F211 Biology revision notes

have one, **** your lives that you all study biology - if I could get an A at AS level I'm sure you all can. good luck ***

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  • Created on: 10-09-12 21:25
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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
Resolution ­ the ability to distinguish between 2 separate points that are very close together
A measure of the detail in the image
Light microscopes
Can be used by non-professional's
Used out of the lab
Electron microscopes use a shorter wave length ­ allows for better resolution
Better resolution
Better magnification
Used by professionals
Cannot be carried around
Specimen has to be dead
Black and white images ­ artificial colours have to be added to make the images more eye catching
SEM ­ scatters the electrons, produces a 3D structure, and allows us to see the internal structure
TEM ­ electrons travel through the specimen, produces 2D image, external structure
To make the organelles more visible
So non-professionals can easily recognise organelles
Light microscopy: use of stains such as...
Acetic orcein ­ chromosomes and nuclei red
Methylene blue ­ nuclei appear darker blue than the cytoplasm (appears pale blue)
stains living cells
Eosin ­ stains cytoplasm and some organelles red ONLY STAINS DEAD CELLS ­ can
compare living and dead sperm cells
Electron microscopes stained with metal or gold so the electrons can bounce of (heavier stains)

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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.…read more

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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 surface) membrane
Surrounds every cell
Made up of lipid and protein molecules
Control what enters and leaves cell
Vacuole ­ only in plant cells, sac of water and liquid e.g.…read more

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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
7nm ­ 10nm wide
Function of membranes
Within the cell At the surface of the cell
Split cell into compartments Allow small/charged molecules in
Separate different processes ­ function more Control what enters/leaves the cell…read more

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Permeable to small polar molecules e.g.…read more

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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)
Therefore down a concentration gradient
For example oxygen and carbon dioxide move this way
Carrier proteins ­ molecule binds with the protein which activates the protein to change shape and
allow the molecule through…read more

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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
(Carrier proteins are an active process but part of facilitated diffusion)
Exocytosis Endocytosis
Substances moving out of the cell. Vesicle binds Substances moving into the cell.…read more

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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 repeatedly to form a zygote
Repair ­ damaged cells can be replaced by stem cells dividing to create new replacement cells for
the damaged ones
Asexual reproduction ­ produces genetically identical clones of the parent…read more

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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 to take up minerals, ions and water from the soil
Guard cells
Remain turgid
Open and close when the leaf is photosynthesising
Tissue ­ a group of specialised cells working together to perform a particular…read more

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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 throat where its swallowed and the acidity in the
stomach can denature the enzymes of the particles/bacteria
Goblet cells Secrete mucus to trap particles breathed in e.g.…read more



These notes are AMAZING! thank you so much 

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