Biological Molecules Flashcards
What are the three types of carbohydrates?
Monosaccharides
Disaccharides
Polysaccharides
Define monosaccharides
Single sugar monomer, all are reducing sugars
Define disaccharide
A sugar formed from two monosaccharides joined by a glycosidic bond in a condensation reaction
Define polysaccharide
A polymer formed by many monosaccharides joined by glycosidic bonds in a condensation reaction
Define monomer
A small molecules that bond with many repeating subunits to form large molecules. e.g. glucose
Define macromolecules
They are long chains of molecular subunits
What are the two structurally different forms of glucose?
alpha-glucose and beta-glucose (isomers)
Molecular formula of glucose
C6H12O6
When does a condensation reaction occur?
When monomers combine by covalent bonds to form polymers or macromolecules and water is removed
What occurs during hydrolysis?
Covalent binds are broken when water is added
Functions of glucose (3)
1) Oxidised to release energy in the process of respiration
2) Glucose is the form in which carbohydrates are transported in the body
3) Building blocks for making larger molecules such as starch, glycogen and cellulose
What is the bond that links two glucose molecules?
Glycosidic bond
What type of sugars are glucose, fructose and maltose?
Reducing sugars
What type of sugar is sucrose?
Non-reducing sugar
Describe the breakage of glycosidic bonds with reference to the test for non-reducing tests
Non reducing sugars can also be tested for using Benedict’s reagent but first require addition of and heating to hydrolyse the sugar (breaks the glycosidic bond). The acid must be neutralised before doing the test
Function of starch
Main storage polysaccharide in plants
Describe the structure of starch
It consists of of two different polysaccharides, amylose and amylopectin. Amylose is unbranched helix shaped chain with 1,4 glycosidic bonds between alpha-glucose molecules. Amylopectin has 1,4 glycosidic bonds between alpha-glucose but also 1,6 glycosidic bonds form between glucose molecules creating branched molecule
Relate structure to function for starch
Amylose- the helix shape enables it to be more compact and resistant to digestion
Amylopectin- the branches may be easily hydrolysed for either respiration or storage
Function of glycogen
Main storage polysaccharide in animals and fungi
Describe structure of glycogen
Similar to amylopectin but with many more branches which are also shorter
Relate structure to function for glycogen
Is branched so it is more compact which helps animals store more, very fast hydrolysis
Function of cellulose
Main structural constituent of plant cell walls
Structure of cellulose
Long, unbranched polymers of glucose joined by beta- 1,4 glycosidic bonds. Many hydrogen bonds form between the long chains
Relate structure to function for cellulose
Hydrogen bonds are very strong and give cellulose its strength, provides strength to plant