* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Polymers and Amino Acids
Survey
Document related concepts
Western blot wikipedia , lookup
Citric acid cycle wikipedia , lookup
Protein–protein interaction wikipedia , lookup
Size-exclusion chromatography wikipedia , lookup
Point mutation wikipedia , lookup
Ribosomally synthesized and post-translationally modified peptides wikipedia , lookup
Fatty acid metabolism wikipedia , lookup
Fatty acid synthesis wikipedia , lookup
Metalloprotein wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Peptide synthesis wikipedia , lookup
Genetic code wikipedia , lookup
Protein structure prediction wikipedia , lookup
Amino acid synthesis wikipedia , lookup
Biosynthesis wikipedia , lookup
Transcript
1 of 36 © Boardworks Ltd 2010 2 of 36 © Boardworks Ltd 2010 What are polymers? A polymer is a long molecular chain built from monomer units. The two main types of polymer are addition and condensation. Feature Addition polymer functional group(s) of monomer(s) Condensation polymer Polyester Polyamide C═C –COOH and –OH –COOH and –NH2 types(s) of monomer 1 1 or 2 1 or 2 product(s) poly(alkene) polyester + water polyamide + water 3 of 36 © Boardworks Ltd 2010 What are addition polymers? During addition polymerization, unsaturated molecules add together forming a polymer. Formation of poly(propene): Formation of poly(chloroethene) (PVC): 4 of 36 © Boardworks Ltd 2010 Naming addition polymers Addition polymers are named after the monomer used to make them: is prepared from ethene poly(ethene) is prepared from poly(propenenitrile) 5 of 36 propenenitrile © Boardworks Ltd 2010 Common addition polymers 6 of 36 © Boardworks Ltd 2010 Naming addition polymers 7 of 36 © Boardworks Ltd 2010 Disposal of addition polymers The unreactivity of addition polymers, which makes them useful for storing food and chemicals, means they are not biodegradable and persist in the environment for many years. Incineration of addition polymers is controversial as it produces carbon monoxide and carbon (soot), as well as carbon dioxide, contributing to global warming. Polymers can also produce toxic chemicals when burnt. For example, PVC produces hydrogen chloride, and nylon produces hydrogen cyanide. 8 of 36 © Boardworks Ltd 2010 9 of 36 © Boardworks Ltd 2010 What are condensation polymers? Condensation polymers, such as polyesters and polyamides, are formed by a condensation reaction, which releases small molecules such as water. Polyesters can be formed from monomers of: a dicarboxylic acid (a carboxylic acid with two –COOH groups) and a diol (an alcohol with two –OH groups) substances containing both –COOH and –OH groups. Polyamides can be formed from monomers of: a dicarboxylic acid and a diamine (an amine with two NH2 groups) amino acids, which contain both –COOH and –NH2 groups. 10 of 36 © Boardworks Ltd 2010 Formation of polyesters 11 of 36 © Boardworks Ltd 2010 Formation of polyamides 12 of 36 © Boardworks Ltd 2010 Disposal of condensation polymers Unlike addition polymers, which don’t readily degrade, condensation polymers can be designed that biodegrade, photodegrade or which can be recycled. Condensation polymers biodegrade by hydrolysis, which is the reverse of the condensation reactions that form them. Some condensation polymers, such as nylon, degrade very slowly, which is necessary for them to be useful. Condensation polymers such as poly(lactic acid) have been designed to biodegrade more quickly and are used in disposable plastic items such as packaging. 