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A membrane invagination develops a clathrin coat before becoming an intracellular vesicle. What is the role of this protein? A. It supplies a scaffold that helps the membrane curve into a budding vesicle B. It hydrolyses the vesicle cargo in an acidic lumen C.…
A mutation prevents clathrin from assembling at the cytoplasmic surface of a membrane. Which process is most directly affected? A. Pairing of bases during chromosome replication B. Translation of mitochondrial genes C. Budding of coated transport vesicles D.…
A membrane contains aquaporin proteins. What role do they perform? A. They hydrolyse ATP to pump water against its potential gradient B. They attach water covalently to phospholipid tails C. They act only on the external membrane surface D. They provide…
A student compares a skeletal muscle fibre with a cardiac muscle cell. Which pair correctly gives a feature shared by both and a feature distinguishing them? A. Shared: contractile myofibrils; difference: the cardiac cell is usually branched B. Shared: one…
A pancreatic beta cell makes a polypeptide destined for insulin secretion. Where is the chain synthesized, and which bonds connect its amino acids? A. On Golgi membranes; ester bonds B. On ribosomes attached to rough ER; peptide bonds C. In lysosomes; hydrogen…
Which outcome is consistent with the developmental potential of an embryonic pluripotent stem cell? A. It can form only one already specialized blood-cell type B. It must make an entire placenta as well as every embryonic tissue C. It can generate many…
Hormone H enters a target cell. Its receptor complex then promotes transcription, as shown. Which hormone could be H? A. Glucagon B. FSH C. Testosterone D. Insulin
The trace shows an action potential in an axon. What is the state of the voltage-gated channels at X? Treat an inactivated sodium channel as closed to ion flow. A. Potassium channels conduct; sodium channels do not conduct B. Sodium channels conduct; potassium…
Adrenaline binds the membrane receptor shown in a cardiac cell. Which sequence can produce an intracellular response? A. Adrenaline crosses the membrane and is converted directly into ATP B. The G protein copies the receptor gene into cyclic DNA C. Receptor…
An impulse reaches the end of a motor neuron. Which event directly signals synaptic vesicles to release acetylcholine? A. Calcium ions enter the presynaptic terminal through opened channels B. Potassium ions bind to receptors on the muscle cell surface C.…