3.8 Nucleic acids

Question 1

What is a nucleic acid? (2 marks)

Answer 1

Large polymers formed by many nucleotides linked together, that were discovered in cell nuclei.

Question 2

Name the two types of nucleic acid. (1 mark)

Answer 2

RNA
DNA

Question 3

What elements do nucleic acids contain? (2 marks)

Answer 3

Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus

Question 4

Describe the structure of a nucleotide. (3 marks)

Answer 4

Pentose sugar bonded to:
A phosphate group
And a nitrogenous base

Question 5

How are nucleotides linked together? (2 marks)

Answer 5

Condensation reactions between the phosphate group on the 5th carbon and the hydroxyl group on the 3rd carbon.

Question 6

What are the covalent bonds between nucleotides called? (1 mark)

Answer 6

Phosphodiester bonds.

Question 7

Nucleotides joined by condensation reactions are sometimes referred to as a strong s_____-p__________ b_______. (1 mark)

Answer 7

Strong sugar-phosphate backbone

Question 8

What does DNA stand for? (2 marks)

Answer 8

Deoxyribonucleic acid

Question 9

Wat pentose sugar does DNA contain? (1 mark)

Answer 9

Deoxyribose

Question 10

What four bases can each nucleotide in DNA contain? (4 marks)

Answer 10

Thymine
Cytosine
Adenine
Guanine

Question 11

Bases can be divided into two groups depending on what?

Answer 11

How many carbon rings they have.

Question 12

What are the two categories of base? (2 marks)

Answer 12

Pyrimidines
Purines

Question 13

How many carbon rings do pyrimidines have? (1 mark)

Answer 13

One

Question 14

How many carbon rings do purines have? (1 mark)

Answer 14

Two

Question 15

Name the two bases in DNA with two carbon rings. (2 marks)

Answer 15

Adenine
Guanine

Question 16

Name the two bases in DNA with one carbon ring. (2 marks)

Answer 16

Thymine
Cytosine

Question 17

Name the bases in DNA that are pyrimidines. (2 marks)

Answer 17

Thymine
Cytosine

Question 18

Name the two bases in DNA that are purines. (2 marks)

Answer 18

Adenine
Guanine

Question 19

What is a DNA molecule made up of? (2 marks)

Answer 19

Two strands of polynucleotides coiled into a helix, known as a double helix.

Question 20

What are the two strands in a DNA molecule held together by? (1 mark)

Answer 20

Hydrogen bonds between bases.

Question 21

The two strands in a DNA molecule are a_____________ because they run in o__________ d_____________.

Answer 21

The two strands in a DNA molecule are anti-parallel because they run in opposite directions.

Question 22

What does the pairing between bases allow for DNA? (1 mark)

Answer 22

Allows DNA to be copied and transcribed.

Question 23

What are the complementary base pairings? (2 marks)

Answer 23

Adenine-thymine
Cytosine-guanine

Question 24

Why is it important that a small base always binds with a larger base? (2 marks)

Answer 24

Maintains a constant distance between the DNA backbones, resulting in parallel polynucleotide chains.

Question 25

What carries the genetic information of an organism in the form of code (1 mark)

Answer 25

The sequence of bases along a DNA strand.

Question 26

What pentose sugar is in RNA? (1 mark)

Answer 26

Ribose

Question 27

What does RNA stand for? (2 marks)

Answer 27

Ribonucleic acid

Question 28

Why can DNA not leave the nucleus, why is this a problem, and how is this problem be solved? (4 marks)

Answer 28

DNA cannot supply the information directly to the sites of protein synthesis. Short sections of the long DNA molecule (corresponding to a single gene) is transcribed into a short messenger RNA (mRNA), this can leave the nucleus.

Question 29

Which base is different in RNA in comparison to DNA? (1 mark)

Answer 29

No thymine Uracil instead

Question 30

Is uracil a pyrimidine or a purine? (1 mark)

Answer 30

Pyrimidine

Question 31

What happens to the RNA molecules after protein synthesis? (2 marks)

Answer 31

They are degraded in the cytoplasm- the phosphodiester bonds are hydrolysed and the RNA nucleotides are released and reused.

Question 32

Describe how DNA can be extracted from plant material. (6 marks)

Answer 32

1. Grind sample using a mortar and pestle 2. Mix sample with detergent 3. Add salt 4. Add protease enzyme 5. Add a layer of alcohol on top of the solution 6. The DNA forms white strands between the layer of sample and layer of alcohol, 'spool' with a glass rod to pick them up.

Question 33

When extracting DNA from plant material, what does grinding the sample do? (1 mark)

Answer 33

Break down the cell walls.

Question 34

When extracting DNA from plant material, what does mixing the sample with a detergent do? (1 mark)

Answer 34

Breaks down the cell membrane, releasing the cell contents.

Question 35

When extracting DNA from plant material, what does adding salt to the sample do? (1 mark)

Answer 35

Breaks hydrogen bonds between the DNA and water molecules.

Question 36

When extracting DNA from plant material, what does adding protease enzyme do? (1 mark)

Answer 36

Break down the proteins associated with the DNA in the nuclei.

Question 37

When extracting DNA from plant material, what does adding a layer of alcohol on top of the sample do? (1 mark)

Answer 37

Causes the DNA to precipitate out of solution.

Question 38

Is RNA single or double stranded? (1 mark)

Answer 38

Single