13.1

Excretion in humans

Cambridge IGCSE Biology (0610)  · Unit 13: Excretion in humans  · 13 flashcards

Excretion in humans is topic 13.1 in the Cambridge IGCSE Biology (0610) syllabus , positioned in Unit 13 — Excretion in humans .  In one line: Excretion is the removal of metabolic waste products from the body. These waste products, such as urea and carbon dioxide, can be toxic if they accumulate. Examples of organs involved are the lungs and kidneys.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical). Past papers from 2022 to 2025 show this topic across 12 questions worth 160 marks (around 2.4% of all Biology marks in those years).

The deck below contains 13 flashcards — 1 definition, 3 key concepts, 4 process cards and 5 identification cards — covering the precise wording mark schemes reward.  Use the definition card to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

Excretion

Excretion is the removal of metabolic waste products from the body. These waste products, such as urea and carbon dioxide, can be toxic if they accumulate. Examples of organs involved are the lungs and kidneys.

What the Cambridge 0610 syllabus says

2026-2028 syllabus, in our words

What the syllabus expects you to be able to do in this topic, in plain English. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks. For the exact wording, see the official syllabus (PDF).

  1. State State that the lungs excrete carbon dioxide.
  2. State State that urea, along with excess water and ions, is excreted by the kidneys.
  3. Identify Identify the bladder, kidneys, urethra and ureters on diagrams and images.
  4. Identify Identify the two regions of the kidney, the cortex and medulla, on diagrams and images (no other kidney structures are needed). Supplement
  5. Outline Outline how a nephron and the blood vessels linked to it are built and what they do, limited to: (a) the glomerulus filtering water, glucose, urea and ions out of the blood (b) the nephron reabsorbing into the blood all of the glucose, most of the water and some of the ions (c) urine forming, made up of excess ions, excess water and urea. You do not need to know how these processes work in detail. Supplement
  6. Describe Describe how the liver assimilates amino acids by turning them into proteins. Supplement
  7. State State that the liver makes urea from amino acids that are in excess. Supplement
  8. Describe Describe deamination as the process that takes the nitrogen-containing part off amino acids, producing urea. Supplement
  9. Explain Explain why excretion matters, limited to the fact that urea is toxic. Supplement
Definition Flip

What is excretion?

Answer Flip

Excretion is the removal of metabolic waste products from the body. These waste products, such as urea and carbon dioxide, can be toxic if they accumulate. Examples of organs involved are the lungs and kidneys.

Key Concept Flip

What waste product is excreted by the lungs?

Answer Flip

The lungs excrete carbon dioxide (CO2), a waste product of aerobic respiration. This is achieved through gas exchange in the alveoli during exhalation, where CO2 diffuses from the blood into the lungs and is expelled.

Example: when we breathe out.
Key Concept Flip

Which organ excretes urea, excess water, and ions?

Answer Flip

The kidneys are responsible for excreting urea, excess water, and excess ions from the body. They filter blood and produce urine containing these waste products.

Example: Kidney filter blood and make urine.
Key Concept Flip

Name the four main components of the urinary system.

Answer Flip

The urinary system consists of the kidneys, ureters, bladder, and urethra. The kidneys filter blood to produce urine, which travels through the ureters to the bladder for storage, and is then expelled through the urethra.

Example: Urine is made in the kidney.
Key Concept Flip

Name the two main regions of the kidney.

Answer Flip

The two main regions of the kidney are the cortex (outer region) and the medulla (inner region). These regions contain different structures and perform different functions in filtering blood and producing urine.

Example: Nephrons reside in both the cortex and the medulla.
Key Concept Flip

What is the functional unit of the kidney?

Answer Flip

The nephron is the functional unit of the kidney, responsible for filtering blood and forming urine. Each kidney contains millions of nephrons that work together to maintain homeostasis in the body.

Example: Nephrons are responsible for filtration and reabsorption.
Key Concept Flip

Outline the role of the glomerulus in urine formation.

Answer Flip

The glomerulus filters blood, allowing water, glucose, urea, and ions to pass into the nephron. This process is called ultrafiltration, and it separates small molecules from larger proteins and blood cells that remain in the blood.

Example: Ultrafiltration occurs at the glomerulus due to high pressure.
Key Concept Flip

Describe the role of the nephron tubule in reabsorption.

Answer Flip

The nephron tubule reabsorbs useful substances like glucose, some ions, and most of the water back into the blood. This process ensures that essential substances are not lost in the urine.

Example: All glucose is reabsorbed in a healthy individual.
Key Concept Flip

What is the final product formed by the nephron?

Answer Flip

The nephron forms urine, which contains urea (a waste product of protein metabolism), excess water, and excess ions. Urine is then transported to the bladder for storage before excretion.

Example: Urine production helps regulate blood volume and composition.
Key Concept Flip

What is the role of the liver in amino acid assimilation?

Answer Flip

The liver assimilates amino acids by converting them into proteins, which are essential for building and repairing tissues. It also plays a role in synthesizing enzymes and hormones.

Example: Albumin is a protein made by the liver from amino acids.
Key Concept Flip

Where is urea formed in the body?

Answer Flip

Urea is formed in the liver from excess amino acids. This process is a part of the urea cycle, which detoxifies ammonia produced during amino acid breakdown.

Example: The liver is a key organ in nitrogenous waste removal.
Key Concept Flip

What is deamination, and why is it important?

Answer Flip

Deamination is the removal of the nitrogen-containing part (amino group) of amino acids. This process forms ammonia, which is then converted to urea in the liver, thus reducing its toxicity.

Example: Deamination produces keto acids, which can be used in respiration.
Key Concept Flip

Why is excretion important for the human body?

Answer Flip

Excretion is important because urea is toxic and can damage cells if it accumulates in the body. Removing urea through urine helps maintain a stable internal environment and prevents harmful effects.

Example: Kidney failure can lead to urea buildup and death.

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Key Questions: Excretion in humans

What is excretion?

Excretion is the removal of metabolic waste products from the body. These waste products, such as urea and carbon dioxide, can be toxic if they accumulate. Examples of organs involved are the lungs and kidneys.

Tips to avoid common mistakes in Excretion in humans

Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0610 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

excretion kidney ureter bladder urethra urine nephron glomerulus Bowman's capsule tubule collecting duct filtration reabsorption urea water glucose dialysis kidney transplant ADH

Key terms covered in this Excretion in humans deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

Excretion

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