Week 3 Flashcards
what does Km represent in relation to Vmax
The Michaelis constant (Km) is the substrate concentration at ½ Vmax.
Late stage (irreversible) cell injury occurs when:
membrane damage and cell death
Mechanism: degradation of phospholipids in the plasma membrane → rupture of the cell membrane → release of cytosolic enzymes into the serum and influx of Ca2+ into the cytoplasm → activation of lysosomal enzymes and protease (e.g., calpain) → ↑ breakdown of cellular proteins and damage cytoskeleton → autolysis
another explanation:
When intracellular acidosis becomes so severe that it injures lysosomal cell membranes, powerful enzymes leak into the cytoplasm and begin to digest the cell. Irreversible nuclear changes (condensation, fragmentation and fading) result, and the plasma membrane is damaged as membrane phospholipids are broken down. Increased mitochondrial permeability induces a change known as vacuolization, where collections of phospholipids are observed within the mitochondria.
In a hypoxic cell, the initial change to the nuclear material is ____________
clumping of chromatin. This is a reversible change. Once nuclear condensation (pyknosis), fragmentation (karyorrhexia) and fading (karyolysis) occur, the change is irreversible.
deficiency of vitamin C causes interferes with which step in collagen synthesis?
Hydroxylation of proline and lysine residues is key for collagen formation, but this process requires vitamin C as a cofactor.
Karyotype of Turners syndrome
45, XO is Turner’s syndrome.
karyotype of klinefelters syndrome
he karyotype is 47, XXY
Cyclin-dependent kinases (CDKs) are a family of proteins that become activated when bound by____________
their corresponding cyclins.
CDKs are constitutively expressed in cells and when activated phosphorylate target proteins. CDK is inhibited by p21
Key cyclin-CDK associations that allow progression from G1 to S are:
_______ and ________
cyclin D-CDK4/6 and cyclin E-CDK2.
symptoms of PKU and what is it?
hypopigmentation, eczema, gait abnormalities and concern for intellectual disability, it is likely that the patient’s brother is suffering from phenylketonuria (PKU), an inherited disorder of amino acid metabolism. PKU results from a deficiency of the enzyme phenylalanine hydroxylase, and is inherited in an autosomal recessive pattern.
Trisomy 21 is what disorder. what are the perinatal findings that indicate its presence?
(Down syndrome) presents with decreased alpha-fetoprotein (AFP), decreased estriol, elevated beta hCG, and elevated levels of inhibin A. Nuchal translucency is a common finding with ultrasound, but is not always present.
Clinical features of Trisomy 21 include:
- Intellectual disability
- Brushfield spots (connective tissue aggregates in the iris)
- Epicanthal folds
- Flat nasal bridge
- Transverse palmar creases
- Gap between first & second toe
- Congenital heart defects (endocardial cushion defects and septal defects)
Trisomy 18 is
(Edward syndrome) is a congenital disorder that develops from meiotic nondisjunction resulting in an extra copy of chromosome 18. This is the second most common trisomy after Down syndrome.
The clinical presentation of an infant with trisomy 18 includes:
- Low birth weight
- Closed fists with the index finger overlapping the 3rd digit, and the 5th digit overlapping the 4th
- Rocker-bottom feet
- Microcephaly
- Micrognathia
- Intellectual disability
- Cardiac & renal malformations
A diagnosis of trisomy 18 is suggested by the following pattern of results on the serum quadruple screening:
- Decreased alpha-fetoprotein (AFP)
- Decreased human chorionic gonadotropin (hCG)
- Decreased estriol
- Normal or low inhibin A
The above pattern of findings on quadruple screening suggests a high risk for trisomy 18, and a patient with these results would likely be referred for amniocentesis so that a definitive diagnosis could be made via karyotype.
XXY is the karyotype associated with _________
Klinefelter’s Syndrome
Symptoms:
***
does not have associated cardiac defects.
22q11.2 deletion causes _________ syndrome
DiGeorge Syndrome ( also called 22q11.2 deletion syndrome).
Symptoms
***
The associated cardiac defects of DiGeorge include Tetralogy of Fallot and interrupted Aortic Arch
45, XO, is the genetic defect associated with ____________
Turner Syndrome
clinical signs of asymptomatic aortic stenosis including classic heart murmur, weak femoral pulses, and upper extremity hypertension. Turner syndrome is associated with congenital heart disease;
common defects include coarctation of the aorta, aortic stenosis, and bicuspid aortic valve.
other characteristics of Turner syndrome include short stature, webbed neck, low posterior hairline, misshapen or rotated ears, a narrow palate with crowded teeth, a broad chest with widely spaced nipples, cubitus valgus, hyperconvex nails, multipigmented nevi, and pubertal delay.
Clinical presentation of Prader-Willi syndrome and what causes it exactly?
Hypotonia, scrotal hypoplasia, and childhood obesity suggest Prader-Willi syndrome. In this condition, the active (non-imprinted) paternal copy of genes on 15q11-13 are lost through deletion or inversion. The maternal copy is already inactivated through genetic imprinting, leaving the patient effectively with loss of both loci.
