Carbohydrates Flashcards
What are monosaccharides?
Monomers from which larger carbohydrates can be made
What are isomers?
Molecules with the same molecular formula, but arranged differently
What are the four monosaccharide isomers?
Galactose, fructose, alpha glucose and beta glucose
What does beta-glucose look like?
HO - H (bottom)
Describe the structure of fructose
It has four carbons and one oxygen atom in its main structure
What does galactose look like?
H - H (bottom)
What does apha-glucose look like?
HO - OH (bottom)
What monomers form the disaccharide maltose?
glucose + glucose
What monomers form the disaccharide sucrose?
glucose + fructose
What monomers form the disaccharide lactose?
glucose + galactose
What is a condensation reaction?
A condensation reaction is when a molecule of water is eliminated to form a chemical bond between two molecules
What is a disaccharide?
Two monosaccharides bond through a condensation reaction
What is a hydrolysis reaction?
A reaction that breaks a chemical bond between two molecules and uses a water molecule.
What bond is formed between monosaccharides after a condensation reaction?
Glycosidic bond
Which bonds form coils?
Alpha, 1-4
Which bonds form branches?
Alpha, 1-6
What bonds form long, straight chains?
Beta, 1-4
What monosaccharide is cellulose made from?
Beta- glucose monosaccharides
What bonds are cellulose molecules joined with and why?
Beta-1,4-glycosidic bonds because it results in long, straight chains
What bonds add to the rigidity of cellulose?
Microfibrils and macrofibrils held by hydrogen bonds
What shape is glycogen and why?
It is coiled with 1-6 and 1-4 bonds for extra storage of energy as it is compact
Why can’t glycogen escape the cell membrane?
Glycogen is a large molecule
Why are polysaccharides insoluble?
If polysaccharides dissolve in the cell cytoplasm, they would decrease water potential. This would affect osmosis and thus the normal functioning of the cell.
Why does glycogen have many alpha,1-6 glycosidic bonds for branching?
Glycogen can be hydrolysed more quickly to release glucose faster
What is the difference between glycogen and starch?
Starch is found in plants, glycogen is found in animals
What is osmotic lysis?
Bursting of the cell due to excess water moving in by osmosis
Test for reducing / non-reducing sugars
How do we test for reducing sugars?
1. Prepare a beaker of fresh, boiling water as a water bath (to speed up the reaction with thermal energy) 2. Place 3cm^3 of the sample to a boiling tube, (water, grinded sample) add 3cm^3 of benedict's solution and place in the water bath 3. If there is no colour change, add HCl to a new sample 4. This will hydrolyse the sample and should break the glycosidic bonds to allow it to become monosaccharides 5. Slowly add 6cm^3 of sodium hydrogen carbonate in the heat to neutralise the acid (so benedict's solution can work effectively on it later on) 6. Test the solution using pH paper (e.g. litmus) 7. Add Benedict's solution 8. Blue to copper red would indicate the presence of a reducing sugar as the cu2+ ions would be reduced (they go blue to red, they lost electrons)
What is the difference between amylose and amylopectin?
Amylose is unbranched and compact for extra storage of energy
Amylopectin is branched with many side bonds for fast energy release
What is the chemical formula for disaccharides?
C12H22O11
What is the chemical formula for monosccharides?
C6H12O6
What type of bonding is there between the chains of beta-glucose in cellulose?
Cellulose has many weak hydrogen bonds between the unbranched and straight chains of beta-glucose.
Give 3 properties of glycogen
Insoluble, large, compact
What is the role of glycogen and its location?
It is a storage molecule in animals
How does the structure of glycogen aid with fast respiration?
There is a greater number of branches, so there are a greater number of ‘ends’ for the enzymes to attach to. A greater number of glucose molecules will be released
