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  • Question 1 - Samantha is 49-years-old and is being treated for hypertension and gout. Besides a...

    Correct

    • Samantha is 49-years-old and is being treated for hypertension and gout. Besides a recent gout flare-up, she is currently in good health. Her current medications include Lisinopril, Amlodipine, Bendroflumethiazide, Naproxen, and Allopurinol. During her bi-annual GP review, a random venous glucose test shows a reading of 12.1 mmol/L, and a subsequent oral glucose tolerance test reveals a result of 9.2 mmol/L. What is the most probable reason for her abnormal glucose levels?

      Your Answer: Bendroflumethiazide

      Explanation:

      Drugs that can cause impaired glucose tolerance

      Impaired glucose tolerance can be caused by certain medications. These drugs include thiazides, furosemide (although less common), steroids, tacrolimus, ciclosporin, interferon-alpha, nicotinic acid, and antipsychotics. Beta-blockers can also cause a slight impairment of glucose tolerance and should be used with caution in diabetics as they can interfere with the metabolic and autonomic responses to hypoglycemia. It is important for healthcare providers to be aware of these potential side effects and monitor patients accordingly, especially those with pre-existing diabetes or at risk for developing diabetes. Adequate management and monitoring can help prevent further complications and ensure optimal patient care.

    • This question is part of the following fields:

      • General Principles
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  • Question 2 - A researcher is investigating how the use of technology has impacted the communication...

    Incorrect

    • A researcher is investigating how the use of technology has impacted the communication patterns of teenagers. The aim of the study is to determine how frequently teenagers communicate with their peers through social media platforms. Participants will be asked to complete a set of questionnaires after using social media.

      What potential issues could arise for the study once the teenagers become aware that their communication patterns are being observed?

      Your Answer: Lead-time bias

      Correct Answer: Hawthorne effect

      Explanation:

      The Hawthorne effect, also known as the observer effect, refers to a group altering its behavior due to the awareness of being studied. This can significantly impact the validity of a study’s results. To minimize this effect, study subjects should be kept unaware of being observed.

      Bias in epidemiology is a systematic error that can lead to incorrect conclusions about a study’s truth. Berkson’s bias, also called admission bias, can be a potential issue in case-control studies, where the control group participants are primarily chosen from hospitalized patients. This can overestimate the study results in the control group.

      Lead-time bias can misrepresent disease outcome statistics if the timing of diagnosis is not considered. For example, early diagnosis of Autosomal Dominant Polycystic Kidney Disease (ADPKD) may incorrectly suggest better survival rates than late diagnosis.

      The Pygmalion effect, or expectation bias, occurs when study observers believe data that align with their expectations and downgrade conflicting data. This can be a problem in non-blinded clinical trials.

      Understanding Bias in Clinical Trials

      Bias refers to the systematic favoring of one outcome over another in a clinical trial. There are various types of bias, including selection bias, recall bias, publication bias, work-up bias, expectation bias, Hawthorne effect, late-look bias, procedure bias, and lead-time bias. Selection bias occurs when individuals are assigned to groups in a way that may influence the outcome. Sampling bias, volunteer bias, and non-responder bias are subtypes of selection bias. Recall bias refers to the difference in accuracy of recollections retrieved by study participants, which may be influenced by whether they have a disorder or not. Publication bias occurs when valid studies are not published, often because they showed negative or uninteresting results. Work-up bias is an issue in studies comparing new diagnostic tests with gold standard tests, where clinicians may be reluctant to order the gold standard test unless the new test is positive. Expectation bias occurs when observers subconsciously measure or report data in a way that favors the expected study outcome. The Hawthorne effect describes a group changing its behavior due to the knowledge that it is being studied. Late-look bias occurs when information is gathered at an inappropriate time, and procedure bias occurs when subjects in different groups receive different treatment. Finally, lead-time bias occurs when two tests for a disease are compared, and the new test diagnoses the disease earlier, but there is no effect on the outcome of the disease. Understanding these types of bias is crucial in designing and interpreting clinical trials.

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  • Question 3 - You are assessing a 68-year-old female patient in your general practice. She complains...

    Correct

    • You are assessing a 68-year-old female patient in your general practice. She complains of muscle pain and stiffness in her shoulders and hips for the past two weeks. Her creatine kinase levels are normal, but her erythrocyte sedimentation rate (ESR) is 60 mm/hr. You diagnose her with polymyalgia rheumatica (PMR) and initiate a one-week trial of prednisolone 15mg once daily. Which receptor does this medication target?

      Your Answer: Nuclear receptor

      Explanation:

      Prednisolone decreases inflammation and leukocyte migration by acting on nuclear receptors, making it the correct answer.

      Lidocaine and amlodipine are examples of common medications that act on ion channels.

      Adenosine and oxymetazoline are examples of common medications that act on GPCR.

