3.1.1 | biological molecules Flashcards
What is the monomer of carbohydrates?
monosaccharides
What are 3 examples of monosaccharides?
fructose
glucose
galactose
How are disaccharides formed?
Two monosaccharides are joined together by a glycosidic bond in a condensation reaction, releasing water
What are monosaccharides?
sweet-tasting, soluble substances that are the monomer of carbohydrates
What is the general formula for monosaccharides?
(CH2O)n
What are the two isomers of glucose?
Alpha and beta glucose.
What is an isomer?
a molecule that has the same molecular formula as another molecule, but a different arrangement of atoms
How do you test for reducing sugars?
Benedict’s test
How do you carry out the Benedict’s test?
Add liquid sample to a test tube
add Benedict’s Reagent in excess
heat the mixture
positive result= blue to brick red
What type of test is the Benedict’s test?
semi-quantitative test
Why is the Benedict’s test semi-quantitative?
Colour change is used to estimate the amount of reducing sugar present, where blue is the least and brick red the most
What are 3 examples of disaccharides?
Sucrose, lactose, maltose
What are the monomers of maltose?
Glucose + glucose
What are the monomers of sucrose?
Glucose + fructose
What are the monomers of lactose?
Galactose + glucose
What are polysaccharides?
Polymers made by combining more than 2 monosaccharides in a condensation reaction, releasing a water molecule for each glycosidic bond
what are 3 polysaccharides?
starch, cellulose and glycogen
What is the test for non-reducing sugars?
Hydrolysis into monosaccharides and then Benedict’s test.
How do you test for reducing sugars?
carry out Benedict’s to produce and negative result
- add new sample to test tube and add hydrochloric acid and heat to hydrolyse
-add sodium hydrogen carbonate to neutralise
-test that the solution is now alkaline with pH paper
-retest with Benedict’s
-positive result= blue to brick red
How do you test for starch?
-add sample to test tube
-add 2 drops of potassium iodide and shake
-positive result= yellow to blue-black
What is starch?
a polysaccharide found in plants as grains, which occur in seeds and storage organs
What is the structure of starch?
Made of alpha glucose linked by 1-4 and 1-6 glycosidic bonds, it can be branched (amylose) or unbranched (amylopectin)
How is starch’s structure suitable for it’s function?
compact, fit more in, good for storage
Insoluble - doesn’t affect water potential
Branched chains - more efficient hydrolysis for respiration
Large - can’t leave cell
What is glycogen?
Polysaccharide found in bacteria and animals as a carbohydrate storage found in the liver and muscles
