3.1.2 Carbohydrates Flashcards
(Carbohydrates) What monomers make up carbohydrates?
Monosaccharides
(Carbohydrates) What are three examples of monosaccharides?
Glucose, fructose and galactose.
(Carbohydrates) Glucose is a hexose sugar, what is a hexose sugar?
A monosaccharide with six carbon atoms in each molecule.
(Carbohydrates) Alpha and beta glucose are isomers. What is an isomer?
A molecule with the same molecular formula as each other, but with the atoms connected in a different way.
(Carbohydrates) When is a disaccharide formed?
When two monosaccharides join together by condensation reactions.
(Carbohydrates) What type of bond is formed when monosaccharide join together?
A glycosidic bond forms between the two monosaccharides as a molecule of water is released.
(Carbohydrates) Surcose is a disaccharide formed a condensation reaction between what two molecules?
A glucose molecule and a fructose molecule.
(Carbohydrates) Lactose is a disaccharide formed between what two molecules?
A glucose molecule and a galactose molecule.
(Carbohydrates) When is a polysaccharide formed?
When more than two monosaccharides are joined together by a condensation reaction.
(Carbohydrates) What can polysaccharides be broken down into?
Into their constituent monosaccharides by hydrolysis reactions.
(Carbohydrates) Where do cells get energy from?
Glucose
(Carbohydrates) What two polysaccharides of alpha-glucose is starch a mixture of?
Amylose and amylopectin
(Carbohydrates) Is starch soluble or insoluble in water?
Insoluble
(Carbohydrates) Starch is insoluble in water and doesn’t affect water potential, so was doesn’t it cause?
It doesn’t cause water to enter the cells by osmosis, which would make them swell - good for storage.
(Carbohydrates) Describe the structure of the polysaccharide ‘amylose’.
- Long, coiled, unbranched chain of alpha-glucose
- Angles of glycosidic bonds give it a coiled structure
- Which makes it compact: good for storage
- Glycosidic C1-4 bonds formed through condensation reaction
- Polymer of alpha glucose
(Carbohydrates) Describe the structure of the polysaccharide ‘amylopectin’.
- Long, branched chain of (polymer of) alpha-glucose
- Glycosidic C1-4 bonds form chains with C1-6 side branches
- Side branches allow enzymes that break down the molecule to get the glycosidic bonds easily, glucose can be released easily
(Carbohydrates) What do animal cells store excess glucose as?
Glycogen
(Carbohydrates) Describe the structure of the polysaccharide ‘glycogen’.
- Similar structure to amylopectin, but with more side branches
- Loads of branches means that glucose stored can be released quickly (important for energy release)
- Glycosidic C1-4 bonds from chains with C1-6 side branches
- Very compact molecule, good for storage
- Insoluble
(Carbohydrates) Describe the structure of the polysaccharide ‘cellulose’.
- Fibrous
- Unbranched
- Provides structure in plants
- Consists of several thousand beta-glucose joined together in a long straight chain by beta 1-4 glycosidic links
(Carbohydrates) What happens when beta-glucose molecules bond in cellulose?
Form straight cellulose chains that are linked together with hydrogen bonds to form microfibrils.
(Carbohydrates) What do microfibrils provide in cellulose?
Structural support for cells.
(Carbohydrates) Describe the food test for starch.
Add 2cm3 of iodine in a potassium iodine solution. Colour change from orange to blue/black.
(Carbohydrates) Maltose is a disaccharide formed by a condensation reaction was what two molecules?
Two glucose molecules
(Carbohydrates) What are the 4 functions of monosaccharides?
- Source of energy in respiration
- Building blocks for much larger polysaccharide molecules - starch, glycogen, cellulose, chitin
- Required to build nucleotides (deoxyribose in DNA, ribose in RNA, ATP)
- Intermediates in biochemical reactions
