3.8 Nucelic Acids

Question 1

What are nuclelic acids

Answer 1

large molecules in the nucleus

Question 2

What are the 2 types of nucleic acid

Answer 2

DNA

RNA

Question 3

What do DNA and RNA have in common?

Answer 3

both have roles in storage and transfer of genetic info and synthesis of polypeptides (proteins)

Question 4

What do nucleic acids contain

Answer 4

carbon, hydrogen, oxygen, phosphorous and nitrogen

Question 5

How are they formed

Answer 5

From nucleotides (the monomers) linked together in a long chain, to make a large polymer

Question 6

What is a single nucleotide made up of?

Answer 6

1. a nitrogenous base (adenine, thymine, guanine, cytosine)
2. a phosphate group (acidic & neg. charged)
3. a sugar (pentose monosaccharide)

Question 7

How are nucleotides held together?

Answer 7

through condensation reactions to form a polynucleotide; a covalent bond forms between the phosphate group at the 5th carbon of the sugar of one nucleotide and the hydroxyl group (OH) of the 3rd carbon of another nucleotide.
These bonds are called PHOSPHODIESTER BONDS

Forms a ‘backbone’ of sugar and phosphates

Question 8

How are phosphodiester bonds broken

Answer 8

Hydrolysis reactions (with H2O), making singular nucleotides

Question 9

What does DNA stand for

Answer 9

Deoxyribonucleic acid

Question 10

What are pyrimidines

Answer 10

smaller bases that contain only single carbon ring structures (thymine and cytosine)

Question 11

what are purines

Answer 11

larger bases that contain double carbon ring structures (guanine and adenine)

Question 12

How do nucleotides make up DNS’s double helix structure

Answer 12

There are 2 strands of nucleotides held together by hydrogen bonds; the 2 strands are said to be antiparallel because they run in opposite directions.

The pairings between bases allows DNA to be transcribed properly - key properties required of the molecule heredity.

Question 13

How many bonds do adenine and thymine make?

Answer 13

Two hydrogen bonds

Question 14

How many bonds do guanine and cytosine make

Answer 14

Three hydrogen bonds

Question 15

What is complementary base pairing

Answer 15

A/T and C/G can only pair with each other because they make the same amount of hydrogen bonds

Question 16

What does RNA stand for

Answer 16

Ribonucleic acid

Question 17

What is the role of RNA

Answer 17

An essential role in transferring genetic material from DNA to the proteins that make the tissues and enzymes of the body

Question 18

Why is RNA useful in transcription?

Answer 18

DNA is too long to leave the nucleus so when the info is copied into a shorter mRNA messenger (secondary messenger) it can leave the nucleus with the same info needed.

Question 19

What is RNA made up of

Answer 19

It’s a polymer made of lots of nucleotides

Question 20

How do RNA nucleotides differ to DNA nucleotides

Answer 20

1. in RNA, thymine is uracil (another small pyrimidine that makes 2 hydrogen bonds)
2. the pentose sugar is ribose (not deoxyribose)

Question 21

Why can RNA polymers be reused after protein synthesis?

Answer 21

Because they’re small enough to leave the nucleus (formed through condensation reactions = phosphodiester bonds) and travel to ribosomes where they’re used in protein synthesis.

After this the RNA molecules are degraded in the cytoplasm, the bonds break and the nucleotides are reused.

Question 22

PAG: DNA EXTRACTION (PROCESS)

Answer 22

In plant material:

1. grind sample in small mortar and pestle to break cell walls
2. mix sample with detergent to break cell membrane
3. add salt - this breaks hydrogen bonds between DNA and H2O molecules
4. add protease enzyme - to break down enzymes in the nuclei
5. add a layer of ethanol - alcohol causes the DNA to come out of the precipitate
6. the strands will appear as white wisps between the ethanol and sample.