CARBOHYDRATES Flashcards
What are carbohydrates made from?
They are made from monosaccharides and contain carbon, hydrogen and oxygen atoms.
What are monosaccharides?
Monosaccharides are glucose, galactose(found in milk) and fructose(found in fruit).
What is glucose?
Glucose is a hexose(6 carbon) sugar which has the chemical equation C6H12O6
What is the difference between alpha and beta glucose?
Alpha and beta glucose are isomers meaning they have the same molecular formula but just in different arrangments.
What is a monomer?
Individual molecules that make up a polymer.
What a polymers?
Polymers are long chains of individual molecules called monomers that have been bonded together in a repeating pattern.
What are the seperate terms for saccharides?
Single monomer= monosaccharide
Two monomers= disaccharide
Polymer= Polysaccharide
What is the structure for alpha glucose?
It’s a hexagon shape with the two hydrogens on top and the OH’s on the bottom.
What’s the structure for beta glucose?
It’s a hexagon shape with a H and an OH on the top and bottom.
How are disaccharide and polysaccharides formed?
When two monomers join together via a condensation reaction. Whereas a polysaccharide forms when more than two monomers join together in a condensation reaction
What is the difference between condensation and hydrolysis?
Condensation joins two molecules together chemically and hydrolysis breaks the bond between two molecules
What are examples of disaccharides?
glucose + glucose –> maltose
glucose + fructose –> sucrose
glucose + galactose –> lactose
What are the functions of disaccharides?
Sucrose is common in table sugar and lactose is the sugar found in milk (lactose intolerant).
What are polysaccharides?
Are made up of three or more monosaccharides joined together by glycosidic bonds. Examples are glycogen, starch and cellulose.
What is the test for reducing sugar?
Benedict’s solution can be reduced by reducing sugars. Benedict’s solution is clear blue and changes colour due to how much it’s been reduced.
Step 1: add 2ml of a substance in a boiling tube
Step 2: add 10 drops of Benedict’s solution
Step 3: place in a boiling water bath for 3-10 minutes
What is reduction and a reducing sugar?
Reduction is a chemical reaction involving the gain of electrons or hydrogen therefore reducing sugars have the ability to donate an electron or reduce a chemical eg Benedict’s.
All monosaccharides are reducing sugars but only some disaccharides (maltose and lactose) are.
What are the results of a Benedict’s test?
Blue= no reducing sugar
Green/ yellow= traces of reducing sugar
Orange/ red = moderate amounts of reducing sugar
Brick red= large amounts of reducing sugar
What is the test for non-reducing sugars?
Step 1 - Boil in dilute HCL to (hydrolyse the non-reducing sugar)
Step 2- Neutralise the solution by adding sodium hydrogen carbonate
Step 3- Repeat the benedict’s test
It will remain blue if it’s a non-reducing sugar
What is the function of starch?
- Starch is the main energy storage in plants
- Starch is broken down into glucose by plants when they need more energy
- Starch can be a source of food for animals and humans
What is the test for starch?
Iodine solution.
Step 1: Place a sample into the dimple of a spotting tile or boiling tube.
Step 2: Add a few drops of iodine solution and observe any colour change.
If starch is present the solution will change to orange to blue to black.
What is starch?
Starch is a polysaccharide that is found in many parts of a plant eg the seed. It is made up of chains of alpha glucose monosaccharides linked by glycosidic bonds formed in condensation reactions. The chain might be branched or unbranched.
Why is the structure of starch suitable for it’s storage function?
- It’s large and insoluble so it doesn’t diffuse out of cells.
- It’s compact so can be stored in a small space
- When hydrolyse it froms alpha glucose which can be easily transported and readily used in respiration
- The branch form has many ends meaning it can be acted on by enzymes simultaneously meaning glucose monomers are released rapidly.
What is starch made up from (not polysacchharide)?
Amylopectin and amylose which are both alpha glucose polysaccharides.
What is the structure of amylose and amylopectin?
Amylopectin has a long unbranched helical structure which makes it ideal for storage and amylose has a long branched structure which makes it ideal for quick energy release.
