Ever wonder how stuff gets in and out of your...
Biology149 views·Updated 30 Jun 2026·5 pagesUnderstanding Types of Cell Transport
Reuben Cowell@reubencowell
1 / 5
1
of 5
The Basics of Cell Transport
Your cells are like busy train stations with substances constantly moving in and out. Diffusion is the most straightforward process - it's simply molecules moving from where there's loads of them to where there's fewer.
Think of it like this: if you spray perfume in one corner of a room, it'll spread out until the smell is everywhere. That's diffusion in action! The molecules are always jiggling about, but overall they move from the high concentration area to the low concentration area.
Diffusion happens across cell membranes and doesn't need any energy - it's completely natural. Once the molecules are spread out evenly, they keep moving but there's no net movement in any direction.
Quick Tip: Diffusion always goes from high to low concentration - remember this for your exams!
2
of 5
Diffusion in Action and What Affects Its Speed
Your lungs are brilliant examples of diffusion at work. Carbon dioxide diffuses from your blood (where there's loads of it) into your lung air sacs where there's less. Meanwhile, oxygen does the opposite - moving from your lungs into your blood.
Several factors control how fast diffusion happens. A bigger concentration gradient (difference between high and low areas) means faster diffusion. Higher temperatures speed things up because particles move more when they're hot.
Surface area is crucial too - more membrane surface means more space for molecules to cross. This is why smaller organisms are actually better at diffusion than larger ones - they've got a bigger surface area compared to their volume.
Remember: Temperature, concentration difference, and surface area all affect diffusion speed!
3
of 5
Osmosis - Water's Special Journey
Osmosis is just diffusion, but only for water molecules moving through partially permeable membranes. Water moves from where there's lots of it to where there's less of it.
In plant cells, osmosis creates some dramatic effects. Turgid cells are plump with water - the vacuole swells up and keeps the plant standing tall and strong. This happens when there's pure water outside the cell.
Flaccid cells are the opposite - they've lost water and gone a bit floppy. If things get really bad, plasmolysis occurs where the cytoplasm actually pulls away from the cell wall, leaving the plant droopy and weak.
Plant Tip: Turgid = strong and upright, Flaccid = weak and droopy!
4
of 5
Osmosis in Animals and Active Transport
Animal cells don't have cell walls like plants, so they actually change size during osmosis. Put animal cells in pure water and they swell up; put them in salty water and they shrink. Too much change either way stops them working properly.
Sometimes cells need to move stuff the "wrong" way - from low to high concentration. This is called active transport and it's like pushing a boulder uphill. It needs energy from respiration and special enzymes to make it work.
Active transport is essential for things like getting mineral ions into plant roots and moving glucose through your intestines into your blood. Without it, your body couldn't get the nutrients where they need to go.
Key Difference: Diffusion and osmosis are passive (no energy needed), active transport requires energy!
5
of 5
Calculations You Need to Know
You'll likely need to calculate water uptake rates in practicals. The formula is: Water uptake per hour = change in mass × (60 ÷ time in minutes). So if a plant gained 0.59g in 40 minutes, that's 0.59 × (60÷40) = 0.89g per hour.
Percentage change in mass shows you how much water was gained or lost compared to the starting point. Use: ÷ starting mass × 100. This gives you positive numbers for water gain and negative for water loss.
These calculations pop up loads in osmosis experiments, so practice them! They help you compare different conditions and understand which setup caused the most water movement.
Exam Success: Always show your working clearly and don't forget units in your final answers!
We thought you’d never ask...
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Biology149 views·Updated 30 Jun 2026·5 pagesUnderstanding Types of Cell Transport
Reuben Cowell@reubencowell
Ever wonder how stuff gets in and out of your cells? Your cells are constantly moving substances around - oxygen in, carbon dioxide out, water everywhere! There are three main ways this happens, and understanding them will help you ace...
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of 5
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The Basics of Cell Transport
Your cells are like busy train stations with substances constantly moving in and out. Diffusion is the most straightforward process - it's simply molecules moving from where there's loads of them to where there's fewer.
Think of it like this: if you spray perfume in one corner of a room, it'll spread out until the smell is everywhere. That's diffusion in action! The molecules are always jiggling about, but overall they move from the high concentration area to the low concentration area.
Diffusion happens across cell membranes and doesn't need any energy - it's completely natural. Once the molecules are spread out evenly, they keep moving but there's no net movement in any direction.
Quick Tip: Diffusion always goes from high to low concentration - remember this for your exams!
2
of 5Sign up to see the content. It's free!
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Diffusion in Action and What Affects Its Speed
Your lungs are brilliant examples of diffusion at work. Carbon dioxide diffuses from your blood (where there's loads of it) into your lung air sacs where there's less. Meanwhile, oxygen does the opposite - moving from your lungs into your blood.
Several factors control how fast diffusion happens. A bigger concentration gradient (difference between high and low areas) means faster diffusion. Higher temperatures speed things up because particles move more when they're hot.
Surface area is crucial too - more membrane surface means more space for molecules to cross. This is why smaller organisms are actually better at diffusion than larger ones - they've got a bigger surface area compared to their volume.
Remember: Temperature, concentration difference, and surface area all affect diffusion speed!
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Osmosis - Water's Special Journey
Osmosis is just diffusion, but only for water molecules moving through partially permeable membranes. Water moves from where there's lots of it to where there's less of it.
In plant cells, osmosis creates some dramatic effects. Turgid cells are plump with water - the vacuole swells up and keeps the plant standing tall and strong. This happens when there's pure water outside the cell.
Flaccid cells are the opposite - they've lost water and gone a bit floppy. If things get really bad, plasmolysis occurs where the cytoplasm actually pulls away from the cell wall, leaving the plant droopy and weak.
Plant Tip: Turgid = strong and upright, Flaccid = weak and droopy!
4
of 5Sign up to see the content. It's free!
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By signing up you accept Terms of Service and Privacy Policy
Osmosis in Animals and Active Transport
Animal cells don't have cell walls like plants, so they actually change size during osmosis. Put animal cells in pure water and they swell up; put them in salty water and they shrink. Too much change either way stops them working properly.
Sometimes cells need to move stuff the "wrong" way - from low to high concentration. This is called active transport and it's like pushing a boulder uphill. It needs energy from respiration and special enzymes to make it work.
Active transport is essential for things like getting mineral ions into plant roots and moving glucose through your intestines into your blood. Without it, your body couldn't get the nutrients where they need to go.
Key Difference: Diffusion and osmosis are passive (no energy needed), active transport requires energy!
5
of 5Sign up to see the content. It's free!
- Access to all documents
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By signing up you accept Terms of Service and Privacy Policy
Calculations You Need to Know
You'll likely need to calculate water uptake rates in practicals. The formula is: Water uptake per hour = change in mass × (60 ÷ time in minutes). So if a plant gained 0.59g in 40 minutes, that's 0.59 × (60÷40) = 0.89g per hour.
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Exam Success: Always show your working clearly and don't forget units in your final answers!
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.
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