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

2. Q2 Breaking down large molecules into smaller ones
Digestion

3. Q3 2 types of digestion
Chemical
Mechanical

4. Q4 Where does ingestion occur
Mouth

5. Q5 Using the products of digestion in cells?
assimilation

6. Biological Molecules
AS Biology

7. 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

8. 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

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

10. Macromolecules Carbon chains can be straight
Carbon chains can be branched

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

12. CARBOHYDRATES
Divided into 3 main types;
Monosaccharides
Single sugars

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

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

15. Alpha Glucose

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

17. Disaccharides– 2 monosaccharide residues joined together
Examples
Alpha Glucose
sucrose

18. 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.

19. 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.

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

21. 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

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

23. 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

24. Polysaccharides – many monosaccharide residues joined together
Examples

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

26. Carbohydrate digestion
Polysaccharide
insoluble
disaccharide
monosaccharide
soluble

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

28. 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”

29. 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.

30. 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.

31. 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

32. 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

33. 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.

34. 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

35. 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

36. 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

37. 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

38. 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

39. 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

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

41. 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

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

43. 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

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