Topic 1A- Biological Molecules (Carbohydrates) Flashcards

Question

Outline the test for reducing sugars

Answer 1

1) You add Benedict's reagents (which is blue) to a sample and heat it in a water bath to 95°C. Wait for 5 minutes. 2) If a reducing sugar is present (therefore the test positive), a brick red precipitate will form. If the test is negative, the solution will remain blue.

Answer 2

1) carry out the Benedict's test for reducing sugars. If the result of the reducing sugars is negative, there could still be a non-reducing sugar present. To test for non-reducing sugars, like sucrose, first you have to break them down into monosaccharides. 2) You do this by getting a new sample of the solution, adding dilute hydrochloric acid and carefully heating it in a water bath that's been brought to boil. 3) You then neutralise it with with sodium hydrogencarbonate. 4) Then just carry out the Benedict's test as you would for reducing sugars. 5) If the test's positive, it will form a coloured precipitate (because there are now reducing sugars), and if it's negative there are no sugars (either reducing or non-reducing.

Answer 3

It's formed when more than two monosaccharides are joined together by condensation reactions.

Answer 4

plants store excess glucose as starch (when a plant needs more glucose for energy, it breaks down the starch to release glucose.)

Answer 5

Amylose Amylopectin

Answer 6

-Polysaccharide- polymer of alpha glucose. Stores glucose which can be hydrolysed and broken down during respiration. -Long, branched chains of alpha glucose (These branches mean there are more ends from which the enzymes can easily hydrolyse the glucose molecules for quick energy release) -Contains 1,4 and 1,6 glycosidic bonds which causes the branches to occur -Very large, which means it can't fit through the partially permeable membrane, so stays where it's formed -It's insoluble which means it doesn't effect the water potential (so doesn't cause water to enter the cell by osmosis-which would cause it to swell) All of this makes it good for both storage and quick energy release.

Answer 7

-Polymer of Alpha Glucose - Long, unbranched chain of alpha glucose (this alpha glucose can later be broken down for energy) -Joined together by 1,4 glycosidic bonds which causes the alpha glucose molecules to be at angles angles to each other, causing a coiled structure (this makes it compact, therefore it's good for storage as you can fit more glucose into a small space) -Very large which means it can't fit through the partially permeable membrane, so stays where it's formed, -(it's soluble in water) -This all makes it very good for storage.

Answer 8

Iodine test -add iodine dissolved in potassium iodide solution to the test sample. -If there is starch present, the sample changes from browny-orange to a dark, blue-black colour.

Answer 9

It's the main energy storage material in animals

Answer 10

-Polymer of Alpha Glucose. -Formed by many long branched chains of alpha glucose (more branches than amylopectin, which allows for even quicker hydrolysis of the glucose molecules off the ends of the branches and therefore quicker energy release) -Joined together by 1,4 and 1,6 glycosidic bonds which causes branches. -Very compact molecule, which means it can store a lot of glucose in a small space and therefore is very good for storage -Very large, which means it can't pass through the partially permeable membranes and therefore stays where it's formed -Insoluble, so doesn't effect the water potential of cells and cause lots of water to enter the cell which would make it swell. -All if these features make it very good for storage and quick release

Answer 11

1) It's function is to strengthen cell walls 2) It's a polymer of beta glucose, which benefits the plant because many animals are unable to digest beta glucose and therefore they are discouraged from eating the plant. 3) Cellulose is made of long, straight , unbranched chains of beta glucose. Every other beta glucose molecule is inverted and they are held together by 1,4 glycosidic bonds. (This causes the straight, unbranched structure) 4) lots of these chains are joined together by lots of hydrogen bonds (together they are very strong) and this forms microfibrils. Lots of these microfibrils join together to form fibres 5) the fibres then cross over each other to create mechanical strength in the cell walls.

Answer 12

Human judgement= qualitative Numbers= quantitative

Answer 13

METHOD 1: USING A COLOURIMETER: 1) First, produce a dilution series of known concentrations of glucose solutions 2) Add Benedict's solution to each one and heat to 95° in a water bath for 5 minutes. 3) Calibrate the colourimeter by measuring the absorbance of a sample of distilled water first, then measure the absorbance of each solution. (The higher the absorbance, the more reducing sugar present). Then test your unknown sample. 4) plot a calibration curve of absorbance on the y axis and the concentration on the x axis, drawing a curve of besy fit.You can use this line to estimate the concentration of reducing sugar in the sample METHOD 2: MEASURING PRECIPITATE: 1) Complete the Benedict's test for reducing sugars on the sample 2) filter the sample and dry the precipitate 3) find the mass using a balance. The bigger the mass, the more sugar is present. FOR EACH METHOD, ADHERE TO THESE CONTROL VARIABLES: 1) volume of Benedict's solution 2) concentration of Benedict's solution 3) volume of sample tested 4) temperature in the water bath 5) duration of heating

Answer 14

Chromatography: 1) first stain the monosaccharide sample. Place a spot of this sample on the line drawn in pencil at the bottom of the chromatography paper. 2) place spots of standard solutions of different known monosaccharides on the line beside the sample. 3) lower the paper into a beaker with the solvent, and wait for the solvent to travel up the paper. 4) analyse the chromatogram. If the mixture contains a monosaccharide, it will match up to the height of the known sample of that known monosaccharide.