Biological Molecules

Question 1

What is a macromolecule?

Answer 1

It is a large molecule such as a polysacchsride, protein or nucleic acid.

Question 2

What is meant by the term polymers?

Answer 2

They are made up of many repeating subunits which are similar or identical to each other. Examples include: Polysaccharides, proteins and nucleic acid.

Question 3

What is meant by monomer?

Answer 3

a relatively simple molecule which is used as a basic building block for the synthesis of the polymer. Many monomers are joined together by covalent bonds to form the polymer. These are usually condensation reactions.

Common examples of monomers: Monosaccharides, amino acids and nucleotides.

Question 4

What is meant by Condensation reaction.

Answer 4

A chemical reaction involving the joining together of two molecules by removal of a water molecule.

Question 5

Describe the process of hydrolysis.

Answer 5

a chemical reaction in which a chemical bond is broken by the addition of water molecule; commonly used to break down complex molecules into simpler molecules.
For instance, adding water and breaking the polymer again into two monomers.

Question 6

what is meant by monosaccharides.

Answer 6

a molecule consisting of a single sugar unit and with the general formula (CH2o)n
The main types of monosaccharides are trioses (3 carbons), pentoses ( 5 carbons) and hexoses (6 carbons)

Common hexoses are glucose, fructose and galactose.
two common pentoses are ribose and deoxyribose.

Question 7

• **How is the molecular and structural formulae for hexose written as?[]

Answer 7

The molecular formula for the hexose can be written as C6 h12 06. It shows that there are 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms in the molecule.

glucose is one of the most common monosaccharide. It is a hexose.

Question 8

Describe the difference between alpha and beta glucose. Display their structure

Question 9

describe the functions of monosaccharides in living organisms.

Answer 9

Firstly, they are commonly used as a source of energy in respiration. This is due to the large number of carbon and hydrogen bonds.These bonds can be broken to release alot of energy, which is transferred to help make ATP adenosine triphosphate from ADP plus phosphate during the process of respiration.

Monosaccharides are important as building blocks for larger molecules. For example, glucose is used to make the polysaccharide starch, glycogen and cellulose.
Ribose (pentose) is one of the molecules used to make RNA (ribonucleic acid) and ATP.
Deoxyribose also a pentose is one of the molecules used to make DNA.

Question 10

What is meant by disaccharide?

Answer 10

It is a sugar molecule consisting of two monosaccharides joined together by glycosidic bond.
The three most common disaccharides are:
maltose (glucose+glucose) , sucrose (glucose+fructose) and lactose ( glucose+ galactose)
The process of joining two monosaccharides is an example of condensation reaction.
The reverse process of splitting a disaccharide into two monomers is an example of hydrolysis.

Question 11

What is meant by the glycosidic bond

Answer 11

For each condensation reaction, two hydroxyl groups line up alongside each other, one combines with hydrogen atom from the other to form a water molecule.
this allows to form an oxygen bridge to form between two molecules, holding them together and forming a dissacharide. The bridge is called glycosidic bond.

Question 12

what is meant by the term polysaccharide?

Answer 12

a polymer whose subunits are monosaccharides joined together by glycosidic bond. The most important polysaccharides ae starch, glycogen and cellulose all of which are polymers of glucose.

Question 13

name the storage polysaccharide in plants and animals.

Answer 13

The storage polysaccharide in plants is starch, in animals, it is glycogen.
When needed, glucose is quickly made available again by enzyme controlled hydrolysis reactions.

Question 14

Name the two parts of starch and explain the first part of starch.

Answer 14

Starch is a mixture of two substances, amylose and amylopectin. Amylose the first part of starch is made by condensations between alpha glucose molecules.

in this way, a long unbranching chain of several thousand 1,4 linked glucose molecules is built up.1,4 linked between carbon 1 and 4 of sucessive glucose units.

Question 15

Describe the structure of Amylopectin second part of Starch.

Answer 15

Amylopectin is also made up of many 1,4 linked alpha glucose molecules, but the chains are shorter than in amylose and also contains 1,6 linkages. These start branches over the sides of the chain.

Question 16

Describe and explain in terms of structure what is meant by the term glycogen?

Answer 16

Glycogen is the storage carbohydrate in animals. it has molecules very like those of amylopectin because it is made up of 1,4 linked alpha glucose with 1,6 linkages making branching points.

glycogen molecules clump together to form granules, which are visible in liver cells and muscle cells, where they form an energy reserve.

Question 17

How does the beta glucose molecules line up in a cellulose molecule?

Answer 17

Two beta glucose molecules lined up to form a 1,4 link. Note that one glucose molecule must be rotated 180 degrees relative to the other.

Question 18

Describe the role of microfiber bundles in strengthening the Cell wall.

Answer 18

The hydrogen bonds are generally weak, but there are soo many of them due to large number of OH groups that collectively they provide enormous strength. between 60 to 70 molecules become tightly cross linked by hydrogen bonding to form microfibrils.

Question 19

how is the hydrogen bond formed?

Answer 19

when atoms in molecules are held together by covalent bonds, they share electrons with each other. each shared pairs of electrons form one covalent bond.
However electrons are not shared absolutely equally. In water, oxygen atom gets slightly more than its fair share, and so has small negative charge. The hydrogen atoms get slightly less than their fair share, and so has small positive charge, written delta plus.

in water, the negatively charged oxygen of one molecule is attracted to positively charged hydrogen of another and this attraction is called hydrogen bond.

Question 20

what are hydrophilic water molecules?

Answer 20

Molecules that have groups with dipoles such as sugars are said to be polar. Polar molecules are attracted to water molecules because the water molecules also have dipoles.

Question 21

what are hydrophobic water molecules?

Answer 21

molecules which do not have dipoles are said to be non polar. They are not attracted to water so are hydrophobic water hating.

Question 22

how are lipids formed and explain the difference between fats and oils.

Answer 22

Most lipids are formed by fatty acids combining with an alcohol. The most familiar ones are fats and oils. Fats are solid at room temperature and oils are liquid at room temperature, but chemically they are very similar,