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Cell structure

Magnification Resolution
Light microscope x 1500 200nm
TEM x 500 000 0.2um
SEM x 500 000 0.2um

Magnification ­ the degree to which the size of an image is larger than the object itself

Calculate by dividing the image size by the actual size of the specimen


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Structures within the cell


Double membrane (sometimes called the nuclear envelope) continuous with the RER
Membrane has pores to allow mRNA and ribosomes out, nutrients etc. in
Contains the DNA in linear chromosomes associated with histone proteins
largest organelles

Nucleolus ­ inside the nucleus, contains the DNA



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Inner membrane folder into cristae to increase the surface area
Background material ­ matrix

Chloroplasts ­ only in plant cells

Double membrane
Grana (membranes) which contain chlorophyll ­ form stacks of thylakoids
Site of photosynthesis
Contains starch grains (carbohydrate which act as energy stores)
Stroma ­ colourless matrix

Plasma (cell…

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Prokaryotic Eukaryotic
No nucleus nucleus
No membrane bound organelles Membrane bound organelles
Cell wall made of peptidoglycan Cell wall made of cellulose
No cytoskeleton Has a cytoskeleton
Smaller Bigger
Ribosomes ­ 18nm Ribosomes ­ 22nm
Circular DNA not associated with histone Linear DNA associated with histone
proteins proteins

Cell membranes…

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Permeable to small polar molecules e.g.
Arranged in a bilayer

Cholesterol Maintains fluidity when too hot it reduces
fluidity, when too cold it increases fluidity
Membrane stability
Reduces permeability

Proteins Allow larger or charged molecules in or out
of the cell
Transmembrane proteins ­ channels and

Glycolipids and…

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Agonists ­ mimic the effect of hormones

Transport across membranes

Passive processes ­ diffusion, facilitated diffusion, osmosis

Involve substances moving down a concentration gradient
Does not require ATP energy
Uses kinetic energy


Small, non-charged molecules move across the membrane
From higher concentration to lower concentration (and vice versa)

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Animal cells

Take up a lot of water ­ cell swells and can burst and cell membrane cannot withstand the pressure
Lose a lot of water ­ lose a lot of water and the cell shrinks

ACTIVE TRANSPORT ­ uses ATP energy to move large/charged molecules against a concentration gradient…

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Spindle fibres completely contracted and

CYTOKINESIS Animals ­ cell surface membrane `rips' in
Plants ­ cell plate forms at the equator

Homologous pair of chromosomes ­ pair of chromosomes from the same karyotype, different alleles bring
rise to variation

Function of mitosis:

Growth ­ cells in an embryo divide…

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Haploid nucleus ­ fuse with the nucleus of the egg cell to become a diploid nucleus
Lots of mitochondria ­ energy to propel the flagellum
Thin, streamline structure so it can swim to the egg

Root hair cells

Increase the surface area of the leaf
Short life span
Maximum space…

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Elastic fibres Yes Yes Yes Yes

Cartilage Allows movement of the neck which doesn't block the airways
Oesophagus can expand when swallowing food without constricting the
Hold open the airways to avoid collapse when pressure is low
Supports trachea and bronchi

Cilia Waft mucus up the trachea to the…




These notes are AMAZING! thank you so much 

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