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MD1 > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

Carbonic Anhydrase

A

Catalyses CO2 + H2O H+ + HCO3-

Important for acid base balance
High in RBC

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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)

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3
Q

Myasthenia Gravis

A

Anti-AChR prevents Ach binding to nicotinic receptors and activation of skeletal muscle

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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

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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.
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6
Q

Ehlers Danlos Syndrome

A 
Collagen mutant (fibrous proteins and enzymes)
Extra flexibility
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7
Q

Marfan Syndrome

A

Mutation / decreased production / delayed transport of fibrillin 1 into ECM

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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

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9
Q

Porphyria

A

Haem feedback inhibition failure

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10
Q

Haem binding site

A

His F8

Oxy between Fe2+ and His E7

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11
Q

Osteogenesis Imperfecta

A

Glycine at position 748 in collage mutates to cysteine causing kink in strand and brittle bones.

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12
Q

Cholesterol Structure

A

ABCD rings
hydroxy group on 3rd position
hydrophobic section is planar

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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

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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)
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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).

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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

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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

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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)
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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]

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20
Q

Ascending Loop of Henle

A

LUMINAL
Na+, K+, 2Cl- cotransporter (in) [passive]

BASAL
Na+ / K+ (in) ATPase [active]

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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

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22
Q

P450 reaction

A

RH + NADPH + H+ + O2
->
ROH + H2O + NADP+

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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

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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

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25
Q

Bilirubin

A

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

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26
Q

Haptoglobin (Hp)

A

plasma protein, binds haemoglobin
high hemolysis decreases free haptoglobin levels
when Hp is depleted free Hb is excreted in urine

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27
Q

Hemopexin

A

carries haem (not Hb) to liver
higher affinity than albumin
low haemopexin is indicator of haemolytic anaemia

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28
Q

Alcohol content of 1 std drink

A

10g

Cleared in approx 1 hour

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29
Q

Alcohol key features

A

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

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30
Q

Alcohol Oxidation

A

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

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31
Q

GI Digestive Secretions

A

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

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32
Q

Gallstones

A

Mostly cholesterol
Stained with bilirubin derivatives
Normal cholesterol crystalisation time is approx 20 days

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33
Q

Duodenal Gland secretion Mechanism

  • ACh & CCK
  • Secretin
A

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

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34
Q

Breakdown of sugars

A

Lactose -(Lactase)-> Galactose & Glucose (SLGT1)
Sucrose -(Sucrase)-> Fructose (GLUT5) & Glucose
Starch -(Amylase)-> Maltose -(glucosidases)> Glucose

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35
Q

Major Causes of Jaundice

A

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)
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36
Q

Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency

A

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)

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37
Q

Galactosaemia

A

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

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38
Q

Hepatocyte Enzyme Locations & Half Lives

A

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

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39
Q

Liver Enzymes

Hepatocellular Damage

A

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)

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40
Q

Liver Enzymes

Biliary Disease

A

ALP, GGT
Extrahepatic biliary obstruction (intrahepatic may have slightly raised levels)
- colon/pancreatic cancer, cholestasis

Biliary Disease can lead to hepatocellular death

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41
Q

Liver Enzymes

Inducing Drugs

A

GGT, ALP
Antibiotics, Statins (rhabdomyopathy), EtOH, Paracetamol
GGT involved in glutathione production, important in removing ROS

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42
Q

Henderson-Hasselbalch for HCO3- and CO2

A

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

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43
Q

Gastric acid secretion (internal biochemistry)

A

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

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44
Q

Gastric acid secretion (stimulation)

A

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

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45
Q

Alcohol Cytochrome

A

2E1

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46
Q

TRPV1

A

Noiceceptive transducer
Receptor for capsaicin

Capsaicin lowers heat threshold so that essentially the channel is always open (i.e. pain)

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47
Q

Unstable Repeat Expansions

A

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

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48
Q

Iodine & Thyroxine

A

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)

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49
Q

Steroid Elimination Cytochrome

A

CYP3A4
Most abundant CYP in entire body
Introduces -OH into steroid ring then other enzymes form bile acids

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50
Q

Where do steroids bind?

