A-Level Biology: Homeostasis — Blood Glucose and the Kidney

Homeostasis questions at A-level are systems questions: hormones, organs and feedback loops that must be described in the right order with the right molecular details. This quiz covers the two flagship systems — blood glucose and the kidney — at full specification depth.

The glucose questions open with the design principle: why paired antagonistic hormones (insulin and glucagon) give finer, faster bidirectional control than any single signal could. The metabolism vocabulary is tested precisely — glycogenesis, glycogenolysis and gluconeogenesis attached to the right hormones — and the second-messenger model gets its own question: adenylate cyclase converting ATP to cyclic AMP after adrenaline binds, the cascade the specification names explicitly. The diabetes question separates type 1's autoimmune beta-cell destruction from type 2's insulin resistance.

The kidney questions follow the nephron in order: ultrafiltration driven by glomerular hydrostatic pressure, selective reabsorption in the proximal convoluted tubule — tested through its structural adaptations, microvilli for surface area and mitochondria for active transport — and the presence-absence logic of filtrate versus urine, with glucose and amino acids filtered but fully reclaimed. Osmoregulation completes the loop: the hypothalamus detecting falling water potential, ADH release, and aquaporin insertion in the collecting duct — the full detection-to-response chain.

Every explanation states the mechanism in mark-scheme order, making this set an efficient consolidation of a section where sequencing errors are the main source of lost marks.

• Explain why antagonistic hormone pairs give superior homeostatic control
• Attach glycogenesis, glycogenolysis and gluconeogenesis to their hormones
• Describe the adrenaline second-messenger cascade via cyclic AMP
• Sequence nephron function from ultrafiltration to selective reabsorption
• Trace the ADH response from hypothalamic detection to aquaporin insertion

Topic scope follows the homeostasis content of the DfE A level biology subject content as delivered in current exam-board specifications: negative feedback, blood glucose regulation, diabetes, and kidney structure and osmoregulation.