Proteins (2.4)

Proteins (2.4)

1. Functions

   • Catalysts-Enzymes: They cut and paste molecules
   • Muscle contraction
   • Cytoskeletons: help the skeleton of cells keep their form
   • Tensile strenghtening: proteines give strength and resistance to our muscles so that if our (example) ankle bends, it does not break
   • Blood clotting
   • Transport of nutrients and gases
   • Cell adhesion: cells stick to each other
   • Immunity​
   • Membrane transport​: getting things in and out of the cell
   • Hormones​: (example) insuline
   • Receptors​: recieving messages from other parts of the body
   • Packing of DNA: DNA curls around the protein

2. Examples

   • Rubisco
     • Function: catalyse the reaction that fixes CO2 from the atmosphere
   • Insulin​
     • Function: signal cells to absorb glucose and help reduce glucose concentration in blood
   • Immunoglobulin​
     • Function: fight off bacteria and pathogens
   • Rhodopsin​
     • Function: recept light through the eye
   • Collagen​
     • Function: 1) help prevent cracks and fractures in bones and teeth, 2) form a mesh of fiber in the skin and blood vessel walls that resists tearing, and3) strengthen ligaments and blood vessel walls
   • Spider silk
     • Function: create the spokes of the spider web and the spider's lifelines. It also makes the silk extensible and resistant to breaking

3. Basics of proteins

   • The sequence of amino acids is determined by genes. This means that the genes are the cake recipe and the amino acid structure is the cake.
   • Amino acids can be combined in any way
   • Every individual has a unique proteome: set of proteins expressed in an organism.​
   • What are proteins?
     • Proteins are made of amino acids, they are the basic unit
       • Amino acids are combined by condensation to form polypeptides
         • This process happens in ribosomes
         • http://www.thevitaminmag.com/amino-acids-benefits/​
   • Charges
     • It can be either positive, negative or non-charged
     • This determines the interaction between amino acids
     • Polar (when they are charged) are going to attract the opposite and repel the equal charge (like a magnet)
   • Structure
     • http://www.thevitaminmag.com/amino-acids-benefits/​
   • Proteins and water
     • Hydrophobic
       • This kind of amino acids don't like water and therefore are likely to be found in the inside part of a protein's structure
     • Hydrophilic
       • This kind of amino acids like water and therefore are likely to be found in the outside part of a protein's structure
   • Changes in PH and heat damage proteins

4. Structure and formation of proteins

   • Primary structure: Amino acids are joined by condensation, therefore forming peptide bonds. In this stage, the sequence of amino acids is formed
   • Secondary structure: in this stage, the protein starts to take a 3D shape. This means that in the secondary structure, chains of polypeptides are forming 3D structures that are often found as helical shapes.
   • Tertiary structure: In this structure is where most of the proteins start to become functional. On this stage, the previously formed helix and pleated sheets are combined to form complex structures.
   • Quaternary structure: Only some proteins have this stage. What happens is that two or more polypeptides are folded and assembled like a puzzle

5. A protein's from and its properties

   • When the protein is already 3D and functional it acquires maily 2 shapes
     • Rope like (fibrous protein)
       • Long and narrow
       • Role: structural (strengthening and support)
       • Mostly insoluble in water
       • Repetitive sequence of amino acids
       • Less sensitive to changes in PH and heat
       • Examples: Collagen and keratin
     • Ball like (globular protein)
       • Rounded or spherical
       • Role: Functional (catalysts and transport)
       • Mostly soluble in water
       • Irregular amino acid sequence
       • More sensitive to changes in heat and PH
       • Examples: Hemoglobin and insulin

6. Denaturation

   • A structural change in a protein that results in the loss (usually permanent) of its biological properties.
   • It is a process that involves the breaking of weak bonds.
   • It can be caused by exposition to extreme heat and pH (both, too low and too high)

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