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| Question | Answer |
| What are the 4 carbon based compounds? | Nucleic acids, proteins, carbohydrates, lipids. |
| What is a monomer? | Those are smaller units from which larger molecules are made. |
| What are the 4 most common elements in living organisms in order of most abundant? | Nitrogen, Oxygen, Carbon and Hydrogen. |
| Why is carbon particularly important? | Because carbon atoms have the tendency to join together into large chains and rings. |
| What is Condensation? | This is the reaction by which monomers join together and remove a water molecule. It forms a bond between the monomers. |
| What is Polymerization? | This is the term used when many monomers join together. |
| What is hydrolysis? | The process by which bonds are broken to produce individual monomers and it involves the addition of water and the use of enzymes. |
| What are monosaccharides? | Those are the basic units/monomers from which larger carbohydrates are made. |
| Give 3 examples of monosaccharides. | Fructose, Galactose and Glucose. |
| What are the two isomers of glucose and what is the difference between them? | The two isomers are alpha glucose and beta glucose. The OH group in carbon 1 in alpha glucose is at the bottom, but for beta both OH groups are at the bottom. |
| What monomers join together to give; disaccharides, maltose, sucrose and lactose. | 1. Monosaccharide + monosaccharide --> disaccharide. 2. Glucose + glucose --> maltose 3. Glucose + Fructose --> Sucrose 4. Glucose + Galactose --> Lactose |
| How are those disccharides formed? | They are formed by condensation reactions between the two monosaccharides to form a glycosidic bond. |
| How is Starch formed? | Starch is formed by alpha glucose molecules linking together by condensation reaction to form glycosdici bonds. |
| In what form is starch found in plants? | It is found in the form of a small grain. Hence, it is a storage compounds. |
| Where is a large amount of starch stored in the plant? | a vast amount of starch is stored in the seeds in the form of small grains. |
| What are the 2 types of starch? | 1. Amylose 2. Amylopectin |
| Describe amylose. | Amylose forms when many alpha glucose join together by condensation reactions. They form a 1,4 glycosidic bond. The chain is coiled into a spiral, hydrogen bonds hold this spiral together, |
| Describe amylopectin | It is made from many alpha glucose molecules joined together. It is branched therefore it formed 1,4 glycosidic bonds and 1,6 glycosidic bonds. |
| Why is amylopectin quicker to digest? | It is branched. |
| Why is starch the ideal storage compound? | 1.Starch folds into a tight shape and so a large amount off starch can be stored in a small volume. 2.It is insoluble so it will not move out of the cell readily, or affect the water potential. 3.It is easily broken down by enzymes into glucose. |
| Describe Glycogen. | Glycogen is made from many alpha glucose molecules joined together. They join together by condensation reactions to form 1,4 glycosidic bonds and 1,6 glycosidic bonds, therefore it is branched. The branches in glycogen are shorter than the branches in amylopectin, this makes glycogen even more compact and quicker to digest, therefore it is rapdily broken down to glucose. |
| Where is glycogen stored in humans and why is it stored there? | Glycogen is stored in the muscles but the liver stores a very large amount of glycogen. Some glycogen is stored in the muscles as a readily accessible from of glucose, it can be broken down to glucose when the rate of respiration in the muscles rises rapidly all of a sudden. The liver continually breaks down the glycogen to glucose to maintain a constant blood glucose concentration. |
| Describe Cellulose. | It is made up of beta glucose molecules and each molecule is rotated 180 degrees compared to the next one. This alternate bonding makes the chain straight. The cellulose molecule is very long and it is made up of parallel chains which are cross linked by hydrogen bonds. They from microgibirls which are very strong, they are grouped together to make the structure thicker and stronger. In cell walls the micrfibrils criss-cross to make them resistant to stretching. They also have a flexible structure that is completely permeable. |
| Why is cellulose not easy to digest? | The links between beta glucose are stronger than those between alpha glucose. |
| What are reducing sugars and give examples. | Reducing sugars are monosaccharides such as glucose, fructose and galactose as well as maltose. Sucrose is NOT a reduing sugar it is a non-reducing sugar. |
| How would you test for a reducing sugar? | Add blue benedict's reagent, heat it and it will turn green/orange/red. |
| How would you test for a non-reducing sugar? | First add dilute hydrochlorcic acid, then heat then add dilute sodium hydroxide, this neutralizes the HCl because benedict's solution does no work well in acidic pH. It will turn from blue to orange/green/red. |
| How would you test for starch? | Add iodine to potassium iodide, it will turn from brown to blue/black. |
| Cotton is in plant fibre used to make cloth. Explain how cellulose gives cotton its strength. | Each beta glucose molecule is rotated 180 degrees compared to the next one this forms a long straight chain which form microfibrils those microfibrils are very strong. The chains are held together by hydrogen bonds. |
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