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  • Question 1 - Microfilaments exist in: ...

    Incorrect

    • Microfilaments exist in:

      Your Answer: Muscle cells

      Correct Answer: All of the options

      Explanation:

      Microfilaments, also called actin filaments, are filamentous structures in the cytoplasm of cells and form part of the cytoskeleton.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      16.1
      Seconds

  • Question 2 - Which is true of the citric acid cycle? ...

    Incorrect

    • Which is true of the citric acid cycle?

      Your Answer:

      Correct Answer: Involves a series of reactions where oxaloacetate is regenerated

      Explanation:

      The cycle consumes acetate (in the form of acetyl-CoA) and water, reduces NAD+ to NADH, and produces carbon dioxide as a waste by-product. The NADH generated by the citric acid cycle is fed into the oxidative phosphorylation (electron transport) pathway. At the end of each cycle, the four-carbon oxaloacetate has been regenerated, and the cycle continues. The net result of these two closely linked pathways is the oxidation of nutrients to produce usable chemical energy in the form of ATP. Acetyl-CoA, is the starting point for the citric acid cycle and in eukaryotic cells, the citric acid cycle occurs in the matrix of the mitochondrion. Though the Krebs cycle does not directly require oxygen, it can only take place when oxygen is present because it relies on by-products and is therefore an aerobic process.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 3 - The processing of NH3 to urea occurs in: ...

    Incorrect

    • The processing of NH3 to urea occurs in:

      Your Answer:

      Correct Answer: Mitochondria and cytoplasm

      Explanation:

      The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions that produces urea ((NH2)2CO) from ammonia (NH3). The urea cycle consists of four enzymatic reactions: one mitochondrial and three cytosolic.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 4 - The cell membrane: ...

    Incorrect

    • The cell membrane:

      Your Answer:

      Correct Answer: Is a bilayer of amphipathic lipids

      Explanation:

      The cell membrane consists of a bilayer of amphipathic lipids with embedded proteins. The basic function of the cell membrane is to protect the cell from its surroundings. It is selectively permeable to ions and organic molecules. The entire membrane is held together via non-covalent interaction of hydrophobic tails, however the structure is quite fluid and not fixed rigidly in place. Membranes are typically 7.5–10 nm in thickness and typically have a large content of proteins, around 50% of membrane volume.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 5 - With regard to cell membrane proteins: ...

    Incorrect

    • With regard to cell membrane proteins:

      Your Answer:

      Correct Answer: Carriers are involved in facilitated diffusion

      Explanation:

      Pumps use a source of free energy such as ATP to transport ions against a gradient and is an example of active transport. Unlike channel proteins which only transport substances through membranes passively, carrier proteins can transport ions and molecules either passively through facilitated diffusion, or via secondary active transport. Channels are either in open state or closed state. When a channel is opened, it is open to both extracellular and intracellular. Pores are continuously open to both environments, because they do not undergo conformational changes. They are always open and active.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 6 - Which intercellular connections are responsible for fastening the cells to one another? ...

    Incorrect

    • Which intercellular connections are responsible for fastening the cells to one another?

      Your Answer:

      Correct Answer: Hemidesmosomes, zonula adherens & desmosomes

      Explanation:

      There are three major types of cell junction:Adherens junctions, desmosomes and hemidesmosomes (anchoring junctions),Gap junctions (communicating junction) &Tight junctions (occluding junctions)

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 7 - Regarding oxidative deamination of amino acids, which of the following is true? ...

    Incorrect

    • Regarding oxidative deamination of amino acids, which of the following is true?

      Your Answer:

      Correct Answer: Occurs in the kidney & liver

      Explanation:

      Oxidative deamination is a form of deamination that generates α-keto acids and other oxidized products from amine-containing compounds, and occurs largely in the liver and kidney. Oxidative deamination is an important step in the catabolism of amino acids, generating a more metabolizable form of the amino acid, and also generating ammonia as a toxic by-product. The addition of ubiquitin to a substrate protein is called ubiquitination.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 8 - Hydroxyl radicals are broken down by which of the following substance? ...

