What are proteins?
What this introductory video to understand the importance of proteins for organism. On your sheet, take notes and answer the questions.
Generalized structure of amino acids Some selected amino acids from the 20 known ones:
Do you recognize the general structure in all of these amino acids?
Condensation reactions forming dipeptides ....and longer amino acid
chains
Condensation
When two amino acids join together in a condensation reaction to form a dipeptide, the –OH of the carboxyl group combines with the –H of the amino group of the second amino acid and a peptide bond is formed.
Condensation reactions forming dipeptides
....and longer amino acid
Draw the condensation reaction between two amino acid chains to form a dipeptide:
chains
Two amino acids form a dipeptide, an amino acid chain which contains up to 20 amino acids is called oligopeptide. Anything more is called a polypeptide. A combination of polypeptides is called a protein.
Condensation reactions forming dipeptides ....and longer amino acid
chains
Multiple condensation reactions will result in the formation of a polypeptide
Insulin is a small protein that contains two polypeptides, one with 21 amino acids and the other one with 30. The largest polypeptide known is called titin, which in humans contains 34 350 amino acids. Titin is a protein part of
Condensation reactions forming dipeptides ....and longer amino acid
chains
Dietary requirements for amino acids
Essential amino acids cannot be synthesized and must be obtained from food. Non essential amino acids can be made from other amino acids.
9 essential amino acids (out of 20 amino acids that exist) have to come from our nutrition. Many of those are found in animal or dairy products. Vegans need to replace those with plant based sources.
https://www.myclinicalnutrition.com/blogs/details/2864a31a-9bba-4ef6-b0ad-b6fb2690d
https://swolverine.com/blogs/blog/essential-vs-nonessential-amino-acids
Infinite variety of possible peptide chains
The amino acid sequence of each polypeptide is stored in a coded
form in the base sequence of a gene.
Protein synthesis is accomplished in 2 stages:
Polypeptide synthesis occurs at ribosomes
Amino acids are linked together by peptide bonds forming long chained polypeptides. The synthesis of these polymers occurs at ribosomes.
Infinite variety of possible peptide chains
Amino acids are added one by one to form a polypeptide. They are always added in the same sequence to make a particular polypeptide
https://upload.wikimedia.org/wikipedia/commons/thumb/c/c9/Main_protein_structure_levels_en.svg/2000px-Main_protein_structure_levels_en.svg.png
Depending on the type of amino acid used – each with a specific characteristic according to their R-groups (polar, non-polar, charged, etc) will cause an interaction within the amino acid sequence, and therefore a specific three dimensional constellation.
Infinite variety of possible peptide chains
Amino acids can be linked together in any sequence
giving a huge range of possible polypeptides.
A polypeptide is composed of a specific number and sequence of amino acids in a polypeptide. Most polypeptides consist of between 50 and 1000 amino acids.
The structure of the amino acid chain is determined by the base sequence of the gene that codes for the poly-peptide.
Infinite variety of possible peptide chains Calculate the polypeptide diversity by working out
the missing numbers:
Ribosomes link amino acids together one at the time until a polypeptide is fully formed. The peptide bonds can occur between any pair of amino acids, so any sequence is possible.
The number of possible amino acid sequences can be calculated starting with dipeptides. Both amino acids in a dipeptide can be any of the 20, so there are 20x20 (or 202) possible sequences.
If a polypeptide has 400 amino acids, there are 20400 possible amino acid sequences.
Infinite variety of possible peptide chains
Haemoglobin
Haemoglobin is a protein composed of 4 polypeptides (2 alpha and 2 beta globin chains) which is found in red blood cells.
It’s main function is to transport oxygen around the body.
Infinite variety of possible peptide chains
Immunoglobulin
Immunoglobins are also called antibodies in the immune/defense system. They are produced by white blood cells (B-cells) and function by binding to antigens (foreign proteins structures) on bacteria or pathogens.
Infinite variety of possible peptide chains
Rhodopsin
*
Found in the retina of the eye
*
Light sensitive pigment of rod cells
*
Absorbs photons of light, and changes
its shape in response to this
*
The change in shape causes a nerve
impulse to be sent to the brain.
Infinite variety of possible peptide chains
Collagen
http://www.botanicskinessentials.com/wp-content/uploads/2013/07/what-does-a-skin-toner-do.jpg?676951
*
Proteins in the cells which form the dermis of skin
*
Rope-like, fibrous protein with three polypeptides wound together
*
Very abundant
*
Forms a mesh of fibres in skin and
blood vessel walls that resist tearing.
*
Also, a structural component in teeth,
bones and tendons
Infinite variety of possible peptide chains
r/
Keratin
https://www.healthshots.com/beauty/natural-cures/5-home-remedies-for-smooth-hai
Keratin is a fibrous protein composed of two polypeptide chains. Equipped with high tensile strength it is found in hair, nails, claws and hooves as a structural component and building block.