CELLS Flashcards
Electron microscope
-Uses electrons rather than light to produce images
-The electron microscope can magnify much more than a light microscope as electrons have a shorter wavelength than light
Resolution
The ability to see two adjacent points as distinct entities following magnification
TEM
-Transmission electron microscope
-Electrons passing through a very thin specimen, produces very high quality images
SEM
-Scanning electron microscope
-Electrons reflecting off the surface of the image as opposed to going through it
-Resolution and maginifcation are not as high but it gives a 3D image
Eukaryotic cells
-Found in animals, plants and fungi
Mesosome
Tightly folded region of the cell membrane containing all the membrane-bound proteins required for respiration and photosynthesis
Flagellum
Rigid rotating helical-shaped tail used for propulsion
Cell membrane
-Two layers of phospholipids (bilayer)
-hydrophillic heads facing out, hydrophobic tails facing in
Function of the hydrophobic centre of the phospholipid bilayer
Prevents the free diffusion of water and polar molecules through the membrane
Structure of the plasma membrane
-Phospholipid bilayers
-Intrinsic and extrinsic proteins
-Carbohydrate glycocalyx
-Glycoproteins
-Glycolipids
-Cholesterol
arranged in a fluid mosaic structure
Proteins in the cell membrane
-Help provide stability and support as they ‘anchor’ the phospholipid molecules
-May act as enzymes
-Some act as adhesion sites, where adjacent cells are held together
-Involved in cell recognition and as receptors or antigens
-Particularly important in transporting substances across the bilayer
Advantages to having enzymes in the membrane
-Kept in the ideal place in terms of substrate availabiity and pH
-Need replaced less often
Examples of enzymes in the membrane
-In the membrane of the small intestine which are important in the digestion of disaccharides
Channel proteins
-Span the membrane and work by creating a hydrophillic channel that allows polar molecules to bypass the hydrophobic centre of the bilayer
-May be permenantly open or have their opening controlled (gated)
-Gated channels are very important in controlling the passage of ionsinto and out of neurons during nervous conduction
Carrier proteins
-Carry specific ions and molecules across the membrane
-May be because the ions have charged groups, or because the molcules have to be moved across the concentration gradient
-Can change shape to carry the substance from one isde of the membrane to the other