Biochemistry-Endterm Flashcards
Inborn errors of metabolism
Monogenic disease but can be polygenic.
Leads to changing in an enzyme in a primary pathway or in a secondary pathway
Treat through diet restrictions
Disorders of amino acid metabolism
- Phenylketonuria
- Urea cycle enzymes
- Hypergylcinemia
Disorders of carbohydrate metabolism
- Glycogen storage disease
- Diabetes
- Galactosemia
Disorders of lipid and lipoprotein metabolism
- Familial hypercholesterolemia
- Tangier disease (HDL deficiency)
Disorders of purine and pyrimidine metabolism
- Lesch-Nyhan syndrome
- ADA
- SCID
Hormone disorders
- Thyroid diseases
- Androgen resistance syndrome
Nutritional disorders
- Obesity
- Problems in transporting folate
Organelle diseases
-Mucopolysaccharidosis in lysosomes
Tissue disorders
- Collagen diseases
- Muscular dystrophies
Systemic disorders
-Hemophilia
Marfans syndrome
Autosomal dominant condition due to a defect in fibrillin on the FBN1 gene located on chromosome 15
Affects:
- Cardiovascular system (weak heart+blood vessels)
- Ocular problems
- Skeletal system: spine, chest & joints
Major criteria for diagnosing Marfans syndrome
- Enlarged aorta and tear in aorta
- Skeletal problems
- Family history
- Dislocation of lens
Minor criteria for diagnosing Marfans syndrome
- Loose joints
- Short sightedness (myopia)
- Unexplained stretch marks
Akhenetons Marfans syndrome
- Long face and fingers
- Slit-like eyes
- Arachnodactyl: spider-like fingers
- Wide hops
- Protruding belly
Fibrillin
Major component of microfibrils. Need 3 fibrillin to make a microfibril. Serves as a substrate for elastin
2 mutations of FBN1
- In-frame mutation (missense)
- Premature termination (nonsense)
Diagnosing Marfans syndrome
- Reliable reverse transcriptase PCR
- Next generation sequencing
Reliable reverse transcriptase PCR
Single cell genotyping
Next generation sequencing
Take the patients DNA and make specific primers to check if the patient has Marfans syndrome
Treating Marfans syndrome
There is no treatment
Can take beta blockers to reduce stress on the aorta
Gene therapy is also an option but not reliable
-Would use ribozymes and RNA anti-sense technology to reduce mutant FBN1
Hemophilia
Condition in which a person is unable to form a stable clot
Phenotype: easily bruised, prolonged bleeding
Can lead to death since person will have an internal hemmorhage
X-linked recessive inheritance
Three types of hemophilia: A, B, C
Hemophilia A
Absence or almost no clotting factor 8
Factor 8
Serves as a coenzyme to change X to Xa in the clotting cascade (tense reaction)
Produced by the HEMA gene
HEMA gene
Located on X chromosome on position 28
2 mutations of HEMA gene:
- Point mutation: less severe as have some activity of factor 8
- Inversion: severe
Hemophilia B
Lack of clotting factor 9
Detecting mutations in hemophilia
Amplify the factor 8 and 9 genes by PCR. Then screen by restriction fragment length polymorphism analysis (RFLP) or repeat sequence polymorphism
This will show the genotype and the transition of it through generations
Treatment of hemophilia
- Replacement therapy: injecting the clotting factors
- Desmopressin: an analogue of the diuretic vasopressin found to increase the levels of clotting factor 8 slightly. Used when there is a minor surgery
- Gene therapy: not effective as the clotting factors are too big
Cystic fibrosis
An autosomal recessive condition that affects the exocrine glands. People with cystic fibrosis have thick mucus and high levels of chlorine in their sweat.
It is diagnosed within the first month of life
Rates of cystic fibrosis
Highest in Europe and lowest in Asia
Cause of cystic fibrosis
Caused by a defect in the CFTR gene which is located in chromosome 7. CFTR gene is responsible for producing the CFTR protein
CFTR protein
Helps transport chlorine and sodium in epithelial cells by hydrolyzing ATP to transport the ions
Without the protein, thick mucus accumulates in the body leading to respiratory insufficiency and systemic obstruction
Mutations of CFTR gene
Most common mutation is the delta F508 mutations. However, there are a lot more mutations
Mutation means that there is no ATP hydrolysis for chlorine transport
Delta F508 mutation
Caused by a deletion of 3 nucleotides on exon 10 which results in the deletion of phenylalanine at position 508.
Classes of CFTR mutation
Six classes and each class has a different severity level
Class 1
Can’t produce the protein so need to find a way to fix protein synthesis
Class 2
No trafficking of proteins so need to correct protein folding
The delta F508 mutation belongs to this class
Class 3
No protein function so need to restore channel conductance
Class 4
Less protein function so need to restore channel conductance
Class 5
Less protein production so need mature protein and correct misplicing
Class 6
Less stable protein so need to stabilize it
Cystic fibrosis and sweat glands
Normally, sodium chloride carry water to skins surface and then is tea sorbet back in the body
In the case of cystic fibrosis, the sodium chloride is not reabsorbed leading to the skin to be salty
Also, when a person exercises, they experience fatigue, nausea, dizziness, etc.
