cell structure

?
microscope
produce magnified image of an object using a convex lense
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magnification
how many times bigger the image is compared to the object
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magnification calculation
size of image / size of real image
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resolution
minimum distance apart that two objeccts can be in order for them to appear as seperate times. greater resolution is greater clarity
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increasing magnification
increases size of image but not always resolution
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cell fractionation
process where cells are brocken up and the different organelles they contain are seperated out
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what happens before cell fractionation?
tissue placed in cold, buffered solution of the same water potential as the tissue
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why is solution cold
reduce enzyme activity that might break down organelles
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why is solution same water potential
prevent organelles bursting or shrinking as a result of osmotic gain or loss of water
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why is solution buffered
so Ph does not fluctuate as it could alter structure of the organelles or functioning enzymes
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homogenation
cells brocken up by homogeniser, releasing organelles in the cell. fluid is the result which is then filtered
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ultracentrifugation
process by which fragments in the filtered homogenate are sperated in a centrifuge
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process of ultracentrifugtion
tube placed in centrifuge and spun at slow speed. heaviest organelles forced to bottom and fluid at top is supernatent which is removed. supernatent spun again at faster speed.
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advantages of cell fractionation and ultracentrifugation
detail study of structure and function of organelles, by showing what isolated components do
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light microscope disadvantage
poor resolution as a result of the relatively long wavelength of light
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electron miscroscope advantage
short wavelength so microscope can resolve objects well- high resolving power
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electron microscope advantage (2)
electrons negatively charged so the beam can be focused using electromagnets
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why are electron miscroscopes good as resolving objects
electrons are absorbed or deflected by the molecules in air, a near vacuum has to be created within the chamber of an electron miscroscope in order for it to work efectively
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what are the two types of electron microscopes
transmission electron microscope and scanning electron microscope
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what is the TEM
electron gun that produces a beam of elctrons that is focused onto the specimen by a denser electromagnet. it passes through a thin section of specimen which absorbs parts of the electrons and therefore appears darker
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TEM image
produced on screen and can be photographed to give photomicrograph. produced 2d but can go to 3d by looking at all pictures produced
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why cant resolving power always be achieved of TEM
difficulties preparing specimen and a higher energy electron beam is required which may distroy specimin
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limitations of the TEM
whole system in vacuum so living sperved. staining process required. specimen must be thin. image may contain artefacts ( on picture but not on specimen)
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what is the SEM
directs a beam of electrons on to the surface of specimen from above, rather than below. beam passed back and forth in a regular pattern and electrons are scattered which contours surface
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image produced by SEM
3d image produced by computer analysis
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disadvantage of SEM
lower resolving power but ten times bigger than light microscope
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eyepiece graticule
glass disc in eyepiece of microscope to help measure the size of an object. it must be calibrated
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eukaryotic cell
have distinct nucleus and membrane bound organelles
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what nucleus contains
contains hereditarty material and control cells activities
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what does nucleus contain
envolope, pores, nucleoplasm, chromosomes, nucleolus
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nuclear envolope
double membrane. outer is continuous with endoplasmic reticulum and ribosomes. controls entry and exist of materials in and out of nucleus and contains reaactions taking place
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nuclear pores
allow passage of large molecules out of nucleus
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nuclearplasm
jelly like material which makes up the bulk
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nucleolus
small round region which makes ribosomal rna and asembles ribosomes
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what nucleus does
control centre of the cell through production of mrna and trna, retains geetic material, makes robosomal rna and ribosomes
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whats in the mitochondrion
double membrane, cristae, matrix
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what is cristae
extentions of inner membrane which provide large surface area for attatchment of enzymes
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matrix
makes up remainder of mitochondrion. contins lipids, proteins, ribosomes and DNA
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what does mitochondrion do
sites of aerobic stages of respiration , responcible for energy carrier ATP
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what are chloroplasts
carry out photosynthesis
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what is in chloroplasts
envolope, grana, chlorophyll, stroma
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chloroplast envolope
double plasma membrane that surrounds the organelle
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grana
stacks of disc like structures called thylakoids which contain chlorophyll
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stroma
fluid filled matrix where second stage og photosynthesis takes place, contain starch grains
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chloroplasts are adapted by:
membranes provide large surface area for attatchment of chlorophyll and enzymes. fluid pocesses enzymes to make sugard, contain DNA and robosomes so they can quickly make proteins needed.
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rough endoplasmic reticulum contains?
ribosomes present on outer surface of membranes
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funtions of rough ER
large surface area for synthesis of proteins and gycoproteins. provides pathway for material
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smooth endoplasmic reticulum contains?