      Insulin and levothyroxine are examples of common medications that act on tyrosine kinase receptors.

      Pharmacodynamics refers to the effects of drugs on the body, as opposed to pharmacokinetics which is concerned with how the body processes drugs. Drugs typically interact with a target, which can be a protein located either inside or outside of cells. There are four main types of cellular targets: ion channels, G-protein coupled receptors, tyrosine kinase receptors, and nuclear receptors. The type of target determines the mechanism of action of the drug. For example, drugs that work on ion channels cause the channel to open or close, while drugs that activate tyrosine kinase receptors lead to cell growth and differentiation.

      It is also important to consider whether a drug has a positive or negative impact on the receptor. Agonists activate the receptor, while antagonists block the receptor preventing activation. Antagonists can be competitive or non-competitive, depending on whether they bind at the same site as the agonist or at a different site. The binding affinity of a drug refers to how readily it binds to a specific receptor, while efficacy measures how well an agonist produces a response once it has bound to the receptor. Potency is related to the concentration at which a drug is effective, while the therapeutic index is the ratio of the dose of a drug resulting in an undesired effect compared to that at which it produces the desired effect.

      The relationship between the dose of a drug and the response it produces is rarely linear. Many drugs saturate the available receptors, meaning that further increased doses will not cause any more response. Some drugs do not have a significant impact below a certain dose and are considered sub-therapeutic. Dose-response graphs can be used to illustrate the relationship between dose and response, allowing for easy comparison of different drugs. However, it is important to remember that dose-response varies between individuals.

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  • Question 4 - Which of the following Human Immunodeficiency Virus (HIV) enzymes does the pathogen use...

    Incorrect

    • Which of the following Human Immunodeficiency Virus (HIV) enzymes does the pathogen use prior to integrating its genome into the DNA of the host cell?

      Your Answer: DNA helicase

      Correct Answer: Reverse transcriptase

      Explanation:

      The HIV virus relies on reverse transcriptase for its pathogenesis. This enzyme is responsible for converting viral RNA into DNA, which is then integrated into the host cell’s genetic material.

      Understanding the HIV Virus: Structure, Cell Entry, and Replication

      HIV is a retrovirus that belongs to the lentivirus genus. It has two variants, HIV-1 and HIV-2, with the latter being more common in West Africa. The virus has a spherical shape with two copies of single-stranded RNA enclosed by a capsid of the viral protein p24. The capsid is surrounded by a matrix composed of viral protein p17, and the envelope proteins gp120 and gp41. The pol gene encodes for viral enzymes reverse transcriptase, integrase, and HIV protease.

      HIV can infect CD4 T cells, macrophages, and dendritic cells. The virus enters the cell by binding to CD4 and CXCR4 on T cells and CD4 and CCR5 on macrophages. Mutations in CCR5 can give immunity to HIV.

      After entering a cell, the enzyme reverse transcriptase creates dsDNA from the RNA for integration into the host cell’s genome. This process allows the virus to replicate and produce new virions, which can infect other cells and continue the cycle of infection. Understanding the structure, cell entry, and replication of the HIV virus is crucial in developing effective treatments and prevention strategies.

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      • General Principles
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  • Question 5 - A clinical trial is investigating the impact of a new medication Y on...

    Incorrect

    • A clinical trial is investigating the impact of a new medication Y on overall mortality. The mortality rate in the group taking medication Y is 5%, while it is 10% in the control group. What is the number of individuals who need to receive medication Y to prevent one death?

      Your Answer: 50

      Correct Answer: 20

      Explanation:

      Steps to Calculate NNT:

      Calculate the Absolute Risk Reduction (ARR):

      ARR=Control Event Rate (CER)−Experimental Event Rate (EER)

      Here:

      • Control Event Rate (CER) = 10% or 0.10
      • Experimental Event Rate (EER) = 5% or 0.05

      So,

      ARR=0.10−0.05=0.05

      Calculate the NNT:

      NNT=1/ARR

      NNT=1/0.05=20

      Conclusion:

      The Number Needed to Treat (NNT) is 20. This means that 20 individuals need to receive medication Y to prevent one death.

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  • Question 6 - A 67-year-old man visits his primary care physician complaining of excessive thirst and...

    Correct

    • A 67-year-old man visits his primary care physician complaining of excessive thirst and frequent urination. He has no medical history and is not on any medications. He is a non-smoker and does not consume alcohol.

      His HbA1c level is 50 mmol/mol (<48). Despite attempting to manage his condition through diet and exercise, his HbA1c level remains unchanged.

      What is the probable mechanism of action of the medication that will likely be prescribed?

