Chapter 3: 3.8

Question 1

What is the structure of nucleic acids like?

Answer 1

They are large polymers formed from many nucleotides linked together in a chain.

Question 2

What is an individual nucleotide made up of?

Answer 2

• a pentose monosaccharide (sugar), containing 5 carbon atoms
• a phosphate group that is inorganic, acidic and negatively charged (PO4{2-])
• a nitrogenous base - a complex organic molecule containing 1 or 2 carbon rings in its structure as well as nitrogen.

Question 3

How are nucleotides linked together?

Answer 3

Condensation reactions to form a polymer called a polynucleotide.

Question 4

How is a phosphodiester bond formed?

Answer 4

The phosphate group at the 5th carbon of the pentose sugar of 1 nucleotide forms a covalent bond with the hydroxyl (OH) group at the 3rd carbon of the pentose sugar of an adjacent nucleotide.

Forms a long, sugar-phosphate backbone with a base attached to each sugar.

Question 5

How are the phosphodiester bonds broken?

Answer 5

Hydrolysis - reverse of condensation. Releases individual nucleotides.

Question 6

What does deoxyribonucleic acid (DNA) contain?

Answer 6

Contains the sugar deoxyribose. The nucleotides in DNA each have 1 of 4 different bases. This means there are four different DNA nucleotides, which can be divided into 2 groups: pyrimidines and purines.

Question 7

What are pyrimidines?

Answer 7

The smaller bases, which contain single carbon ring structures - thymine (T) and cytosine (C).

Question 8

What are purines?

Answer 8

The longer bases, which contain double carbon ring structures - adenine (A) and guanine (G).

Question 9

The double helix in DNA

Answer 9

• Can range in length
• Made up of 2 polynucleotide strands coiled into a helix.
• Held together by H-bonds between the bases
• Two strands run anti-parallel, arranged so that they run in opposite directions
• Base pairing allows DNA to be copied and transcribed: key properties required of the molecule of heredity.

Question 10

What are the rules for base pairing?

Answer 10

• Adenine and Thymine are both able to form 2 H-bonds and always join with each other
• Cytosine and Guanine form 3 H-bonds and also only bind to each other [in complementary base pairing]
• Small pyrimidine base always bind to large purine base
• DNA always contains equal amount of Adenine & Thymine and Cytosine & Guanine due to Complementary Base Pairing

Question 11

What role does ribonucleic acid (RNA) play?

Answer 11

• Transfer of genetic information from DNA to the proteins that make up the enzymes and tissues of the body

Question 12

Why can’t DNA leave the nucleus?

Answer 12

• The DNA of each eukaryotic chromosome is a very long molecule, formed from many hundreds of genes

Question 13

What ways does DNA use in order to leave the nucleus?

Answer 13

• The relatively short section of the long DNA molecule corresponding to a single gene is transcribed into a similarly short messenger RNA (mRNA) molecule
• Each individual mRNA is therefore much shorter than the whole chromosome of DNA.

Question 14

Do DNA and RNA form polymers in the same way?

Answer 14

Yes - by the formation of phosphodiester bonds in condensation reactions.

Question 15

What happens to RNA after protein synthesis?

Answer 15

The RNA molecules are degraded in the cytoplasm. The phosphodiester bonds are hydrolysed and the RNA nucleotides are released/reused.

Question 16

What elements make up nucleic acid?

Answer 16

Carbon Hydrogen, Oxygen, Nitrogen Phosphorus.

Question 17

How do you carry out DNA extraction?

Answer 17

1) You will grind the sample in a motar and pestle - which breaks down the cell wall
2) Mix the sample with detergent - which breaks down the cell membrane, releasing cell contents into solution
3) Add salt that breaks the hydrogen bond between DNA and water molecules
4) Add pro-tease enzyme - which breaks down the proteins associated with the DNA in the nuclei
5) Layer of alcohol is then added on top of the sample - alcohol causes the DNA to precipitate out of solution
6) DNA can then be seen as white strands forming between layer of the sample and layer of alcohol

DNA is then picked up by spooling onto a glass rod

Question 18

What does DNA store?

Answer 18

DNA stores all genetic information needed by an organism, which is then passed from generation to generation

Question 19

What mRNA made up of?

Answer 19

: it is a polymer composed of many nucleotide monomers

Question 20

What is the role of nucleic acid?

Answer 20

They are responsible for the storage and transfer of genetic information and the synthesis of polypeptides (proteins)

Question 21

The two types of nucleic acid?

Answer 21

DNA and RNA

Question 22

What are the differences between RNA and DNA?

Answer 22

RNA has a pentose sugar that is ribose rather than deoxyribose

Has uracial base rather than a thymine base

Question 23

How is RNA and DNA similar>

Answer 23

Uracil form 2 hydrogen bonds with adenine similar like thymine in DNA

RNA nucleotide bind to DNA following the base pairing rules