Understanding cells and how they work is fundamental to biology...
Biology1,551 views·Updated 13 Jul 2026·2 pagesAQA Biology Combined Science B1 & B2 Notes
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Cell Structure and Function
Ever wondered how scientists can see the tiniest parts of living things? Magnification makes objects appear bigger than they really are, whilst resolution determines how clearly you can distinguish between two separate points in an image. Think of it like zooming in on a photo - magnification makes it bigger, but resolution keeps it sharp.
Animal cells contain several key organelles that keep them functioning. The nucleus acts like the cell's control centre, containing all the genetic material and directing cellular activities. Mitochondria are the powerhouses where aerobic respiration happens, giving cells the energy they need. Meanwhile, ribosomes are busy making proteins through protein synthesis.
Plant cells are similar to animal cells but have some extra features that make them special. They're surrounded by a tough cellulose cell wall for support, contain chloroplasts for photosynthesis, and have a large permanent vacuole that helps maintain the cell's shape. These additions help plants stand upright and make their own food.
Quick Tip: Remember that bacterial cells are completely different - they're much simpler and don't have a nucleus, with their DNA floating freely in the cytoplasm instead.
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of 2
Cell Division and Stem Cells
Your body is constantly growing and repairing itself through cell division - it's how you've grown from a baby and how cuts heal. Mitotic cell division follows a precise cycle: first during interphase, cells grow bigger and copy their DNA, then during mitosis, chromosomes get pulled apart by spindle fibres, and finally cytokinesis splits everything into two identical daughter cells.
Meiosis works differently and is crucial for reproduction. Unlike mitosis, it produces four genetically different cells through two divisions, which is essential for creating genetic variety in offspring. A gene is simply a section of DNA that codes for a particular characteristic, like eye colour or height.
Stem cells are incredibly versatile and come in three main types. Adult stem cells can treat diseases like leukaemia but have limited abilities and can be painful to extract. Embryonic stem cells are more powerful and can become any type of cell, making them valuable for treating paralysis and diabetes, though their use raises ethical concerns. Umbilical cord stem cells offer a middle ground with low rejection rates.
Did You Know: Plant stem cells are found in areas called meristems and can help scientists clone vast numbers of plants for agriculture and conservation!
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Biology1,551 views·Updated 13 Jul 2026·2 pagesAQA Biology Combined Science B1 & B2 Notes
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db@dvgbz
Understanding cells and how they work is fundamental to biology - these tiny building blocks make up everything from your skin to the plants around you. Whether you're looking at cells under a microscope or learning how they divide to...
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Cell Structure and Function
Ever wondered how scientists can see the tiniest parts of living things? Magnification makes objects appear bigger than they really are, whilst resolution determines how clearly you can distinguish between two separate points in an image. Think of it like zooming in on a photo - magnification makes it bigger, but resolution keeps it sharp.
Animal cells contain several key organelles that keep them functioning. The nucleus acts like the cell's control centre, containing all the genetic material and directing cellular activities. Mitochondria are the powerhouses where aerobic respiration happens, giving cells the energy they need. Meanwhile, ribosomes are busy making proteins through protein synthesis.
Plant cells are similar to animal cells but have some extra features that make them special. They're surrounded by a tough cellulose cell wall for support, contain chloroplasts for photosynthesis, and have a large permanent vacuole that helps maintain the cell's shape. These additions help plants stand upright and make their own food.
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Cell Division and Stem Cells
Your body is constantly growing and repairing itself through cell division - it's how you've grown from a baby and how cuts heal. Mitotic cell division follows a precise cycle: first during interphase, cells grow bigger and copy their DNA, then during mitosis, chromosomes get pulled apart by spindle fibres, and finally cytokinesis splits everything into two identical daughter cells.
Meiosis works differently and is crucial for reproduction. Unlike mitosis, it produces four genetically different cells through two divisions, which is essential for creating genetic variety in offspring. A gene is simply a section of DNA that codes for a particular characteristic, like eye colour or height.
Stem cells are incredibly versatile and come in three main types. Adult stem cells can treat diseases like leukaemia but have limited abilities and can be painful to extract. Embryonic stem cells are more powerful and can become any type of cell, making them valuable for treating paralysis and diabetes, though their use raises ethical concerns. Umbilical cord stem cells offer a middle ground with low rejection rates.
Did You Know: Plant stem cells are found in areas called meristems and can help scientists clone vast numbers of plants for agriculture and conservation!
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