Revision Cards for Cell Structure

Cell organelles,

Cell fractionation,

Microscopy- light vs electron

Magnification,

Resolution

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  • Created by: Lucy
  • Created on: 10-12-12 19:17
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Topic 1- Cell Structure
Organelles of a Eukaryotic Cell
Nucleus- Cytoplasm-
Largest organelle. Solution within cell membrane.
Surrounded by nuclear envelope- double membrane with Contains enzymes for metabolic reactions.
nuclear pores. Contains sugars, salts, amino acids and nucleotides.
Nucleoplasm full of chromatin. Endoplasmic Reticulum-
Nucleolus- dense region of chromatin involved in making Membrane channels involved in synthesis and
ribosomes. transportation.
Mitochondria- RER covered in ribosomes which synthesise proteins to
Site of aerobic respiration. be processed by the RER before exportation.
Release energy as ATP from energy rich molecules. SER processes materials like lipids for use within cell.
More of them in more active cells. Golgi Body-
Double membrane- permeable outer and folded inner. Flattened membrane vesicles made from ER.
Inner membrane forms cristae: large surface area Transports materials from RER to cell membrane.
covered in stalked particles. Fuses with RER and vesicles bud off towards membrane.
Matrix- liquid with ribosomes and DNA suspended in it. Vesicles fuse to membrane and release contents by
Ribosomes- exocytosis.
Smallest and most numerous of organelles. Lysosomes-
Sites of protein synthesis. Membrane bound vesicles formed from RER containing
Free in cytoplasm or attached to RER. digestive enzymes.
Proteins produced for export of for cells own use. Break down unwanted chemicals/ toxins/ organelles.
Consists of a small and a large subunit. Fuse with vacuoles to digest contents.
Eukaryotic cells have larger 80s ribosomes.
Cytoskeleton-
Network of protein fibres- support, transport, mobility.
Gives cell its shape, holds organelles in position.
Responsible for cell movements- cell division, cilia,
flagella, cell crawling, muscle contractions.
Undulipodium-
Extension of the cell membrane.
Full of microtubules and motor proteins.
Cilia- short and numerous.
Flagella- longer than the cell and usually 1 or 2.
Not present in all cells.
Microvilli-
Small finger like extensions of the cell membrane.
Increase area for absorption.
Sub-cellular structures.
Plasma membrane-
Thin flexible layer around outside of a cell.
Made of phospholipids and proteins.
Controls the exit and entry of materials.
Centrioles-
Pair of short cylinders, each of 9 fibres.
Help with cell division.

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Cell Fractionation
Used to extract organelles from cells.
Extracts undamaged, intact organelles.
Differential centrifugation most common method.
1. Tissue sample cut in a cold, buffered, isotonic solution.
2. Sample homogenised, cell organelles remain intact.
3. Homogenised suspension filtered to remove fat, connective tissues, cell walls etc. producing a cell free extract.
4. Filtrate centrifuged at a low speed to remove partially opened cells and debris.
5. Supernatant containing organelles decanted off and used for next round of centrifugation.
6.…read more

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Light Microscopes-
Visible Light used to illuminate specimens.
Image magnified using lenses.
Light source either a lamp or a mirror.
Specimens often need to be stained to show up.
Pros-
Can view living specimens.
Produces colour images.
Video images possible.
Simple.
Cheap.
Magnification up to 1000X
Cons-
Poor resolution.
Can't view organelles smaller than nuclei.
Specimens need to be stained.
Electron Microscopes-
Use a beam of electrons rather than visible light.
Very small wavelength (1nm).
Can view subcellular structure.
Electrons produced using a hot wire.…read more

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Colle
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Pros- Pros-
High magnification (5 000 000X). P
High resolution (1nm). r
Good for sections. o
Good for organelles and prokaryotes that can't be seen d
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Cons- Cons-
Takes place in a vacuum. C
Needs very thin specimens. a
Can't use living specimens. n
Specimens often need stains. 't
No colour because electrons don't have colour. s
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