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Similarities
- rough endoplasmic reticulum-form an extended system of flattened compartments, called sacs, continuous with nuclear envelope, covered in tiny ribosomes, proteins made in ribosomes enter sacs and move through them modifying them on the journey.
- Smooth endoplasmic reticulum- lacks ribosomes, makes lipids and steroids such as cholesterol and oestrogen
- Golgi body- stack of flattened sacks, buds off from RER and at the other end to form golgi vesicles. The golgi collects, sorts and processes molecules ready for transport around the cell or secretion. Eg addition of sugars to proteins to make glycoproteins, convert sugar to cell wall components, make lysosomes.
- nucleus-largest organelle, surrounded by 2 membranes known as the nuclear envelope. has many pores called nuclear pores. these allow control between nucleus and cytoplasm. chromosomes are loosely coiled as chromatin, controls activity of cells.
- lysosomes- spherical sacs surrounded by a single membrane, 0.1-0.5um, contain digestive enzyme, breakdown old cells or whole cells. in white blood cells lysosomes are used to digest bacteria.
- mitochondria-1um in diameter, sausage shaped, 2 membranes, inner cristae project into matrix, space between membranes is intermembranr space, outer membrane contains porin
- cell surface membrane- 7nm thick, phospholipid bilayer, trilaminar appearance, partially permeable,
- microtubules-long rigid hollow tubes in the cytoplasm. they are 25nm in diameter, they make up the cytoskeleton. They are made of a protein called tubulin. Alpha and Beta tubulin join to form dimers. Dimers join end to end to form profilaments, 13 of these line up tp form a cylinder-this is a microtubule. They form part of an intracellular transport system, spindle used for separation of chromatids is made from microtubules. The assembly of microtubules from tubulin is controlled by microtubule orgaising center.
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Differences
- centrioles and centrosomes-centrioles lie close together at 90 degree angles, hollow cylinder 500nm long, each centriole contains 9 triplet rings of microtubules, function is a mystery. can be found at the base of cilia where they act as MTOC.
- chloroplasts-elongated shape and diameter of 3-10um, they are surrounded by 2 membranes forming chloroplast envelope, replicate individually of cell division. Membrane system of fluid filled sacs called thylakoids, thylakoids can form fllat disk like structures called grana, stroma stores starch grains.
- cell walls- rigid layer of cellulose fibres, gives cell definite shape, may be reinforced with lignin, freely permeable. They are linked to neighbouring cells by plasmodesmata (strands of cytoplasm)
- Vacuoles-plants have a large permanent vacuole, surrounded by the tonoplast, the fluid is filled with pigments, enzymes, sugars and other organic compounds, help to regulate osmotic properties of cells.
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Overall comparison
Plant and animal cells have many similarities but the cell wall, plasmodesmata, vacuole, chloroplasts and centrioles are some major differences between them. Chloroplasts and mitochondria have many similarities such as double membrane, circular DNA and 70s ribosomes showing their origin is similar (endosymbiont theory)
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