🧬 Biochemistry Solved MCQs with Answers

Practice 1490 approved 🧬 Biochemistry questions with verified answers from the 🧬 Medical Science subject for Pakistan exams.

1490 solved MCQs

The unfavourable free energy associated with not satisfying a hydrogen bond after formation of the double helix is approximatelyAnswer: 20 kJ/mol The most stabilizing force for nucleic acids isAnswer: Van der Waals A purine with an amine (NH₂) group on the 6ᵗʰ carbon isAnswer: Adenine Which of the following is found on RNA but not DNA?Answer: Uracil Which of the following is a purine?Answer: Adenine Small charged molecules, often biogenic amines function asAnswer: Both (a) and (b) SH₂ domains specifically bind toAnswer: Phosphorylated tyrosine residues In paracrine signaling, the signaling molecules affects onlyAnswer: Target cells close to the cell from which it was secreted Simple nerve reflexes use signaling molecules calledAnswer: Neurotransmitters Which of the following is not a type of signaling molecule?Answer: Adenylate cyclase Self-phosphorylation is an excellent mechanism for triggering specific catalytic function of the proteins involved in signal cascades because itAnswer: Changes the shape and thus the enzymatic activity of the proteins involved Which of the following statements about G proteins is false?Answer: They become activated when bound to GDP When a __________ reaches its __________ , there is a specific means of receiving it and acting on the message. This task is the responsibility of specialized proteins called __________ .Answer: signaling molecule; target cell; receptors Why is it that inhaling nitric oxide reduces blood pressure only in the lung tissue and not elsewhere in the body*?Answer: Because nitric oxide breaks down quickly and thus cannot travel far Which of the following comes under the category of cell surface receptor?Answer: All of the above Which of the following is true about a hydrophilic signaling molecule?Answer: It might trigger a signal cascade that causes some effect in a cell cAMP and cGMP are derived fromAnswer: ATP and GTP by the actions of adenylate cyclase and guanylate cyclase respectively Nitroglycerin has long been administered to human patients suffering from chronic chest pain (angina). This medication works because itAnswer: Breaks down into nitric oxide, which increases blood flow to the heart If a disease of the blood vessels caused the endothelial cells of the vessel to die, what effect would that have on the cellular activities associated with vasodilation?Answer: All of the above In terms of cell communication, what do bacterial pathogens such as cholera and anthrax have in common?Answer: They block the normal functioning of signal transduction mechanisms What is the name of the protein signaling molecule that alters glucose uptake, and where would its receptors be located?Answer: Insulin; many different cell types that use glucose for fuel In the signal transduction mechanism known as protein phosphorylationAnswer: All of the above Cell signaling can be classified intoAnswer: Three distinct types based on the distance over which the signaling molecules act Which of the following statement is correct?Answer: Cell communicate with one another in multicellular organisms using extracellular signaling molecules or hormones In vasodilation, proper nerve signals sent to blood vessels causeAnswer: All of the above A cell is known to respond to a particular signaling molecule. Which of the following must be true of this cell?Answer: It contains the receptor for the signaling molecule The enzyme that catalyzes the splitting of PIP2 into two molecules of inositol triphosphate (IP3) and diacylglycerol in cell signaling, isAnswer: phospholipase C The binding of ligands to many G-proteins linked receptors leads to shortlivedAnswer: Increase in the concentration of certain intracellular signaling molecules called second messenger Which of the following processes involve the combining of a message from one signaling molecule with that of another to either enhance or inhibit a cellular effect?Answer: Signal integration A signal cascade induced by adrenaline or thyroxineAnswer: All of the above