1.1 Biological Molecules: Carbohydrates Flashcards
Maltose is made of which monosaccharides?
By the condensation of two glucose molecules.
Sucrose is made by which monosaccharides?
Is friend by the condensation of glucose and fructoses.
Lactose is made by which monosaccharides?
Is formed by Condensation of glucose and galactose.
What’s a polysaccharides?
Polysaccharides are a large chain of many monosaccharides bonded together.
Name three polysaccharides. Name what monosaccharides they are made up of
Glycogen and starch both made by alpha glucose
Cellulose made by beta glucose
What is glycogen? Explain its structure and why it’s good as a energy storage molecule.
Glycogen is the main energy storage molecule in animals and is formed from many molecules of alpha glucose joined together by 1, 4 and 1, 6 glycosidic bonds. It has a large number of side branches meaning that energy can be released quickly as enzymes can act simultaneously on these branches. Moreover, it is a relatively large but compact molecule thus maximising the amount of energy it can store. Finally being insoluble means it will not affect the water potential of cells and cannot diffuse out of cells.
What is starch? Name the two molecules which make up starch?
Starch stores energy in plants and is a mixture of two polysaccharides called amylose and amylopectin:
Amylose – amylose is an unbranched chain of glucose molecules joined by 1, 4 glycosidic bonds, and as a result amylose is coiled and thus a very compact molecule storing a lot of energy.
Amylopectin is branched and is made up of glucose molecules joined by 1, 4 and 1, 6 glycosidic bonds. Due to the presence of many side branches these can be acted upon simultaneously by many enzymes and thus broken down to release its energy.
Some key properties of starch that make it suitable are that; its insoluble so will not affect cell water potential, it is compact so a lot of energy can be stored in a small space and when it is hydrolysed the released alpha glucose can be transported easily.
What is hydrolysis?
Breaking of bonds using water
What is a condensation reaction?
The forming of bonds which produces water as a side product
Name the functions of Cellulose.
1)
Cellulose is the main structural component of cell walls due to its strength which is a result of the many hydrogen bonds found between the parallel chains of microfibrils
2)
The high tensile strength of cellulose allows it to be stretched without breaking which makes it possible for cell walls to withstand turgor pressure
3)
The cellulose fibres and other molecules (eg. lignin) found in the cell wall forms a matrix which increases the strength of the cell walls
4)
The strengthened cell walls provide support to the plant
5)
Cellulose fibres are freely permeable which allows water and solutes to leave or reach the cell surface membrane
As few organisms have the enzyme (cellulase) to hydrolyse cellulose it is a source of fibre
Name the test for reducing sugars and the positive test result.
Add Benedict’s reagent (which is blue as it contains copper (II) sulfate ions) to a sample solution in a test tube
Heat the test tube in a water bath or beaker of water that has been brought to a boil for a few minutes
If a reducing sugar is present, a coloured precipitate will form as copper (II) sulfate is reduced to copper (I) oxide which is insoluble in water
It is important that an excess of Benedict’s solution is used so that there is more than enough copper (II) sulfate present to react with any sugar present
A positive test result is a colour change somewhere along a colour scale from blue (no reducing sugar), through green, yellow and orange (low to medium concentration of reducing sugar) to brown/brick-red (a high concentration of reducing sugar)
This test is semi-quantitative as the degree of the colour change can give an indication of how much (the concentration of) reducing sugar present
Describe how you would test for the presence of non-reducing sugars.
Break down the sugar into monosaccharides using concentrated HCL heated in a boiling water bath. Then, neutralise this solution with sodium hydrogen carbonate. Then add Benedict’s reagent heat if brick red precipitation form it’s a postive test if it stays blue it’s negative
what is the test for detecting starch? Describe how it works.
Add a solution of iodine in potassium iodide to the sample if starch is present the colour will change from a browny-orange to a dark-blue or black.
name key monomers.
Monosaccharides, Amino acids, Nucleotides
