Biologi Secondary 4

1. water molecules have +0 charged ends and can form weak hydrogen bonds . water is said to be a dipolar molecule. 2. The basic uits of CO2 are monosaccharides , characterized by the number of carbon atoms, e.g pentose sugars have 5 carbons 3. Two monossaccharids can link together to form a disaccharide . the bond between them is a glycosidic linkage formed in a condensation reaction 4. Starch is a polysaccharide composed of amylose and amylopectin. Its main function is as a storage carbohydrate, starch and glycogen are suitable for this function because there are insoluble and compact. 5. A triglyceride composed of 1 molecule of glycerol and 3 fatty acids 6. A triglyceride is formed from a condensation reaction called esterification 7. Fatty acids with double bonds are said to be unsaturated and have a lower melting point than fatty acids with no double bonds. 8. Amino acids are amphoteric, acting as both an acid and a base through condensation of two amino acids they from dipeptides 9. The primary structure of a protein is the sequence of its amino acids. Further structures are controlled by the formation of weal hydrogen bonds and disulphide bridges between amino acids 10. In chromatography , the amino acids can be identified by calculatoing the RF value 11. In reducing sugars are present in foods . benedict’s solution will turn form blue to a brick red on heating Carbohydrate | Insoluble | Forms fibrils | Reducing sugar | Polymer of ∝-glucose | Starch | ✔ | ✗ | ✗ | ✔ | Cellulose | ✔ | ✔ | ✗ | ✗ | Maltose | ✗ | ✗ | ✔ | ✔ | Glycogen | ✔ | ✗ | ✗ | ✔ |

12. a) columnar ephithelial cell
b) describe & explain two visible features shown that are useful in the uptake of food molecules.
- two of = many mitochondria – to produce ATP for active transport; microvilli = to increase surface area ; many vesicles – showing endocytosis 13. a) essential fatty acid – fatty acids that cannot be