Biochem step 1 contd Flashcards
For monosaccharides such as glucose, galactose, and fructose to be absorbed after ingestion, they need to first pass through the apical side of the gastrointestinal (GI) epithelium. Then they pass through the basolateral side of the epithelium into the blood, as illustrated in the diagram. The apical side of the GI epithelium has numerous microvilli with dedicated transporters. Both glucose and galactose traverse the apical membrane by the action of ?
the transporter sodium-dependent glucose transporter 1 (SGLT1).
SGLT1 is a symporter, since it simultaneously transports sodium and either monosaccharide into the cell
This patient’s presentation of thin, translucent skin over her abdomen with prominent varicose veins and many bruises on her shins and a family history of a similar problem suggest a diagnosis of ?
vascular Ehlers-Danlos syndrome (EDS). The image shows a berry aneurysm (red circle). Berry aneurysms are congenital and associated with several syndromes. Patients with vascular EDS are at risk for the development of berry aneurysms like the one seen in this patient. She likely experienced an acute rupture of a berry aneurysm resulting in intracranial hemorrhage and acute onset of unconsciousness and, eventually, death.
EDS is a group of disorders resulting from defects in collagen synthesis and processing. Vascular EDS (type IV) is associated with a defect in the formation of type III procollagen, a precursor of the collagen found in many tissues.
Marfan syndrome is caused by a ?
mutation of the fibrillin-1 gene on chromosome 15 and is associated with long, thin extremities; loose and occasionally hyperextensible joints; and aortic aneurysms
Patients with epidermolysis bullosa have an abnormality in ?
either keratin 14 or keratin 5, resulting in skin that readily breaks and forms blisters with minor trauma.
Osteogenesis imperfecta is caused by a ?
defect in type I procollagen and is characterized by multiple spontaneous bone fractures, retarded wound healing, and characteristically blue sclerae
A defect in type IV collagen is the underlying cause of ?
Alport syndrome. Alport syndrome is characterized by nephritis with hematuria, hearing loss, and eye disorders.
relatively young patient with severe dyslipidemia, tendon xanthoma (a nodule composed of lipid deposits) over the Achilles tendon, and a family history of early MI most likely has a form of ?
familial hypercholesterolemia. Dietary modification, drastically limiting intake of saturated and trans fats and cholesterol; weight loss; and aerobic exercise are the first-line treatment options for any patient with elevated cholesterol levels, including this one. However, these measures often have only minimal effect.
The enzyme, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, catalyzes the rate-limiting step of the de novo cholesterol synthesis pathway. Statin medications are HMG-CoA reductase inhibitors and are the first-line pharmaceutical treatment for both familial and acquired forms of hypercholesterolemia. By blocking the rate-limiting step in cholesterol synthesis, statins can increase hepatic synthesis of LDL receptors, thereby lowering serum LDL levels. One characteristic side effect of HMG-CoA reductase inhibitors is statin-induced myopathy, which causes muscle soreness and weakness, as seen in this patient. Her elevated serum creatine kinase indicates muscle injury.
This patient’s abdominal distention, hyperactive bowel sounds, and tenderness on palpation should raise the suspicion of a bowel obstruction caused by an abdominal tumor. In light of his relative youth and the frequency of cancer in his close relatives, this patient most likely has?
hereditary nonpolyposis colon cancer (HNPCC), also called Lynch syndrome. HNPCC is an autosomal dominant condition and an example of the “two-hit hypothesis”: the first mutation in the mismatch repair mechanism is inherited, and the second mutation is acquired spontaneously later in life. The process of mismatch repair is defective in patients with this condition.
Base excision repair occurs by?
removal of the base at an apurinic or apyrimidinic site. Once the nucleotide is removed, DNA polymerase fills the gap
Double-strand break repair is a complicated repair mechanism for ?
double-strand injuries secondary to radiation and free radicals.
Pyrimidine dimer repair is a mechanism that fixes ultraviolet light–induced pyrimidine dimers; deficiency of this repair mechanism is the cause of ?
xeroderma pigmentosum
APC-mediated tumor suppression is implicated in ?
familial adenomatous polyposis (FAP).
This pregnant patient presents with a very high level of β-hCG, and ultrasound findings of lucent and echogenic areas (a “snowstorm” appearance) with no fetal heartbeat detected. Based on these findings, she most likely has a ?
molar pregnancy (hydatidiform mole) Molar pregnancy classically manifests with the triad of hyperemesis, vaginal bleeding, and hyperthyroidism. Investigators hypothesize that the symptoms of hyperthyroidism may arise because of homology between the structure of hCG and thyroid-stimulating hormone (TSH).
Three separate spontaneous abortions strongly suggests that a genetic defect is causing the fetal death. Each fetus had massive abdominal swelling and edema consistent with ?
hydrops fetalis. Defined as an abnormal accumulation of fluid in 2 or more fetal compartments resulting in general swelling of the whole body (anasarca), hydrops fetalis is incompatible with life.
Each of the parents has microcytic anemia (MCV < 80 fL). The microcytic anemia that’s associated with hydrops fetalis is α-thalassemia. There are four forms of α-thalassemia, with differing severity according to how many α-globin alleles are deleted (see table). When only one of the four alleles is deleted (thus forming only one nonfunctional α-globin chain), there is no gross clinical phenotype because three functioning alleles is sufficient to support normal hemoglobin production. However, people with such a deletion are silent carriers. This type of disease is known as α-thalassemia minima.
The patient is a young boy who presents with delayed developmental milestones, short stature, hypotonia (poor suckling as an infant), obesity, small hands and feet, and hypogonadism. These signs and symptoms are most suggestive of ?
Prader-Willi syndrome. The images below illustrate some of the typical facial features (eg, narrow forehead, downward corners of the mouth) associated with this syndrome.
Prader-Willi syndrome (deletion of q12 on paternally derived chromosome 15) is a genetic disease that manifests with hypotonia at birth and later with intellectual disability, short stature, and obesity.
