Cell Biology

CELL BIOLOGY

Modern cell theories
 All living matter is composed of cells  All new cells arise from other cells  All metabolic reactions of an organism take place in cells  Cells contain the hereditary information of the organisms of which they are a part, and

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 All cells are similar in comprising a selfcontained and more or less self-sufficient unit, surrounded by a cell membrane and having a nucleus at some stage of their existence.  At the same time cells show a remarkable biodiversity of structure and function.

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 Cells are basically spherical in shape, although modification to suit function leads to a degree of diversity  In size, they mostly range from 1030µm in diameter  Their size is restricted by:
 The surface area to volume ration, which must be large to allow exchange of metabolic substances  The capacity of the nucleus to exercise control over the rest of the

THE DISCOVERY OF CELLS

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MICROSCOPE
 To observe the dramatic properties of a single cell  Visible parts of the cell  Light microscope - achieve magnifications of up to 1500  Electron microscope- over 500,000 times
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Comparison of light and electron microscopes
Light microscope Advantages Cheap to purchase and operate Small and portable Unaffected by magnetic fields Preparation of material is relatively quick and simple Living as well as dead material may be viewed Natural colour can be observed Electron microscope Disadvantages Expensive to purchase and operate Very large and must be in special room Affected by magnetic field Preparation of material is lengthy and complex Living material cannot be observed All images in black and white

Image by microscopes
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Light microscope

Electron microscope

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Light microscope Disadvantages Magnifies object up to 1500x Can resolve objects up to 200 nm apart The depth of field is restricted Electron microscope Advantages Magnifies objects up to 500,000x Has a resolving power for biological specimens of around 1 nm It is possible to investigate a greater depth of field

BASIC CELL POPERTIES

Cells are highly complex and organized
 Cellular activities remarkably precise  Eg DNA duplication (error rate 1 in 10 million nucleotides incorporated)  Organizations: atom, molecules, polymers, polymeric molecules, subcellular organelles, and finally into cells  From cells into tissues, organ and system

 Organisms are built accoding to information encoded in a collection of genes  A set of chromosomes that occupies th space of a cell nucleus  Genes are more than storage lockers for information  They constitute the blueprints for constructing cellular structure, the directions for running cellular activities and the program for making more of themselves

Cells possess a genetic program and the means to use it

 Reproduce by division, a process in which the contents of a mother cell QuickTimeª and a are distributed into two TIFF (Uncompressed) decompressor cells daughter are needed to see this picture.  Prior to division, genetic material is duplicated, and each daughter cells receives complete and equal share of genetic information  In certain cases (eg oocyte), the cells retain

Cells are capable of producing more of themselves

Cells acquire and utilize energy
 Developing and maintaining complexity requires the constant input of energy  The energy from sunlight is trapped by light-absorbing pigments present in the membranes of photosynthetic cells  Light energy is then converted into chemical energy that is stored in energy-rich carbohydrates  ATP is produced when breakdowns

Cells carry out a variety of chemical reactions
 Chemical changes which require enzymes  The biochemical reactions - cell’s metabolism

CELLULAR BIOCHEMISTRY AND PHYSIOLOGY
 Knowledge of the submicroscopic molecular pattern of the protoplasm is necessary to comprehend the structure and function of cells  Biochemistry  Describe and analyze the chemical changes that occur in organisms  Investigations into the chemistry of living systems have shown that individual cells, whether of plants, animals and microorganisms, are fundamentally

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 Physiology  response of organisms and cells to their environment,  mechanism of cell growth,  duplication, and reproduction,  ability of cells to take up nutrients from the environment,  function and method of control of an organism’s metabolic machine

CYTOLOGY
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 A study of cells  Two basic types prokaryotic and eukaryotic cells

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MOLECULAR ORGANISATION

ATOM
 Smallest unit of a chemical element which can exist independently QuickTimeª and a TIFF (Uncompressed) decompressor  It are needed to see this picture. has a nucleus made up of  Positively charged particles - protons  Particles with no charge - neutrons  Around this positively charged nucleus orbit negatively charged

IONS

 When an atom loses an electron (a process called oxidation), it becomes positively charged due to the excess of protons over electrons QuickTimeª and decompressor TIFF (Uncompressed) a picture.  A positive ion are needed to see this