TOPIC 2B — PROTEINS AND GENETICS Flashcards
What are proteins made of?
The monomers of proteins are amino acids. A dipeptide is formed when two amino acids join together.
A polypeptide is formed when more than two mino acids join together. Proteins are made up of one or more polypeptides.
What are amino acids made from?
A carboxyl group (-COOH), an amine group (-NH2) and a carbon containing R group.
How many amino acids are there in living things?
20 amino acids. The only difference between them is what makes up their carbon-containing R group.
How are polypeptides formed?
Amino acids are linked together by condensation reactions to form polypeptides. A water molecule is released during the reaction. The bonds formed between amino acids are called peptide bonds.
What is the primary structure?
The sequence of amino acids in the polypeptide chain.
What are the four structural levels in a protein?
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
What is the secondary structure?
Hydrogen bonds formed between amino between the amino acids in the chain. This makes it automatically coil into alpha helix or fold into a beta pleated sheet.
What is the tertiary structure?
More bonds form between different parts of the polypeptide chain, including hydrogen bonds and ionic bonds. Disulphide bonds can also form. For proteins made from a single polypeptide change the tertiary structure forms their final 3D structure.
What is the quaternary structure?
Some proteins are made of several different polypeptide chains held together by bonds. The quaternary structure is the way these polypeptide chains are assembled together. For proteins made from more than one polypeptide chain (e.g. haemoglobin, insulin, collagen), the quaternary structure is the protein’s final 3D structure.
What are the kind of bonds in the primary structure?
Held together by the peptide bonds between the amino acids.
What are the kind of bonds in the secondary structure?
Held together by hydrogen bonds.
What are the kind of bonds in the tertiary structure?
Ionic bonds. These are attractions between the negative nd positive charges on different parts of the molecule.
Disulphide bonds. When two molecules of amino acid cysteine come closer together, the sulphur atom in one cysteine bonds to the sulphur in the other cysteine.
Hydrophobic and Hydrophilic interactions. When hydrophobic groups are close together in the protein, they tend to clump together, Meaning that the hydrophilic groups are more likely to be pushed to the outside.
Hydrogen bonds.
What are the kind of bonds in the quaternary structure?
Tend to be determined by the tertiary structure of the individual polypeptide chains being bonded together.
What does the amino acid sequence of a protein determine?
What bonds will form and how the protein will fold up into its 3D structure, e.g. if there are many cysteines, these will form disulphide bonds with each other, protein will form in a certain way.
What does the 3D structure of a protein determine?
Its properties. Properties relate to its function in the body.
What is the structure of a globular protein?
Globular proteins are round, compact proteins made up of many polypeptide chains.
What is the property of a globular proteins?
Soluble as the chains are coiled up so that the hydrophilic parts of chains are on the outside of the molecule and hydrophobic parts of chains face inwards.
What is the function of globular proteins?
E.g. Haemoglobin is a globular protein made of four polypeptide chains. Carries oxygen around the body in blood. It’s soluble so it can be easily transported in blood. Has iron-containing haem groups that bind to oxygen.
What is the structure of a fibrous proteins?
Fibrous proteins are made up of long, insoluble polypeptide chains that are tightly coiled around each other to form a rope shape.
What is the property of a fibrous protein?
Chains are held together by lots of bonds (e.g. disulphide and hydrogen bonds), which make the protein strong. As they are strong fibrous proteins are often found in supportive tissue.
What is the function of a fibrous proteins?
E.g. Collagen is a strong, fibrous protein regar forms connective tissue in animals.
What is an enzyme?
Enzymes are proteins which act as biological catalysts and catalyse metabolic reactions. Enzymes can be intracellular (catalyse reactions inside cells) or extracellular (produced and secreted by cells to catalyse reactions outside cells.
What happens to the enzyme’s active site?
Enzymes have an active site, which has a specific shape. The active site is the part of the enzyme where the substrate molecules bind to. Enzymes are highly specific due to their tertiary structure.
What is the activation energy?
The certain amount of energy that needs to be supplied to the chemicals before the reaction will start. Often provided as heat.