    Incorrect

    • Hydroxyl radicals are broken down by which of the following substance?

      Your Answer:

      Correct Answer: Antioxidants

      Explanation:

      Unlike superoxide, which can be detoxified by superoxide dismutase, the hydroxyl radical cannot be eliminated by an enzymatic reaction but it is believed can be counteracted by antioxidants.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 9 - What is the function of the pro-apoptotic Bcl-2 family of proteins, Bax and...

    Incorrect

    • What is the function of the pro-apoptotic Bcl-2 family of proteins, Bax and Bak?

      Your Answer:

      Correct Answer: Form permissive pores in the mitochondrial membrane

      Explanation:

      The pro-apoptotic proteins in the BCL-2 family, including Bax and Bak, normally act on the mitochondrial membrane to promote permeabilization and release of cytochrome C and ROS, that are important signals in the apoptosis cascade. Growing evidence suggests that activated BAX and/or Bak form an oligomeric pore, MAC in the mitochondrial outer membrane. This results in the release of cytochrome c and other pro-apoptotic factors from the mitochondria, often referred to as mitochondrial outer membrane permeabilization, leading to activation of caspases.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 10 - Which of the following statements is most suitable to describe necrosis? ...

    Incorrect

    • Which of the following statements is most suitable to describe necrosis?

      Your Answer:

      Correct Answer: Significant inflammatory response

      Explanation:

      Necrosis is the death of most or all of the cells in an organ or tissue due to disease, injury, or failure of the blood supply. Cellular death due to necrosis does not follow the (regulated) apoptotic signal transduction pathway, but rather various receptors are activated, and result in the loss of cell membrane integrity and an uncontrolled release of products of cell death into the extracellular space. This initiates in the surrounding tissue an inflammatory response which attracts leukocytes and nearby phagocytes which eliminate the dead cells by phagocytosis.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 11 - Cyclic AMP is formed from ATP via which enzyme ...

    Incorrect

    • Cyclic AMP is formed from ATP via which enzyme

      Your Answer:

      Correct Answer: Adenylate cyclase

      Explanation:

      Cyclic AMP is synthesized from ATP by adenylate cyclase located on the inner side of the plasma membrane and anchored at various locations in the interior of the cell.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 12 - In which organelle is the intrinsic apoptotic pathway initiated? ...

    Incorrect

    • In which organelle is the intrinsic apoptotic pathway initiated?

      Your Answer:

      Correct Answer: Mitochondria

      Explanation:

      Apoptosis is a programmed form of cell death involving the degradation of cellular constituents by a group of cysteine proteases called caspases. The caspases can be activated through either the intrinsic (mitochondrial mediated) or extrinsic (death receptor mediated) apoptotic pathways.

      The intrinsic apoptotic pathway, also known as the mitochondrial pathway, is primarily initiated within the mitochondria. This pathway is activated in response to various internal stimuli, such as DNA damage, oxidative stress, and other cellular stresses.

      When the intrinsic pathway is triggered, several events occur in the mitochondria:

      1. Release of cytochrome c: Cytochrome c is released from the mitochondrial intermembrane space into the cytoplasm.
      2. Formation of the apoptosome: Cytochrome c in the cytoplasm binds to apoptotic protease activating factor-1 (Apaf-1) and procaspase-9, forming a complex known as the apoptosome.
      3. Activation of caspase-9: The apoptosome activates caspase-9, an initiator caspase.
      4. Caspase cascade: Activated caspase-9 then activates executioner caspases, such as caspase-3, leading to the execution phase of apoptosis, which results in the orderly dismantling of the cell.

      The mitochondria play a crucial role in this pathway by regulating the release of pro-apoptotic factors that are essential for the activation of downstream apoptotic processes.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 13 - Inhibition of cell division at the end of G1 occurs through: ...

    Incorrect

    • Inhibition of cell division at the end of G1 occurs through:

      Your Answer:

      Correct Answer: Unphosphorolated retinoblastoma protein (uRb)

      Explanation:

      A cell’s decision to enter, or re-enter, the cell cycle is made before S-phase in G1 at what is known as the restriction point, and is determined by the combination of promotional and inhibitory extracellular signals that are received and processed. Ultimately unphosphorylated Rb acts as an inhibitor of G1.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 14 - With regards to the Na+/K+ ATPase, which one of the following is correct?...

