3) Flashcards
A researcher in a Pharmaceutical company is asked to identify the amino acid residues that make up the agonist binding site of the human P2X1 receptor. P2X receptors are ion channels that are gated by extracellular ATP (a negatively charged molecule). After conducting a series of experiments the researcher identifies two key amino acid residues that facilitate agonist binding in this channel.
Which 2 amino acid residues are most likely to be the ones identified by the researcher?
Glutamic acid (E) and Aspartic acid (D) Alanine (A) and Methionine (M) Cysteine (C) and Methionine (M) Lysine (K) and Arginine (R) Phenylalanine (F) and Tryptophan(W)
Lysine (K) and Arginine (R)
CORRECT. Lysine and arginine are both positively charged. As opposite charges attract these would be the most likely amino acids to interact with the negative charges of ATP in the binding site of the channel.
A 56 year old woman with Chronic Obstructive Pulmonary Disease (COPD) always makes sure that she appears happy and cheerful when her family comes to visit, even when she is in a lot of pain, as she doesn’t want to worry them.
Which type of work best describes this scenario?
Biographical work Emotional work Everyday life work Identity work Illness work
Correct. Emotional work is the work people do to protect the emotional well-being of others (linked to identity work) that may also lead to a changed role and/or purpose for the person living with a chronic illness
A histopathologist looking at a H&E stained section from a lung biopsy notes the presence of anthracosis (image below).
Anthracosis
What accumulates in the lungs to cause this condition?
Carbon Denatured haemoglobin Haemosiderin Melanin Pigment containing macrophages
carbon
CORRECT – Anthracosis is the build-up of carbon within the lungs, however, it is asymptomatic. It is common among anyone who has lived in cities and is caused by the inhalation of air pollutants. The pollutants are phagocytosed by alveolar macrophages but cannot be broken down, meaning that the pollutant accumulates within the lungs. Anthracosis is harmless, however if large amounts of pollutants are inhaled, then fibrosis and emphysema of the lungs can occur. This is called coal workers pneumoconiosis.
A 28 year old builder falls from a ladder landing on his head and right shoulder greatly increasing the angle between his neck and shoulder on impact. He is admitted to the accident and emergency department for assessment. No bones are fractured or broken but he is found to have developed Erb’s palsy as a result of his fall.
Which presentation is characteristic of this type of palsy?
Arm laterally rotated, with a flexed elbow, and an extended and supinated wrist
Arm laterally rotated, pronated, adducted and with the elbow fully flexed
Arm medially rotated, supinated, adducted and with the elbow fully flexed
Arm medially rotated, pronated, adducted and with the elbow fully extended
‘Claw hand’ with hyperextension of all of the metacarpophalangeal joints and flexion of the interphalangeal joints,
Arm medially rotated, pronated, adducted and with the elbow fully extended
CORRECT – During the man’s fall, the increase in the angle between the man’s neck and right shoulder has led to damage to the upper part of his right brachial plexus, leading to Erb’s palsy. This means that he has damaged the superior trunk of the brachial plexus and thereby lost the supply of the anterior rami of the C5 and C6 spinal nerves to the peripheral nerves of the brachial plexus. Therefore, any muscles supplied that peripheral nerves which take contributions from the C5 and C6 spinal nerves will be weakened. The overall effect is to lose the functions of the C5 (shoulder abduction and lateral rotation) and C6 (elbow flexion, wrist extension and supination) myotomes. Therefore, the man will present to the accident and emergency department with an adducted arm that is medial rotated and fully extended. The man’s wrist will be pronated and flexed. This is because all of these actions are now unopposed. This presentation is sometimes called “waiter’s tip”.
Erb’s palsy
During 1980 the subjects in the Framingham Heart study had eye examinations with the goal to assess the prevalence of cataracts.
How would this parameter be calculated in this study?
(Number of people with cataracts x Number of people with cataracts) / Total number of people studied
Number of people without cataracts / Number of people with cataracts
Number of people with cataracts / Number of people without cataracts
Number of people with cataracts / Total number of people studied
Number of people with cataracts / Total number of people studied
Correct.
Prevalence
Which of the following is an iron binding plasma glycoprotein which acts as a carrier for iron in the bloodstream?
Divalent metal transporter 1 (DMT1) Ferroportin Hepcidin Hephaestin Transferrin
Correct. Transferrin is an iron binding plasma glycoprotein which acts as a carrier for iron in the bloodstream.
A 34 year old woman presents to her GP with symptoms of dysuria and frequency suggesting that she has a urinary tract infection. The UHL antimicrobial website suggests that woman should be treated with Trimethoprim.
What is the mechanism of action for this drug?
Inhibition of folic acid synthesis
Inhibits protein synthesis
Inhibits pathogen pili binding to host tissue
Interferes with bacterial cell wall synthesis
Destroys bacterial cell walls
Inhibition of folic acid synthesis
CORRECT – Urinary Tract Infections (UTIs) are common. Trimethoprim is commonly used alone for the treatment of UTIs. Trimethoprim inhibits folic acid synthesis in bacteria and thereby affects nucleic acid synthesis. Enzymes requiring folate-derived cofactors are essential for the synthesis of purines, pyrimidines and other compounds necessary of cellular growth and replication. Therefore, in the absence of folate, cells cannot grow or replicate.
In malignant tumours:
A. Grading and staging require microscopic examination only
B. Grading requires microscopic examination only
C. Grading requires radiological examination only
D. Staging requires microscopic examination only
E. Staging requires radiological examination only
B. Grading requires microscopic examination only
The grade of a tumour (how well differentiated it is, i.e., how closely it resembles the tissue from which it has arisen) is assessed by microscopic examination only. The stage of a tumour (how large a tumour is and how far it has spread in the body) requires both microscopic assessment (e.g., providing an accurate size measurement, histological examination of lymph nodes) and radiological assessment (e.g., CT or bone scans to determine the presence or absence of distant metastases).