      Your Answer: Activation of AMP-activated protein kinase (AMPK)

      Explanation:

      Metformin is a medication commonly used to treat type 2 diabetes mellitus, as well as polycystic ovarian syndrome and non-alcoholic fatty liver disease. Unlike other medications, such as sulphonylureas, metformin does not cause hypoglycaemia or weight gain, making it a first-line treatment option, especially for overweight patients. Its mechanism of action involves activating the AMP-activated protein kinase, increasing insulin sensitivity, decreasing hepatic gluconeogenesis, and potentially reducing gastrointestinal absorption of carbohydrates. However, metformin can cause gastrointestinal upsets, reduced vitamin B12 absorption, and in rare cases, lactic acidosis, particularly in patients with severe liver disease or renal failure. It is contraindicated in patients with chronic kidney disease, recent myocardial infarction, sepsis, acute kidney injury, severe dehydration, and those undergoing iodine-containing x-ray contrast media procedures. When starting metformin, it should be titrated up slowly to reduce the incidence of gastrointestinal side-effects, and modified-release metformin can be considered for patients who experience unacceptable side-effects.

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  • Question 7 - As a medical student working in a general practice, a 63-year-old woman comes...

    Correct

    • As a medical student working in a general practice, a 63-year-old woman comes in with swelling in both legs. Which medication is the most probable cause of this symptom?

      Your Answer: Amlodipine

      Explanation:

      Peripheral oedema is not a known side effect of aspirin, atorvastatin, or clopidogrel. Furosemide is a suitable treatment for peripheral oedema. On the other hand, amlodipine is frequently linked to peripheral oedema as a side effect.

      Calcium channel blockers are a class of drugs commonly used to treat cardiovascular disease. These drugs target voltage-gated calcium channels found in myocardial cells, cells of the conduction system, and vascular smooth muscle. The different types of calcium channel blockers have varying effects on these areas, making it important to differentiate their uses and actions.

      Verapamil is used to treat angina, hypertension, and arrhythmias. It is highly negatively inotropic and should not be given with beta-blockers as it may cause heart block. Side effects include heart failure, constipation, hypotension, bradycardia, and flushing.

      Diltiazem is used to treat angina and hypertension. It is less negatively inotropic than verapamil, but caution should still be exercised when patients have heart failure or are taking beta-blockers. Side effects include hypotension, bradycardia, heart failure, and ankle swelling.

      Nifedipine, amlodipine, and felodipine are dihydropyridines used to treat hypertension, angina, and Raynaud’s. They affect peripheral vascular smooth muscle more than the myocardium, which means they do not worsen heart failure but may cause ankle swelling. Shorter acting dihydropyridines like nifedipine may cause peripheral vasodilation, resulting in reflex tachycardia. Side effects include flushing, headache, and ankle swelling.

      According to current NICE guidelines, the management of hypertension involves a flow chart that takes into account various factors such as age, ethnicity, and comorbidities. Calcium channel blockers may be used as part of the treatment plan depending on the individual patient’s needs.

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  • Question 8 - A 35-year-old woman presents with a 4 week history of weakness that worsens...

    Incorrect

    • A 35-year-old woman presents with a 4 week history of weakness that worsens towards the end of the day. She has difficulty getting out of her chair in the evening and complains of difficulty keeping her eyes open while driving at night, despite not feeling tired.

      During examination, bilateral facial nerve weakness, complex ophthalmoplegia, and symmetrical proximal power loss (MRC power 4/5) are noted. Repetitive stimulation of movements reveals fatigability.

      What Gell and Coombs hypersensitivity class is likely causing her symptoms?

      Your Answer: Type 4

      Correct Answer: Type 5

      Explanation:

      The individual is a young woman who is exhibiting symptoms of proximal myopathy and complex ophthalmoplegia, along with signs of fatigue. These symptoms are indicative of myasthenia gravis, an autoimmune disorder that occurs due to the presence of antibodies that target acetylcholine nicotinic postsynaptic receptors.

      Classification of Hypersensitivity Reactions

      Hypersensitivity reactions are classified into four types according to the Gell and Coombs classification. Type I, also known as anaphylactic hypersensitivity, occurs when an antigen reacts with IgE bound to mast cells. This type of reaction is commonly seen in atopic conditions such as asthma, eczema, and hay fever. Type II hypersensitivity occurs when cell-bound IgG or IgM binds to an antigen on the cell surface, leading to autoimmune conditions such as autoimmune hemolytic anemia, ITP, and Goodpasture’s syndrome. Type III hypersensitivity occurs when free antigen and antibody (IgG, IgA) combine to form immune complexes, leading to conditions such as serum sickness, systemic lupus erythematosus, and post-streptococcal glomerulonephritis. Type IV hypersensitivity is T-cell mediated and includes conditions such as tuberculosis, graft versus host disease, and allergic contact dermatitis.

      In recent times, a fifth category has been added to the classification of hypersensitivity reactions. Type V hypersensitivity occurs when antibodies recognize and bind to cell surface receptors, either stimulating them or blocking ligand binding. This type of reaction is seen in conditions such as Graves’ disease and myasthenia gravis. Understanding the classification of hypersensitivity reactions is important in the diagnosis and management of these conditions.

