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Question 1
Correct
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What are the defining features of an amino acid?
Your Answer: It has the formula H2N - CHR - COOH where R is the variable group
Explanation:The Versatility of Amino Acids and its Applications in Electrophoresis
Amino acids are the building blocks of proteins and are composed of a basic structure of H2N – CHR – COOH, where R represents the variable group that distinguishes one amino acid from another. The simplest amino acid is glycine, where the R group is just H. Amino acids are capable of forming complex and useful molecules due to their dipolar or amphoteric nature, which makes them simultaneously acidic and basic. In solution, they form zwitterions, which can act as either an acid or a base depending on the pH of the solution. This versatility of amino acids is what allows for the process of electrophoresis, which separates proteins based on their charge in a solution. By using solutions of different pH, different proteins can be assessed, making it a useful tool in the diagnosis of bone marrow malignancies like myeloma.
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This question is part of the following fields:
- Basic Sciences
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Question 2
Correct
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A premature baby is born and the anaesthetists are struggling to ventilate the lungs because of insufficient surfactant. How does Laplace's law explain the force pushing inwards on the walls of the alveolus caused by surface tension between two static fluids, such as air and water in the alveolus?
Your Answer: Inversely proportional to the radius of the alveolus
Explanation:The Relationship between Alveolar Size and Surface Tension in Respiratory Physiology
In respiratory physiology, the alveolus is often represented as a perfect sphere to apply Laplace’s law. According to this law, there is an inverse relationship between the size of the alveolus and the surface tension. This means that smaller alveoli experience greater force than larger alveoli for a given surface tension, and they will collapse first. This phenomenon explains why, when two balloons are attached together by their ends, the smaller balloon will empty into the bigger balloon.
In the lungs, this same principle applies to lung units, causing atelectasis and collapse when surfactant is not present. Surfactant is a substance that reduces surface tension, making it easier to expand the alveoli and preventing smaller alveoli from collapsing. Therefore, surfactant plays a crucial role in maintaining the proper functioning of the lungs and preventing respiratory distress. the relationship between alveolar size and surface tension is essential in respiratory physiology and can help in the development of treatments for lung diseases.
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This question is part of the following fields:
- Basic Sciences
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Question 3
Correct
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What are the vitamins that are soluble in fat?
Your Answer: Vitamins A, D, E and K
Explanation:Absorption of Fat-Soluble Vitamins
Fat-soluble vitamins, namely A, D, E, and K, have a different absorption process compared to water-soluble vitamins. In the gut, these vitamins are combined with other fat-soluble substances such as monoacylglycerols and cholesterol to form micelles. These micelles are then transported to the lymphatic system and eventually enter the bloodstream through the subclavian vein.
However, any issues that affect the absorption of fats will also impact the absorption of fat-soluble vitamins. This means that individuals with conditions that affect fat absorption, such as cystic fibrosis or celiac disease, may have difficulty absorbing these vitamins. It is important to ensure adequate intake of fat-soluble vitamins through a balanced diet or supplements to prevent deficiencies and associated health problems.
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This question is part of the following fields:
- Basic Sciences
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Question 4
Incorrect
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What is the primary function of riboflavin in the B vitamin group?
Your Answer: Visual acuity
Correct Answer: Mopping up free radicals
Explanation:The Role of Riboflavin in the Body
Riboflavin, also known as vitamin B2, is a B-vitamin that plays a crucial role in the body. One of its functions is to act as an antioxidant, mopping up free radicals that can cause damage to cells. However, if the metabolites formed during this process are not excreted promptly, the free radicals can be generated again. Riboflavin is also involved in the production of blue-light sensitive pigments in the eye, which help establish the circadian rhythm. This function is not related to visual acuity.
Riboflavin is found in a variety of foods, including milk and offal. Deficiency of this vitamin is rare, but when it does occur, it can cause non-specific effects on the skin and mucous membranes. There is no evidence of clear long-lasting damage from riboflavin deficiency. Overall, riboflavin is an important nutrient that plays a vital role in maintaining good health.
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This question is part of the following fields:
- Basic Sciences
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Question 5
Correct
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What is the primary factor that increases the risk of thiamine (vitamin B1) deficiency?
