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Description
Flashcards by Johanne Straube, updated more than 1 year ago
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Created by Johanne Straube
almost 9 years ago
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| Question | Answer |
| What is the ration between carbon, hydrogen and oxygen in carbohydrate? | 1:2:1 |
| What is a carbohydrate? | Carbohydrates form a large group of organic molecules that can be synthesised by plants. Animals require carbohydrates as an energy source which is obtain either directly or indirectly from plant sources. |
| What are the three major groups of carbohydrates? | Monosaccharides, disaccharides and polysaccharides. |
| What are monosaccharides? | Small single molecule. All monosaccharides contain a carbonyl group C = O and at least two hydroxyl groups (OH). The carbonyl and hydroxyl groups form the reactive groups |
| What is Trioses | The simplest monosaccharides have three carbon atoms and are known as trioses. |
| What are isomers? | When two compounds have the same molecular formula, but different structural arrangements. Aldose and Ketose; positioning of the oxygen atom is the only difference structurally. |
| What are Pentoses? | Pentoses are monosaccharides with five carbon atoms in the molecule. They have a carbonyl group and at least two hydroxyl groups.Important pentose sugars are ribose (RNA) and deoxyribose (DNA), these are both aldose sugars and can exist as a chain or in a ring form. |
| What are Hexoses? | Hexoses are six carbon sugars, like pentose they can exist as straight chains or rings. Three common hexoses are glucose, galactose and fructose. |
| What is the difference between α-glucose and β-glucose?! | Glucose and other monosaccharides can exist as two different ring forms; one where the hydroxyl (OH) on carbon 1 is below the ring (α-glucose) and the other where the hydroxyl is above the ring (β-glucose). |
| What are Disaccharides? | Disaccharides are formed from a condensation reaction between two monosaccharide molecules. During the reaction water is removed and the bond formed between the two monosaccharide residues is known as a glycosidic bond. |
| Give an example of two disaccharides bonded with a glycosidic bond. | 2 glucose molecules combine to form a molecule of maltose. The bond is formed between groups attached to carbon 1 on one molecule and carbon 4 on the other molecule of α-glucose and so it is referred to as a α 1,4 glycosidic bond. |
| How do you know a sugar is reduced or none reduced? | If you heat a reducing sugar (monosaccharide) with Benedicts reagent it will a red colour is shown. This is because the monsaccharide is oxidised and the copper reduced during the reaction. |
| What are Polysaccharides? | Polysacchaides are polymers formed from a large number of monosaccharide residues, joined together by covalent bonds by a process known as condensation polymerisation. |
| Give some examples of polysaccharides. | The commonly occurring polysaccharides starch, cellulose and glycogen are all polymers of glucose. The glucose residues are linked together by glycosidic bonds. The type of glycosidic bond depends on the isomer of glucose involved. |
| Explain starch | Starch is a polysaccharide. It is a polymer of α-glucose monomers and is a mixture of amylose (30%) and amylopectin (70%). Both are polymers of glucose with α-1.4 glycosidic bonds. Amylopectin has branches made from α 1,6 glycosidic linkages at various points along the chain, usually every 20 to 30 residues. |
| What is glycogen? | Glycogen is a polymer of α-glucose linked by α 1,4 glycosidic linkages. It has branches every 8 - 10 residues along the chain which makes it pack tightly. |
| What is Cellulose? | Cellulose is a polymer of β-glucose monomers joined by β 1,4 glycosidic linkages to form straight unbranched chains. Cellulose is an important structural component of plant cell walls, where it provides great tensile strength. |
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