A 67 year old man presents to the accident and emergency department with abdominal pain and jaundice. He is a known alcoholic and the doctor suspects that the man may be suffering from cirrhosis. When viewed under the microcope, Mallory’s Hyaline (Mallory bodies) can often be obsered in hepatocytes from patients suffering from alcoholic liver disease.
Mallory’s Hyaline
Accumulation of which substance forms these inclusions?
Carbohydrate DNA remnants Haemoglobin Haemosiderin Keratin
Keratin
CORRECT – Mallory’s hyaline is an accumulation of damaged keratin filaments within hepatocytes that occurs as a result of chronic alcohol consumption.
A 48 year old builder falls from a roof and the impact leads to a compression fracture of a vertebral body of his spine. He has lost sensation in the medial side of both of his thighs, his kneecaps, all the skin distal to his knee-joints and his posterior thigh. He has also lost sensation around his buttocks. The man is unable to extend his knee joints, dorsiflex or plantar-flex his ankles and extend or flex his great toes. He is still however able to flex his hips.
What is the man’s neural level?
T12 L1 L2 L3 L4
L2
CORRECT – From the information provided, the man appears to have lost all sensation is his dermatomes from L3 until S5 as these dermatomes supply the medial thigh, distally to the toes and then the posterior leg. He does not appear to have lost sensation in his anterior thigh, which is supplied by the L2 dermatome. With regards to myotomes, the man has lost the ability to extend his knees (L3), dorsiflex (L4) or plantar-flex (S1) his ankles and extend (L5) or flex (S2) his great toe. The man is still able to flex his hip, this movement is controlled by the L2 myotome. Therefore, the man’s compression fracture appears to be compressing the L3 spinal segment, which is affecting all of the spinal nerves distally. The clinical definition of a neural level refers to the level at which an individual has fully intact sensory and motor function, in this case the man’s L2 spinal nerve, which is proximal to the L3 spinal segment, is the last of the man’s spinal nerve that is fully functional. Therefore, L2 is the man’s neural level.
spinal_nerve spinal_nerve
A 67 year old man presents to the accident and emergency department of his local hospital with chest pain, difficulty breathing and is coughing up blood. The man has previously been diagnosed with left sided heart failure. The on-call junior doctor believes that the man is suffering from a pulmonary embolism.
How will the optimal ventilation perfusion ratio be maintained in the case of a pulmonary embolism that occludes part of the pulmonary arterial tree?
The patient’s heart rate will decrease
The patient’s pulmonary arteries will vasodilate
The patient’s respiratory rate will increase
The patient’s respiratory rate will decrease
The patient’s heart rate will increase
The patient’s respiratory rate will increase
CORRECT – An occlusion of part of the pulmonary arterial tree will force all of the blood entering the pulmonary circulation to fewer alveoli. These alveoli will now be more perfused than they otherwise would have been. This means that the ventilation-perfusion ratio will be disturbed in favour of perfusion. As a reaction to this disruption, the patient will increase their respiratory rate in order to increase the ventilation of the perfused alveoli, in an attempt to restore the optimum ventilation-perfusion ratio (0.8:1) for gas exchange.
A 45 year old woman develops rheumatoid arthritis in her elbow joint.
What would be the first step in the repair process that would be triggered as a result of this condition?
Granulation tissue becomes less vascular
Phagocytosis of necrotic tissue debris
Proliferation of endothelial cells
Proliferation of fibroblasts and myofibroblasts
Unipotent stem cells differentiate to replace damaged tissue
Phagocytosis of necrotic tissue debris
CORRECT – In response to chronic inflammation, the body will try to heal by fibrosis. The first step of the fibrous repair mechanism is phagocytosis of necrotic tissue
A 42 year old man with malignant melanoma has surgery to remove the axillary lymph nodes on his right side. During the surgery the man’s thoracodorsal nerve is accidently damaged.
Which muscle will be affected by this damage?
Latissimus Dorsi
Serratus Anterior
Pectoralis Minor
Teres Major
Trapezius
Latissimus Dorsi
CORRECT – The latissimus dorsi muscles cover a wide area on the lower back. At their origin, the superior fibres of latissimus dorsi lie deep to the inferior fibres of trapezius. Latissimus dorsi has a broad origin, arising from the spinous processes of T6-T12, the iliac crest, thoracolumbar fascia (a large sheet of deep fascia enclosing the intrinsic muscles of the back e.g. quadratus lumborum) and the inferior three ribs. The fibres converge into a tendon that inserts into the intertubercular sulcus of the humerus. Latissimus dorsi extends, adducts and medially rotates the upper limb. Latissimus dorsi is innervated by the thoracodorsal nerve (a branch of the posterior cord of the brachial plexus).
latissimus_dorsi
Which form of thyroid hormone has the lonest half-life?
T3
T4
T4
Correct. T3 is a more potent hormone than T4 but T4 has a longer half-life
A computerised (axial) tomography (CAT) scan of a 57 year old female reveals a tumour in her left breast.
Which peptide produced by some tumours is associated with hypercalcaemia?
Atrial natriuretic peptide Calcitonin gene related peptide Neuropeptide Y Parathyroid hormone related peptide Peptide YY
Parathyroid hormone related peptide
CORRECT. Parathyroid hormone related peptide (PTHrP) produced by tumours can lead to hypercalcaemia. The measurement of PTHrP can be of assistance in determining the cause of an otherwise unexplained hypercalcaemia. PTHrP shares many actions with PTH leading to increased calcium release from bone, reduced renal calcium excretion and reduced renal phosphate reabsorption.