Your Answer: Chronic alcohol excess
Explanation:Thiamine: Its Roles, Sources, Deficiency States, and Manifestations
Thiamine is a vital nutrient that plays several roles in the body. It acts as a cofactor to enzymes involved in energy production, metabolism of branched chain amino acids, and regulation of nerve and muscle action potentials. It is found in many foods, including wheat, oats, and yeast-containing products. However, deficiency states can occur in chronic alcohol dependence, renal dialysis, and cultures that mainly consume white rice. The deficiency can manifest as ‘dry’ beriberi, which causes peripheral neuropathy, muscle weakness, fatigue, and reduced concentration, or ‘wet’ beriberi, which also involves heart failure and edema. In severe cases, Wernicke-Korsakoff syndrome can develop, which is an emergency requiring urgent IV replacement of thiamine. If left untreated, it can lead to irreversible amnesia, confabulation, and dementia. Therefore, all patients with alcohol-related admissions should be considered for Pabrinex, a B vitamin infusion.
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This question is part of the following fields:
- Basic Sciences
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Question 6
Correct
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What is a good dietary source of vitamin A?
Your Answer: Liver
Explanation:The Importance of Vitamin A in Our Body
Vitamin A is an essential nutrient that can be found in various sources such as liver, fish liver oils, dark green leafy vegetables, carrots, and mangoes. It can also be added to certain foods like cereals and margarines. This nutrient plays a crucial role in our body as it is required for vision, growth and development of tissues, regulation of gene transcription, and synthesis of hydrophobic glycoproteins and parts of the protein kinase enzyme pathways.
One of the primary functions of vitamin A is to support our vision. It is a component of rhodopsin, a pigment that is necessary for the rod cells of the retina. Without vitamin A, our eyesight can be compromised, leading to various eye problems. Additionally, vitamin A is also essential for the growth and development of many types of tissues in our body. It helps in maintaining healthy skin, teeth, and bones.
Moreover, vitamin A is involved in regulating gene transcription, which is the process of converting DNA into RNA. This nutrient also plays a role in the synthesis of hydrophobic glycoproteins and parts of the protein kinase enzyme pathways. These processes are essential for the proper functioning of our body.
In conclusion, vitamin A is a vital nutrient that our body needs to function correctly. It is essential for our vision, growth and development of tissues, regulation of gene transcription, and synthesis of hydrophobic glycoproteins and parts of the protein kinase enzyme pathways. Therefore, it is crucial to include vitamin A-rich foods in our diet or take supplements if necessary.
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This question is part of the following fields:
- Basic Sciences
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Question 7
Correct
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What controls the specific stages of the cell cycle?
Your Answer: Cyclins and cyclin-dependent kinases
Explanation:Regulation of the Cell Cycle by Cyclins and Cyclin-Dependent Kinases
The cell cycle is controlled by the activity of proteins known as cyclins and phosphorylating enzymes called cyclin-dependent kinases (CDKs). Cyclins and CDKs combine to form an activated heterodimer, where cyclins act as the regulatory subunits and CDKs act as the catalytic subunits. Neither of these molecules is active on their own. When a cyclin binds to a CDK, the CDK phosphorylates other target proteins, either activating or deactivating them. This coordination leads to the entry into the next phase of the cell cycle. The specific proteins that are activated depend on the different combinations of cyclin-CDK. Additionally, CDKs are always present in cells, while cyclins are produced at specific points in the cell cycle in response to other signaling pathways.
In summary, the cell cycle is regulated by the interaction between cyclins and CDKs. This interaction leads to the phosphorylation of target proteins, which ultimately controls the progression of the cell cycle.
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This question is part of the following fields:
- Basic Sciences
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Question 8
Correct
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You are evaluating a geriatric patient in the emergency department who has fallen and needs a venous cannula for fluid resuscitation. To ensure maximum flow into the vein, you plan to apply the Hagen-Poiseuille equation to select an appropriate cannula size. Which of the following statements is true according to this law?
Your Answer: Flow will be faster through a shorter cannula
Explanation:Poiseuille’s Equation and Fluid Flow in Cylinders
Poiseuille’s equation is used to describe the flow of non-pulsatile laminar fluids through a cylinder. The equation states that the flow rate is directly proportional to the pressure driving the fluid and the fourth power of the radius. Additionally, it is inversely proportional to the viscosity of the fluid and the length of the tube. This means that a short, wide cannula with pressure on the bag will deliver fluids more rapidly than a long, narrow one.
