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Cell Structure - Coggle Diagram
Cell Structure
Mitosis
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The cell cycle is divided into two parts, the mitotic phase and interphase
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Chromatids are identical halves of the original chromsome which is joined at a constricted region known as the centromere
Cell cycle
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In this period the cell might seem inactive however it is carrying the functions for the cell that it is dividing to form
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Eukaryotic cells
Example of eukaryotes are Fungi, Plants and Animal cells
A key feature of Eukaryotic cells is that they contain membrane bound organelles, in particular their DNA is membrane bound
The DNA in Eukaryotic cells is usually wrapped around a protein known as a histone (this later forms chromosomes)
Organelle (function)
Cytoplasm = Gel like substance, which holds the internal components in place to prevent them from being damaged
Cell surface membrane = Contains lipids, carbohydrates and proteins. There are receptor cells on the surface which allows for certain molecules to enter/exit the cell
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Lysosomes = Vesicle that contains digestive enzymes like Lysozymes which break down dead cells to recycle the organic material
Golgi apparatus/vesicle = Packages and redistributes the proteins which are made in the RER around the cell. It also secretes carbs
S/RER = Smooth endoplasmic reticulum produces carbohydrates and lipids. Rough endoplasmic reticulum contains many ribosomes, it produces proteins
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Nucleus = Stores the human genome controls the cell by providing the infomation for protein synthesis and other functions
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Organelle (structure)
Cell surface membrane = Phospholipid bilayer, made of cholesterol, glycoproteins/lipids and proteins.
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Golgi apparatus/vesicle = Stacks of flattened sacs, vesicles join from the RER at the Golgi cisternae
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S/RER = A system of fluid filled membranes, studded with ribosomes and folded to increase the surface area
Mitochondria = Double membrane bound, inner membrane heavily folded to increase surface area (Cristae) this is within a fluid filled matrix
Nucleus = Surrounded by double membrane (nuclear envelope) embeded with channel proteins which form pores
Plant Cells
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Organelle
Cell wall = Bundles of cellulose fibres in plants, in fungi Chitin makes up the cell wall. It provides strength and support to the cell
Vacuole = maintains pressure by pushing the cytoplasm against the cell wall, which helps keep the plant cell turgid
Chloroplasts = Double membrane bound, inner membrane form flat discs known as thylakoids stacks of these are called granum, Surrounding is a flluid matrix called the stroma, its the site of photosynthesis
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Prokaryotic Cells
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Their DNA is isn't bound to proteins or contains any 'free' ends, its arranged in loops
Organelles
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Cell wall = supports the cell and makes it rigid, made of a polymer of protein known as peptidoglycan
Ribosomes = Produces protein, however in Eukaryotic cells they are 70s which are smaller
Pilli = Hair like protrusions on the surface of the prokartyotic cell which allows bacterial cells to transfer DNA and create colonies quickly
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Flagellumn = Allows the bacteria to move by acting as a propeller, sperm cells share this organelle
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Stages of Mitosis
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Prophase
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Nuclear membrane breaks down, nuclelous disappears
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Anaphase
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Centromere divides in two, the spindle fibres shorten
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Microscopes
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Optical light Micrscopes
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Light microscopes have poor resolution because of the wavelengths of light that they use, this means that small organelles are not visible
Electron microscopes
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Because electrons are absorbed in air, electron microscopes can only work in a vacum. in TEMs a thin specimen is stained where electrons pass and a 2D image is produced. SEMs work with the contours of the speciemen and produce a 3D image
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Binary fission
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The circular chromosome is replicated once, plasmids may be replicated numerous times
The replicated circular chromosomes move to either end of the cell, whilst the plasmids are randomly distributed between the two poles
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Cell fractionation
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Homogenising
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Or using a homogensier which is a device that contains a glass tube and a plunger-like device at the top to break the cells open
The solution is added to the glass tube and then a buffer solution is added to it, this is so that the solution remains at a constant pH to prevent denaturation
The water potential of the buffer is the same as the solution which prevents water from entering the solution and breaking the cell via osmosis
Ice is also used which slows down the enzyme activity and prevents any reactions which could break down the cells
Move the plunger up and down to break open the cells in the solution (this is known as the homogenate)
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Centrifugation
The mass of the organelle dictate how quickly it will be collected i.e. nuclei will collect at the bottom of the tube first
Initally the test tube is spun at low speeds and the heavy organelles are collected, then the tube is spun at faster speeds
The homogenate is placed in the centrifuge and then spun, because of gravity the solution collects at the bottom in different directions
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