3.3 Carbohydrates Flashcards
What elements are found in carbohydrates?
Carbon
Hydrogen
Oxygen
General formula of carbohydrates
Cx (H2O)y
What is a monosaccharide?
A single sugar unit
Examples of monosaccharides
Glucose
Fructose
Ribose
What is a disaccharide?
2 monosaccharides joined together
Examples of disaccharides
Sucrose
Maltose
Lactose
What monosaccharides make up sucrose?
Fructose and glucose
What monosaccharides make up maltose?
2 alpha glucose
What monosaccharides make up lactose?
Galactose and glucose
What is a polysaccharide?
Many monosaccharides joined together
Examples of polysaccharides
Glycogen
Cellulose
Starch
What are hexose monosaccharides?
They contain 6 carbons
Example of hexose monosaccharide
Glucose
What are pentose monosaccharides?
They contain 5 Carbons
Eg of pentose monosaccharide
Ribose, Deoxyribose
Two types of glucose
Alpha and beta glucose
Difference between alpha and beta glucose
Alpha - OH on Carbon 1 is on the bottom
Beta - OH on Carbon 1 is at the top
Properties of glucose
Polar and soluble in water, due to the hydrogen bonds between Hydroxyl groups and water molecules
Why is the solubility of glucose in water important?
This means glucose can be dissolved in the cytosol of the cell
Why is glucose a good source of energy?
When the bonds in glucose are broken, a lot of energy is released
What is a hydrolysis reaction?
It breaks a chemical bond between 2 molecules, with the use of a water molecule
What is a condensation reaction?
It joins 2 molecules together, forming a chemical bond, where a water molecule is eliminated
What happens when 2 glucose molecules react together?
The two OH groups react together, forming a glycosidic bond - a type of covalent bond between Carbon 1 and 4, so it is called a 1-4 glycosidic bond
Polysaccharides in starch
Amylose
Amylopectin
How is amylose formed?
By condensation of alpha glucose molecules, forming 1-4 glycosidic bonds ONLY
How does the structure of amylose relate to its function?
The angle of the 1-4 glycosidic bond means amylose twists to form a helix, strengthened by hydrogen bonds. This means the polysaccharide is more compact and less soluble than the glucose - so a good molecule for storage.
What type of glycosidic bonds does amylopectin form?
1-4 and 1-6 glycosidic bonds
How does the structure of amylopectin relate to its function?
It has a branched structure, which makes it compact and better for storage. Also, with branching, there are more free ends where glucose molecules can be added and removed. It is also insoluble.
Equivalent of amylopectin in animals
Glycogen
Differences between glycogen and amylopectin
Glycogen forms more branches, so it’s more compact and less space is required for storage, which is important as animals move around more.
What is the monosaccharide in cellulose?
Beta glucose
How do beta glucose molecules join together in cellulose?
Alternate beta glucose molecules turn upside down and join together
Why do beta glucoses have to bond in a different way?
The OH groups are too far apart to form 1-4 glycosidic bonds otherwise
What is the result of the beta glucoses bonding in a different way?
They cannot coil or form branches, so it’s a straight chain molecule
How are fibres formed?
Cellulose molecules make hydrogen bonds with each other to form microfibrils
Microfibrils join to form macrofibrils
Macrofibrils join to form fibres
Properties of fibres made of cellulose
Strong and insoluble
