2.3 Carbohydrates and lipids Flashcards
What are carbohydrates?
-Organic compounds with the general formula C x (H 2 O) y.
-They form the most important source of energy in the body.
How can carbohydrates be classified?
-Monosaccharides, disaccharides, and polysaccharides.
-Monosaccharides and disaccharides are both considered sugars, which are polar and soluble in water.
-Polysaccharides are macromolecules resulting from the polymerization (condensation) of sugars and are not soluble in water.
What are monosaccharides?
-The simplest types of carbohydrates.
-The number of carbon atoms can range from three to seven.
-The carbons are joined to a hydroxyl group (-OH).
Examples of monosaccharides
Ribose, glucose, fructose and galactose.
Monosaccharides act as ___
Monomers to make larger complex carbohydrate molecules.
Two monosaccharide monomers are linked together by a ___
Condensation reaction which forms a glycosidic bond producing a disaccharide, releasing one water molecule.
What do several monomer units linked together form?
A polysaccharide.
What is a condensation reaction?
-A reaction in which two smaller organic molecules combine to form a larger molecule and a molecule of water or some other simple molecule.
-The reaction opposite to condensation is called hydrolysis.
-This is a chemical reaction in which water is used to break down the bonds of big compounds.
To avoid confusing condensation and hydrolysis, think about the following ideas.
-Condensation is just like the formation of condensation (water droplets) on a cold window: water droplets are produced.
-Hydrolysis is the opposite of condensation. It is when water (‘hydro’) is added and used to break up (‘lyse’) a polymer, a disaccharide or a dipeptide into smaller monomers.
Diagram showing monosaccharides and condensation reactions. (Two monomers of glucose forming the disaccharide maltose and water in a condensation reaction.)
What is glucose?
A monosaccharide.
What two forms does glucose exist in?
-D-glucose and L-glucose.
-They are isomers meaning they have the same chemical formula but a slightly different arrangement of the atoms.
-Furthermore, there are two forms of the D-glucose, α-D-glucose, and β-D-glucose.
-These differ in the placement of the -OH group on carbon 1.
Diagram of Alpha-D-glucose
Diagram of Beta-D-glucose
What form of glucose does this diagram show?
Alpha-D-glucose
What form of glucose does this diagram show?
Beta-D-glucose
Glucose is often drawn in an abbreviated form where the ____
The carbon atoms are omitted.
What are polysaccharides?
Polysaccharides are large molecules, such as cellulose, glycogen and starch.
What is the function of glycogen?
It is a storage substance in animals and fungi.
Plants store ___ in their roots and stems.
Starch
Examples of disaccharides
-Sucrose
-Maltose
-Lactose
What are the monomers of sucrose?
Glucose and fructose
What are the monomers of maltose?
Glucose (2 units)
What are the monomers of lactose?
Glucose and galactose