click below
click below
Normal Size Small Size show me how
Carbohydrates
| Question | Answer |
|---|---|
| How are carbohydrates produced? | By photosynthesis in plants. |
| What are the general features of monosaccharides? | 3-6 carbon atoms. A carbonyl group. several hydroxyl groups. |
| What are aldoses? | Monosaccharides with an aldehyde group and many hydroxyl groups. |
| What are ketoses? | Monosaccharides with a ketone group and many hydroxy groups. |
| What is a Fischer projection? | Used to represent carbohydrates. Places the most oxidised group at the top. Shows chiral carbons as the intersection of vertical and horizontal lines. |
| In a Fischer projection, the OH group on the ... | ...chiral carbon farthest from the carbonyl group determined an L or D isomer. ...left is assigned the letter L for the L-form. ...right is assigned the letter D for the D-form. |
| What are the features of D-glucose? | Found in fruits. An aldohexose. Known as blood sugar in the body. The monosaccharide in polymers of starch, cellulose and glycogen. |
| How are D-glucose and D-galactose different? | Body cannot digest galactose. Must be converted to glucose first. |
| What is Galactosemia? | Lack of enzymes required for galactose metabolism. Can result in accumulation of galactose intermediates. Toxic effects in liver, brain, kidneys and eyes. |
| How do cyclic structures form in monosaccharides? | Form when the hydroxyl group on C-5 reacts with the aldehyde group or ketone group. |
| What happens when D-glucose is placed in solution? | Cyclic structures open and close. Alpha glucose converts to beta glucose and vice versa. At any time, only a small amount of open chain forms. |
| What is the definition of a reducing sugar? | A sugar that will reduce inorganic ions such as Cu++ (Fehling's reagent). All monosaccharides whether an aldose or a ketose are reducing sugars. |
| When can Fehling's reaction be used in medicine? | To determine glucose levels in blood. |
| How does glucose enter red blood cells? | In a non-insulin dependent manner. |
| What does uncontrolled hyperglycemia result in? | The covalent linkage between glucose and the NH2 terminal amino acid of teh hemoglobin beta chain. |
| What is the half life of a red blood cell? | 120 days. |
| What is glycation? | Non-enzymatic addition of sugar. |
| What is lactose intolerance? | Lack of lactase enzyme in the small intestines. |
| What is a problem with lactose intolerance? | Lactose passes into the colon. Bacteria start to ferment lactose. Causes stomach cramps, bloating and flatulence. |
| What is the storage form of glucose? | Glycogen. |
| Where is glycogen predominantly found? | In the liver and muscles. |
| What is starch? | The plant form of carbohydrate, ingested by humans. |
| What is amylose? | An unbranched starch comprised of glucose units. Alpha 1-4 linkage. |
| What is amylopectin? | The branched form of starch comprised of glucose units. |
| Why is cellulose considered as roughage? | Mammals lack cellulases. |
| What are examples of hybrid biomolecules? | Glycoprotein and Glycolipids. |
| What is the structure of nucleotides? | Nitrogen ring linked to a five carbon sugar. Sugar can be ribose or deoxyribose. Phosphate groups attached. |