It is important to note that even small changes in the radius of a tube can greatly affect the flow rate. This is because the fourth power of the radius is used in the equation. Therefore, any changes in the radius will have a significant impact on the flow rate. Poiseuille’s equation is crucial in determining the optimal conditions for fluid delivery in medical settings.
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This question is part of the following fields:
- Basic Sciences
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Question 9
Correct
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Which of the following would not increase the rate of diffusion of a substance across a lipid membrane such as the cell wall?
Your Answer: Thickness of the membrane
Explanation:Diffusion and Fick’s Law
Diffusion is a natural process that occurs when molecules move from an area of high concentration to an area of low concentration. This process is passive and random, meaning that it does not require any external energy input. Fick’s Law states that diffusion occurs more quickly across a large, permeable, and thin membrane. For example, in lung disease, the thickening of the alveolar epithelial barrier can lead to a poor carbon monoxide transfer coefficient because the thicker membrane slows down the diffusion process. the principles of diffusion and Fick’s Law can help us better understand how molecules move and interact in various biological and chemical processes. By optimizing the conditions for diffusion, we can improve the efficiency of many natural and artificial systems.
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This question is part of the following fields:
- Basic Sciences
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Question 10
Correct
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What are the potential clinical consequences of a lack of vitamin E?
Your Answer: Ataxia
Explanation:Vitamin E Deficiency
Vitamin E deficiency is a rare condition that is more likely to occur in individuals with problems affecting the absorption of dietary fats. This includes those with a history of bowel surgery, pancreatic insufficiency, and cystic fibrosis. Premature infants are also at a higher risk of developing this deficiency as vitamin E does not easily cross the placenta. However, supplementation with vitamin E can reverse the damage in some cases.
The effects of vitamin E deficiency can be severe and can cause spinocerebellar degeneration, which includes limb ataxia, loss of joint position sense, loss of sensation of vibration, and loss of deep tendon reflexes. Additionally, it can cause degeneration of retinal pigments, leading to blindness. In premature infants, it can cause haemolytic anaemia, thrombocytosis, and oedema.
Overall, vitamin E deficiency is crucial in preventing and treating its effects. It is important to identify individuals who are at a higher risk of developing this deficiency and provide them with appropriate supplementation to prevent any long-term damage.
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This question is part of the following fields:
- Basic Sciences
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Question 11
Correct
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A 70-year-old male smoker complains of calf pain.
The GP performs a clinical test by raising the patient's legs and observing for the angle at which there is blanching. After one minute, the legs are lowered over the side of the couch so that they are fully dependent with feet on the floor. Reactive hyperaemia is observed.
Which clinical test does this describe?Your Answer: Buerger's test
Explanation:Tests for Assessing Arterial and Venous Circulation, Hip Dysfunction, and Meniscal Tear
Buerger’s test is a method used to evaluate the arterial circulation of the lower limb. The test involves observing the angle at which blanching occurs, with a lower angle indicating a higher likelihood of arterial insufficiency. Additionally, the degree of reactive hyperaemia on dependency of the limb after one minute is another positive sign of arterial insufficiency during the test.
Another test used to assess circulation is the Ankle-Brachial Pressure Index (ABPI), which involves using blood pressure cuffs to determine the degree of claudication. McMurray’s test, on the other hand, is used to evaluate for a meniscal tear within the knee joint.
Perthe’s test is a method used to assess the patency of the deep femoral vein prior to varicose vein surgery. Lastly, Trendelenburg’s test is used to evaluate hip dysfunction. These tests are important in diagnosing and treating various conditions related to circulation and joint function.
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This question is part of the following fields:
- Basic Sciences
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Question 12
Incorrect
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A 32-year-old snowboarder presents to the Emergency department complaining of pain and swelling around the first metacarpophalangeal joint (MCP joint) following a fall during practice.
Upon examination, there is significant swelling and bruising on the ulnar side of the joint.
