Biological Molecules and … Digestion

Carbohydrates All contain the elements carbon hydrogen oxygen Twice as many hydrogen atoms as oxygen atoms in each molecule

Three main types Monosaccharide Disaccharide Polysaccharide

Monosaccharides Are the simple sugars e.g. glucose, fructose, galactose These are the monomers

Glucose  -glucose

Disaccharides Contain two simple sugars joined together Glycosidic bond is formed e.g. maltose, sucrose, lactose

Disaccharides Monomers join by a condensation reaction Water is given out

Condensation

Glycosidic bond

Maltose Two molecules of  -glucose joined together

Sucrose One molecule of  -glucose joined to one molecule of fructose

Polysaccharides Contains many simple sugars e.g. starch

Polysaccharide

Starch – for storage Compact  lots of glucose can be stored in a small space Easily broken down  supply glucose when needed for respiration

Lipids One of the most important types is: triglycerides Usually known as: fats and oils

Fat - Solid at room temperature

Oil - Liquid at room temperature

Triglycerides Consists of :- three fatty acid molecules one glycerol

Saturated and unsaturated triglycerides Depends on the form of the fatty acid chains

Proteins Polymer Monomer is amino acid Draw an amino acid

Amino group Carboxylic group

Amino acids 20 different amino acids Joined together by condensation Peptide bond is formed

Polypeptide is many amino acids joined together

Polypeptide – primary structure Chain of amino acids Held together by peptide bonds Differences due to the type, number and position of amino acid

Secondary structure Folding of polypeptide chain forming an alpha helix

Secondary structure Held together by hydrogen bonds

Tertiary structure Further folding of secondary structure, held together by hydrogen, ionic, disulphide and hydrophobic bonds

Quaternary structure More than one polypeptide joined together

The digestive system

Heterotrophic Nutrition Organisms that can not manufacture the organic molecules they require Must eat them Must consume them – CONSUMERS OR HETEROTROPHS Most of the chemicals eaten are storage molecules

Digestion Definition : Break down of large insoluble organic molecules into small soluble organic molecules

Classes of organic molecules StarchLipidProtein

How are the molecules joined together? StarchLipidProtein

How are the molecules joined together? StarchLipidProtein Glycosidic bond Ester bond Peptide bond

What enzymes break them down? StarchLipidProtein

What enzymes break them down? StarchLipidProtein CarbohydraseLipaseProtease

What type of reaction is involved? StarchLipidProtein

What type of reaction is involved? StarchLipidProtein Hydrolysis

The addition of water to break down a large molecule into a smaller molecule

Condensation Removal of water to join two molecules together

Breakdown of starch Starch amylase salivary gland pancreas Maltose maltase ileum Glucose

Membrane attached enzymes Most enzymes are secreted into the gut BUT Some enzymes are attached to membrane of the epithelial cells of the ileum

Examples of membrane attached enzymes Maltase Sucrase Lactase

Why are the enzymes attached to the membranes? The reactions they control, produce molecules which can be absorbed through the membrane If this happened in the centre of the gut the molecules may never come in contact with the membrane

What is the difference between maltose, sucrose and lactose? Glucose plus glucose - maltose Glucose plus fructose - sucrose Glucose plus galactose - lactose

Absorption Passing the products of digestion into the cells lining the gut

Assimilation Making the absorbed molecules part of the cells of the body