Chapter_47 - Chapter 47 ELEMENTS OF BIOLOGY Biology is the science of life The word microbiology refers to the observation of biological systems in

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1 Chapter 47 – ELEMENTS OF BIOLOGY Biology is the science of life. The word microbiology refers to the observation of biological systems in the optical (micrometer) size scale. Molecular biology is the science of biology at the molecular level. The new term nanobiology could refer to investigations in the nanometer scale. This is our focus. 1. CELL BIOLOGY Understanding the cell drives a great deal of biology research. Microbiology is moving from a mode driven by clinical research to new developments in bio-genetics. The human genone has been mapped out some ten years ago. The 23 pairs of chromosomes contain DNA which codes for around 23,000 protein-coding genes involving some 3 billion base pairs. These control the synthesis of all proteins. The order of the nucleotides in DNA controls the order of amino acids in protein synthesis. Proteins perform most of the biological functions essential for life (Becker et al, 1999). Cells contain organelles which perform specific functions. One of these, the nucleus, contains the DNA double helix packed into the chromosomes. The same DNA is contained in every nucleus of every cell in the body. Cell division involves DNA replication whereby new copies are made. Cells are bounded by a membrane with a hydrophobic interior and a hydrophilic exterior. Lipids are surfactant-like molecules containing (hydrophobic) hydrocarbon tails and polar (hydrophilic) head groups; lipids form the cell membrane. Special proteins help in the transport of essential ingredients into and out of the cell. The passage of small molecules (such as CO 2 and H 2 O) and of essential ionic groups also occurs. The interplay of hydrophobic and hydrophilic interactions is a major diving force in the working of membranes, in the assembly of cellular structures as well as in the folding of macromolecules such as DNA and proteins. Proteins are folded into helical and sheet portions in their active form which is essential for specific functions. Polysaccharides perform storage and structural functions in cells. Starch and cellulose are typical plant polysaccharides. They are formed of repeating sugar glucose units. 2. LIPIDS The simplest components of a cell are the lipid molecules forming the membranes. These are amphiphile (surfactant) molecules with hydrophilic head groups and hydrophobic tails. Membranes surround the cell as well as the organelles inside the cell. Proteins form channels across the membrane and other structures in membranes.
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2 Figure 1: Schematic representation of a membrane. Lipids are formed from a glycerol backbone and fatty acid side chains. These two undergo a condensation reaction that removes a water molecule. Figure 2: Reaction that forms lipids. One specific lipid corresponding to a C17 hydrocarbon tail is included here.
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This note was uploaded on 02/03/2011 for the course BIO 5A taught by Professor Zhu/cardullo/rao during the Fall '08 term at UC Riverside.

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Chapter_47 - Chapter 47 ELEMENTS OF BIOLOGY Biology is the science of life The word microbiology refers to the observation of biological systems in

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