Molecules Flashcards
Explain the structure of a water molecule
Each hydrogen atom shares a pair of electrons with an oxygen atom, forming a covalent bond. The hydrogen has a slight positive charge and the oxygen is slightly negative, meaning water is a polar molecule. The polar nature of water results in the formation of hydrogen bonds between adjacent water molecules, extending between the oxygen atom of one molecule and a hydrogen atom of another.
Describe waters value as a solvent
Most of a cells reaction takes place in aqueous solution.
Its ability to act as a transport medium in living organisms.
The different effects it has on hydrophobic and hydrophilic molecules.
What is a buffer?
Chemical substances that resist changes to pH and ensure that particular environments maintain a particular pH. They ensure that that enzymes involved are operating at their optinum pH.
What is a monosaccharide?
Basic carbohydrates ie simple sugars.
What is disaccharide?
Double sugars formed when 2 monosaccharides are joined together.
What is a polysaccharide?
Complex molecules consisting of many monosaccharide monomers.
Formula for monosaccharides
C6H12O6
What is the basic sub-unit of starch and glycogen?
a-glucose
What is the constituent monomer of cellulose?
B-glucose
How does a-glucose differ from B-glucose?
The hydrogen and hydroxyl group is reversed. Further small changes give fructose.
What are hexose monomers such as glucose important in?
The storage of energy in living organisms.
What is an isomer?
Monomers with the same molecular formula but different structural formulae e.g a-glucose and B-glucose.
What are the bonds formed in disaccharides?
a-1,4 glycosidic bonds
How are the 2 monosaccharides joined?
Condensation reaction with the loss of water. This can be reversed, resulting in a hydrolysis reaction. Hydrolysis reaction = important in digestion of food.
Formula of disaccharides
C12H22O11
Are disaccharides soluble?
Yes, they dissolve in water to produce sweet tasting solutions as they are all sugars.
Maltose
It is formed when starch is digested, and requires further digestion to form glucose. 2 a-glucose monomers joined together by condensation reactions.
Sucrose
It is the form in which carbohydrate is transported through phloem in plants. One a-glucose monomer is condensed with a fructose molecule.
General formula for polysaccharides
(C6H10O5)n
Are polysaccharides soluble in water?
No, and they are not sweet.
Amylose
a-1,4 glycosidic bonds.
Chains are coiled to form a spiral held by hydrogen bonds.
Long, unbranched chains.
Coiled configuration.
20% of starch.
Amylopectin
a-1,4 and a-1,6 glycosidic bonds form side branch to produce a branched molecule.
80% of starch.
Why is starch a good storage molecule?
Both amylose and amylopectin are very compact (coiled configuration) so can store a rich amount of glucose in a small space.
Large molecule- retained in cell and not easily passed through the membrane.
Branching nature creates many terminal ends that are readily hydrolysed , aiding the rapid enzymatic breakdown of starch.
