Foundation biology

  • Subject: Biology
  • Level: AS
  • Exam board: All boards
  • Author: sandy
  • Year created: 2008

notes on foundation biology

Preview of Foundation biology

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BIOLOGY.
FOUNDATION BIOLOGY
All living cells are made up of one cell (unicellular) or more cells (multicellular).
Metabolic processes take place within cells.
New cells are derived from existing ones.
Cells posses the genetic material of an organism which is passed from one parent cell to the
daughter cells.
A cell is the smallest unit of an organism capable of surviving independently.
Microscopy
Magnification = size of image/size of object.
Resolution is the minimum distance two objects can be in order for them to appear as separate
items.
The greater the resolution the more precise the image produced.
Increasing the magnification will increase the size of the image but does not always increase the
resolution.
Light microscope
Compound light microscope.
Condenser lenses located beneath the microscope stage and can be adjusted in height to
ensure that light is focused on the specimen being examined. This allows the resolving power of
the microscope to be used to its full effect.
The objective lenses produce an initial magnified image of the specimen.

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The eyepiece lenses further magnify the image produced by the objective.
Animal cell
Cell surface membrane a thin protein and phospholipids bilayer that controls the movement of
materials in and out of the cell.
Cytoplasm watery material with a jellylike consistency.
Nucleus made up of jellylike nucleoplasm, the nucleolus and chromatin.
Mitochondria tiny rodshaped structures within which the reactions of aerobic respiration occur.
Centriole a hollow cylinder involved in cell division.
Cytoplasmic granules small particles that act as a store of carbohydrate.

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Developed because light microscope has poor resolving power.
Uses beam of electrons.
Short wavelength and therefore could resolve objects well it had high resolving power.
As the electrons are negatively charged the beam could be focused using electromagnets.
Two types of electron microscope. Transmission Electron Microscope (TEM) Scanning Electron
Microscope (SEM).
TEM
Consists of an electron gun that produces a beam of electrons by heating a tungsten filament.

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Gives a 3d image by computer analysis. Resolving power is less than the TEM.
Environmental scanning electron microscope
One major disadvantage of electron microscopes is that the removal of water from the
specimen during its preparation and the vacuum in which it is observed prevent the specimen
being observed in its natural wet state.
This disadvantage can be overcome by using an environmental scanning electron microscope.
Specimen is kept at a much lower vacuum than the rest of the instrument chamber.

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Nucleolus is a small spherical body within the nucleoplasm. It manufactures ribosomal RNA
and assembles ribosomes.
The functions of the nucleus are to:
act as the control centre of the cell through the production of mRNA and protein synthesis.
retain the genetic material of the cell in the form of DNA/chromosomes.
start the process of cell division.
Chloroplasts
Chloroplasts are found in eukaryotic cells which photosynthesise.

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The stalked particles contain enzymes involved in the synthesis of ATP.
matrix makes up the remainder of the mitochondrion. It is a semirigid material containing
protein, lipids, and traces of DNA that allow them to control production of their own proteins. The
enzymes involved in Krebs cycle are found in the matrix, as are mitrochondrial ribosomes.
Are the sites for the Krebs cycle and stages of respiration. They're therefore responsible for
production of ATP molecules from carbohydrates.

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Each ribosome has two subunits one large and one small each contains ribosomal RNA and
protein. There's loads of them, account for 25% of a dried cell.
Important for protein synthesis.
Golgi Apparatus
Occurs in almost all eukaryotic cells and is similar to SER in structure, except that it is more
compact.
It consists of a stack of membranes which make up flattened sacs, or cisternae and associated
with vesicles.

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Up to 50 such enzymes may be contained in a single
lysosome.
Up to 1 micrometer in diameter, lysosomes isolate these potentially harmful enzymes from the
rest of the cell, before releasing them, either to the outside or into a phogcytic vesicle within the
cell.
They:
break down material igested by phagocytic cells such as white blood cells or Amoeba sap.
Release enzymes to the outside of the cell (exocytosis) in order to destroy material around the
cell.

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Cillia
Threads that extend from the cell surface. Only a few types of cells posses it. Produce wave like
motion across the surface of the cell.
It:
moves an entire organism, e.g. cillia on the surface of the protocist propel it through the water.
to move material within an organism, e.g. cillia lining the respiratory tract of mammals move
mucus towards the throat, and cillia lining the oviduct move the secondary ovum towards the
uterus.

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Bacteria occur in every habitat in the world. They are versatile, adaptable and successful, much
of their success is a result of their small size, normally in the range of 0.110 micrometers in
length.
Their cellular structure is relatively simple. All bacteria posses a cell wall which is made up of
peptidoglycan (murein) a polysaccharide crosslinked by peptide molecules. Around this wall
many bacteria further protect themselves by excreting a capsule of mucilaginous slime.

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