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  • Question 9 - A randomized, double-blinded clinical trial was conducted to evaluate the effect of a...

    Incorrect

    • A randomized, double-blinded clinical trial was conducted to evaluate the effect of a new anti-inflammatory drug on the pain relief of patients with osteoarthritis. A total of 200 patients with osteoarthritis were randomly assigned to the drug or placebo group. For the study, 100 patients were assigned to each group. The two groups were then followed for six months for the development of adverse effects. Severe gastrointestinal bleeding was reported as a rare side effect of the drug therapy, but the difference between the two groups was not statistically significant (p=0.08). The same side effect was reported in several small clinical trials of this drug (p=0.05-0.10).

      What is the most likely reason for the failure to detect a significant statistical difference in the occurrence of gastrointestinal bleeding between the treatment and placebo groups?

      Your Answer: Short follow-up period

      Correct Answer: Small sample size

      Explanation:

      A larger sample size can enhance the power of a study and reduce the likelihood of type II error. Power refers to the ability to detect a difference in the outcome of interest between two groups, if such a difference exists. With a bigger sample size, the study’s power to detect a difference increases, and the p-value can reach statistical significance.
      Attrition bias is a systematic error that arises from unequal loss of participants in a randomized controlled trial. However, since patients are not lost to follow-up in this study design, the likelihood of attrition bias is low.
      The Hawthorne effect is a type of reactivity where individuals modify their behavior in response to being observed. This effect does not occur in double-blinded randomized clinical trials.
      Double-blinding techniques can reduce the potential for observer’s bias.
      Increasing the follow-up period may not necessarily increase the power of the study, as side effects can occur in susceptible individuals relatively early after starting the therapy.

      Understanding the Concept of Power in Research Studies

      Power is a statistical concept that refers to the probability of correctly rejecting the null hypothesis when it is false. In other words, it is the ability of a study to detect a clinically meaningful difference or effect. The value of power ranges from 0 to 1, with 0 indicating 0% and 1 indicating 100%. It is often expressed as 1 – beta, where beta is the probability of a Type II error. A power of 0.80 is generally considered the minimum acceptable level.

      Several factors influence the power of a study, including sample size, meaningful effect size, and significance level. Larger sample sizes lead to more accurate parameter estimations and increase the study’s ability to detect a significant effect. The meaningful effect size is determined at the beginning of the study and represents the size of the difference between two means that would lead to the rejection of the null hypothesis. Finally, the significance level, also known as the alpha level, is the probability of a Type I error. Understanding the concept of power is crucial in determining the appropriate sample size and designing a study that can accurately detect meaningful differences or effects.

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  • Question 10 - Look at the following DNA sequence and identify the mutation that has occurred:

    DNA...

    Incorrect

    • Look at the following DNA sequence and identify the mutation that has occurred:

      DNA sequence Amino Acid Sequence
      Original AAA GCC AAA lys, ala, lys
      Mutation AAA ACC ATT lys, thr, lys,

      Has the mutation occurred due to a genetic error?

      Your Answer: Nonsense

      Correct Answer: Missense

      Explanation:

      Missense mutations are point mutations that result in a change in the amino acid sequence, potentially rendering the protein non-functional. Deletions involve the loss of at least one base, while insertions involve the addition of at least one base. Inversions reverse a section of the genetic code. Missense mutations occur when a single base is changed, resulting in the production of a different amino acid than in the original sequence. Nonsense mutations code for a stop codon, halting the production of amino acids beyond that point.

      Types of DNA Mutations

      There are different types of DNA mutations that can occur in an organism’s genetic material. One type is called a silent mutation, which does not change the amino acid sequence of a protein. This type of mutation often occurs in the third position of a codon, where the change in the DNA base does not affect the final amino acid produced.

      Another type of mutation is called a nonsense mutation, which results in the formation of a stop codon. This means that the protein being produced is truncated and may not function properly.

      A missense mutation is a point mutation that changes the amino acid sequence of a protein. This can have significant effects on the protein’s function, as the altered amino acid may not be able to perform its intended role.

      Finally, a frameshift mutation occurs when a number of nucleotides are inserted or deleted from the DNA sequence. This can cause a shift in the reading frame of the DNA, resulting in a completely different amino acid sequence downstream. These mutations can have serious consequences for the organism, as the resulting protein may be non-functional or even harmful.

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  • Question 11 - A 25-year-old, biology student, with a history of insomnia, has approached their college...

    Incorrect

    • A 25-year-old, biology student, with a history of insomnia, has approached their college doctor with inquiries about a newly advertised medication for insomnia treatment. The medication boosts the synthesis of gamma-aminobutyric acid (GABA) from glutamate, resulting in a calming effect.