lacksribosomes and more tubular
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functions of smooth ER
synthesis, store and trasnport lipids and carbohydrates
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what golgi apparatus contains
stack of membranes that make up flattened sacs with small rounded hollow structures
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what golgi apparatus does
modifies proteins often adding non-protein components and labels them allowing them to be sorted and sent to their correct destinations
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golgi apparatus function
form glycoproteins, produce secretory enzymes, secrete carbs, form lysosomes
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how are lysosomes formed
when vesicles produced by golgi apparatus contain enzymes such as proteases and lipases.
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lysosomes funtions:
hydrolyse material, release enzymes tooutside of the cell, digest worn out organelles, break down cells when they have died
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what are ribosomes
small cytoplasmic granules found in cells and site of protein synthesis
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80s
found in eukaryotic cells, 25nm
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70s
found in prokaryotic cells, mitochondria and chloroplasts, slightly smaller
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what cell walls have
microfibrils of cellulose, embedded in a matrix, middle lamella marking boundary between cell walls and cements
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function of cell wall
provide mechanical strength to prevent cell bursting and allow water to pass along it
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how are cell walls different in fungi
no cellulose but chatin
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what plany vacuoles contain
mineral salts, sugars, amino acids, wastes and pigments such as anthocyanins
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vacuole functions
support herbaceous plant by making cells turgid, sugars and amino acids act as food store, pigments colour petals
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what are the first group cells in an embryo like
identicle
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how are the cells in a human produced
mitotic devisions
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how does cell become specialised
every cell contains the genes needed for it to develop into any one of the many different cells, but only some genes expressed at a time
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what is a tissue
many cells aggregated together in a collection to perform a specific structure
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epithelial tissue
consists of sheets of cells. they line surfaces of organs and often have a protective function
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xylem
occurs in plants, transports water and mineral ions throughout rhe plant and gives mechanical support
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what is an organ
tissues collected in groups coordinated to perform a variety of functions
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organs in digestion
muscle, epithelium, connective tissue
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organs in a plant
palisage mesophyl, spongy mesophyll, epidermis, phloem, xylem
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what is an organ system
organs working together as a single unit
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examples of the digestive system
digestive system, respiratory system, circulatory system
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prokaryotic cell
smaller cells and have no nucleus or nuclear envolope
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whats in bacteria
cell wall, ribosomes, dna, plasmids, capsule, cell surface membrane
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how does bacteria store food
stores food as gylcogen granules and oil droplets
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virus
smaller than bacterium, contain nucleic acids emclosed with protein coat called capsid and attatchment proteins
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mitosis
2 daughter cell with same number of chromosomes as parent cells and each other
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meiosis
4 daughter cells, each with half the number of chromosomesof parents cell
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what are the stages of mitosis
interphase, prophase, metaphase, anaphase, telophase, cytokenesis
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what is interphase
where the cell is not dividing but the dna is replicated and join at the centromere
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what is prophase
chromosomes become visable, in animals the centrioles move to opposite ends of the cell where spindle fibres develop. nucleus dissappears
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what is metaphase
chromosomes seen to be made up of two chromatids. each chromatid is an identicle copy of dna from the parent cell. chromatids joined by centromere where microtubules attatchy
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what is anaphase
centromeres divide into two and spindle fibres pull individual chromatids apart
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what is telophase
chromosomes reach their poles and become longer and thinner finally disappearing leaving only widely spread chromatin
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what is cytokinesis
cytoplasm divides
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how does cell devision in prokaryotic cells take place
binary fission
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what is binary fission
dna molecule replicates,both copies attatch to cell membrane, plasmids replicate, cell membrane begins to grow dividing cytoplasm, new cell wall buildss
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how to viruses replicate
attatching to host cell with attatchment of proteins, inject nucleic acid into host which contain genetic material and thereofre a new virus begins to grow
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stages of the cell cycle
interphase, nuclear division, cytokenesis
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what is cancer
growth disorder of cels. damage to the genes that regulate mitosis and the cell cycle. leads to uncontrolled grwoth
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milignant tumour
less compact, more liely to be life threatening
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benign
grow slow, more compact, less life threatening
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how to treat cancer
kiling divided cells by blocking part of the cell cycl
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what cancer treating drugs do
prevent dna from replicating, inhibit metaphase stage of mitosis
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disadvantage of cancer drugs
disrupt normal cells
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Card 2

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magnification

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how many times bigger the image is compared to the object

Card 3

Front

magnification calculation

Back

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Card 4

Front

resolution

Back

Preview of the front of card 4

Card 5

Front

increasing magnification

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