    Incorrect

    • With regards to the Na+/K+ ATPase, which one of the following is correct?

      Your Answer:

      Correct Answer: 3 Na+ released into the extracellular fluid

      Explanation:

      Na+/K+ pump or sodium–potassium pump is an enzyme found in the plasma membrane. This pumping is active (i.e. it uses energy from ATP) and is important for cell physiology. Its simple function is to pump 3 sodium ions out for every 2 potassium ions taken in and since they both have equal ionic charges, this creates a electrochemical gradient between a cell and its exterior.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 15 - Selectins ...

    Incorrect

    • Selectins

      Your Answer:

      Correct Answer: Interact with carbohydrate ligands or mucin complexes on leucocytes and endothelial cells

      Explanation:

      Selectins are involved in constitutive lymphocyte homing, and in chronic and acute inflammation processes, including post-ischemic inflammation. Each selectin has a carbohydrate recognition domain that mediates binding to specific glycans on apposing cells.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 16 - Cyclic AMP is broken down by which enzyme ...

    Incorrect

    • Cyclic AMP is broken down by which enzyme

      Your Answer:

      Correct Answer: Phosphodiesterase

      Explanation:

      cAMP decomposition into AMP is catalysed by the enzyme phosphodiesterase.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 17 - With regards to the function of the p53 protein produced by the p53...

    Incorrect

    • With regards to the function of the p53 protein produced by the p53 gene, which of the following statements is incorrect?

      Your Answer:

      Correct Answer: It permits repair of mutations and other defects in RNA

      Explanation:

      The p53 protein is a crucial tumor suppressor and plays several key roles in maintaining cellular integrity:

      1. Nuclear transcription factor: p53 is a nuclear transcription factor that regulates the expression of various genes involved in cell cycle control, DNA repair, apoptosis, and senescence.
      2. DNA repair: p53 permits repair of mutations and other defects in DNA (not RNA). It activates the transcription of genes involved in DNA repair mechanisms, allowing the cell to correct errors before proceeding with the cell cycle.
      3. Cell cycle regulation: p53 can induce the expression of p21, a protein that inhibits cyclin-dependent kinases, thereby halting the cell cycle at the G1/S checkpoint to allow time for DNA repair or to trigger apoptosis if the damage is irreparable. Mutations in p53 may fail to halt the cell cycle, allowing mutations to persist and potentially leading to cancer.
      4. Apoptosis: If DNA damage is extensive and cannot be repaired, p53 triggers apoptosis to prevent the propagation of damaged cells.
      5. Suppression of proto-oncogenes: p53 indirectly contributes to the suppression of proto-oncogenes by preventing the proliferation of cells with damaged DNA, thereby reducing the risk of oncogenic transformation.

      Given these functions, the statement that p53 “permits repair of mutations and other defects in RNA” is incorrect, as p53 is primarily involved in the repair of DNA, not RNA.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 18 - The interior of lysosomes is kept at a pH of around 5 by...

    Incorrect

    • The interior of lysosomes is kept at a pH of around 5 by the action of:

      Your Answer:

      Correct Answer: H+ ATPase

      Explanation:

      The lysosome maintains its pH differential by pumping in protons (H+ ions) from the cytosol across the membrane via proton pumps and chloride ion channels. Vacuolar H+-ATPases are responsible for transport of protons, while the counter transport of chloride ions is performed by ClC-7 Cl−/H+ antiporter.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 19 - What is the enzyme that is involved in the formation of citrulline? ...

    Incorrect

    • What is the enzyme that is involved in the formation of citrulline?

      Your Answer:

      Correct Answer: Ornithine transcarbamoylase

      Explanation:

      Carbamoyl phosphate is converted to citrulline by ornithine transcarbamoylase.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 20 - Cell membrane proteins may act as: ...