What is the most probable injury that the patient has sustained?Your Answer: Accessory collateral ligament
Correct Answer: Ulnar collateral ligament
Explanation:Skier’s Thumb: A Common Injury in Winter Sports
Skier’s thumb, also known as gamekeeper’s thumb, is a common injury that occurs in winter sports. It is caused by damage or rupture of the ulnar collateral ligament, which is located at the base of the thumb. This injury can result in acute swelling and gross instability of the thumb. In severe cases where a complete tear of the ligament is suspected, an MRI may be necessary to confirm the diagnosis, and surgical repair may be required.
Once the acute swelling has subsided, treatment for skier’s thumb typically involves immobilization in a thumb spica. This is the standard therapy for cases of partial rupture.
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This question is part of the following fields:
- Basic Sciences
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Question 13
Correct
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During which stage of the cell cycle does the replication of DNA occur?
Your Answer: S phase
Explanation:The Five Phases of the Cell Cycle
The cell cycle is a complex process that is divided into five main phases, each with its unique cellular events. The first phase is the G0 phase, which is a resting phase where the cell has stopped dividing and is out of the cell cycle. The second phase is the G1 phase, also known as interphase Gap 1, where cells increase in size, and a checkpoint control mechanism prepares the cell for DNA synthesis.
The third phase is the S phase, where DNA replication occurs. The fourth phase is the G2 phase, also known as Gap 2, which is a gap between DNA synthesis and the onset of mitosis. During this phase, the cell continues to grow until it is ready to enter mitosis. Finally, the fifth phase is the M phase, also known as mitosis, where cell growth stops, and the cell focuses its energy to divide into two daughter cells.
A checkpoint in the middle of mitosis, known as the metaphase checkpoint, ensures that the cell is prepared to complete division. the five phases of the cell cycle is crucial in how cells divide and grow.
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This question is part of the following fields:
- Basic Sciences
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Question 14
Correct
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A 40-year-old male complains of a painful and swollen right calf. The possibility of deep vein thrombosis (DVT) is being considered. What tests should be conducted to confirm the diagnosis?
Your Answer: Dopplers of the leg veins
Explanation:Diagnostic Methods for Deep Vein Thrombosis
When it comes to diagnosing deep vein thrombosis (DVT), there are several methods available. The most common ones are Doppler studies and venography. Doppler studies use B mode ultrasonography to examine the venous system, while venography involves injecting a contrast dye into the veins and taking X-rays. CT scans are not typically used for DVT diagnosis because they require contrast and expose the patient to radiation. D-Dimer concentrations can help rule out DVT if they are negative, but they cannot diagnose it. MRI scans are useful for examining soft tissues and bones, but they are not the best option for visualizing the vasculature. Finally, oxygen saturation of the limbs is not a reliable diagnostic method because tissue perfusion can be the same even if there is arterial disease. Overall, Doppler studies and venography are the most effective methods for diagnosing DVT.
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This question is part of the following fields:
- Basic Sciences
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Question 15
Incorrect
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What is the main role of the Golgi apparatus in eukaryotic cells?
Your Answer: Synthesises proteins
Correct Answer: Process of proteins
Explanation:The Golgi Apparatus, Cell Division, and Homeostasis
The Golgi apparatus is a structure found in eukaryotic cells that consists of flattened membrane stacks. Its primary function is to modify proteins that have been synthesized in the rough endoplasmic reticulum, preparing them for secretion or transport within the cell. However, the Golgi apparatus is not directly involved in cell division, which is controlled by the nucleus.
Cell homeostasis, on the other hand, is primarily maintained by membrane-embedded channels or proteins such as the sodium-potassium pump. This mechanism ensures that the cell’s internal environment remains stable. The sodium-potassium pump is an active transport mechanism that involves the binding of three intracellular sodium ions to the protein. Adenosine triphosphate (ATP) donates a phosphate group to the protein, which causes it to change shape and release the sodium ions out of the cell.
The protein then accepts two extracellular potassium ions, and the donated phosphate group detaches, causing the protein to revert to its original shape. This allows the potassium ions to enter the cell, increasing the intracellular potassium concentration and decreasing the intracellular sodium concentration. This process is in contrast to the extracellular conditions.
In summary, the Golgi apparatus modifies proteins for secretion or transport, while cell division is controlled by the nucleus. Cell homeostasis is maintained by membrane-embedded channels or proteins such as the sodium-potassium pump, which actively transports ions to stabilize the cell’s internal environment.