      What is the enzyme that the drug is mimicking?

      Your Answer: Glutamate synthase

      Correct Answer: Glutamate decarboxylase

      Explanation:

      The conversion of glutamate to GABA is catalyzed by glutamate decarboxylase. Other enzymes involved in this process include glutamate synthase, which converts glutamine to glutamate, glutamine synthetase, which converts glutamate to glutamine and vice versa, and 4-aminobutyrate transaminase, which converts GABA to succinate semialdehyde.

      Understanding GABA as the Principal Inhibitory Neurotransmitter of the Cortex

      GABA, or gamma-aminobutyric acid, is a crucial neurotransmitter that plays a significant role in regulating brain activity. It is considered the principal inhibitory neurotransmitter of the cortex, which means that it helps to reduce the activity of neurons in this region of the brain. This is important because excessive neuronal activity can lead to seizures, anxiety, and other neurological disorders.

      GABA is produced in a region of the brain called the substantia nigra pars reticulata. This area is responsible for regulating movement and is also involved in the production of dopamine, another important neurotransmitter. GABA is released by neurons in the cortex and binds to specific receptors on other neurons, which helps to reduce their activity.

      The importance of GABA in the brain cannot be overstated. It is involved in a wide range of functions, including sleep, anxiety, and mood regulation. It is also a target for many drugs used to treat neurological disorders, such as epilepsy and anxiety. Understanding the role of GABA in the brain is crucial for developing new treatments for these conditions and improving our overall understanding of brain function.

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  • Question 12 - A newborn is found to have ambiguous genitalia. Further examinations indicate the absence...

    Incorrect

    • A newborn is found to have ambiguous genitalia. Further examinations indicate the absence of epididymis, seminal vesicles, and ductus deferens. What is the typical embryonic structure that develops into these organs?

      Your Answer:

      Correct Answer: Mesonephric duct

      Explanation:

      The male reproductive structures are derived from the mesonephric (Wolffian) duct, while it regresses in females. The allantois regresses and forms the urachus. The pharyngeal arches give rise to the structures of the head and neck. The internal female reproductive structures are derived from the paramesonephric duct. The kidney is formed from the ureteric bud.

      Urogenital Embryology: Development of Kidneys and Genitals

      During embryonic development, the urogenital system undergoes a series of changes that lead to the formation of the kidneys and genitals. The kidneys develop from the pronephros, which is rudimentary and non-functional, to the mesonephros, which functions as interim kidneys, and finally to the metanephros, which starts to function around the 9th to 10th week. The metanephros gives rise to the ureteric bud and the metanephrogenic blastema. The ureteric bud develops into the ureter, renal pelvis, collecting ducts, and calyces, while the metanephrogenic blastema gives rise to the glomerulus and renal tubules up to and including the distal convoluted tubule.

      In males, the mesonephric duct (Wolffian duct) gives rise to the seminal vesicles, epididymis, ejaculatory duct, and ductus deferens. The paramesonephric duct (Mullerian duct) degenerates by default. In females, the paramesonephric duct gives rise to the fallopian tube, uterus, and upper third of the vagina. The urogenital sinus gives rise to the bulbourethral glands in males and Bartholin glands and Skene glands in females. The genital tubercle develops into the glans penis and clitoris, while the urogenital folds give rise to the ventral shaft of the penis and labia minora. The labioscrotal swelling develops into the scrotum in males and labia majora in females.

      In summary, the development of the urogenital system is a complex process that involves the differentiation of various structures from different embryonic tissues. Understanding the embryology of the kidneys and genitals is important for diagnosing and treating congenital abnormalities and disorders of the urogenital system.

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  • Question 13 - A 72-year-old patient presents with a sudden collapse and an ECG reveals atrial...

    Incorrect

    • A 72-year-old patient presents with a sudden collapse and an ECG reveals atrial fibrillation. His medical history includes type II diabetes mellitus, hypertension, trigeminal neuralgia, and lymphoedema. He has been taking warfarin for a few years, but his INR from today is 1.2. The patient's records show that he was prescribed a new medication by his family doctor 8 days ago. Which of the following drugs is most likely to have been prescribed?

      Your Answer:

      Correct Answer: Carbamazepine

      Explanation:

      Carbamazepine enhances the activity of the CYP3A4 system, leading to the acceleration of warfarin metabolism and a decrease in its therapeutic efficacy. On the other hand, the other medications are P450 system inhibitors, which may interfere with warfarin breakdown and cause an elevated therapeutic effect.