    Incorrect

    • Cell membrane proteins may act as:

      Your Answer:

      Correct Answer: All of the options

      Explanation:

      Membrane proteins perform a variety of functions including:Membrane receptor proteins relay or carry signals between the cell’s internal and external environments.Transport proteins move molecules and ions (ionic channels) across the membrane. Membrane enzymes may have many activities, such as oxidoreductase, transferase or hydrolase andCell adhesion molecules

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 21 - The Cellular Theory of Ageing involves? ...

    Incorrect

    • The Cellular Theory of Ageing involves?

      Your Answer:

      Correct Answer: Loss of telomeres

      Explanation:

      Cellular theories of aging propose that human aging is the result of cellular aging, whereby an increasing proportion of cells reach senescence, a terminal stage at which cells will cease to divide. This will limit the body’s ability to regenerate and to respond to injury or stress. Telomeres are bits of DNA on the ends of chromosomes that protect chromosomes from sticking to each other or tangling, which could cause DNA to abnormally function. As cells replicate, telomeres shorten at the end of chromosomes, and this process correlates to senescence or cellular aging.

      Other theories include:

      1. The Free Radical Theory: Implicates the gradual accumulation of oxidative cellular damage as a fundamental driver of cellular aging. This theory has evolved over time to emphasize the role of free radical induced mitochondrial DNA (mtDNA) mutations and the accumulation of mtDNA deletions. Given the proximity of mtDNA to the electron transport chain, a primary producer of free radicals, it postulates that the mutations would promote mitochondrial dysfunction and concomitantly increase free radical production in a positive feedback loop. It is known that diet, lifestyle, drugs (e.g. tobacco and alcohol) and radiation etc., are all accelerators of free radical production within the body.
      2. Error theory: based on the idea that errors can occur in the transcription of the synthesis of DNA. These errors are perpetuated and eventually lead to systems that do not function at the optimum level. The organism’s aging and death are attributable to these events (Sonneborn, 1979).
      3. The Cross-Linking Theory: also referred to as the Glycosylation Theory of Aging. In this theory it is the binding of glucose (simple sugars) to protein, (a process that occurs under the presence of oxygen) that causes various problems. Once this binding has occurred the protein becomes impaired and is unable to perform as efficiently. Living a longer life is going to lead to the increased possibility of oxygen meeting glucose and protein and known cross-linking disorders include senile cataract and the appearance of tough, leathery and yellow skin.
      4. The Neuroendocrine Theory First proposed by Professor Vladimir Dilman and Ward Dean MD, this theory elaborates on wear and tear by focusing on the neuroendocrine system. This system is a complicated network of biochemicals that govern the release of hormones which are altered by the walnut sized gland called the hypothalamus located in the brain. The hypothalamus controls various chain-reactions to instruct other organs and glands to release their hormones etc. The hypothalamus also responds to the body hormone levels as a guide to the overall hormonal activity. But as we grow older the hypothalamus loses it precision regulatory ability and the receptors which uptake individual hormones become less sensitive to them. Accordingly, as we age the secretion of many hormones declines and their effectiveness (compared unit to unit) is also reduced due to the receptors down-grading
      5. The Membrane Theory of Aging: According to this theory it is the age-related changes of the cell’s ability to transfer chemicals, heat and electrical processes that impair it. As we grow older the cell membrane becomes less lipid (less watery and more solid). This impedes its efficiency to conduct normal function and in particular there is a toxic accumulation
      6. The Decline Theory: The mitochondria are the power producing organelles found in every cell of every organ. Their primary job is to create Adenosine Triphosphate (ATP) and they do so in the various energy cycles that involve nutrients such as Acetyl-L-Carnitine, CoQ10 (Idebenone), NADH and some B vitamins etc. Enhancement and protection of the mitochondria is an essential part of preventing and slowing aging. Enhancement can be achieved with the above mention nutrients, as well as ATP supplements themselves.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 22 - Which one of the following transporters is involved in facilitated diffusion? ...

    Incorrect

    • Which one of the following transporters is involved in facilitated diffusion?