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This question is part of the following fields:
- Basic Sciences
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Question 16
Incorrect
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What is the fundamental meaning of carbohydrate?
Your Answer: A compound containing carbon, hydrogen and oxygen in any proportion.
Correct Answer: A compound following the formula Cx(H2O)y
Explanation:Carbohydrates: Building Blocks of Energy and Storage
Carbohydrates are organic compounds made up of carbon, hydrogen, and oxygen, with a general formula of Cx(H2O)y. They can be classified as either aldehydes or ketones and contain multiple hydroxyl groups. Monosaccharides are the simplest form of carbohydrates, consisting of a single unit. They are categorized based on the number of carbon atoms they contain, with trioses having three, pentoses having five, and hexoses having six carbon atoms. These monosaccharides are essential for energy production and building larger carbohydrate structures.
Disaccharides are formed when two monosaccharides are joined together through a condensation reaction, releasing a water molecule. The most common disaccharides are lactose, maltose, and sucrose. Polysaccharides, on the other hand, are long, branched polymers made up of multiple single units. They serve as convenient storage molecules for energy reserves, such as glycogen in humans and starch in plants.
In summary, carbohydrates are vital building blocks for energy production and storage in living organisms. Monosaccharides, disaccharides, and polysaccharides all play important roles in maintaining the body’s energy balance and overall health.
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This question is part of the following fields:
- Basic Sciences
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Question 17
Incorrect
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What occurs in eukaryotic prometaphase?
Your Answer: Chromatin condenses into chromosomes
Correct Answer: The nuclear membrane and the nucleoli disintegrate and kinetochores appear
Explanation:The Significance of Prometaphase in Cell Division
Prometaphase is a crucial phase in cell division that marks the transition from prophase to metaphase. Although it is often considered as a part of these two phases, it has distinct events that make it an individual phase. During prometaphase, the nuclear membrane disintegrates, and the nucleoli are no longer visible. Additionally, each chromosome forms two kinetochores near the centromere, which serve as attachment points for spindle fibers. These fibers connect to the opposite poles of the cell, forming travelling lines that will separate the sister chromatids during anaphase.
Prophase is characterized by chromatin condensation, while DNA and centrosome duplication occur during interphase. Chromosome alignment takes place during metaphase, and the sister chromatids separate during anaphase. Prometaphase, therefore, plays a crucial role in preparing the chromosomes for separation during anaphase. Its distinct events make it an essential phase in cell division, and its proper execution is necessary for successful cell division.
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This question is part of the following fields:
- Basic Sciences
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Question 18
Correct
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A 10-year-old patient presents with recurrent skin cancer and is diagnosed with xeroderma pigmentosum. What is the defective biochemical mechanism in this disease?
Your Answer: DNA excision repair
Explanation:Xeroderma Pigmentosum and DNA Repair
Deoxyribonucleic acid (DNA) found in the skin cells can absorb ultraviolet (UV) light, which can cause the formation of pyrimidine dimers. These dimers are removed through a process called excision repair, where the damaged DNA is cut out and replaced with new DNA. However, if this process fails, it can lead to mutations in genes that suppress tumors or promote their growth, potentially leading to cancer.
Xeroderma pigmentosum is a genetic disorder that is inherited in an autosomal recessive pattern. This means that an individual must inherit two copies of the mutated gene, one from each parent, to develop the disorder. Generally, disorders that affect metabolism or DNA replication on a cellular or genetic level are inherited in an autosomal recessive pattern. On the other hand, genetic disorders that affect larger structural components are usually inherited in an autosomal dominant pattern. While there are exceptions to these rules, they can serve as a helpful guide for exam preparation.
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This question is part of the following fields:
- Basic Sciences
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Question 19
Correct
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Over the last five years, the total number of patients admitted and deaths in the East and North Hertfordshire NHS Trust have been recorded. In the year 2010/2011, there were 95,071 patients admitted and 1,912 deaths. What is the crude mortality ratio for this group in that year (per 100 admissions)?
Your Answer: 2
Explanation:In this scenario, the crude mortality ratio is established by comparing the number of deaths occurring within the hospital in a given year to the total number of admissions, disregarding age or gender-specific mortality rates. For instance, with 1,912 deaths out of 95,071 admissions, the ratio computes to 0.02, or 2.0% when calculated per 100 admissions (1,912/95,071 = 0.02/100= 2.0%. When recalculated per 1,000 admissions, the crude admission rate would be 20 per 1,000.
