Dive into the fascinating world of microscopy, bacteria, and osmosis!... Show more
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Light Microscope and Bacterial Growth
When using a light microscope, always start with the lowest magnification objective lens first. Place your thinly sliced sample (like onion epidermis) on a slide, add a few drops of stain such as iodine, and cover with a coverslip before examining.
Bacteria multiply through a process called binary fission - one cell simply divides into two cells. The time it takes for bacteria to divide is called the mean division time. Under ideal conditions, some bacteria can divide every 20 minutes!
You can calculate future bacterial populations by multiplying the current population by 2 for every mean division time that passes. For example, starting with 4 bacteria with a 30-minute division time, after 4 hours (8 divisions), you'll have 1,024 bacteria.
Did you know? If bacteria could continue dividing without limitations, a single bacterium dividing every 20 minutes would produce a mass of bacteria greater than the Earth in just a few days! Fortunately, environmental factors limit their growth.
Understanding Osmosis and Area Calculations
Osmosis is the movement of water across a partially permeable membrane from a dilute solution (high water concentration) to a concentrated solution (low water concentration). Think of it as water trying to even out the concentrations on both sides.
The partially permeable membrane is quite selective - it lets water molecules through but blocks larger molecules like sugar. Remember that water molecules actually move in both directions, but the net movement is from dilute to concentrated solutions.
When calculating areas of bacterial colonies, you'll often use the formula Area = π × (radius)². For instance, a bacterial colony with a 1.6 cm diameter has a 0.8 cm radius, giving an area of approximately 2.01 cm².
Quick tip: When thinking about osmosis, focus on where the water is going rather than the dissolved substances. Water always moves toward the more concentrated solution (where there's less water).
Osmosis Experiments and Food Tests
In a typical osmosis experiment, you can cut potato discs, measure their mass, then place them in different concentrations of sugar or salt solutions. After about 30 minutes, measure them again to see how much water has moved in or out of the potato cells.
Calculate the percentage change in mass by subtracting the final mass from the initial mass, dividing by the initial mass, and multiplying by 100. The solution concentration where the least mass change occurs matches the water concentration inside the potato cells.
Food tests help identify key biological molecules. For sugar, add Benedict's reagent and heat ; for proteins, add Biuret solution (turns purple); and for starch, add iodine .
Remember: Root hair cells are the specialised plant tissue that uses osmosis to absorb water from the soil. Their large surface area makes them perfectly adapted for this function!
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Elisha
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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
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
GCSE AQA Science: Key Basic Science Revision Slides
Dive into the fascinating world of microscopy, bacteria, and osmosis! These biological concepts are essential for understanding how we study cells, how bacteria multiply, and how water moves in living systems. Let's explore the key experiments and calculations that make... Show more
Light Microscope and Bacterial Growth
When using a light microscope, always start with the lowest magnification objective lens first. Place your thinly sliced sample (like onion epidermis) on a slide, add a few drops of stain such as iodine, and cover with a coverslip before examining.
Bacteria multiply through a process called binary fission - one cell simply divides into two cells. The time it takes for bacteria to divide is called the mean division time. Under ideal conditions, some bacteria can divide every 20 minutes!
You can calculate future bacterial populations by multiplying the current population by 2 for every mean division time that passes. For example, starting with 4 bacteria with a 30-minute division time, after 4 hours (8 divisions), you'll have 1,024 bacteria.
Did you know? If bacteria could continue dividing without limitations, a single bacterium dividing every 20 minutes would produce a mass of bacteria greater than the Earth in just a few days! Fortunately, environmental factors limit their growth.
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Understanding Osmosis and Area Calculations
Osmosis is the movement of water across a partially permeable membrane from a dilute solution (high water concentration) to a concentrated solution (low water concentration). Think of it as water trying to even out the concentrations on both sides.
The partially permeable membrane is quite selective - it lets water molecules through but blocks larger molecules like sugar. Remember that water molecules actually move in both directions, but the net movement is from dilute to concentrated solutions.
When calculating areas of bacterial colonies, you'll often use the formula Area = π × (radius)². For instance, a bacterial colony with a 1.6 cm diameter has a 0.8 cm radius, giving an area of approximately 2.01 cm².
Quick tip: When thinking about osmosis, focus on where the water is going rather than the dissolved substances. Water always moves toward the more concentrated solution (where there's less water).
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Osmosis Experiments and Food Tests
In a typical osmosis experiment, you can cut potato discs, measure their mass, then place them in different concentrations of sugar or salt solutions. After about 30 minutes, measure them again to see how much water has moved in or out of the potato cells.
Calculate the percentage change in mass by subtracting the final mass from the initial mass, dividing by the initial mass, and multiplying by 100. The solution concentration where the least mass change occurs matches the water concentration inside the potato cells.
Food tests help identify key biological molecules. For sugar, add Benedict's reagent and heat ; for proteins, add Biuret solution (turns purple); and for starch, add iodine .
Remember: Root hair cells are the specialised plant tissue that uses osmosis to absorb water from the soil. Their large surface area makes them perfectly adapted for this function!
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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
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