Protein Notes Study Notes

Protein Notes • • • • There are few common secondary structures that can occur. The most common ones involve hydrogen bonds. Secondary structures can be something like alpha helix. These are very common in proteins as well as pleated sheets. We put all secondary structures we get the tertiary structure. Only some proteins not all have quaternary structures. This may occur when more than one protein combines. It can be from the same type or from different types of protein. Post-translational modifications • • • Change the structure and function of the coded protein. The idea is once the protein has been made, there are lots of things that can happen to that protein. - Enzymes will come along and do things to that protein that will change its shape and change its function. Lots of protein misfolding protein diseases result from inappropriate posttranslational modifications. - Cancer is one of these side effects Post-translational modifications • When we decide to transcribe this gene into mRNA it can be cut up in different ways. This is called post-translational modifications. If we cut up the mRNA in different ways, we get different codes, so we get different strands of amino acids. - Once we have that string of amino acids, then we have the post translational modifications. - Lots of things can happen to that protein to make it function in different ways. Protein structure Secondary: • • • The protein chains can fold into two types of secondary structures, stabilised by hydrogen bonds. A protein chain can fold into a rigid alpha helix, forming regular patterns of hydrogen between the backbones of near by amino acids. Backbone atoms of the chain can interact side by side to form beta sheets. Tertiary: • • • Many proteins fold into a compact globular shape, with hydrophobic side chains sheltered inside away from the surrounding water. The functions of many proteins rely on this folded structure. For instance, haemoglobin forms a pocket to hold heme, a small molecule with an iron atom in the centre that binds oxygen. Quaternary • • Two or more polypeptide chains can come together to form one functional molecule with several subunits. The four subunits of haemoglobin cooperate so that complex can pick up more oxygen in the lungs and release it in the body. Molecule shape and function • • • • • Many proteins rely on the ability to organise the shape of a specific molecules in order to function correctly. The flexible arms of the antibodies protect the body from disease by recognising and binding to foreign molecules and thus preventing the viral RNA or DNA to enter the cell. Collagens forms a strong triple helix that is used throughout the body for structural support. The calcium pump moves ions across the cell membranes allowing the synchronised contractions of muscle cells. The hormone insulin is small, stable protein that can easily maintain its shape while travelling through the blood to regulate blood sugar levels. Alpha amylase is an enzyme with a catalytic site that begins the breakdown of carbohydrates in our saliva. Amino Acids • • We can make a lot of amino acids, but some we have to eat and if we don’t them then we will die. Breakdown: - Oxidised to urea and CO2 Amino group enters the urea cycle. If you eat too much meat, then we will have too much urea and then you will get urea crystals in your joints, that goes Keto. Keto acid enters to Krebs cycle. Different protein functions • Globular – enzymes, hormones • Fibrous – connective tissue, bone, hair (long and hard) • Membrane – neuronal receptors, cell adhesion molecules