Cell structure Flashcards by fatima ali

Define magnification

how many times bigger the image produced by microscope is than real life object

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Define resolution

the shortest distance between 2 points that can be distinguished

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whats Homogenisation

Biological term for breaking up of cells

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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

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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)

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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

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Ultracentrifugation

fragments in homogenate are separated in machine (ultracentrifuge) which spins tube of homogenate at high speeds to create centrifugal force

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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)

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optical/light and resolution

uses visible light to magnify images
lower resolution as light has long wavelength

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electron microscope and resolution

uses beam of electrons
higher resolution as electrons have shorter wavelength

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How ScanningEM works

electrons bounce off the top surface of a specimen to produce a 3D image

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How transmissonEM works

beam of electrons pass through the specimen producing a 2D image
if absorbed = dark
if passed through = bright

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Advantages of Light microscope

can see living plants and animals
relatively cheap
light & portable

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Disadvantages of light microscope

preserving and staining tissue can produce artefacts
limited resolution

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Advantages of electron microscope

higher resolution and magnification

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Disadvantages of electron microscope

only examines non-living material
artefacts produced
expensive

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SEM limitations

lower res. than TEM
cannot observe live specimen
doesnt produce coloured image

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SEM advantages

can be used o 3D specimen
allows external structure of specimen to be observed

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TEM limitations

non-living material only
preparation may give artefacts
no colour

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TEM advantages

Greater res. than SEM
allow internal structure within cells to be seen

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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