      The P450 system is responsible for metabolizing many drugs in the body, and drug interactions can occur when certain drugs inhibit or induce the activity of these enzymes. The most common and important enzyme system involved in drug interactions is CYP3A4. Macrolides, antiretrovirals, and calcium channel blockers are substrates for this enzyme, while macrolides, protease inhibitors (including ritonavir), and imidazoles are inhibitors. Carbamazepine, phenytoin, phenobarbitone, rifampicin, and St John’s Wort are inducers of CYP3A4. Other enzyme systems affected by common drugs include CYP2D6, CYP2C9, CYP1A2, and CYP2E1. Tricyclic antidepressants and antipsychotics are substrates for CYP2D6, while SSRIs and ritonavir are inhibitors. Warfarin and sulfonylureas are substrates for CYP2C9, while imidazoles, amiodarone, and sodium valproate are inhibitors. Theophylline is a substrate for CYP1A2, while ciprofloxacin and omeprazole are inhibitors. Chronic alcohol and isoniazid are inducers of CYP2E1. It is important to be aware of these interactions to avoid adverse effects and ensure optimal drug therapy.

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  • Question 14 - A 5-day-old infant has undergone newborn blood spot screening test before being discharged...

    Incorrect

    • A 5-day-old infant has undergone newborn blood spot screening test before being discharged from the hospital. The test suggests a possible diagnosis of medium-chain acyl-CoA dehydrogenase deficiency (MCADD), which can be caused by the disturbance of RNA splicing.

      Which organelle is responsible for carrying out this process?

      Your Answer:

      Correct Answer: Nucleus

      Explanation:

      RNA splicing occurs within the nucleus, where pre-mRNA is transcribed and spliced before it moves out of the nucleus to a ribosome. This process involves removing introns and joining exons to create the final mRNA sequence. In MCADD, disruption of a splicing enhancer can lead to exon skipping and a missense mutation, causing difficulty in breaking down fat as an energy source. The Golgi apparatus, mitochondrion, and nucleolus are not involved in RNA splicing, but have other important cellular functions.

      Functions of Cell Organelles

      The functions of major cell organelles can be summarized in a table. The rough endoplasmic reticulum (RER) is responsible for the translation and folding of new proteins, as well as the manufacture of lysosomal enzymes. It is also the site of N-linked glycosylation. Cells such as pancreatic cells, goblet cells, and plasma cells have extensive RER. On the other hand, the smooth endoplasmic reticulum (SER) is involved in steroid and lipid synthesis. Cells of the adrenal cortex, hepatocytes, and reproductive organs have extensive SER.

      The Golgi apparatus modifies, sorts, and packages molecules that are destined for cell secretion. The addition of mannose-6-phosphate to proteins designates transport to lysosome. The mitochondrion is responsible for aerobic respiration and contains mitochondrial genome as circular DNA. The nucleus is involved in DNA maintenance, RNA transcription, and RNA splicing, which removes the non-coding sequences of genes (introns) from pre-mRNA and joins the protein-coding sequences (exons).

      The lysosome is responsible for the breakdown of large molecules such as proteins and polysaccharides. The nucleolus produces ribosomes, while the ribosome translates RNA into proteins. The peroxisome is involved in the catabolism of very long chain fatty acids and amino acids, resulting in the formation of hydrogen peroxide. Lastly, the proteasome, along with the lysosome pathway, is involved in the degradation of protein molecules that have been tagged with ubiquitin.

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  • Question 15 - A 32-year-old female presents to the clinic with complaints of fatigue and lack...

    Incorrect

    • A 32-year-old female presents to the clinic with complaints of fatigue and lack of energy. She has a medical history of gout, epilepsy, asthma, hay fever, tension headaches, and low back pain. Her blood work reveals low Hb levels, high MCV levels, and normal LFT and TFT results. What could be the possible cause of her symptoms and abnormal blood results?

      Your Answer:

      Correct Answer: Phenytoin

      Explanation:

      The cause of this woman’s macrocytic anaemia may be due to her epilepsy medication, phenytoin, which is known to hinder the absorption of folate in the intestines. Her normal thyroid function tests rule out hypothyroidism and hyperthyroidism as potential causes. Paracetamol and antihistamines are not associated with macrocytic anaemia.

      Interference with Folate Metabolism by Drugs

      Folate metabolism is a crucial process in the body that involves the conversion of folic acid into its active form, which is essential for DNA synthesis and cell division. However, certain drugs can interfere with this process, leading to various health complications.

      Trimethoprim, methotrexate, and pyrimethamine are some of the drugs that can interfere with folate metabolism. These drugs inhibit the activity of dihydrofolate reductase, an enzyme that converts dihydrofolate to tetrahydrofolate, which is required for DNA synthesis. As a result, the body’s ability to produce new cells is impaired, leading to anemia, immune system dysfunction, and other health problems.

      Phenytoin is another drug that can reduce the absorption of folate in the body. This drug inhibits the absorption of folate in the small intestine, leading to a deficiency of this essential nutrient. Folate deficiency can cause birth defects, anemia, and other health problems, especially in pregnant women.

