs (mRNA clevage and degradation)
micro miRNAs (repressed translation)
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Role of Epigenetics in Regulation of Gene Expression
Change in DNA expression/repression with no change in DNA sequence
DNA (methylation)
histones (variants and acetylation/methylation)
nucleosomes (factors influencing how close nucleosomes are)
non-histone scaffold
location within nucleus (inactive near periphery)
non coding ncRNA gene silencing
genetic imprinting & X chromosome inactivation (Xist)
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DNA methylation
typically occurs at CpG (CG pairs)
methyl groups are chemical tags
CpG-rich islands associated with promotor regions
methylation of CpG islands = reduced gene expression
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Bi-allelic Expression
majority of genes are expressed from both gene copies
aneuploidy = unbalanced sets of chromosomes due to excess or deficiency = increased or decreased gene expression
(e.g. polyploidy, trisomy, monosomy) - can be due to failure of chromosomes to separate during division
monoallelic gene expresion
- certain genes must be expressed from only one copy for normal cell function
- specific mechanisms INACTIVATE one of the two copies (e.g. X chromosome inactivity in females)
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Autosomal recessive inheritance
- diseases
- mechamism
cystic fibrosis, sickle cell anaemia, thalassaemia, haemochromotosis
one altered copy does not cause phenotype
can tolerate 50% sufficient for cell function
two altered non-functional copies cause phenotype
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Autosomal dominant inheritance
e.g. huntingtons
loss of single gene causes a specific phenotype
may have novel 'gain of function' or insufficient function (haploinsufficiency)
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X-chromosome inactivation
random inactivation in cells of early embryo
DNA methylation
hypochromatin structure
non-coding RNA (Xist)
female cells are mosaic (different X chromosomes inactivated in each cell)
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Genomic Imprinting
approx 1% of genes expressed exclusively from one chromosome (maternal or paternal)
epigentic process (DNA methlylation, chromatin condensation, ncRNAs)
imprints present in paternal and maternal somatic cells
imprints erased during gametogenesis
all mature gametes absorb maternal or paternal pattern
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Mechanisims of Disorders of Genomic Imprinting
Loss of heterozygosity (deletion of coding region from m or p chromosomes)
Uniparental disomy (two copies of chromosome inherited from one parent)
epimutation - loss of imprinting (low folate = reduced DNA methylation)
mutations of DNA sequence of imprinted gene
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Mutations in Imprinted Genes & Patterns of Inheritance
mutation in active maternal gene
= carrier & affected females can have affected children (but not carrier children)
carrier males and affected males cannot have affected children (but can have carrier children)
126
Prenatal Screening vs Diagnostic Testing
Screening
- offered to all pregnant women
- non invasive
- not definitive
Diagnostic
- offered to women at increased risk
- invasive (risk of miscarriage)
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Prenatal Screening Tests
- chromosomal (tri 21, 18)
- neural tube
- genetic tests (parents)
1st trimester combined screening (T21,T18)
- blood taken 9-13 weeks (2 biochem analytes)
- PAPP-A
- hCG
- Ultrasound performed between 11-13 weeks
- nuchal translucency (oedema)
- crown rump length
2nd trimester screening (T21, T18, neural tube)
- blood taken 14-20 weeks (4 biochem analytes)
- hCG
- inhibin A
- α-fetoprotein
- oestriol
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Procedures in Sampling Fetal Cells/DNA
Chorionic Villus sampling (CVS)
- from 11 weeks gestation
- Ultrasound guidance needle inserted
- aspiration of placental tissue
- ~1% increased risk of miscarriage
Amniocentesis
- frim 15 weeks gestation
- ultrasound guidance needle inserted
- aspiration of amniotic fluid
- ~0.5% increased risk of miscarriage
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Tests Used to Analyse Chromosomes
Fluorescence in situ hybridisation
- performed on non-dividing cells
- fluorescence binds to chromosomes in Interphase
- fast but less accurate
Karyotyping
- grow cells, arrest in metaphase
- burst and count chromosomes & banding
Microarrays (SNPs and CNVs)
cfDNA massive parallel sequencing (NIPT)
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Robertsonian Translocation
Translocation between long arms of acrocentric chromosomes
e.g.
45,XX,der(14;21)(q10;q10)
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Chromosomal Abnormality Nomenclature
- deletion
- inversion
- translocation
- duplication
- derivative
DELETION - 46,XX,del(4)(p15)
deletion in chromosome 4 at breakpoint p15
INVERSION - 46,XY,inv(2)(p12;q12)
inversion of chromosome 2 with breakpoints at p12 and q12
TRANSLOCATION - 46,XX,t(3;9)(p14;q21)
Balanced translocation between chromosomes 3 and 9
breakpoints at band p14 on chromosome 3 and q21 on chromosome 9
DUPLICATION - 46,XX,dup(5)(p13;p14)
Segment between bands p13 and p14 on chromosome 5 is duplicated
DERIVATIVE - 45,XX,der(13,14)(q10,q10)
- balanced robertsonian translocation between chromosomes 13 and 14
