Cells and Microscopes-basic components of living systems Flashcards
magnification
-how many times larger the image is than the actual size of the object being viewed
resolution
-the ability to see individual objects/ points as separate entities
why is an electron microscope more effective than a light microscope
-a beam of electrons has a wavelength a thousand times smaller than light. This means objects which are much smaller and closer together can be seen without diffraction blurring the image
magnification calculation
-magnification = size of image / actual size of object
disadvantages of electron microscope
- v expensive
- specimens can be damaged by the electron beam
transmission electron microscope
-a beam of electrons is transmitted through a specimen and focused to produce an image. Resolving power= 0.5nm
scanning electron microscopes
-a beam of electrons is sent across the surface of a specimen and the reflected electrons are collected.
artefact
a visible structural detail caused by processing the specimen and not a feature of the specimen.
laser scanning confocal microscopy
- moves a single spot of focused light across the specimen which causes fluorescence from the components with a ‘dye’
- the emitted light from the specimen is filtered through a pinhole aperture. the light radiated from very close to the focal plane is detected
diff between prokaryotic and eukaryotic
- prokaryotic= single celled organisms with a simple structure of a single undivided area called the cytoplasm
- eukaryotic= make up multicellular organisms. Have a complicated internal structure, containing a membrane-bound nucleus and cytoplasm which contains many membrane-bound cellular components (organelles)
role of membranes
-selectively permeable and control the movement of substances into and out of the cell and organelles
role of DNA in the nucleus
- directs the synthesis of all proteins required by the cell (however this protein synthesis occurs in the ribosomes outside the nucleus)
- DNA controls the metabolic activities of the cell as many of these proteins are the enzymes necessary for metabolism to take place
- DNA is too large to be transported out of nucleus so it is transcribed into smaller RNA molecules, which are exported via nuclear pores
Nuclear envelope
-where DNA is contained to protect it from damage in the cytoplasm
-contains nuclear pores that allow molecules to move into and out of the nucleus
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chromatin
- made up of proteins called histones
- coils and condenses to form chromosomes
nucleolus
- an area within the nucleus
- responsible for producing ribosomes
- composed of proteins and RNA
RNA
-used to produce ribosomal RNA which is combined with proteins to form ribosomes necessary for protein synthesis
role of mitochondria
-site of the final stages of cellular respiration, where the energy is stored in the bonds of complex, organic molecules made available to use for production of ATP
structure of mitochondria
- have a double membrane
- inner membrane highly folded to form structures called cristae and the fluid interior is called the matrix
- membrane forming the cristae contains enzymes used in aerobic respiration
- contain a small amount of DNA =can produce their own enzymes
role and structure of vesicles
- membranous sacs that have storage and transport roles
- consist simply of a single membrane with fluid inside
- used to transport materials inside the cell
role and structure of lysosomes
- specialized forms of vesicles that contain hydrolytic enzymes
- responsible for breaking down waste material in cells
- responsible for breaking down pathogens ingested by phagocytic cells
role and structure of cytoskeleton
- network of fibres necessary for the shape and stability of a cell
- organelles are held in place and it controls cell movement and the movement of organelles within cells
role and structure of cytoskeleton
- network of fibres necessary for the shape and stability of a cell
- organelles are held in place and it controls cell movement and the movement of organelles within cells
3 components of cytoskeleton
-microfilaments, microtubules, intermediate fibres
microfilaments
- contractile fibres formed from the protein actin
- responsible for cell movement and cell contraction during cytokinesis- the process in which a cytoplasm divides to form 2 daughter cells
Microtubules
- determine the shape of the cell (globular tubulin proteins polymerise to form tubes that determine shape)
- act as tracks for the movement of organelles e.g vesicles
intermediate fibres
-gives mechanical strength to cells and help maintain integrity
centrioles
- component of cytoskeleton
- composed of microtubules
- 2 associated centrioles form a centrosome, which assembles and organises spindle fibres during cell division
flagella
- whip like extensions
- used for to enable cells motility
why do objects need to be stained
- coloured dye binds to structures, facilitating the absorption of wavelengths of light to produce an image
- differential staining; the contrast between heavy and lightly stained areas distinguish different structures
outline how to prepare a sample of blood to be observed under microscope
- onto a slide
- add Leishmans stain which stains the nuclei of leucocytes purple
- add a buffer and rinse
specialised cell types in blood
red blood platelets neutrophils-lobed nucleus, engulf foreign material lymphocytes monocytes-respond to inflammation
role and structure of golgi apparatus
- planar stack of membrane bound, flattened sacs
- vesicles bud off trans face via exocytosis
- modifies and packages proteins for transport
- synthesises glycoproteins
role and structure of vesicles
- temporary membrane bound sacs containing water and chemicals (neurotransmitters)
- storage of enzymes
- involved in exo/endocytosis and transport of material into cytoplasm
structure of endoplasmic reticulum
- cisternae, network of tubules and flattened sacs which extend from cytoplasm and connects to nuclear envelope
- 2 types, rough er and smooth
smooth endoplasmic reticulum
-lipid synthesis
rough endoplasmic reticulum
-ribosomes attach for protein synthesis and transport
explain how to use an eyepiece graticule and stage micrometre to measure the size of a structure
- place micrometer on stage to calibrate eyepiece graticule
- line up scales on graticule and micrometer
- count how many graticule divisions are in 100 nano meters on micrometer
- length of 1 eyepiece division = 100/no of divisions
- use calibrated values to find actual length
describe function of membranes inside cells
- provide internal transport system
- selectively permeable to manage transport of materials into/out of organelles
- isolate organelles from cytoplasm for specific metabolic reactions
Outline how the organelles in pancreatic cells work together to produce and release these
protein molecules from the cells
- nucleus , contains gene (for protein) / site of
transcription / produces mRNA ;
2 ribosomes / rough endoplasmic reticulum / RER, site
of, protein synthesis / translation ;
3 vesicles for transport (of protein) ;
4 Golgi (apparatus / body), processes / modifies /
(re)packages, proteins ;
5 (vesicles) fuse to, cell surface / plasma, membrane
