Process
OCR A-Level Biology H420
Cell Structure
Biological Molecules
Nucleotides and Nucleic Acids
Enzymes
Biological Membranes
Cell Division, Cell Diversity and Cellular Organisation
Exchange Surfaces
Transport in Animals
Transport in Plants
Communicable Diseases, Disease Prevention and the Immune System
Biodiversity
Classification and Evolution
Communication and Homeostasis
Excretion as an Example of Homeostatic Control
Neuronal Communication
Hormonal Communication
Plant and Animal Responses
Topic overviewTropisms and plant responses to stress and herbivoryPlant hormones and their commercial usesThe nervous system and the brainReflex actions and the knee jerk reflexFight or flight and the control of heart rateThe structure of skeletal muscleThe neuromuscular junction and the sliding filament model
Photosynthesis
Respiration
Cellular Control
Patterns of Inheritance
Manipulating Genomes
Cloning and Biotechnology
Topic overviewNatural plant cloning and taking cuttingsMicropropagationAdvantages and disadvantages of plant cloningAnimal cloning: embryo twinning and nuclear transferAdvantages and disadvantages of animal cloningMicroorganisms in food productionAseptic techniqueFermentation and its conditionsThe microbial growth curveImmobilised enzymes
Ecosystems
Populations and Sustainability
Practical Skills and Mathematical Requirements
Excretion as an Example of Homeostatic Control
- 9 subtopics
- 17 things to know
- Components 01 and 03
What Excretion as an Example of Homeostatic Control covers
Excretion as an example of homeostatic control is the second section of Module 5. It covers why nitrogenous waste must become urea, the structure of the liver, the nephron and the stages of filtration and reabsorption, how ADH controls water balance, kidney failure and its treatments, and what a urine test can detect.
Where it is assessed
Components 01 and 03
Module 5 is examined on Biological Processes, then the unified paper.
Check the OCR specification ↗The 9 subtopics
Each one has its own page.
- Excretion and nitrogenous wasteWhat excretion is and why it matters for homeostasis, and how ammonia produced by deamination is converted to urea before it leaves the body.Open →
- The liver: structure and functionThe hepatic artery, hepatic portal vein and bile duct, lobules, hepatocytes, sinusoids and Kupffer cells, and the storage, detoxification and urea formation the liver carries out.Open →
- The structure of the kidneyThe cortex, medulla and renal pelvis, the vessels supplying and draining the kidney, the ureter, and the parts of a nephron named in the order filtrate passes through them.Open →
- The nephronBowman's capsule and the glomerulus, the afferent and efferent arterioles, and what the proximal convoluted tubule, loop of Henle, distal tubule and collecting duct each do.Open →
- UltrafiltrationWhat is forced through the filtration barrier and what is held back, and the roles of the capillary endothelium, the basement membrane and the podocytes.Open →
- Selective reabsorption and the loop of HenleHow glucose, amino acids, sodium and water are reabsorbed and the adaptations of the tubule cells, and the countercurrent multiplier that concentrates the medulla.Open →
- Osmoregulation and ADHOsmoreceptors in the hypothalamus, where ADH is made and released, the aquaporins it places in the collecting duct, and the feedback loop that results.Open →
- Kidney failure, dialysis and transplantGlomerular filtration rate and what failure does to urea, electrolytes and fluid balance, and how haemodialysis and transplant compare.Open →
- Urine testing and monoclonal antibodiesWhy urine is useful in diagnosis, how a pregnancy test uses monoclonal antibodies to detect hCG, and the detection of anabolic steroids and other drugs.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
Explain selective reabsorption in the proximal convoluted tubule.
Process
How does ADH regulate water balance?
Evaluation
Evaluate kidney transplantation compared with dialysis.
Key term
Define detoxification in the context of liver function.
Key term
Where is urea formed and what substances react to produce it?
Key term
Why must ammonia be converted to urea before excretion?
Key term
What is the name of the hairpin-shaped section of the nephron that extends into the medulla and is involved in creating a water potential gradient?
Key term
What is the glomerulus?
Key term
Define selective reabsorption.
Key term
Where is ADH produced and where is it stored and released from?
Key term
Describe the basic principle of haemodialysis.
Key term
What is the function of the ureter?
Key term
What are Kupffer cells and what is their function?
Key term
What is the function of the basement membrane in the filtration barrier?
Process
What is hyperkalaemia and what is a dangerous consequence of this condition?
Process
How are monoclonal antibodies used in pregnancy tests?
Take Excretion as an Example of Homeostatic Control further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Ultrafiltration vs Selective reabsorption
Ultrafiltration: the pressure-driven separation of small molecules from blood at the glomerulus. Selective reabsorption: the recovery of useful substances from the filtrate back into the blood.
Osmoregulation vs Thermoregulation
Osmoregulation: the control of the water potential of the body's fluids. Thermoregulation: the control of body temperature.
Excretion vs Egestion
Excretion: the removal of the waste products of metabolism. Egestion: the removal of undigested material that was never absorbed.
Questions from this topic
Each one with the model answer underneath.
- 1
Define excretion.
Model answer
Excretion is the removal of metabolic waste products from the body.
- 2
Why is excretion important for maintaining metabolism?
Model answer
Accumulation of metabolic wastes would inhibit enzyme activity and disrupt metabolic reactions.
- 3
How does excretion contribute to homeostasis?
Model answer
Excretion maintains constant internal conditions, including blood pH and water potential.
- 4
Why must carbon dioxide be excreted from the body?
Model answer
Carbon dioxide combines with water to form carbonic acid, which lowers blood pH.
- 5
Through which organ is carbon dioxide excreted?
Model answer
The lungs.
- 6
In what form is nitrogenous waste primarily excreted in mammals?
Model answer
Urea.
What is inside Levo
Six ways to work the same material.
Excretion as an Example of Homeostatic Control revision questions
- What does Excretion as an Example of Homeostatic Control cover in OCR A-Level Biology?
- 9 subtopics: excretion and nitrogenous waste, the liver: structure and function, the structure of the kidney, the nephron, ultrafiltration, selective reabsorption and the loop of henle, osmoregulation and adh, kidney failure, dialysis and transplant and urine testing and monoclonal antibodies. Each one has its own page with questions and model answers.
- How is Excretion as an Example of Homeostatic Control organised?
- By the OCR H420 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Excretion as an Example of Homeostatic Control, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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