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Unit 3: How do cells maintain life?
Quick questions on Cell signalling and apoptosis: VCE Biology Unit 3
10short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What are signalling molecules?Show answer
Signalling molecules include hormones (insulin, adrenaline, oestrogen, testosterone), neurotransmitters (acetylcholine, dopamine), cytokines (in immune responses) and growth factors. They fall into two broad classes based on solubility.
What are receptors?Show answer
A receptor is a protein with a binding site specific to one signalling molecule (or a small family of related molecules). Binding is reversible and complementary in shape and chemistry, like an enzyme-substrate fit.
What is signal transduction?Show answer
Signal transduction is the chain of events between receptor binding and the cellular response. A surface receptor cannot directly change cytoplasmic enzymes or gene expression, so it triggers a cascade of intracellular messengers.
What is apoptosis?Show answer
Apoptosis is a controlled, programmed sequence of events that dismantles a cell from within. It is triggered when receptors detect signals such as DNA damage, viral infection, withdrawal of growth factors, or developmental cues.
What are hydrophilic signalling molecules?Show answer
Examples: peptide and protein hormones (insulin, glucagon, adrenaline), most neurotransmitters. They cannot cross the phospholipid bilayer, so they bind surface receptors on the plasma membrane.
What are hydrophobic signalling molecules?Show answer
Examples: steroid hormones (oestrogen, testosterone, cortisol), thyroid hormone, vitamin D. They diffuse straight through the membrane and bind intracellular receptors in the cytosol or nucleus. The activated receptor-hormone complex usually acts as a transcription factor, changing which genes are expressed.
What is role in development?Show answer
Apoptosis sculpts tissues during embryonic development. The webbing between fingers and toes in the human embryo is removed by apoptosis. Tadpole tails resorb in the same way.
What is q1?Show answer
Outline the stimulus-response model with reference to signalling molecule, receptor and effector response. [3 marks]
What is q2?Show answer
A patient's liver cells lose insulin receptor function due to a genetic mutation. Predict the effect on blood glucose after a meal and explain. [3 marks]
What is q3?Show answer
Refer to apoptosis in CAR-T therapy. (a) Identify the trigger of caspase-8 activation. (b) Describe two morphological changes in the dying cell.