      Your Answer:

      Correct Answer: GLUT2

      Explanation:

      GLUT 2 is a bidirectional transporter, allowing glucose to flow in 2 directions via facilitated diffusion. Is expressed by renal tubular cells, liver cells and pancreatic beta cells. It is also present in the basolateral membrane of the small intestine epithelium.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 23 - The role of the hemidesmosome is? ...

    Incorrect

    • The role of the hemidesmosome is?

      Your Answer:

      Correct Answer: Attaches cells to underlying basal lamina

      Explanation:

      Hemidesmosomes connect the basal surface of epithelial cells via intermediate filaments to the underlying basal lamina. The transmembrane proteins of hemidesmosomes are not cadherins, but another type of protein called integrin.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 24 - The p53 tumour suppressor gene is located on? ...

    Incorrect

    • The p53 tumour suppressor gene is located on?

      Your Answer:

      Correct Answer: Chromosome 17

      Explanation:

      P53 is classified as a tumour suppressor gene and is located on the short arm of chromosome 17.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 25 - The function of the Golgi apparatus is ...

    Incorrect

    • The function of the Golgi apparatus is

      Your Answer:

      Correct Answer: Maturation of peptides secreted by the rER into functional proteins by glycosylation

      Explanation:

      Steroidogenesis is a multi-step process that occurs in two organelles, the endoplasmic reticulum (ER) and the mitochondrion. The Golgi apparatus is a major collection and dispatch station of protein products received from the endoplasmic reticulum (ER). Proteins synthesized in the ER are packaged into vesicles, which then fuse with the Golgi apparatus. The majority of proteins synthesized in the rough ER undergo glycosylation which occurs in the Golgi apparatus. Glycosylation mainly refers in particular to the enzymatic process that attaches glycans to proteins, lipids, or other organic molecules. These cargo proteins are modified and destined for secretion via exocytosis or for use in the cell. The Golgi apparatus is also involved in lipid transport and lysosome formation.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 26 - What is the function of gap junctions? ...

    Incorrect

    • What is the function of gap junctions?

      Your Answer:

      Correct Answer: Diffusion of small molecules between neighbouring cells

      Explanation:

      Gap junctions are a specialized intercellular connection between a multitude of cell-types. They directly connect the cytoplasm of two cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 27 - Free radicals are best defined by which of the following statements. ...

    Incorrect

    • Free radicals are best defined by which of the following statements.

      Your Answer:

      Correct Answer: Atoms or molecules with unpaired electrons

      Explanation:

      Free radicals form when one of weak bond between electrons is broken and an uneven number of electrons remain. This means the electron is unpaired, making it chemically reactive and attempt to steal an electron from a neighbouring molecule to stabilize itself.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 28 - The formation of superoxide is catalysed by which enzyme? ...

    Incorrect

    • The formation of superoxide is catalysed by which enzyme?

      Your Answer:

      Correct Answer: NADPH oxidase

      Explanation:

      Superoxide is biologically toxic and is deployed by the immune system to kill invading microorganisms. In phagocytes, superoxide is produced in large quantities by the enzyme NADPH oxidase for use in oxygen-dependent killing mechanisms of invading pathogens.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 29 - In the body what are fatty acids broken down to? ...

    Incorrect

    • In the body what are fatty acids broken down to?

      Your Answer:

      Correct Answer: Acetyl Co A

      Explanation:

      Fatty acids are broken down into acetyl Co A. The acetyl-CoA produced by beta oxidation enters the citric acid cycle in the mitochondrion by combining with oxaloacetate to form citrate.

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

  • Question 30 - Which caspase is part of both the intrinsic and extrinsic apoptotic pathways? ...

    Incorrect

    • Which caspase is part of both the intrinsic and extrinsic apoptotic pathways?

      Your Answer:

      Correct Answer: Caspase-3

      Explanation:

      Once initiator caspases are activated in both the intrinsic and extrinsic pathway, they produce a chain reaction, activating several other executioner caspases (Caspase 3, Caspase 6 and Caspase 7).

    • This question is part of the following fields:

      • Cell Biology
      • Medicine
      0
      Seconds

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