Homeostasis

Homeostasis and Negative Feedback ControlSign up

understand negative feedback and positive feedback control · understand the principle of negative feedback in maintaining systems within narrow limits · understand homeostasis and its importance in maintaining dynamic equilibrium during exercise, including the role of the hypothalamus in thermoregulation

The Kidney: Excretion, Urine Formation and OsmoregulationSign up

know the gross and microscopic structure of the mammalian kidney · understand how urea is produced from excess amino acids in the liver (ornithine cycle detail not required) and removed by ultrafiltration · understand selective reabsorption in the proximal tubule and how the loop of Henle acts as a countercurrent multiplier to increase water reabsorption · understand how the pituitary, osmoreceptors in the hypothalamus, and ADH bring about negative feedback control of plasma concentration and blood volume

Cell Signalling and the Control of Blood GlucoseSign up

describe the principles of cell signalling using the control of blood glucose by glucagon: hormone binds cell-surface receptor causing conformational change -> activation of G-protein -> stimulation of adenylyl cyclase -> formation of the second messenger cyclic AMP (cAMP) -> activation of protein kinase A -> initiation of an enzyme cascade -> amplification of the signal via successive phosphorylation -> final enzyme catalyses the breakdown of glycogen (9700 14.1.9) · explain how negative feedback control mechanisms regulate blood glucose concentration, with reference to the effects of insulin on muscle cells and liver cells and the effect of glucagon on liver cells (9700 14.1.10) · explain the principles of operation of test strips and biosensors for measuring glucose concentration in blood and urine, with reference to glucose oxidase and peroxidase enzymes (9700 14.1.11)

Homeostasis in Plants: Stomata and Guard CellsSign up

explain that stomata respond to changes in environmental conditions by opening and closing, and that regulation of stomatal aperture balances CO2 uptake by diffusion against minimising water loss by transpiration (9700 14.2.1) · explain that stomata show daily rhythms of opening and closing (9700 14.2.2) · describe the structure and function of guard cells and explain the mechanism by which they open and close stomata, including K+ and water movement and resulting turgor changes (9700 14.2.3) · describe the role of abscisic acid (ABA) in the closure of stomata during times of water stress, including the role of calcium ions as a second messenger (9700 14.2.4)