      In conclusion, drugs that interfere with folate metabolism can have serious health consequences. Patients taking these drugs should be closely monitored for signs of folate deficiency and treated accordingly. It is also important to ensure that patients receive adequate folate supplementation to prevent complications.

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  • Question 16 - A new test to screen for breast cancer in patients with a positive...

    Incorrect

    • A new test to screen for breast cancer in patients with a positive family history is tested on 920 patients. The test is positive in 18 of the 22 patients who are proven to have breast cancer. Of the remaining patients, only 12 have a positive test. What is the negative predictive value of the new test?

      Your Answer:

      Correct Answer: 890/894 = 99.6%

      Explanation:

      The negative predictive value can be calculated using the formula TN / (TN + FN), where TN represents true negative and FN represents false negative. In the given data, a contingency table can be created with the categories of ovarian cancer and no ovarian cancer, and the results of the test being positive or negative. Using this table, the negative predictive value can be determined as 890 / (890 + 4) = 890/894.

      Precision refers to the consistency of a test in producing the same results when repeated multiple times. It is an important aspect of test reliability and can impact the accuracy of the results. In order to assess precision, multiple tests are performed on the same sample and the results are compared. A test with high precision will produce similar results each time it is performed, while a test with low precision will produce inconsistent results. It is important to consider precision when interpreting test results and making clinical decisions.

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  • Question 17 - A 25-year-old male patient complains of lymphadenopathy, fatigue, and weight loss. Upon diagnosis,...

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    • A 25-year-old male patient complains of lymphadenopathy, fatigue, and weight loss. Upon diagnosis, he is found to have tuberculosis. What is the most similar pathological process underlying this condition?

      Your Answer:

      Correct Answer: Type 4 hypersensitivity reaction

      Explanation:

      Type 4 hypersensitivity reactions are characterized by the formation of granulomas, which are observed in tuberculosis.

      Classification of Hypersensitivity Reactions

      Hypersensitivity reactions are classified into four types according to the Gell and Coombs classification. Type I, also known as anaphylactic hypersensitivity, occurs when an antigen reacts with IgE bound to mast cells. This type of reaction is commonly seen in atopic conditions such as asthma, eczema, and hay fever. Type II hypersensitivity occurs when cell-bound IgG or IgM binds to an antigen on the cell surface, leading to autoimmune conditions such as autoimmune hemolytic anemia, ITP, and Goodpasture’s syndrome. Type III hypersensitivity occurs when free antigen and antibody (IgG, IgA) combine to form immune complexes, leading to conditions such as serum sickness, systemic lupus erythematosus, and post-streptococcal glomerulonephritis. Type IV hypersensitivity is T-cell mediated and includes conditions such as tuberculosis, graft versus host disease, and allergic contact dermatitis.

      In recent times, a fifth category has been added to the classification of hypersensitivity reactions. Type V hypersensitivity occurs when antibodies recognize and bind to cell surface receptors, either stimulating them or blocking ligand binding. This type of reaction is seen in conditions such as Graves’ disease and myasthenia gravis. Understanding the classification of hypersensitivity reactions is important in the diagnosis and management of these conditions.

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      • General Principles
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  • Question 18 - An 82-year-old male patient visits their GP with a swollen and red knee...

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    • An 82-year-old male patient visits their GP with a swollen and red knee joint that has been hot for the past 3 days. The patient has a medical history of diabetes and osteoarthritis, leading the GP to suspect septic arthritis. During the humoral response to an infection, what receptor is present on Helper T cells that allows them to interact with MHC II molecules on antigen-presenting cells to eliminate pathogens?

      Your Answer:

      Correct Answer: CD4

      Explanation:

      Helper T cells express CD4, which interacts with MHC II molecules on antigen presenting cells. CD20 is present on B cells from late pro-B cells through memory cells, but not on early pro-B cells or plasma cells. CD8 is expressed on cytotoxic T cells and binds with MHC I molecules.

      The adaptive immune response involves several types of cells, including helper T cells, cytotoxic T cells, B cells, and plasma cells. Helper T cells are responsible for the cell-mediated immune response and recognize antigens presented by MHC class II molecules. They express CD4, CD3, TCR, and CD28 and are a major source of IL-2. Cytotoxic T cells also participate in the cell-mediated immune response and recognize antigens presented by MHC class I molecules. They induce apoptosis in virally infected and tumor cells and express CD8 and CD3. Both helper T cells and cytotoxic T cells mediate acute and chronic organ rejection.

      B cells are the primary cells of the humoral immune response and act as antigen-presenting cells. They also mediate hyperacute organ rejection. Plasma cells are differentiated from B cells and produce large amounts of antibody specific to a particular antigen. Overall, these cells work together to mount a targeted and specific immune response to invading pathogens or abnormal cells.

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      • General Principles
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  • Question 19 - A 32-year-old woman visits her GP with a swollen and hot lower limb....

