Summary of Textbook Section 5.4

Assignment:
Write a summary of 5.4

Section 5.4: Proteins perform most functions in cells


defining key terms

• protein: polymer constructed from a set of 20 amino acid monomers
• amino acid: monomer that makes up proteins; contains carboxyl and amino functional groups
• polypeptide: chain of linked amino acids
• denaturation: loss of normal shape of a protein due to heat or other factor

Functions of proteins

• vital in life
• form hair and fur
• make up muscles
• long-term nutrient storage
• circulate in blood, defend body
• conveying cellular messages
• controls chemical reactions of cell

Amino acids structure

• central carbon atom w/ 4 bonds
• 3 of 4 bonds same between all amino -> H, amino group, carboxyl group
• last link called "R-group"
• R-group is responsible for chemical properties of amino acid

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Protein structure

• one or more chain of amino acids
• links created by dehydration reaction of amino and carboxyl groups of each amino
• huge variety by differing orders of aminos

20 amino acids kinds, 100 amino in protein chain

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Factors of protein shape

• a single protein not much use, functional when one or more polypeptides precisely twisted, folded, coiled into unique shape
• not clear how protein bends with such precision
• sequence of amino acids are important -> bonds of differing side groups, holds polypeptide together
• influenced by surrounding -> if aqueous, hydrophilic aminos parts surround, hydorphobic amino parts cluster in center
• denaturation, protein loses shape and tangled with other chain because heat, pH, etc
• some links of amino parts weak, heat colliding, takes apart
• function of protein being by shape, denaturation render protein useless
  

image of protein
image from: http://www.epobio.net/photos/protein_structure.jpg

Concept check:

1. 2 examples of proteins you can see in the world around you. Well, protein itself would be too small to see by itself. However, if you refer to visible objects formed by protein, two examples would be human hair and dog fur. If you'd like to group them together, I recommend dissected flog muscle tissue. Of course, the species are of your choice.
   
2. Relate amino acids, polypeptides, and proteins. A protein is a polymer of 100 amino acids linked together, and a polypeptide the unit in which protein gets useful. Polypeptides are protein chains twisted and coiled.
   
3. How can heat destroy protein? Protein being amino acids connected by the relatively weak bonds of the amino and carboxyl group on the ends of aminos acids, heat colliding with the weak links can break them apart; thus, rendering the protein useless towards its original purpose.
   
4. Similar and dissimilar parts in amino acids? Amino acids share the central C atom, along with the H and amino and carboxyl functional groups. The differing part is the R-group.