Biological Molecules - Carbohydrates and Lipids Flashcards
Define monomer
Monomers are the smaller molecules from which polymers are made
Define polymers
Polymers ae molecules made from a large number of monomers joined together
Name 3 types of monosaccharides
Glucose, Fructose, Galactose
Name three types of disaccharides
Maltose, Lactose, Sucrose
Name 3 types of polysaccharides
Starch, Glycogen, Cellulose
How are disaccharides maltose, sucrose and lactose formed?
glucose + glucose —> maltose
glucose + fructose —> sucrose
glucose + galactose —> lactose
What is the name given to the bond between 2 alpha glucose molecules?
A glycosidic bond
Describe and explain how the structure of starch relates to its function
- Insoluble - Does not lower the water potential of the cell so does not affect osmosis
- Large and insoluble - Does not diffuse across the cell membrane and out of the cell
- Coiled into a helix - Compact
- Branched - Provides more ends / larger surface area for faster hydrolysis
Describe and explain how the structure for glycogen relates to its function
- Coiled into a helix - Compact so that a lot can fit into a small space
- Insoluble - Does not lower the water potential of the cell so does not affect osmosis
- Large and insoluble - Does not diffuse across the cell membrane and out of cells
- Very highly branched - Provides many ends/ larger surface area for faster hydrolysis by enzymes to form alpha glucose for use in respiration
Describe and explain how the structure of cellulose relates to its function
- Long straight + unbranched chains of beta glucose linked together by many hydrogen bonds to form microfibrils and cellulose fibres - Provides strength to the cell wall
Describe the biochemical test for starch including the outcome of a positive test
- Add iodine solution to the sample
- For positive test result: a colour change from orange to blue-black
Describe the biochemical test for a reducing sugar including the outcome of a positive test
- Add benedict’s solution to the sample and heat to 95 degrees C
- For positive test result : a colour change from blue to red precipitate
Describe the biochemical test for a non-reducing sugar including the outcome of a positive test
- Add benedict’s solution to the sample and heat to 95 degrees C
- If there is no change then boil a fresh sample with dilute hydrochloric acid for a few minutes
- Neutralise by adding solid sodium hydrogen carbonate
- Then add the Benedict’s solution and heat to 95 degrees C
- For positive test result: a red precipitate will form and a colour change from blue to red
Name the reducing and non-reducing sugars
- Reducing sugars - Glucose, galactose, lactose, maltose and fructose
- Non-reducing sugars - Sucrose
Define condensation
A reaction which joins two glucose molecules together by a chemical bond and involves the elimination of a molecule of water
Define hydrolysis
Breaking a achemical bond between 2 molecules and involves the use of a water molecule
Describe the structure of triglycerides
Triglycerides are made up of one glycerol molecule and three fatty acid molecules
Relate the structure of triglycerides to their function
- Long hydrocarbon fatty acid chains - Contains lots of stored chemical energy which is why triglycerides are used as an energy storage molecule
- Hydrophobic fatty acid tails - Insoluble in water therefore it does not affect the water potential of a cell
Describe how triglycerides form
Triglycerides are formed by the condensation of one glycerol and three fatty acid molecules forming three ester bonds and three water molecules produced
Describe the stages of the emulsion test including what a positive result will be
- Add ethanol to the sample and shake
- Then add water drop wise
- If a lipid id present, a white emulsion will be visible
Describe the structure of phospholipids
Phospholipids are made of one glycerol molecule, two fatty acid molecules and a phosphate group
Relate the structure of phospholipids to their function
- Hydrophobic fatty acid tails and hydrophilic phosphate heads - Will form a bilayer in water. This forms cell membranes and the fatty acid centre means that water soluble molecules cannot easily pass across the membrane
Describe and explain how phospholipids arrange themselves in cell membranes
- Phosphate head is hydrophillic wheras the fatty acid tails are hydrophibic
- This allows the phospholipids to form a bilayer in water
- Hydrophobic fatty acid tails are pointing inwards away from the water while the hydrophilic phosphate heads are pointed outwards facing the water
Compare and contrast the structure of triglycerides and phospholipids
- Tryglycerides have three fatty acid tails and phospholipids have two fatty acid tails
- Phospholipids have a phosphate group and triglycerides do not
- Phospholipids are polar and triglycerides are non-polar
Define saturated fatty acid
No carbon to carbon double bonds are in the hydrocarbon chain
Define unsaturated fatty acid
Contains carbon to carbon double bonds in the hydrocarbon chain
What is a monosaccharide
The monomers from which larger carbohydrates are made
What are the two isomers of glucose
Alpha glucose and Beta glucose
What are the differences between the structures of starch and glycogen
- Glycogen has shorter chains than starch
- Glycogen is more highly branched than starch
- Glycogen has a larger surface area than starch
