Eukaryotes (e.g animals and plants) are made from complex cells called eukaryotic cells.
Prokaryotes (e.g. bacteria) are smaller and simpler cells called prokaryotic cells.
Both types of cells contain sub-cellular structures - parts of cells that each have a specific function.
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Subcellular structures in an animal cell
Nucleus - contains DNA (genetic material) in the form of chromosomes that controls the cell's activities.
Cytoplasm - gel-like substance where most of the chemical reactions happen.
Mitochondria - these are the site of of cellular respiration and contain the enzymes needed for the reactions involved.
Cell membrane - holds the cell together and controls what goes in and out by providing a selective barrier. They also contain receptor molecules that are used for cell communication. E.g. by hormones
Ribosomes - where proteinsynthesis occurs.
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Subcellular structures in a plant cell
Nucleus - contains DNA (genetic material) in the form of chromsomes that controls the cells activities.
Cytoplasm - gel-like substance where most of the chemical reactions happen.
Mitochondria - these are the site of cellular respiration and contain the enzymes needed for the reactions involved.
Cell membrane - holds the cell together and controls what goes in and out by providing a selective barrier. They also contain receptor molecules that are used for cell communication, e.g. by hormones.
Ribosomes - where proteinsynthesis occurs
Rigid cell wall - made of cellulose, gives support for the cell.
Chloroplasts - where photosynthesis occurs. They contain a green substance called chlorophyll.
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Subcellular structures within a prokaryotic cell
Chromosomal DNA - (one long circular chromosome) controls the cell's activities and replication. It floats free in the cytoplasm (not in the nucleus).
Plasmids - small loops of extra DNA that aren't part of the chromosome. Plasmids contain genes for things like drug resistance, and can be passed between bacteria.
Cell membrane - controls what goes in and out. The cell is also supported by a cell wall.
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Cells are studied using microscopes
Microscopes use lenses to magnify images (make them look bigger).
They also increase resolution of an image. This means they increase the detail you can see. Resolution is how well a microscope distinguishes between two points that are close together.
Light microscopes were invented in the 1590s. They let us see things like nuclei and chloroplasts.
Electron microscopes were invented in the 1930s. They let us see much smaller things in more detail like the internal structure of mitochondria. This has allowed us to have a much greater understanding of sub-cellular structures. Only electron microscopes will let us see things as tiny as plasmids or viruses.
Transmission electron microscopes (TEMs) have a higher magnification and resolution than light microscopes but they're not portable, they're expensive and it's complicated process to prepare specimens for use (which means they can't be used to look at living tissue, unlike light microscopes).
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