1.1/1.2Carbohydrates Flashcards
What are monomers and polymers?
● Monomers - smaller, repeating molecules / units from which larger molecules / polymers are made
Polymers - molecules made from many (a large number) identical / similar monomer molecules
What happens in condensation reactions?
Condensation reaction
● 2 molecules join together ● Forming a chemical bond ● Releasing a water molecule
What happens in hydrolysis reactions?
Hydrolysis reaction
● 2 molecules separated
● Breaking a chemical bond ● Using a water molecule
Give examples of polymers and the monomers from which they’re made
Nucleotide -> polynucleotide
Monosaccharide -> polysaccharide
Amino Acid -> polypeptide
What are monosaccharides? Give 3 common examples
● Monomers from which larger carbohydrates are made
● Glucose, fructose, galactose
Describe the difference between the structure of α-glucose and β-glucose
● Isomers - same molecular formula but differently arranged atoms
● OH group is below carbon 1 in α-glucose but above carbon 1 in β-glucose
What are disaccharides and how are they formed?
● Two monosaccharides joined together with a glycosidic bond
● Formed by a condensation reaction, releasing a water molecule
List 3 common disaccharides & monosaccharides from which they’re made
Maltose = Glucose + glucose
Sucrose = Glucose + fructose
Lactose = Glucose + galactose
What are polysaccharides and how are they formed?
● Many monosaccharides joined together with glycosidic bonds
● Formed by many condensation reactions, releasing many water molecules
Describe the basic function and structure of starch
Energy store in plant cells
● Polysaccharide of α-glucose
● Some has 1,4-glycosidic bonds so is unbranched (amylose)
● Some has 1,4- and 1,6-glycosidic bonds so is branched (amylopectin)
Describe the basic function and structure of glycogen
Energy store in animal cells
● Polysaccharide made of α-glucose
● 1,4- and 1,6-glycosidic bonds → branched
Explain how the structures of starch relate to its functions
Starch (amylose)
● Helical → compact for storage in cell
● Large, insoluble polysaccharide molecule → can’t leave cell / cross cell membrane
● Insoluble in water → water potential of cell not affected (no osmotic effect)
Starch (amylopectin)
● Branched → compact / fit more molecules in small area
● Branched → more ends for faster hydrolysis → release glucose for respiration to make ATP for energy release
● Large, insoluble polysaccharide molecule → can’t leave cell / cross cell membrane ● Insoluble in water → water potential of cell not affected (no osmotic effect)
Explain how the structures of glycogen relate to its functions
● Branched → compact / fit more molecules in small area
● Branched → more ends for faster hydrolysis → release glucose for respiration to make ATP for energy release
● Large, insoluble polysaccharide molecule → can’t leave cell / cross cell membrane ● Insoluble in water → water potential of cell not affected (no osmotic effect)
Describe the basic function and structure of cellulose
Function :
● Provides strength and structural support to plant / algal cell walls
Structure:
● Polysaccharide of β-glucose
● 1,4-glycosidic bonds so forms straight, unbranched chains ● Chains linked in parallel by hydrogen bonds, forming microfibrils
Explain how the structure of cellulose relates to its function
● Every other β-glucose molecule is inverted in a long, straight, unbranched chain
● Many hydrogen bonds link parallel strands (crosslinks) to form microfibrils (strong fibres)
● Hydrogen bonds are strong in high numbers
● So provides strength to plant cell walls
Describe the test for reducing sugars
Reducing sugars = monosaccharides, maltose, lactose
1. Add Benedict’s solution (blue) to sample
2. Heat in a boiling water bath
3. Positive result = green / yellow / orange / red precipitate
Describe the test for non-reducing sugars
Non-reducing sugars = sucrose
1. Do Benedict’s test (as above) and stays blue / negative
2. Heat in a boiling water bath with acid (to hydrolyse into reducing sugars) 3. Neutralise with alkali (eg. sodium bicarbonate)
4. Heat in a boiling water bath with Benedict’s solution
5. Positive result = green / yellow / orange / red precipitate
Suggest a method to measure the quantity of sugar in a solution
● Carry out Benedict’s test as above, then filter and dry precipitate
● Find mass / weight
Suggest another method to measure the quantity of sugar in a solution
- Make sugar solutions of known concentrations (e.g.. dilution series)
- Heat a set volume of each sample with a set volume of Benedict’s solution for the same time 3. Use colorimeter to measure absorbance (of light) of each known concentration
- Plot calibration curve - concentration on x axis, absorbance on y axis and draw line of best fit 5. Repeat Benedict’s test with unknown sample and measure absorbance
- Read off calibration curve to find concentration associated with unknown sample’s absorbance
Describe the biochemical test for starch
- Add iodine dissolved in potassium iodide (orange / brown) and shake / stir 2. Positive result = blue-black