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This question is part of the following fields:
- Basic Sciences
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Question 20
Correct
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What function does vitamin E serve in the body?
Your Answer: Antioxidant
Explanation:Vitamin E and its Functions
Several substances are classified as vitamin E, with alpha-tocopherol being the most common, accounting for 90% of human vitamin E. Alpha-tocopherol is composed of two carbon rings and a long saturated hydrocarbon chain, making it hydrophobic. It has an aromatic ring with an OH- group attached to it. Other substances with vitamin E activity include other tocopherols and tocotrienols, all of which act as antioxidants. Alpha-tocopherol is particularly important in cell membranes, preventing the peroxidation of unsaturated fatty acids by free radicals. It also has other functions, such as regulating gene transcription, inhibiting clotting formation, reducing proliferation of vascular smooth muscle, and playing a role in immunity.
Despite claims that taking vitamin E can reduce the risk of heart disease, cancer, and enhance sexual performance, there is currently no strong evidence to support these claims.
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This question is part of the following fields:
- Basic Sciences
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Question 21
Correct
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In scientific experimentation, what is the term used to describe the movement of charged particles or solutes in a liquid medium due to an electric field?
Your Answer: Electrophoresis
Explanation:Electrophoresis: Separating Molecules Based on Charge and Mass
Electrophoresis is a technique that separates solutes, molecules, or nucleic acids based on their mass and charge. It involves the migration of charged particles in a liquid medium under the influence of an electric field. The apparatus consists of two electrodes placed at either end of a support medium, or gel, which is suspended in a buffer solution. The sample is inserted into a well and a current is applied. Over time, positively charged solutes move towards the negative electrode, while negatively charged substances move towards the positive electrode. Once the migration is complete, the gel is removed and stained to color the substance being tested for, such as protein.
This technique is widely used in medical testing, but it requires a higher degree of operational and interpretive skill than many other tests, which is why it often takes longer to get a result. Electrophoresis has various uses and adaptations, such as standard electrophoresis for protein detection in the diagnosis of myeloma, identification of unusual lipid fractions in patients with inherited diseases, and detection of viral DNA through Southern Blotting. There is also Northern blotting, primarily a research technique at present, which uses electrophoresis to separate RNA. Additionally, Western blotting is used to test for the presence of antibodies to DNA through protein separation.
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This question is part of the following fields:
- Basic Sciences
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Question 22
Correct
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The diabetes prevention program has been running for the last 5 years. At baseline, a well conducted study with a sample size of 500 showed that the prevalence of diabetes among adults aged 40 and above was 15%.
Five years later another survey (of 400 responders) showed that the prevalence of diabetes was 10%.
In the above example, which definition of prevalence is correct?Your Answer: Prevalence is the number of new and old smokers in a year
Explanation:Prevalence and Incidence in Smoking
Prevalence and incidence are two important concepts in the smoking habits of a population. Prevalence refers to the number of people who smoke at a particular time point, such as at the beginning or end of a study period. This is calculated by dividing the number of smokers by the total population.
On the other hand, incidence refers to the number of new cases of smoking at a particular time point. For example, this could be at the beginning of a study period for the whole year or at the 10th year. This is calculated by dividing the number of new smokers by the number of smoke-free individuals who are potentially at risk of taking up smoking.
prevalence and incidence is important in evaluating the effectiveness of smoking cessation programs and policies. By tracking changes in prevalence and incidence over time, researchers and policymakers can determine whether their efforts are making a difference in reducing smoking rates. Additionally, these concepts can help identify populations that are at higher risk of taking up smoking, allowing for targeted interventions to prevent smoking initiation.
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This question is part of the following fields:
- Basic Sciences
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Question 23
Correct
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A 65-year-old patient with suspected spinal cord compression has been admitted to the neurosurgical team for an urgent MRI of the spine. The MRI technique primarily relies on the magnetic properties of which particle?
Your Answer: Hydrogen ion (proton)
Explanation:How MRI Scanners Use Hydrogen Ions to Create Images
MRI scanners use the magnetic properties of hydrogen ions, also known as protons, to create images of the human body. These protons have nuclear spin, which means they have magnetic vectors that can be aligned in an electromagnet. The scanner bombards the protons with radiofrequency radiation, causing them to release energy when they return to their resting state. This energy release is recorded and used to construct the MRI image.
