Q1 Uptake of the products of digestion (small intestine) Absorption

Q2 Breaking down large molecules into smaller ones Digestion

Q3 2 types of digestion Chemical Mechanical

Q4 Where does ingestion occur Mouth

Q5 Using the products of digestion in cells? assimilation

Biological Molecules AS Biology

Biological Molecules 80% of the mass of living organisms is water. 13% is composed of organic (carbon-based) MACROMOLECULES, of which there are 4 groups CARBOHYDRATES PROTEINS LIPIDS (FATS) NUCLEIC ACID

Carbon Carbon-containing molecules=organic molecules Carbohydrates, proteins and lipids all contain carbon Carbon atoms can form 4 chemical bonds with other carbons or different atoms

Polymers & monomers What are polymers? What are monomers? Long chained molecules consisting of repeating units The repeating unit that join together to form polymers

Macromolecules Carbon chains can be straight Carbon chains can be branched

CARBOHYDRATES This type of molecule contains only the elements: C H O

CARBOHYDRATES Divided into 3 main types; Monosaccharides Single sugars

Monosaccharides – single sugars Examples Alpha Glucose 6 carbons Fructose 6 carbons Galactose 6 carbons

Glucose – C6H12O6 Glucose is the best known monosaccharide, having the general formula C6H12O6.

Alpha Glucose

CARBOHYDRATES Divided into 3 main types; Monosaccharides = single sugars Disaccharides sugars containing 2 monosaccharide residues

Disaccharides– 2 monosaccharide residues joined together Examples Alpha Glucose sucrose

Making Chains Disaccharides are formed when two monosaccharides join together. The reaction involves the formation of a water molecule, & so is called a condensation reaction. The type of bond formed is called a glycosidic bond.

Breaking Chains The bonds between the individual monomers in disaccharides and polysaccharides can be broken by hydrolysis, which is the reversal of condensation reactions. A hydrolysis reaction does not occur by putting a carbohydrate in water – an enzyme is required. In the case of starch, this enzyme is amylase.

Disaccharides (to learn) There are 3 common disaccharides: Maltose: glucose + glucose Sucrose: glucose + fructose Lactose: glucose + galactose

Draw how the disaccharides: maltose and lactose are formed For each identify the water molecule that is produced Draw out the complete disaccharide & identify the glycosidic bond galactose

CARBOHYDRATES Divided into 3 main types; Monosaccharides = single sugars Disaccharides = sugars containing 2 monosaccharide residues Polysaccharides = very large molecules that contain many monosaccharide residues

Making Longer Chains Starch Glycogen Cellulose Polysaccharides are long chains of many monosaccharides joined together by glycosidic bonds. There are three important polysaccharides: Starch Glycogen Cellulose

Polysaccharides – many monosaccharide residues joined together Examples

Carbohydrates Sugars Monosaccharides (monomers) Disaccharides (dimers) Polysaccharides (polymers) Maltose Sucrose Lactose Starch Glycogen Cellulose Glucose Fructose Galactose

Carbohydrate digestion Polysaccharide insoluble disaccharide monosaccharide soluble

Carbohydrate digestion example Starch Salivary amylase & pancreatic amylase Polysaccharide Starch Disaccharide Maltose Maltase in intestinal epithelium (cells lining small intestine) monosaccharide Alpha glucose

Starch Starch is the plant storage polysaccharide. It is insoluble and forms starch granules inside many plant cells. It’s insolubility means it does not affect the water potential of cells. It is not a pure substance, but a mixture of two structures (both alpha glucose polymers though) Amylose Amylopectin Amylopectin can be broken down more easily because it has “more ends”

Glycogen Glycogen is similar in structure to amylopectin. It is made by animals as their storage polysaccharide, being found mainly in muscle and the liver. Its branched structure means it can be mobilised (broken down to glucose) very quickly.

Cellulose Cellulose is only found in plants where it is the main constituent of cell walls. Cellulose is made from beta glucose arranged in long parallel chains. The chains are held together in a bundle by hydrogen bonds, forming microfibrils which are very strong. The beta glycosidic bond cannot be broken down by amylase, but requires a specific cellulase enzyme. Only bacteria contain this enzyme, so herbivores like cows & termites have bacteria in their guts. Humans cannot digest cellulose – it is what we call fibre or roughage.