A

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

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51
Q

What is tested for in a pregnancy test

A

hCG

Human Chorionic Gonadotropin
Produced by trophoblast and placenta

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52
Q

Energy in ATP

A
  1. 5kj/mol

* Adenosine Triphosphate Phospate backbone stabilised by Mg2+ forming Mg-ATP as substrate

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53
Q

Energy in NADH

A

220kj/mol

Nicotinamide Adenine Dinucleotide (from vitamin B3)
Storage molecule for electrons from Glycolosis/Krebs to ETC

54
Q

ATP production of Aerobic vs Anerobic Metabolism

A

Aerobic: 30-32ATP
Anaerobic: 2ATP

*106 ATP is generated from palmitate (fatty acid)

55
Q

Glucose

  • structure
  • dangers
A

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
Q

Aldose vs Ketose sugars

A

ALDOSE:
Glucose & Galactose
Aldehydes O=CR-H

KETOSE:
Fructose
Ketones O=CR-R’

57
Q

Cell Glucose Transporters

A 
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
Q

Beta-oxidation

A

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
Q

Glycolysis

A

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
Q

Glycogenesis

A

Creation of glycogen

61
Q

Glycogenolysis

A

Breakdown of glycogen

62
Q

Gluconeogenesis

A

Generation of glucose from glycerol of amino acids, NOT fatty acids (they undergo beta-oxidation)

Carbon sources:
Lactate
Amino Acids
Glycerol (from TAGs) -

63
Q

Anaerobic Glycolysis

A

Produces 2ATP
Occurs in cell cytosol
Produces Lactate

*Only pathway for RBCs, lens, retina, as they have no mitochondria

64
Q

Normal Blood Glucose Levels

  • Fasting
  • Fed (100g glucose)
A

Fasting: 4-5mM
Fed: <10mM (the renal threshold)

65
Q

Hb A1C

A

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
Q

Glycogen

A

Fasting reserve of glucose

Chemically intert, low osmotic profile

67
Q

Hexokinase

A

Catalyses Glucose -> Glucose 6-phosphate reaction in glycolysis
Transfers phosphate from ATP to glucosee

68
Q

Phosphohexose Isomerase

A

Catalyses Glucose 6-phosphate -> Fructose 6-phosphate reaction in glycolysis

69
Q

Phosphofructokinase

A

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
Q

Glucose-6-Phosphotase

A

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
Q

Lactose

A

β1-4 linked disaccharide of galactose and glucose

inability to epimerise the galactose to glucose is the cause of galactosaemia

72
Q

Glycerol metabolism

A

Backbone of TAGs
enters glycolisis (or exits) at GAP / DHAP stage
can also be created from fructose (via GAP / DHAP)

73
Q

Why is fructose bad?

A

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
Q

Mitochondria Functions & Disorders

A

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
Q

Urea

A

Produced from protein breakdown
100g excreted per day
Non-toxic
Highly soluble

76
Q

Products of The Citric Acid Cycle

A

Each turn produces:
3 molecules of NADH
1 molecule of FADH2
1 molecule of GTP or ATP

77
Q

Which ETC complexes are encoded by nDNA and which are encoded by mtDNA?

A 
nDNA = II
mtDNA = I, III, IV, V
78
Q

Malate-aspartate shuttle

A

Transfers reducing power of NADH from cytosol to mitochondria for oxidative phosphorylation (ETC)

79
Q

Glycerol-3-phosphate shuttle

A

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
Q

Typical adult dietary energy need per day

A

10MJ

All of which is radiated as heat regardless of work performed

81
Q

Calcium

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
  • control
A

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
Q

Phosphorous

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

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
Q

Potassium

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

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
Q

Sulphur

  • sources
  • functions
A

Best sources: Proteins (methionine, cysteine)

Primary functions: Keratin in hair and nails

85
Q

Sodium

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

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
Q

Chloride

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

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
Q

Magnesium

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

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
Q

Iron

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

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
Q

Zinc

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

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
Q

Copper

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

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
Q

Manganese

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

Best sources: Nuts, grains, vegetables
Primary functions: enzyme cofactor, bone formation
Deficiency: Rare
Toxicity: nervous system disorders

5-5.5mg/day

92
Q

Iodine

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

Best sources: Seafood, iodised foods
Primary functions: T3/T4
Deficiency: goitre, cretanism
Toxicity: elevated TSH, goitre

150ug/day

93
Q

Selenium

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

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
Q

Chromium

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

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
Q

Molybdenum

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

Best sources: Legumes, cereals, nuts
Primary functions: enzyme cofactor
Deficiency: N/A
Toxicity: N/A - reproductive effect?

