Question N-07: A 40-year-old, overweight female patient presents to her physician. She was very proud of having lost 40 lbs. during the previous year, but now noticed that her “hair is falling out.” and she is losing vision, mainly at night. On questioning, she reports having followed a strict fat-free diet. Her complains are probably related to a deficiency of which of the following vitamins?
a) Vitamin A
b) Vitamin D
c) Vitamin E
d) Vitamin F
e) Vitamin K
Question N-06: A 45 year-old patient presents with severe pallor, peripheral neuropathy and psychosis. Lab tests show: severe anemia, MCV (Mean Corpuscular Volume) = 140 fl (Reference range: 80-100 fl), WBC and platelets low, and presence of antibodies to intrinsic factor, produced by parietal cells.
This anemia is caused in this patient by a deficit of:
Thyroid Follicle (Picture taken by Mamin, Flickr)
Due to its role in thyroid hormones biosynthesis, a radioactive form of this mineral can be use for the diagnosis of Thyroid diseases
Observe the following clip from the movie: “A beautiful mind”:
(I-06) In the clip that appears above, the patient present seizures as a result of:
a) An electroshock treatment
b) A sudden increase of the entrance of glucose into the brain as a consequence of the insulin shot.
c) The paranoic eschizophrenia the patient suffered.
d) A sudden decrease of glucose in blood.
e) A hepatic coma as a consequence of sudden entrance of glucose to the liver.
f) A sudden increase of ketonic bodies in blood.
See the explanation at the Biochemistry at the Movies page.
Questions C-06 to C-08
Another format you can expect to see in your Multiple Choice exams:
Choose, among the following polysaccharides, which correspond to each of the questions that appear below:
d) Hyaluronic acid
f) Chondroitin Sulfate
(C-06) This carbohydrate acts as lubricant of synovial fluid and contributes to
tensile strength and elasticity of cartilages and tendons. It is also an
important component of skin.
(C-07) It is the most important polysaccharide in human diet:
(C-08 ) It is the form in which glucose is stored in muscle and liver for ulterior use as fuel:
Answer to Question E-05
b) Induced fit
The Induced fit model describes the formation of the E-S as a result of the interaction between the substrate and a flexible active site. The substrate produces changes in the conformation on the enzyme, aligning properly the groups in the enzyme. It allows better binding and catalytic effects.
This model opposes to the former Lock and Key model (c) , that explained the formation of the E-S complex as a result of the binding of complementary geometrical rigid structures, as a lock and a key.
Follow this link to find a very good animation that represents these two models:
The Concerted model (a) and the Sequential model (e) are models used to explain the allosteric changes of conformation of an enzyme from the T structure to the R structure and viceversa. In the concerted model all the subunits that form the allosteric protein change conformation at once, while in the sequential model the change in conformation of one subunit favors the change in conformation of the other subunits and so on.
The Michaellis Menten model (d) is related to the kinetics of enzyme catalyzed reactions, and describes the relationship between the concentration of substrate and enzyme velocity in a reaction where no allosteric effects exist.
More information about:
Michaelis Menten model:
Induced fit model:
Concerted Model and Sequential Model:
(Q AM-06) H.C, a 4 month-old male infant, emigrated with his parents from a Latin American country to the United States a month ago. He was normal at birth but in the past several days a tremor in his extremities has appeared. Last night he presented gross twitching movements in his crib. When you examine the patient, you note a musty odor to the baby’s wet diaper.
Immediately you order a screening test for PKU and it results positive.
Besides diet restrictions, but warranting an appropriate amount of the essential amino acids, which of the following amino acids you should supplement in higher quantities than in a normal diet, since it is essential for this patient?
e) Phenyl alanine