While other nuclei, such as carbon 13, also have net nuclear spin and could be used in MRI imaging, hydrogen ions are much more abundant in human tissues. This makes them the preferred choice for creating images of the body. By using the magnetic properties of hydrogen ions, MRI scanners can create detailed images of internal structures without the use of harmful radiation.
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This question is part of the following fields:
- Basic Sciences
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Question 24
Correct
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What occurs in eukaryotic prophase?
Your Answer: Chromatin condenses into chromosomes
Explanation:The Stages of Prophase in Eukaryotic Mitosis
Prophase is the first stage of eukaryotic mitosis, except for plant cells which have a preprophase stage. During prophase, the cell’s chromatin, which is made up of DNA and associated proteins, condenses into double rod-shaped structures called chromosomes. This process is facilitated by the condensin protein I and/or II complexes. As the chromosomes form, the nuclear membrane and nucleoli disintegrate and disappear, making the chromatin visible.
Before prophase, the cell’s DNA is replicated during interphase, resulting in identical pairs of chromosomes called chromatids. These chromatids attach to each other at a DNA element called the centromere. DNA and centrosome duplication occur during interphase, while chromosome alignment takes place during metaphase. The nuclear membrane and nucleoli re-form during telophase, and the sister chromatids separate during anaphase.
In summary, prophase is the initial stage of eukaryotic mitosis where chromatin condenses into chromosomes, and the nuclear membrane and nucleoli disappear. Chromosome alignment, DNA and centrosome duplication, and re-formation of the nuclear membrane and nucleoli occur in subsequent stages.
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This question is part of the following fields:
- Basic Sciences
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Question 25
Correct
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What significance do leucine, lysine, and phenylalanine hold?
Your Answer: They are essential amino acids
Explanation:Essential Amino Acids and their Importance in the Diet
There are approximately 20 essential amino acids that are crucial for human health. These amino acids are considered essential because the body cannot produce them on its own and they must be obtained through the diet. While some of these essential amino acids can be used to create other non-essential amino acids, they are still necessary for overall health and wellbeing.
Some examples of essential amino acids include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. However, the amount of these essential amino acids can vary depending on the type of dietary protein consumed. Additionally, cooking or preserving proteins can alter the amino acid composition, making them less effective for the body.
In summary, essential amino acids play a vital role in maintaining human health and must be obtained through the diet. the importance of these amino acids and their sources can help individuals make informed decisions about their dietary choices.
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This question is part of the following fields:
- Basic Sciences
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Question 26
Correct
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What is the end result of meiosis in a cell?
Your Answer: 4 haploid cells
Explanation:Meiosis
Meiosis is a crucial process that occurs in the genetic cells of eukaryotic organisms. Its primary purpose is to recombine genes, which results in genetic variation while also ensuring genetic preservation. Although meiosis shares some similarities with mitosis, it is restricted to genetic cells, also known as gametes, of eukaryotic organisms.
During meiosis, a gamete duplicates each of its chromosomes and divides into two diploid cells. These cells then divide into four haploid cells by the end of the second stage of meiosis (telophase II and cytokinesis). These haploid cells are either sperm cells (male) or eggs (female) in mammals. When these haploid cells fuse together, they produce a diploid zygote that contains two copies of parental genes.
In summary, meiosis is a crucial process that ensures genetic variation and preservation in eukaryotic organisms. It involves the duplication and division of genetic cells into haploid cells, which can then fuse together to produce a diploid zygote.
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This question is part of the following fields:
- Basic Sciences
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Question 27
Correct
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What is the term for the process described below in laboratory testing?
Enzymes are immobilised on a solid surface, such as a bead or well, and allowed to come into contact with the sample. After washing, another enzyme is added with a label allowing quantitation of the analyte.Your Answer: Enzyme-linked immunosorbent assay
Explanation:ELISA: A Common Immunoassay in Medical Diagnostic Testing
An enzyme-linked immunosorbent assay (ELISA) is a type of immunoassay that is widely used in medical diagnostic testing. This method uses antibodies to identify and/or quantify the analyte being tested. The ELISA process involves several steps, including coating a plate with the antigen, adding the patient’s sample, washing the plate to remove any unbound material, adding an enzyme-linked antibody, washing the plate again, and adding a substrate to produce a measurable signal.