Proteins Proteins are the most complex and diverse group of bioligical compounds. They have an astonishing range of different functions: structure e.g. collagen (bone, cartilage, tendon), keratin (hair), actin (muscle) Enzymes e.g. amylase, catalase, pepsin (>10000) Transport e.g. haemoglobin (oxygen), transferrin (iron) Pumps e.g. sodium-potassium pumps in cell membranes Hormones e.g. insulin, glucagon, adrenalin Antibodies Blood clotting And many more

Proteins Proteins are made of amino acids which have a central carbon atom with three different chemical groups attached: R-group Carboxylic acid group Amino group Alpha carbon Amino acids are so called because they have both amino groups (-NH2) and acidic groups (-COOH). Amino acids are made of the five elements C H O N S There are 20 different R-groups and so 20 different amino acids. This means that there are many, many different proteins with differing numbers and combinations of amino acids

Proteins- making and breaking Joining amino acids involves, again, a condensation reaction. The bond formed is called a peptide bond Two amino acids form a dipeptide, many amino acids form a polypeptide. In a polypeptide, one end is still the amino group and the other end the acidic group. The same type of reaction, hydrolysis, is again involved in breaking down (or hydrolysing) proteins. This can be achieved in the presence of protease enzyme or by boiling with dilute acid.

Protein structure Polypeptides are just a string of amino acids, but they fold up to form the complex structures of working proteins. To help understand protein structure it is broken down into four levels – but be aware that these are not real sequential stages in protein formation PRIMARY STRUCTURE SECONDARY STRUCTURE TERTIARY STRUCTURE QUARTERNARY STRUCTURE

Protein: primary structure This is just the sequence of amino acids in the polypeptide chain, so is not really a structure at all This can also be shown using the three letter abbreviations for each amino acid: Gly – Pro – His – Leu – Tyr – Ser – Trp – Asp - Lys

Protein: secondary structure This is the folding that then occurs, being held together by hydrogen bonds between the amino and carboxyl groups. The two main types of secondary structure are the alpha helix and the beta pleat. In the alpha helix the polypeptide chain is wound round to form a helix that is held together by many hydrogen bonds. In the beta pleat, the polypeptide chain zig-zags back and forward, once again held together by hydrogen bonds

Protein: tertiary structure This is the three dimensional structure formed by the folding up of the whole chain, with every proteins properties and functions being related to this. E.g. the unique shape of an enzymes active site is due to its tertiary structure. Three kinds of bond hold this structure together: Hydrogen bonds,which are relatively weak Ionic bonds between the R-groups, which are quite strong Sulphur bridges between the sulphur containing amino acids, which are strong

Protein: quarternary structure This structure is found only in those proteins that contain more than one polypeptide chain, and simply means how the different chains are arranged together e.g. haemoglobin

Globular or Fibrous? The final 3-D shape of a protein can be described as globular or fibrous GLOBULAR: most proteins, soluble, have biochemical roles e.g. enzymes, receptors, hormones FIBROUS: look like “ropes”, are insoluble and have structural functions e.g. Collagen, keratin

Biochemical test for proteins, carbohydrates (sugars, starch), and lipids

Lipids You can test for the presence of lipids by using the EMULSION TEST. 1.Add alcohol to the sample of food.Shake to dissolve any lipid. 2. Two layers of liquid will form. Pour the top layer of & add water. 3. A cloudy white EMULSION shows the presence of a lipid

Starch The presence of starch can be teated using the iodine test. Starch + iodine blue-black colour With other polysaccharides, iodine remains yellow-brown

Sugars Sugars can be identified with blue Benedict’s solution. However there are two types of sugar: Reducing Sugars – these carry out reduction reactions and include all monosaccharides and most disaccharides. When heated with Benedict’s, the colour changes from blue to green to orange/red Non-reducng sugars (mainly sucrose in fact) do not react with Benedict’s unless first hydrolysed by heating with acid first. As Before adding Benedict’s, you must neutralise the acid with an alkali

Proteins Proteins can be identified with blue Biuret Reagent (copper sulphate and sodium hydroxide). Blue Biuret reagent turns lilac in the presence of protein