2.3 Carbohydrates and Lipids Flashcards
How do you make carbohydrates?
You link together monosaccharides by condensation reactions. They lose an OH and a H and produce water. Linking together monosaccharides is an anabolic process and energy has to be used to go it. ATP supplies this energy.
Alpha glucose?
DDUD
Beta glucose?
UDUD
How do you make cellulose?
Cellulose is made by linking together molecules of beta glucose, and because beta glucose has the OH group on the 1st carbon pointing upwards, the 1 and 4 carbons have the OH’s in different spaces, so in order to join them they have to be at 180 degrees to each other. The consequence of this is that cellulose as a molecule is a straight chain rather than being curved. They are unbranched and therefore form bundles with hydrogen linking the cellulose molecules. These bundles are called cellulose microfibrils and have a very high tensile strength and are used as the basis of plant cell walls. The tensile strength of cellulose prevents plant cells from bursting even when very high pressures have developed inside the cell due to entry of water by osmosis.
How is cellulose good for plant walls.
Cellulose is made by linking together molecules of beta glucose, and because beta glucose has the OH group on the 1st carbon pointing upwards, the 1 and 4 carbons have the OH’s in different spaces, so in order to join them they have to be at 180 degrees to each other. The consequence of this is that cellulose as a molecule is a straight chain rather than being curved. They are unbranched and therefore form bundles with hydrogen linking the cellulose molecules. These bundles are called cellulose microfibrils and have a very high tensile strength and are used as the basis of plant cell walls. The tensile strength of cellulose prevents plant cells from bursting even when very high pressures have developed inside the cell due to entry of water by osmosis.
How is starch made?
Starch is made by linking together alpha glucose molecules. Condensation reactions link the OH group on the 1st carbon to the OH on the 4th of another molecule. These molecules both point downwards and therefore a starch molecule is curved rather than straight.
There are two forms of starch. In amylose the chain of alpha glucose molecules is unbranched and forms a helix. In amylopectin the chain is branched and so has a more globular shape.
Benefits of starch over glucose?
Starch is too large to be soluble and therefore does not mess with the osmosis water balance like glucose would. Starch is therefore produced BY PLANTS as an energy store of glucose. It is used in seeds or storage organs such as potatoes. But it is also used temporarily in leaves.
What is the difference between starch and glycogen?
Glycogen is very similar to the branched form of starch but there is more branching making it more compact. It is made by animals and some fungi, whereas starch is only made by plants and in humans it is stored in the liver and some muscles. It acts as a store of energy in the form of glucose when lots of glucose would cause osmotic problems. It is easy to add molecules to the end of them both or remove them.
What are the two types of starch?
Amylose - non branched
Amylopectin - branched
What is the difference between fats and oils?
Fats are liquid at body temperature but solid at room temperature, whereas oils are liquids at both.
What are lipids made of?
One molecule of glycerol and three fatty acids. Each fatty acid is linked to the glycerol by a condensation reaction. The reaction is between the COOH of a fatty acid and an OH of the glycerol to make an ester bond. COO.
How do you make a lipid?
Each fatty acid is linked to the glycerol by a condensation reaction. The reaction is between the COOH of a fatty acid and an OH of the glycerol to make an ester bond. COO.
Which is better for long term storage lipids or carbohydrates?
Lipids
The lipids that are used are fats, they are stored in specialised groups of cells called adipose tissue.
Why are lipids better than carbohydrates for long term energy storage?
The lipids that are used are fats, they are stored in specialised groups of cells called adipose tissue.
- The amount of energy released per gram of fat is double that released from carbohydrates. So animals can be lighter and carry the same amount of energy.
- Lipids are stored with no water associated whereas each gram of glycogen is associated with about two grams of water. So lipids are 6 times more efficient in the energy stored per gram.
- Lipids have secondary roles, because they are poor conductors of heat they are heat insulators. This is why we have so much adipose tissue close to the skin, this saves more energy.
- Because fat is a liquid at body temperature it can also act as a shock absorber, this is the reason for fat around the kidneys and some other organs.
HOWEVER Glycogen is used for short term energy storage in the liver and in the muscles because glycogen can be broken down much more quickly and then transported to the blood when it is needed, whereas fats in the adipose tissue cannot be.
When do you need fat and when do you need glycogen?
Glycogen is used for short term energy storage in the liver and in the muscles because glycogen can be broken down much more quickly and then transported to the blood when it is needed, whereas fats in the adipose tissue cannot be.
Fats are used for long term energy storage.
