Notes on f211

biology notes on f211

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  • Created on: 12-05-12 22:54
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Cells, Exchange and Transport
Cells
(a) state the resolution and magnification that can be achieved by a light microscope, a transmission electron
microscope and a scanning electron microscope;
Resolution Magnification
Light microscope 200nm x1,500
Transmission Electron Microscope 0.1nm x500,000
Scanning Electron Microscope 0.1nm X100,000
(b) explain the difference between magnification and resolution;
Magnification is the degree to which the size of an image is larger than the image itself.
Resolution is the degree to which it is possible to distinguish between two objects that are very close together.
(c) explain the need for staining samples for use in light microscopy and electron microscopy;
A lot of biological material inside a cell isn't coloured, so it might be difficult to distinguish between different
features. Coloured stains are used to stain specimens for use with the light microscope. Chemicals which bind to
other chemicals on, or in, the specimen, which allows the specimen be to seen. Some chemicals bind to specific
structures, such as Acetic orcein staining DNA red.
Electron micrographs start off black and white, with the colour being added by a specialised computer program
afterwards.
(d) calculate the linear magnification of an image;
Image size =Actual size x Magnification
I
A M
(e) describe and interpret drawings and photographs of eukaryotic cells as seen under an electron microscope and be
able to recognise the following structures:
Nucleus,
Larges organelle.
Nucleolus,
Dense, spherical structure inside nucleus
Nuclear envelope,
Surrounds the nucleus
Rough and smooth endoplasmic reticulum (ER),
Continuous with the nuclear envelope. RER is studded with ribosomes, SER is not.
Golgi apparatus,
Stack of membrane-bound flattened sacs
Ribosomes,
Tiny. Some are in the cytoplasm and some are bound to the RER
Mitochondria,
Spherical or sausage shaped. Double membrane.
Lysosomes,
Spherical sacs. Single membrane.
Chloroplasts,
Only in plant cells. Two membranes. Contain Thylakoids.
Plasma (cell surface) membrane,
Phospholipid bilayer
Centrioles,
Small tubes of protein fibres. Pair of them next to Nucleus in Animal cells.
Flagella and cilia;
Hair-like extensions projecting from the surface of a cell.
ALM June 10

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Cells, Exchange and Transport
(f) outline the functions of the structures listed in (e);
Nucleus,
Houses all of the cell's genetic material in the form of DNA, which contains the instructions for protein synthesis.
Nucleolus,
Makes ribosomes and RNA which pass into the cytoplasm and are used in protein synthesis
Nuclear envelope,
A double membrane with nuclear pores.
Rough endoplasmic reticulum,
Transports proteins made by the attached ribosomes.
Smooth endoplasmic reticulum (ER),
Involved in the making of lipids.…read more

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Cells, Exchange and Transport
(h) compare and contrast, with the aid of diagrams and electron micrographs, the structure of prokaryotic cells and
eukaryotic cells;
Prokaryotic cells do not have a nucleus. They are bacteria and are much smaller than Eukaryotic cells.
They have:
· One membrane
· No membrane-bound organelles
· Cell wall made of peptidoglycan not cellulose
· Their ribosomes are smaller
· Circular DNA
· DNA is not surrounded by a membrane.…read more

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Cells, Exchange and Transport
Cell Membranes
(a) outline the roles of membranes within cells and at the surface of cells;
· Separate cell contents from the outside environment
· Separate cell components from the outside environment
· Cell recognition and signalling
· Holding the components of some metabolic pathways in place
· Regulating the transport of materials into or out of cells
(b) state that plasma (cell surface) membranes are partially permeable barriers;
(c) describe, with the aid of diagrams, the fluid mosaic model of…read more

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Cells, Exchange and Transport
ALM June 10…read more

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Cells, Exchange and Transport
Cell Division, Cell Diversity and Cellular Organisation
(a) state that mitosis occupies only a small percentage of the cell cycle and that the remaining percentage includes
the copying and checking of genetic information;
(b) describe, with the aid of diagrams and photographs, the main stages of mitosis (behaviour of the chromosomes,
nuclear envelope, cell membrane and centrioles);
· In Interphase (Pre-Mitosis):
o The DNA replicates.
· In Prophase:
o The chromosomes supercoil & become visible under a light microscope.…read more

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Cells, Exchange and Transport
(i) describe and explain, with the aid of diagrams and photographs, how cells of multicellular organisms are specialised
for particular functions, with reference to
erythrocytes (red blood cells),
Biconclave disc shape to maximise surface area
No nucleus = more room for haemoglobin
neutrophils,
Flexible shape to engulf foreign particles or pathogens
Many lysosomes contain digestive enzymes to break down the engulfed particles
epithelial cells,
Some have cilia to move particles
Some have mnicrovilli to increase surface area
sperm cells,
Organelle content…read more

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Cells, Exchange and Transport
Ciliated epithelial tissue
· Column- shaped
· Exposed surface covered with cilia
· Move in synchronised waves
· Found on surface of tubes (e.g. bronchi, oviduct)
· Waft mucus in lungs, egg in oviduct
Xylem
· Composed of xylem vessel cells and parenchyma cells
· Parenchyma cells fill the gaps between xylem vessels to provide support
Phloem
· Comprises of sieve tubes and companion cells
· Companion cells are highly metabolically active, moving products of photosynthesis up and down
the phloem.…read more

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Cells, Exchange and Transport
Exchange Surfaces and Breathing
(a) explain, in terms of surface area:volume ratio, why multicellular organisms need specialised exchange surfaces and
single-celled organisms do not;
Organisms need to absorb certain substances, (e.g. oxygen, glucose, proteins, fats, water and minerals) from
the surrounding environment and remove waste products (carbon dioxide, oxygen and other wastes).
Single celled organisms have a large surface-area-to-volume ratio so they can exchange the necessary gases,
nutrients and wastes.…read more

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Cells, Exchange and Transport
(e) describe the functions of
cartilage,
Structure.
Holds the trachea and bronchi open
Prevents collapse when the air pressure is low during inhalation
cilia,
Move in a synchronised pattern to waft mucus up the airway to the back of the throat. Once there, the mucus
is swallowed and the acidity of the stomach will kill any bacteria
goblet cells,
Secrete mucus.…read more

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