Top answers

Biology
A Level

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

LH
Answered by Laura H. Biology tutor
3851 Views

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+ ...

JM
Answered by Jessica M. Biology tutor
19681 Views

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<...

Answered by Biology tutor
6733 Views

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 pO2, typically in the lungs....

Answered by Biology tutor
14310 Views

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 allopat...

Answered by Biology tutor
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