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    • A 32-year-old woman visits her GP with a swollen and hot lower limb. She reports that the condition developed a week ago, a few days after a stray cat scratched her on her way home. The patient also complains of feeling generally unwell, with fever and nausea. Besides her limb, she has type 2 diabetes and is clinically obese.

      Upon a thorough examination, the GP diagnosis cellulitis and prescribes oral antibiotics. The patient is advised to return if her symptoms worsen or fail to improve after the antibiotic course.

      What parts of the patient's leg are infected in this case?

      Your Answer:

      Correct Answer: Deeper dermis & subcutaneous tissues

      Explanation:

      Cellulitis is a type of infection that affects the deeper dermis and subcutaneous tissues, while erysipelas only affects the upper dermis and superficial lymphatics. If left untreated, cellulitis can lead to serious complications such as amputation, sepsis, and even death. The most common bacteria that cause cellulitis are Streptococcus pyogenes and Staphylococcus aureus.

      It’s important to note that the epidermis is not typically affected in cellulitis. Impetigo, on the other hand, is a common infection of the epidermis that is highly contagious and often affects children.

      If the upper dermis and superficial lymphatics are infected, erysipelas is the likely diagnosis. This condition is similar to cellulitis and is managed in a similar way.

      Necrotising fasciitis, a rapidly progressive and life-threatening infection, is not cellulitis. This type of infection affects the deep muscles and fascia.

      Lastly, it’s worth noting that deep vein thrombosis, which presents similarly to cellulitis, is not a type of cellulitis. It’s a condition where clots form in the deep veins.

      Understanding Cellulitis: Symptoms, Diagnosis, and Treatment

      Cellulitis is a common skin infection caused by Streptococcus pyogenes or Staphylococcus aureus. It is characterized by inflammation of the skin and subcutaneous tissues, usually on the shins, accompanied by erythema, pain, swelling, and sometimes fever. The diagnosis of cellulitis is based on clinical features, and no further investigations are required in primary care. However, bloods and blood cultures may be requested if the patient is admitted and septicaemia is suspected.

      To guide the management of patients with cellulitis, NICE Clinical Knowledge Summaries recommend using the Eron classification. Patients with Eron Class III or Class IV cellulitis, severe or rapidly deteriorating cellulitis, very young or frail patients, immunocompromised patients, patients with significant lymphoedema, or facial or periorbital cellulitis (unless very mild) should be admitted for intravenous antibiotics. Patients with Eron Class II cellulitis may not require admission if the facilities and expertise are available in the community to give intravenous antibiotics and monitor the patient.

      The first-line treatment for mild/moderate cellulitis is flucloxacillin, while clarithromycin, erythromycin (in pregnancy), or doxycycline is recommended for patients allergic to penicillin. Patients with severe cellulitis should be offered co-amoxiclav, cefuroxime, clindamycin, or ceftriaxone. Understanding the symptoms, diagnosis, and treatment of cellulitis is crucial for effective management and prevention of complications.

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  • Question 20 - A researcher is investigating the function of regulatory proteins in intracellular trafficking. He...

    Incorrect

    • A researcher is investigating the function of regulatory proteins in intracellular trafficking. He has discovered several intracellular proteins marked with significant ubiquitination.

      To which organelles are these proteins targeted?

      Your Answer:

      Correct Answer: Proteasome

      Explanation:

      Proteins are marked with ubiquitin for degradation in both proteasomes and lysosomes.

      Functions of Cell Organelles

      The functions of major cell organelles can be summarized in a table. The rough endoplasmic reticulum (RER) is responsible for the translation and folding of new proteins, as well as the manufacture of lysosomal enzymes. It is also the site of N-linked glycosylation. Cells such as pancreatic cells, goblet cells, and plasma cells have extensive RER. On the other hand, the smooth endoplasmic reticulum (SER) is involved in steroid and lipid synthesis. Cells of the adrenal cortex, hepatocytes, and reproductive organs have extensive SER.

      The Golgi apparatus modifies, sorts, and packages molecules that are destined for cell secretion. The addition of mannose-6-phosphate to proteins designates transport to lysosome. The mitochondrion is responsible for aerobic respiration and contains mitochondrial genome as circular DNA. The nucleus is involved in DNA maintenance, RNA transcription, and RNA splicing, which removes the non-coding sequences of genes (introns) from pre-mRNA and joins the protein-coding sequences (exons).

      The lysosome is responsible for the breakdown of large molecules such as proteins and polysaccharides. The nucleolus produces ribosomes, while the ribosome translates RNA into proteins. The peroxisome is involved in the catabolism of very long chain fatty acids and amino acids, resulting in the formation of hydrogen peroxide. Lastly, the proteasome, along with the lysosome pathway, is involved in the degradation of protein molecules that have been tagged with ubiquitin.

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