Screening cystic fibrosis
Done by:
- Mutation testing
- Sweat test
- Immunoreactive trypsinogen
Mutation testing
At birth, babies are screened for cystic fibrosis. Common mutations are detected however less common ones aren’t detected
Sweat test
Is the gold standard for diagnosing cystic fibrosis. Chlorine levels in the sweat is 5 times higher than in normal sweat. This allows for the diagnosis of cystic fibrosis in hound children and in adults
Immunoreactive trypsinogen
Mucus blocks the pancreatic ducts so trypsinogen can’t go to the intestine. However, if a person tests positive for this test, should also do the sweat test as well
Treating cystic fibrosis
Can’t treat it but can alleviate symptoms
Can use CFTR modulators to correct the defective function of the CFTR protein. However, it only works for a couple of mutations
If the lungs are severely damaged, then a lung transplant is required
Nucleotides
Composed of a nitrogenous base, sugar, and phosphate group (either 1,2, or 3)
Purine
Nitrogenous bases that are made of fused rings
Pyrimidine
Nitrogenous bass that is made of a single ring
Roles of nucleotides
- Carry activates metabolic intermediates (UDP-glucose)
- Part of coenzyme structures (NAD, FAD)
- Energy currency
- Secondary messenger signals
Nucleoside
Base and sugar. No phosphate groups
Adenyalte kinase
Enzyme responsible for turning AMP into ADP and vice versa. Uses ATP to help in the conversion.
So AMP+ATP -> 2 ADP
Guanylate cyclase
Changes GMP to GDP with the help of ATP
ATP helps change…
- GDP to GTP
- CDP to CTP
De novo purine synthesis
Ribose 5 phosphate (from PPP) is changed to PRPP by PRPP synthetase with the help of magnesium and ATP
PRPP is changed to amido PRT by GPAT and this is the rate limiting step.
9 more reactions form inosine monophosphage (IMP)
In general, the nitrogenous base is added to the sugar which is PRPP
Low PRPP means that the de novo synthesi
IMP
IMP can be changed to GMP and AMP. ATP is required to make GMP and GTP is required to make AMP
Feedback inhibition of the products leads to stoping of the reaction of IMP
PRPP synthetase regulation
Activated by inorganic phosphate
Inhibited by purines since already have a lot of purines in the body so don’t need to make more
Regulation of GPAT
PRPP activates the enzyme in a positive feedback manner
Purines inhibit the enzyme
Salvage pathway
Taking free nitrogenous bases and changing them into nucleotides
Have two enzymes:HGPRT and APRT
Uses PRPP so depletes the supply of PRPP
HGPRT
Changes hypoxanthine to IMP and guanine to GMP
APRT
Changes adenine to AMP
Creating deoxyribonucleotides
Need to convert ribonucleotodes into deoxyribonucleotides by reducing it at the 2’ end
Reduction is carried out by ribonucleotode reductase
Creates the correct amount of each deoxyribonucleotides by binding to specific allosteric sites
Ribonucletoide reductase
Needs ribonucleoside diohospahte as a substrate
After ribonucleotide reductase reduces, it becomes divided so need to reduce it again and this is done by thioredoxin
Thioredoxin
Regulated by thioredoxin reductase
De novo pyrimidine synthesis
The nitrogenous ring is first created and then it attaches to PRPP.
Orotic acid is added to PRPP by orotate phospho-ribosyl tranferase to form orotic monophosphate (OMP)
OMP is changed to UMP by orotidine carboxylase and releases carbon dioxide
UMP is further metabolized into the different pyrimidine bases
Purine nucleotide cycle
Need it to replenish the supply of TCA molecules.
AMP is changed to adelynosuccinate which is then converted back to AMP. Whole process is done by adenylate kinase
Aspartate is changed to fumarate (TCA intermediate) and this cycle can continue since large reservoir of aspartate in the cell and can get more from the bloodstream
If no purine nucleotide cycle…
Then muscles become very fatigued
Pyrimidine metabolism
Happens readily in humans
Purine matabolism
Can’t be done by human cells so turned into uric acid as a waste product
Breaking down AMP
Changed into adenosine by nucleotidase
Converted to inosine by adenine deaminase
Breaking down IMP
Converted into inosine by nucleotidase.
Changed to hypoxanthine by PRP.
Hypoxanthine changed to xanthine by xanthine oxidase
Breaking down GMP
Converted into guanosine by nucloeotidase
Changed into xanthine by guanine deaminase
Breaking down XMP
Changed into xanthosine by nucleotidase
Changed into xanthine by PRP
Uric acid
Formed by xanthine oxidase
Soluble at alkaline pH in its anionic form
When uric acid precipitates, it leads to gout
Xanthine oxidase
Is a bifunctional enzyme
- Changes hypoxanthine to xanthine
- Changes xanthine to uric acid
Gout
Inflammatory joint disease mostly located in the distal parts of the body since low temperature leads to low solubility
Caused by the formation of uric acid crystals
Treatment of gout
- Inhibiting xanthine oxidase by drugs such as allopurinol
- Dialysis removal of uric acid
- Taking in a low purine diet