•

15 Jan 2026

•

5 pages

Exchange and Transport Systems in Animals | Edexcel GCSE Biology

gmelonergan

@gmelonergan_pquc

Your body is basically a massive transport network that needs... Show more

1 / 5

Efficient Transport and Exchange

Think about why small animals like mice can survive without complex transport systems, but you can't. It's all about the surface area to volume ratio - the bigger this ratio, the easier it is for substances to get in and out of cells.

Your gas exchange system is perfectly designed for efficiency. In your lungs, oxygen-poor blood meets oxygen-rich air in tiny sacs called alveoli. These have incredibly thin walls (just one cell thick) and massive surface area, making gas exchange lightning fast.

Fick's law shows exactly what makes diffusion work: rate of diffusion ∝ (surface area × concentration difference) / membrane thickness. Basically, bigger surface area and steeper concentration gradients speed things up, whilst thicker membranes slow things down.

Key Point: Your alveoli have about 70 square metres of surface area - that's roughly the size of a tennis court crammed into your chest!

The Circulatory System

Your blood vessels are like a three-tier motorway system. Arteries are the motorways - thick, muscular walls handle high pressure as they carry oxygenated blood away from your heart. Capillaries are tiny side streets with walls just one cell thick, perfect for quick substance exchange. Veins are the slow lanes back home, carrying deoxygenated blood with low pressure (that's why they need valves to prevent backflow).

Your blood is basically a liquid transport service. Plasma (55%) is the delivery truck - a straw-coloured liquid carrying everything else. Red blood cells (41%) are oxygen taxis with no nucleus (more room for haemoglobin) and a biconcave shape for maximum surface area.

White blood cells (3%) are your security team. Phagocytes literally eat foreign invaders, whilst lymphocytes produce antibodies that tag enemies for destruction. Platelets (<1%) are your emergency repair crew - they clot blood when you're injured by forming an insoluble mesh that traps blood cells.

Key Point: A single drop of blood contains about 5 million red blood cells - that's more people than live in most countries!

The Heart

Your heart is essentially two pumps stuck together, creating a double circulatory system. The right side handles deoxygenated blood (vena cava → right atrium → right ventricle → pulmonary artery to lungs), whilst the left side deals with oxygenated blood (pulmonary vein → left atrium → left ventricle → aorta to body).

The left ventricle has much thicker muscle walls because it needs to pump blood all around your body, not just to your nearby lungs. Heart valves act like one-way doors, preventing blood from flowing backwards.

Your heart has its own built-in pacemaker cells that naturally control heart rate. You can calculate how much blood your heart pumps using: cardiac output = stroke volume × heart rate. During exercise, both stroke volume and heart rate increase to deliver more oxygen to your muscles.

Key Point: Your heart beats roughly 100,000 times per day, pumping about 7,500 litres of blood - that's enough to fill a small swimming pool!

Heart Disease and Treatments

Coronary heart disease happens when fatty deposits build up in the arteries supplying your heart muscle. This narrows the arteries, reducing blood flow and oxygen delivery - basically giving your heart a constant traffic jam.

Doctors have several treatment options. Statins are daily pills that reduce cholesterol, slowing down fatty build-up (though they can cause muscle aches). Stents are tiny tubes inserted to keep arteries open - great for improving blood flow but can cause dangerous blood clots.

For severe cases, heart transplants replace the entire damaged heart. They're incredibly durable but expensive, with risks of rejection and clotting. Heart valve replacements come in two types: mechanical valves last longer but increase clotting risk, whilst biological valves from animals are safer but don't last as long.

Key Point: Heart disease is the leading cause of death globally, but most cases are preventable through healthy lifestyle choices you can make right now!

Cellular Respiration

Cellular respiration is how your cells extract energy from glucose - think of it as your cellular power stations working 24/7. Aerobic respiration happens in your mitochondria and needs oxygen: glucose + oxygen → carbon dioxide + water. This process is exothermic, meaning it releases energy.

During exercise, your body works overtime. Your heart beats faster to pump more oxygenated blood to muscles, and you breathe faster to get more oxygen into your bloodstream. Your muscle cells gobble up glucose and oxygen at an incredible rate.