13 of 36 © Boardworks Ltd 2010 Hydrolysis of polyesters The hydrolysis of polyesters with pure water is too slow to be useful, so an acid or base catalyst is required. acid hydrolysis: reflux with dilute H+ (e.g. HCl, H2SO4) base hydrolysis: reflux with dilute NaOH Hydrolysis with a base is preferable as it is not a reversible reaction like hydrolysis with an acid. 14 of 36 © Boardworks Ltd 2010 Hydrolysis of polyamides Polyamides can be split into their constituent carboxylic acids and amines by hydrolysis with a hot aqueous acid or base. acid hydrolysis: reflux with dilute H+ (e.g. HCl, H2SO4) base hydrolysis: reflux with dilute NaOH 15 of 36 © Boardworks Ltd 2010 Recycling polymers Some polymers, such as PET, are widely recycled. This reduces the amount of plastic disposed of in landfill sites and conserves crude oil, which is the source of most of the monomers used. Some polymers are simply melted and reused but condensation polymers can be hydrolyzed back to form monomers. The disadvantage of recycling is that the plastics must be collected, sorted and processed, which is expensive. 16 of 36 © Boardworks Ltd 2010 Polymers summary 17 of 36 © Boardworks Ltd 2010 Type of polymerization 18 of 36 © Boardworks Ltd 2010 Which polymer? 19 of 36 © Boardworks Ltd 2010 20 of 36 © Boardworks Ltd 2010 Proteins and amino acids Proteins are a diverse group of large and complex polymer molecules, made up of long chains of amino acids. Amino acids contain both amine (NH2) and carboxyl (COOH) functional groups. In alpha amino acids, these groups are attached to the same carbon atom. glycine (gly) The R group, also attached to the same carbon atom, can vary. There are 22 amino acids that are used to make proteins (proteinogenic). The simplest is glycine, where R = H. 21 of 36 © Boardworks Ltd 2010 Proteinogenic amino acids 22 of 36 © Boardworks Ltd 2010 Zwitterions 23 of 36 © Boardworks Ltd 2010 Acid–base properties of amino acids The presence of a carboxyl group and an amine group mean that amino acids have both acidic and basic properties. NH2 group acts as a base COOH acid group acts as an acid When acting as an acid, the COOH group loses a H+ ion: H2NCHRCOOH + OH- H2NCHRCOO- + H2O When acting as a base, the NH2 group gains a H+ ion: H2NCHRCOOH + H+ H3N+CHRCOOH 24 of 36 © Boardworks Ltd 2010 Effect of pH on amino acids 25 of 36 © Boardworks Ltd 2010 Peptide formation 26 of 36 © Boardworks Ltd 2010 Hydrolysis of peptide bonds A peptide bond can be split by refluxing with hydrochloric acid. During hydrolysis, the water molecule adds across the peptide bond, forming a mixture of the two amino acids. Peptide links can also be broken using a solution of alkali, such as aqueous sodium hydroxide at above 100°C. 27 of 36 © Boardworks Ltd 2010 Protein structure 28 of 36 © Boardworks Ltd 2010 Bonds in proteins The 3D shape of a protein is maintained by several types of bond, including: hydrogen bonds: involved in all levels of structure. hydrophobic interactions: between non-polar sections of the protein. disulfide bonds: one of the strongest and most important type of bond in proteins. Occur between two cysteine amino acids. 29 of 36 © Boardworks Ltd 2010 Types of protein There are two broad classes of protein: fibrous and globular. Fibrous proteins are formed from parallel polypeptide chains held together by cross-links. These form long, rope-like fibres, with high tensile strength and are generally insoluble in water. Examples of fibrous proteins include collagen, keratin and silk. Globular proteins usually have a spherical shape caused by tightly folded polypeptide chains with hydrophobic groups on the inside, and hydrophilic groups on the outside. Examples of globular proteins include enzymes and some hormones. 30 of 36 © Boardworks Ltd 2010 Structure of enzymes All enzymes are globular proteins. They are soluble in water due to the presence of many hydrophilic side groups on their constituent amino acids. Most enzymes are very large molecules but only a small part of them is involved in catalysis. This is called the active site and it may consist of just a few amino acids. active site The remainder of the amino acids maintain the precise shape of the enzyme and the active site. 31 of 36 © Boardworks Ltd 2010 Amino acids and proteins: summary 32 of 36 © Boardworks Ltd 2010 33 of 36 © Boardworks Ltd 2010 Glossary 34 of 36 © Boardworks Ltd 2010 What’s the keyword? 35 of 36 © Boardworks Ltd 2010 Multiple-choice quiz 36 of 36 © Boardworks Ltd 2010