biology f211measuring cells

magnification - does NOT increase the level of detail seen

resolution - the ability to see two distinct points seperately

• light microscope use # lenses to produce a clear image
• light passes from a bulb under the stage, through condenser, through specimen
• light is the focused through object lenese and then eye peice
• # of objective lense that can be rotated to see different magnifications(4 - X4 X10 X40) (X100 - OIL IMMERSION LENSE)
• advantages
• most light micro. can x1500
• wide range of specimen can be viewed - (living)
• used widely in education, labs, research
• weaknesses
• not high resolution so cant give detail about internal cell structure
• max resolution power is 200nm objects closer than 200nm look like 1 object
• preparing for light microscope
• staining - allows them to be seen, dark red DNA indentify it :)
• sectioning - embedded in wax then cut without distorting the structure of them, useful for making sections of soft tissue - brain

MICROMETRE :D

ACTUAL SIZE = IMAGE SIZE /MAGNIFICATION

MAGNIFICATION = IMAGE SIZE/ACTUAL SIZE

EXAMPLE --->  (IMAGE SIZE) = 50MM

                         (MAGNIFICATION) = 1200

50MM/1200 = 0.0414MM =41.6 UM

ALWAYS SHOW WORKING OUT GET MARKS FOR IT :)

• use of electrons:
• beam of electrons 100,000 x shorter than light wavelength
• tell objects 0.2nm apart
• use magnets to focus beam
• projects image onto a screen and 'greyscale'  image is seen (electron micrographs)
• resolution 500,000x greater than human eye :O

TWO TYPES 

• TRANSMISSION ELECTRON MICROSCOPE
• beam passes through thin sample, passing through denser parts easier
• final image 2 dimensional (mag. possible 500,000x)
• SCANNING ELECTRON MICROSCOPE
• beam directed onto sample, not through it and bounced off
• final image is 3D view of surface of sample mag.possible (x100,000)

• ADVANTAGES
• 2000x more resolution than light microscope
• so detailed images can be seen
• the SEM produces 3D images revealing contourus, tissues or cellular arrangement (cant do that in a light microscope)
• weaknesses
• electron beams are deflected by particles of air so samples have to be in a vacuum
• very expensive
• preparing samples and using electron microscopes require high skill & training

• actin filaments -move against eachother cam move organelles around inside the cell
• microtubles - cylinders 25nm in diametre made of protein called tublin, move microorgans movements through liqiud or waft liquid past a cell (use ATP)
• eukaryotes/flagella/cilia - hair like extensions from surface of cells, contain nine microtubules in a circle, 2 microtubules in a central bundle
• ATP through microtubules allows these cells to create movement so cilia can waft and undulipodium forms tail of sperm

• vesicles & vaculous
• vesicles - memebrane bound sacs in a cell carry substances
• plants -vacuole maintains cell stability filled with water/solutes =turgid pushes against cytoplasm
• plant cells wall made of cellulose carbohydate polymer =glucose subunits

• THE NUCLEUS - structure: surrounded by a nulear envelope, 2 membranes with fluid between them contains a nucleolus. function: houses cells gentic information. chromatin consitis of DNA/proteins - can make proteins. the nucleolus makes RNA/robosomes pass into cytoplasm proteins assemble there.
• ENDOPLASMIC RETICULUM - structure:flatterned membrane bound sacs called cisternae, ROUGH er - studded with ribosomes. SMOOTH - no ribosomes. function:transports proteins, somes can be secreted/place on cell surface membrane. SMOOTH - makes lipids the cell needs.
• GOLGI APPARATUS:structure:membrane bound fatterned sacs. function: recieves proteins and modifys them adds sugar. then packs them into vesicles to be transported
• MITOCHONDRIA:structure:spherical shaped two membranes seperated by fluid highly folded from cristae. function: ATP is produced during respiration.
• CHLOROPLASTS:structure:two membranes seperated by fluid. inner - continuous network of flattened membrane sacs - thylakoids. function:make carbohydrates 
• LYSOSOMES:structure: spherical sacs surrounded by a single membrane. function: powerful digestive enzymes that break down materials.
• RIBOSOMES:structure:some in cytoplasm bound to ER consists of 2 sununits. function:protein synesis.mRNA from nucleus assembles proteins from amino acids.
• CENTRIOLES:structure: tubes of protein fibres pair of them next to nucleus. functions: cell divisionform spindle move chromosomes in nuclear divsion.

• membranes = seperate cell contents from the environement/cytoplasm
• cell recognition and signalling
• holding compents of some metabolic pathways
• regulating transort materials in/out of cell

• the plasma membranes of a growing shoot contain receptors that allow them to detect the molecules that relate to growth
• muscle cells membranes contain a large number of channels that allow rapid uptake of glucose to provide energy for mucle contraction
• internal membranes of chloroplasts contain chlorrophyll and other molecules needed for photosynesis
• the plasma membranes of white blood cells contain special proteins that enable the cells to recognise foreign cells and particles

FLUID MOSAIC = the molecular arrangements in membranes. the main features are: phospholipid molecules from basic structure, various proteins either freely floating or attached to structures. some extrinsic proteins embedded in the bilayer.

• MEMBRANE COMPONENTS/ROLES
• chlesterol gave membranes stability
• channel proteins allow movement of some substances across membrane
• carrier proteins actively move substances across the membrane
• receptor sites some allow hormones to bind to the cell so cell respenses can be carried out can only respond if it has a receptor for that hormone
• glycoproteins may be invloved in cell signalling to allow recognition by immune system can also bind cells together in tissues.
• enzymes/coenzymes may be bound to membranes of chkoroplast/mitochondria help reactions photosynesis/respiration.