When exercise gets really intense, oxygen runs out faster than you can replace it. Your cells switch to anaerobic respiration in the cytoplasm, which doesn't need oxygen but produces lactic acid: glucose → lactic acid. That burning feeling in your muscles during intense exercise? That's lactic acid building up.

Key Point: Your body can switch between aerobic and anaerobic respiration instantly - it's like having both electric and petrol engines in a hybrid car!

We thought you’d never ask...

What is the Knowunity AI companion?

Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.

Where can I download the Knowunity app?

You can download the app from Google Play Store and Apple App Store.

Is Knowunity really free of charge?

That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.

Biology

Menstrual Cycle Hormones

Explore the key hormones involved in the menstrual cycle, including FSH, LH, estrogen, and progesterone. Understand their roles in egg maturation, ovulation, and the maintenance of the uterine lining. This summary provides a clear overview of hormonal coordination in human reproduction, ideal for GCSE Biology students.

Biology

Most popular content

An Inspector Calls: Character Insights

Explore in-depth analysis and key quotes for characters in J.B. Priestley's 'An Inspector Calls'. This resource covers Gerald Croft, Inspector Goole, Sheila Birling, Mrs. Birling, Eric Birling, and Eva Smith, focusing on themes of class, gender roles, and social responsibility. Ideal for students aiming for Grade 8 and above.

English Literature

aqa higher tier combined science - biology b1 : cell biology, paper 1

b1: cell biology - paper 1

Biology

Comprehensive Crime & Deviance Overview

Explore an extensive revision of crime and deviance topics, including theories, types of crime, and the impact of media. This resource covers key concepts such as Marxism, functionalism, gender and crime, and the influence of globalization on criminal behavior. Ideal for students seeking a thorough understanding of criminology and its various theories. Type: Full Topic Revision.

Sociology

Sociology of Families: Comprehensive Revision

Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.

Sociology

Sociology of Education Overview

Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.

Sociology

Macbeth: Guilt and Ambition

Explore the complex themes of guilt and ambition in Shakespeare's 'Macbeth'. This analysis covers key characters, including Macbeth and Lady Macbeth, their moral dilemmas, and the tragic consequences of their ambition. Ideal for students studying character motivations, thematic elements, and the psychological impact of power. Includes insights on the natural order, manipulation, and the descent into madness.

English Literature

Criminal Justice Evidence Rules

Explore the essential rules governing the use of evidence in criminal cases, including reliability, admissibility, and relevance. This summary covers key concepts such as the roles of personnel in investigations, the impact of witness testimonies, and the implications of plea bargaining. Ideal for Year 13 criminology students preparing for assessments.

Criminology

Biology Paper 1 Overview

Biology

Key Quotes from Macbeth

Explore essential quotes from Shakespeare's 'Macbeth' that highlight key themes such as ambition, guilt, and deception. This analysis includes significant lines from characters like Macbeth and Lady Macbeth, along with their context in the play. Ideal for students studying character development and thematic elements in literature.

English Literature

Can't find what you're looking for? Explore other subjects.

Students love us — and so will you.

4.9/5

App Store

4.8/5

Google Play

The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.

Stefan S

iOS user

This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.

Samantha Klich

Android user

Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.

Anna

iOS user

Best app on earth! no words because it’s too good

Thomas R

iOS user

Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.

Basil

Android user

This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.

David K

iOS user

The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!

Sudenaz Ocak

Android user

In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.

Greenlight Bonnie

Android user

very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.

Rohan U

Android user

I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.

Xander S

iOS user

THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮

Elisha

iOS user

This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now

Paul T

iOS user

Stefan S

iOS user

Samantha Klich

Android user

Anna

iOS user

Best app on earth! no words because it’s too good

Thomas R

iOS user

Basil

Android user

David K

iOS user

Sudenaz Ocak

Android user

In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.

Greenlight Bonnie

Android user

Rohan U

Android user

Xander S

iOS user

Elisha

iOS user

Paul T

iOS user

Biology

•

430

•

15 Jan 2026

•

5 pages

Exchange and Transport Systems in Animals | Edexcel GCSE Biology

gmelonergan

@gmelonergan_pquc

Key Point: Your body can switch between aerobic and anaerobic respiration instantly - it's like having both electric and petrol engines in a hybrid car!