Over time, many modifications have been made to the ELISA, making it a versatile tool in the laboratory for measuring various analytes. Some of the substances that can be measured using immunoassays include thyroid hormone, testosterone, oestrogen, troponin, and vitamin D. The ELISA has been around for a long time and is still widely used today due to its accuracy, sensitivity, and specificity.
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This question is part of the following fields:
- Basic Sciences
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Question 28
Correct
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The arrangement of amphipathic phospholipids in the mammalian cell membrane, what is it like?
Your Answer: A lipid bilayer with hydrophilic heads facing out and hydrophobic tails facing in
Explanation:The Function and Structure of the Mammalian Cell Membrane
The mammalian cell membrane serves as a protective barrier that separates the cytoplasm from the extracellular environment. It also acts as a filter for molecules that move across it. Unlike plant and prokaryotic cells, mammalian cells do not have a cell wall. The main component of the cell membrane is a bilayer of amphipathic lipids, which have a hydrophilic head and a hydrophobic tail. The phospholipids in the bilayer are oriented with their hydrophilic heads facing outward and their hydrophobic tails facing inward. This arrangement allows for the separation of the watery extracellular environment from the watery intracellular compartment.
It is important to note that the cell membrane is not a monolayer and the phospholipids are not linked head-to-tail. This is in contrast to DNA, which has a helical chain formation. Overall, the structure and function of the mammalian cell membrane are crucial for maintaining the integrity and proper functioning of the cell.
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This question is part of the following fields:
- Basic Sciences
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Question 29
Correct
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What is the apoptotic event that occurs just before the formation of an apoptosome?
Your Answer: Release of cytochrome c from mitochondria
Explanation:Apoptosis and the Role of the Apoptosome
Apoptosis, also known as programmed cell death, is a natural process that occurs in all multicellular organisms. It involves a series of changes in cell morphology, including membrane blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation. The formation of the apoptosome is a crucial part of the apoptosis cascade. It is a large protein structure that is triggered by the release of cytochrome c from the mitochondria in response to various stimuli, such as DNA damage, infections, or developmental signals.
The apoptosome is formed when cytochrome c binds to Apaf-1, a cytosolic protein, in a 1:1 ratio. This triggers the recruitment and activation of the initiator pro-caspase-9, which then activates effector caspases, a family of apoptotic proteases, to initiate the apoptotic cascade. It is important to note that the activation of caspase-9 occurs only after the formation of the apoptosome.
In summary, apoptosis is a natural process that occurs in multicellular organisms, and the apoptosome plays a crucial role in triggering the apoptotic cascade. the mechanisms behind apoptosis and the formation of the apoptosome can provide insights into various diseases and developmental processes.
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This question is part of the following fields:
- Basic Sciences
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Question 30
Incorrect
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Which form of vitamin D is the most active in the human body?
Your Answer: Cholecalciferol
Correct Answer: 1, 25 (OH) 2 vitamin D
Explanation:The Process of Vitamin D Production and Activation
Vitamin D comes in two forms, D2 and D3. D3 can be produced in the skin through a reaction that requires UV light, while D2 cannot. Both forms can also be obtained through diet, with some foods now being supplemented with Vitamin D. However, the production of Vitamin D3 in the skin can be affected by various factors such as seasons, latitude, clothing, sun block, and skin tone, making it difficult for individuals to get adequate levels of Vitamin D through sunlight alone, especially in the UK during winter.
Once absorbed into the lymph, Vitamin D2 and D3 circulate in the bloodstream and reach the liver. Here, the liver enzyme 25-hydroxylase adds an OH group to the Vitamin D molecule, resulting in 25(OH) Vitamin D. The compound then travels to the kidney, where the enzyme 1-alpha hydroxylase adds another OH group, creating the active form of Vitamin D, 1,25 (OH)2Vitamin D. When there is enough of this active form, an inactive metabolite called 24,25 (OH)2Vitamin D is produced instead. this process is important in ensuring adequate Vitamin D levels for overall health and well-being.
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This question is part of the following fields:
- Basic Sciences
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