Carbohydrates - Biological Molecules Flashcards
What are carbohydrates
- Carbohydrates are molecules which consists only of carbon hydrogen and oxygen
- They are long chains of sugar units called saccharides.
What is a monosaccharide and disaccharide
Monosaccharides a single monomer
Disaccharide is a pair of monomers
How does a polysaccharide form
Combing many monosaccharides form a polysaccharides.
What happens when all polysaccharides join together
Through a glycosidic bond which is formed in a condesation reaction all of these molecules join together.
What is glucose
Glucose is a monosaccharide conatining six carbon atoms in each molecule and is the main substrate for respiration and therefore of great importance.
What are the two isomers of glucose
Alpha and Beta glucose
What are examples of disaccharides
Maltose
sucrose
Lactose
How is maltose formed
Maltose is formed by the condensation of two glucose molecules
How is sucrose formed
Sucrose is formed by the condensation of glucose and fructose
How is lactose formed
Lactose is formed by condensation of glucose and galactose
How is glycogen and starch formed
Glycogen and starch is formed by the condensation of alpha glucose
How is cellulose formed
Cellulose is formed by the condensation of beta glucose.
What is glycogen the main energy store in
Glycogen is the main energy store in animals and is formed from many molecules of alpha glucose joined together by 1,4 and 1,6 glycosidic bonds
Why is glycogen having many branches a good feature for it
It has a large amount of side branches meaning energy can be released quickly as enzymes can act simultaneously on these branches. Moreover its large and compact molecule therefore maximising the amount of energy it can store.
What is the purpose of starch
Starch stores energy in plants and is a mixture of two polysaccharides called amylose and amylopectin.
What is the structure of amylose
Amylose is an unbranched chain of glucose molecules joined together by 1, 4 glycosidic bonds. Therefore amylose is coiled and very compact resulting in a large amount of energy storage.
What is the structure of amylopectin
Amylopectin is branched and made up glucose molecules with a 1-4 and 1-6 glycosidic bond. Due to the presence of side branches these can be acted upon simultaneously by many enzymes and broken down to release energy.
What are the key properties of starch
- It is insoluble so it will not affect cell water potential
- It is compact so a lot of energy can be stored in a small space and when hydrolysed the released alpha glucose can be transported easily.
What is cellulose
Cellulose is a component of cell walls in plants and is composed of long unbranched chains of beta glucose which are bonded by glycosidic bonds.
What are microfibrils
MIcrofibrils are are strong threads which are made up of long cellulose chains running parallel to one another that are joined by hydrogen bonds forming strong cross links.
