Practise nervous and endocrine signalling, action potentials, synapses, muscle contraction and plant responses through membrane traces, pathways and structure-function evidence.
Glucagon is released by the alpha ( ) cells of the pancreas when the blood glucose concentration decreases below the set point.
Fig. 6.1 outlines the response of liver cells to glucagon.
Fig. 6.1
State how glucagon reaches the liver cells.
The Venus fly trap, Dionaea muscipula, is a carnivorous plant. It has traps which catch insects.
Each trap consists of a pair of modified leaves joined by a midrib of hinge cells. The modified leaves have touch-sensitive hairs. If two hairs are touched within 20 seconds, or the same hair is touched twice in rapid succession, the trap closes.
Explain how touching the hairs results in closure of the trap.
Compare the endocrine and nervous systems in control and co-ordination in mammals.
Outline the role of a chemoreceptor cell in the human taste bud in detecting stimuli and in stimulating the transmission of nerve impulses in sensory neurones.
There are more than 600 plant species in the genus Ipomoea. Many species are grown for their attractive flowers, and some species are used as crop plants.
Scientists are researching whether abscisic acid can be used in crop treatment to increase yield. Evidence suggests that abscisic acid modifies the effect of auxin on elongation growth in plants.
The passage outlines the role of auxin in elongation growth in plants.
Complete the passage by using the most appropriate scientific terms.
The binding of auxin to receptors causes ...... to be pumped into cell walls.
This activates proteins called expansins, which disrupt the links between ...... microfibrils. The cell walls are then able to expand.