Proteins
More work needs to be done on this document. Also amino acids need to be linked to RNA and ribosomes.
Almost everything in the human body is protein: muscles, hemoglobin, cartilage, collagen, keratin (in hair and nails, as well as in claws, scales and feathers), enzymes, fibrin (for blood clotting), and crystallin (in the ocular lens).
Some things that are NOT proteins are bones, fat, cell membranes (phospholipid bilayers), molecules used for energy (sugar, starch, fat) and molecules used signaling.
Some hormones are proteins (e.g. insulin, oxytocin, human growth hormone), others are based on steroids (testosterone) or one amino acid (melatonin, adrenaline).
Many proteins cause chemical reactions to happen. These proteins are called enzymes and their names end in –ase.
Any time a molecule name ends in –ase, it is a protein enzyme. (e.g. helicase) Some enzymes (e.g. DNA polymerase) are formed of groups of three or more different sub-enzymes that all work together as one giant enzyme.
Proteins are made from amino acids connected into one string like a bead necklace. This is similar to a polymer. Proteins are chains that are typically 1000 to 30,000 amino acids long.
<show images of children’s bead toys>
There are 20 amino acids that human beings need to make protein. Our bodies can make 10 of them, but the other 10 need to come from eating meat (or other protein). If we just had 19 different amino acids we wouldn’t be able to make all of the different types of proteins that we need.
« Unlike polymers, proteins
(i) are never branched: they are always one single chain
(ii) have a number of different smaller molecules that make them up, and these molecules (amino acids) must be in an exact specific order
(iii) have a special shape that enables them to perform their purpose (the single chain wraps into complicated shapes (kind of like a string to a knot)
« Random chains of amino acids are completely useless. They must be assembled in a specific order.
« Amino acids also do not polymerize naturally: they need a catalyst – a protein enzyme.
Proteins are often depicted as strings of beads of different colours as they are made. This simplification obscures the complicated chemical formula.
« Most proteins’ usefulness depends solely on their shape.
« Other enzymes are also needed to fold proteins to the proper final shape.
· Show pictures of proteins <hexokinase from protopedia> <do Jmol popup>
· Show pictures from the cellular biology folder.
· Show HIV virus video. Ask class to think of ways to stop the virus.
Amino Acids à
The rate of protein synthesis is higher in prokaryotes than eukaryotes and can reach up to 20 amino acids per second.
Show Wikipedia: hexokinase (from protein page)
Protein structure
Primary structure: chain
Secondary structure: alpha helix or beta sheets
Tertiary: structure – linkages and other bonding (when folded)
Quaternary structure: some proteins have 2 or more sub proteins together. (e.g. hemoglobin)