Cell structure Flashcards
Define magnification
how many times bigger the image produced by microscope is than real life object
Define resolution
the shortest distance between 2 points that can be distinguished
whats Homogenisation
Biological term for breaking up of cells
why do you dissolve sample in in cold isotonic buffer solution in homogenisation
cold- to reduce activity of enzymes that break down organelles
isotonic- to manage water potential and prevent water coming in by osmosis
buffered- to maintain ph and stop organelle protein from denaturing
How is a homogenate produced
tissue-containing solution is homogenised using a homogeniser that grinds cells up this breaks plasma membranes and releases organelles into sloution (homogenate)
describe filtration process in homogenistaion
1.homogenate filtered through gauze
2.large debris separates
3.organelles pass through gauze
4.filtirate containing mixture of organelles is left behind
Ultracentrifugation
fragments in homogenate are separated in machine (ultracentrifuge) which spins tube of homogenate at high speeds to create centrifugal force
process of Ultracentrifugation
1.tube of filtrate is placed in ultracentrifuge and spun at low speed
2.heaviest organelles (usually nuclei) forced to bottom of tube where they form thin sediment
3.fluid at top (supertant) is removed is placed in another tube and spun again at higher speed
4.next heaviest organelle forced to bottom of tube (mitochondria)
optical/light and resolution
uses visible light to magnify images
lower resolution as light has long wavelength
electron microscope and resolution
uses beam of electrons
higher resolution as electrons have shorter wavelength
How ScanningEM works
electrons bounce off the top surface of a specimen to produce a 3D image
How transmissonEM works
beam of electrons pass through the specimen producing a 2D image
if absorbed = dark
if passed through = bright
Advantages of Light microscope
can see living plants and animals
relatively cheap
light & portable
Disadvantages of light microscope
preserving and staining tissue can produce artefacts
limited resolution
Advantages of electron microscope
higher resolution and magnification
Disadvantages of electron microscope
only examines non-living material
artefacts produced
expensive
SEM limitations
lower res. than TEM
cannot observe live specimen
doesnt produce coloured image
SEM advantages
can be used o 3D specimen
allows external structure of specimen to be observed
TEM limitations
non-living material only
preparation may give artefacts
no colour
TEM advantages
Greater res. than SEM
allow internal structure within cells to be seen
Eukaryotic cells
Make up organisms such as plants and animals
Genetic material contained in nucleus
May have cellulose wall
Differences between eukaryotic and pro
E = genetic material enclosed in nucleus
P= genetic material found in loop in cytoplasm
E = nucleus present
P = no nucleous
E = 80s ribosomes
P=70s ribosomes
E= no plasmids
P= plasmids
E= no mesosomes
P= mesosomes
Nucleus
Nuclear envelope : double membrane , outer continuous with ER, controls entry and exit of materials and controls reactions taking place within it
Nuclear pores : allow passage of large molecules
Nucleoplasm : makes up bulk of nucleus
Nucleolus : manufacture ribosmal RNA and assembles ribosomes
Vacuoles
Contains solutions of mineral salts, sugars and amino acids
Supports plant by making cell turgid
May act as temporary food store
Pigments may colour petals to attract pollinating insects
Lysosomes
Formed when vesicles produced by Golgi apparatus contain enzymes (protease and lipase)
Acidic internal env to hydrolyze large molecules
- hydrolyze material ingested by phagocytic cells
- release enzyme to destroy material around cell
- digest worn out organelle
- completely break down cells after death
Chloroplast
Chloroplast envelope : surrounds organelle and is highly selective of what enter and leaves
Grana ; where light absorption takes place
Stroma ; where 2nd stage of photosynthesis takes place
Adaptations of chloroplast
Grana provides large SA for photosynthesis
Fluid of stroma has enzymes needed to synthesize sugars in 2nd stage of photosynthesis
Contains DNA and ribosomes to manufacture proteins needed for photosynthesis
Golgi apparatus
Form glycoproteins
Produce secretory enzymes
Synthesize and transport carbs
Form lysosomes
Transport modify and store lipids
Often sited close to plasma membranes as it is a waypoint for newly synthesized proteins
Cell wall
Consist of microfibrils or cellulose that provide mechanical strength
Preventing bursting under osmotic pressure
Movement of water through plant
RER
Ribosomes on surface
Provides large SA for protein and glycoprotein synthesis
Provides pathway for transport of materials like proteins throughout cell
SER
Lacks ribosomes on surface
Synthesize store and transport lipids and carbs
Mitochondrion
Double membranes controls entry and exit of materials
Cristae : provides large SA for attachment of enzymes and proteins
Matrix: contains proteins lipids and ribosomes and dna to allow production of own protein
Ribosomes
Occur in cytoplasm or RER
80s in EUK
70s in PRO
Site of protein synthesis
2 sub units 1 small 1 large
Cytoplasm
Jelly like liquid makes up bulk of cells and contains organelles
Main molecule found in cell wall
Murein or glycoprotein
Main molecule found in cell membranes
Phospholipids
Capsule
Protects from drying out
Protects from phagocytosis
Pillus
For movement
For attachment to surfaces of other cells
Exchange of plasmids
Pillus
For movement
For attachment to surfaces of other cells
Exchange of plasmids
Cell differentiation
Cells become specialized in structure to suit the role it will carry out
Order of cell organizations.
Cells : basic building block of life
Tissue : group of specialized cells with similar structure and functions working tgt
Organs : group of different tissues which work together to do a particular job
Systems : group of organs working tgt to do a particular job
Examples of tissues
Animal : muscles glandular epithelial
Plants : xylem phoneme epidermal
Which cell can divide my meiosis
Nuclei
Which cells have circular DNA
Mitochondria and prokaryotic cells
Which cell associated with histone proteins
Nuclei
Which cell surrounded by 2 membranes
Nuclei and mitochondria
Which cell DNA found in cytoplasm or matrix
Mitochondria and prokaryotes
Why might scientist observe mitochondrial DNA rather than nuclei
Has more copies of same gene so more likely to detect it
Why does DNA code change less in mitochondrial than nuclear
DNA from mitochondria does not undergo independent segregation
Random fertilization if Garnett’s does not occur
How does nucleus control activities of cell
Produces mRNA
Contains DNA / chromosomes
Makes ribosomal RNA
Mitochondrion function
Makes ATP
Provides energy for peptide bond formation or joining of amino acids
