The word macromolecule refers to a small molecule of low molecular weight and is often referred to as a monomer

Unit 6. Proteins.

1. 
   Basing on your knowledge answer the following questions in brief.
   

Do you know the difference between micro molecules and macromolecules?
The word macromolecule refers to a small molecule of low molecular weight and is often referred to as a monomer.
Макромолекулы имеют низкую молекулярную массу и содержат небольшое количество атомов. Микромолекулы регулируют различные биологические процессы.
How big is the molecule of protein?
Proteins are large molecules with high molecular weights (from about 10,000 for small ones [of 50–100 amino acids] to more than 1,000,000 for certain forms); they are composed of varying amounts of the same 20 amino acids, which in the intact protein are united through covalent chemical linkages called peptide bonds.
Why are proteins so important for living organisms? What are their functions?
Our body consists of thousands of different proteins, each of which performs a specific function. They make up the structural components of our cells and tissues, as well as many enzymes, hormones and active proteins secreted by immune cells. These body proteins are constantly being restored throughout our lives. This process (known as ’protein synthesis') requires a constant supply of amino acids. Although some amino acids can be recycled as a result of the breakdown of old body proteins, this process is imperfect. This means that we must consume dietary protein in order to keep up with our body's need for amino acids.

2. 
   Read and translate the text.
   

What are proteins?

Proteins are linear, unbranched polymers constructed from 20 different α-amino acids that are encoded in the DNA of the genome. All living organisms use the same 20 amino acids and the same genetic code. Proteins are large molecules with molecular weight ranging from 10 to 50 kdal for single-chain proteins. Multichain proteins of 150 to 200 kdal are frequently encountered.

Proteins serve a wide range of functions in living organisms. They are involved in the following processes:

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  enzymatic catalysis - all known enzymes are proteins;
  

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  transport and storage of small molecules and ions;
  
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  systematic movements - both striated and smooth muscle are composed chiefly of protein, as are structures involved in the motility of certain free-living cells;
  
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  the structure of skin and bone -collagen, the most abundant protein in body, gives these structures high tensile strength;
  
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  the immune defense system - antibodies are specialized proteins recognizing self and nonself;
  
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  hormonal regulation - some hormones are proteins; the cellular receptors that recognize hormones and neurotransmitters are proteins;
  
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  control of genetic expression - repressor molecules in bacteria are proteins that suppress certain DNA sequences; protein initiation and termination factors serve in the transcription phases of gene function.
  

Proteins show an exquisite specificity of biologic function – a consequence of the uniqueness of the three-dimensional structural shape, or conformation, of each protein. In humans, disease states are often related to the altered function of a protein. This is due to an anomaly in the structure of the protein, which in turn may be due to a deficiency in its synthesis.
Amino acids. The fundamental units of protein polymers are α-amino acids. They are composed of an amino group, a carboxyl group, a hydrogen atom, and a distinctive side chain, all boned to a carbon atom. One of the 20 amino acids, proline, is an amino acid, not an α-amino acids as are the other 19. A few other amino acids are found in a number of proteins but are not coded for in DNA; they are derived from one or another of the 20 fundamental amino acids after these have been incorporated into the protein chain (post-translational modification).