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What is a first messenger hormone?

A first messenger is a hormone which binds to a receptor on the plasma membrane of a cell and causes a change to happen inside the cell
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Answered by Laura H. • Biology tutor
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Explain how the resting potential of -70mV is maintained in a sensory neuron.

The resting potential is a result of the concentrations of the sodium and potassium ions inside the neuron compared to outside. The leaky channels in the sensory neuron membrane allow the movement of Na+ (so...
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Answered by Jessica M. • Biology tutor
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What are three adaptations in a leaf for photosynthesis?

Thin waxy cuticle - to protect the leaf without blocking the lightThin transparent epidermis - to allow more light to reach the palisade cellsLayers of palisade cells on the top surface - to absorb light
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Explain how oxygen is loaded, transported and unloaded in red blood cells

Haemoglobin is a molecule in red blood cells with a high affinity for oxygen. It consists of 4 haem groups, each of which associate with one oxygen molecule at high pO 2 , typically in the lungs. Haemoglobin...
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What's the difference between allopatric and sympatric speciation? What are some evolutionary implications of this?

For speciation to occur, a population must split into at least two isolated parts to avoid the spread of genes between them; the nature of this isolation is what defines sympatry and allopatry. In allopatric...
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