45ug/day

96
Q

Fluoride

  • sources
  • functions
  • deficiency
  • toxicity
  • intake
A

Best sources: Water, tea, seafood
Primary functions: bone/teeth
Deficiency: tooth decay
Toxicity: Fluorosis (pitting and discolouration of teeth)

3-4mg/day

97
Q

Cobalt

A

We actually need vitamin B12 which contains cobalt

98
Q

Fat Soluble Vitamins

A

A, D, E, K

99
Q

Thiamine (B1)

A

Coenzyme in decarboxylations (aerobic metabolism)
Carbohydrate, protein, and fat metabolism
Nerve function

Sources: vegemite, breads, cereals

Deficiency: beriberi, wernicke-korsakoff

100
Q

Riboflavin (B2)

A 
Electron carrier (FMN, FAD)
Carbohydrate, protein, and fat metabolism

Sources: vegemite, dairy, cereals

Deficiency: magenta tongue

101
Q

Niacin (B3) (nicotinamide)

A

Coencyme
Electron carrier (NADH, NADPH)
Carbohydrate, protein, and fat metabolism

Sources: vegemite, wheat bran, cereals

Deficiency: Pellagra (dermatitis, diarrhoea, dementia, death)

102
Q

Pyridoxine (B6)

A

Amino acid metabolism

Sources: vegemite, nuts, bananas, cereals

Deficiency: rare

103
Q

Biotin

A

Glucose, fat, amino acid biosynthesis

Sources: brewers yeast, eggyolk cooked, soy

Deficinecy: dry, shiny, scaly skin of hands

104
Q

Folate

A

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
Q

Cobalamin (B12)

A

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
Q

Ascorbic Acid (VitC)

A

Cofactor in collagen synthesis
Neurotransmitter metabolism
Iron absoroption
Antioxidant

Sources: citrus fruit, cabbage

Deficiency: scurvy

107
Q

Vitamin A

A

Derived from β carotine
Stored in liver
Retinal -> night vision
Retinol -> epithelium growth (skin/eyes)

Deficiency: Xeropthalmia (dry eye)

108
Q

Vitamin D

A

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
Q

Vitamin E

A

Antioxidant (in membranes, intercepts free radicals)

Signal molecule for inflammation & cell division

110
Q

Vitamin K

A

Important in blood clotting (factors II, VII, IX, X)

Gut flora make significant amounts of Vitamin K

111
Q

BMI

A

weight (kg) / height squred (m2)

40 = morbidly obese

  • increased incidence of cancer, stroke, CVD, diabetes
112
Q

Euchromatin vs Heterochromatin (constitutive and facultative)

A

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
Q

Which way do we read genes?

A

5’ to 3’

114
Q

Basics of Gene Expression

A 
DNA
promotor region (TATA box)
transcription (RNA polymerase)
mRNA (5'cap and poly-A tail)
excision of introns (snRNPs form spliceosome loop)
translation
proteins
115
Q

Regulation of Gene Expression

A
  • constitutive - ‘housekeeping’ genes, constant expression
  • regulated - time (development), place (cell type), signal
  • multiple promotors
  • alternative splicing
  • non-coding RNAs
  • acetylation / methylation
116
Q

Non-coding RNAs
lnc
si
mi

A

long non coding lncRNAs (decoy, scaffold, guide, enhance)

short interfering siRNAs (mRNA clevage and degradation)

micro miRNAs (repressed translation)

117
Q

Role of Epigenetics in Regulation of Gene Expression

A

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)

118
Q

DNA methylation

A

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

119
Q

Bi-allelic Expression

A

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)
120
Q

Autosomal recessive inheritance

  • diseases
  • mechamism
A

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

121
Q

Autosomal dominant inheritance

A

e.g. huntingtons

loss of single gene causes a specific phenotype

may have novel ‘gain of function’ or insufficient function (haploinsufficiency)

122
Q

X-chromosome inactivation

A

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)

123
Q

Genomic Imprinting

A

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

124
Q

Mechanisims of Disorders of Genomic Imprinting

A

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

125
Q

Mutations in Imprinted Genes & Patterns of Inheritance

A

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
Q

Prenatal Screening vs Diagnostic Testing

A

Screening

  • offered to all pregnant women
  • non invasive
  • not definitive

Diagnostic

  • offered to women at increased risk
  • invasive (risk of miscarriage)
127
Q

Prenatal Screening Tests

A
  • 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
128
Q

Procedures in Sampling Fetal Cells/DNA

A

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
129
Q

Tests Used to Analyse Chromosomes

A

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)

130
Q

Robertsonian Translocation

A

Translocation between long arms of acrocentric chromosomes
e.g.
45,XX,der(14;21)(q10;q10)

131
Q

Chromosomal Abnormality Nomenclature

  • deletion
  • inversion
  • translocation
  • duplication
  • derivative
A

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

MD1 (11 decks)

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