Biological molecules 2

Question 1

What does DNA stand for?

Answer 1

Deoxyribonucleic acid

Question 2

What does a DNA nucleotide consist of?

Answer 2

Phosphate, nitrogen base, deoxyribose sugar

Question 3

What does an RNA nucleotide consist of?

Answer 3

Phosphate, nitrogen base, ribose sugar

Question 4

What does RNA stand for?

Answer 4

Ribonucleic acid

Question 5

What bases can a DNA nucleotide have?

Answer 5

Adenine, cytosine, guanine, thymine

Question 6

What bases can an RNA nucleotide have?

Answer 6

Adenine, cytosine, guanine, uracil

Question 7

What molecule is usually longer, DNA or RNA?

Answer 7

DNA

Question 8

What is the function of RNA?

Answer 8

To transfer genetic information from DNA to the ribosomes which read the RNA to make polypeptides

Question 9

Why is DNA such a stable molecule?

Answer 9

It has multiple hydrogen bonds between bases and the ladder is held together by sugar-phosphate backbones

Question 10

How many hydrogen bonds do cytosine and guanine form?

Answer 10

3

Question 11

How many hydrogen bonds does adenine and thymine form?

Answer 11

2

Question 12

What bond forms between the phosphates and sugars in the DNA ladder?

Answer 12

Phosphodiester bond

Question 13

What is the process of DNA replication in the semiconservative method?

Answer 13

• DNA helicase separates the strand by breaking the hydrogen bonds
• DNA polymerase binds the complimentary nucleotides to the strands
• The leading strand is formed first, continuously from 5’ to 3’
• The lagging strand is formed from 5’ to 3’ but because the strands are antiparallel, this creates okazaki fragments

Question 14

Who came up with the idea of semi-conservative replication?

Answer 14

Watson and Crick

Question 15

Who proved the theory of semiconservative replication?

Answer 15

Meselson and Stahl

Question 16

What was the process of the experiment that proved semi-conservative replication?

Answer 16

• Two samples of bacteria were grown, one in a nutrient broth of light nitrogen and the other of heavy nitrogen
• A sample of DNA was taken from each bacteria and spun in a centrifuge; the DNA from the heavy nitrogen settled lower down the tube
• The bacteria grown in heavy nitrogen were taken out and put in a broth containing only light nitrogen
• After one round of DNA replication, another DNA sample was taken out and spun in the centrifuge
• Because DNA replication is semi-conservative, the new bacterial molecules contained one strand of heavy nitrogen DNA and one strand of light nitrogen DNA and therefore settled out somewhere between where the light nitrogen DNA and heavy nitrogen DNA settled out

Question 17

What does ATP stand for?

Answer 17

Adenosine triphosphate

Question 18

What is ATP made up of?

Answer 18

Adenine, ribose sugar and a chain of three phosphate groups (it’s therefore considered a nucleotide)

Question 19

Why does ATP have low activation energy?

Answer 19

Because it contains unstable bonds

Question 20

What is the purpose of ATP?

Answer 20

To release lots of energy when broken

Question 21

How does ATP release energy?

Answer 21

By losing a phosphate molecule

Question 22

What is the equation for the breakdown of ATP?

Answer 22

ATP + H2O –> ADP + Pi + E
One phosphate is lost (Pi) which releases energy (E) and leaves adenosine diphosphate (ADP)

Question 23

What kind of reaction is the breakdown of ATP?

Answer 23

A hydrolysis reaction

Question 24

What is phosphorylation?

Answer 24

When a phosphate is added

Question 25

What enzyme catalyses the reaction of the breakdown of ATP?

Answer 25

ATP hydrolase

Question 26

What enzyme catalyses the reaction for phosphorylation?

Answer 26

ATP synthase

Question 27

What kind of reaction is phosphorylation?

Answer 27

A condensation reaction

Question 28

What is an inorganic phosphate?

Answer 28

A phosphate that isn't attached to another carbon containing molecule

Question 29

What is the main role of the iron ion?

Answer 29

It forms part of the structure of haemoglobin which carries oxygen around the body

Question 30

What is the main role of the hydrogen ion?

Answer 30

It determines the pH of a solution which in turn affects enzymes

Question 31

What is the main role of the phosphate ion?

Answer 31

It forms part of ATP and nucleotides and is also involved in phosphorylation

Question 32

What is the main role of the sodium ion?

Answer 32

It's involved in co-transport of glucose and amino acids

Question 33

Why is water described as a dipolar molecule?

Answer 33

Because oxygen has a slight negative charge and hydrogen has a slight positive charge, causing hydrogen bonds to form between the water molecules

Question 34

What is the definition of specific heat capacity?

Answer 34

The amount of energy required to increase 1kg of a substance by 1°C

Question 35

What is latent heat vaporisation?

Answer 35

The amount of energy required to evaporate 1kg of a substance

Question 36

What is cohesion?

Answer 36

The tendency of water molecules to stick together

Question 37

What is a solvent?

Answer 37

A liquid that other substances dissolve in

Question 38

Why is water a good solvent?

Answer 38

The positive region of water will be attracted to negative ions and the negative region of water will be attracted to positive ions, causing water to completely surround and dissolve ions

Question 39

What gives water a high specific heat capacity and when is this useful?

Answer 39

Hydrogen bonds give water a high specific heat capacity which is important for marine ecosystems, as it buffers changes in temperature, keeping them stable

Question 40

Why does water have a high latent heat of vaporisation and when is this useful?

Answer 40

Because a lot of energy is required to overcome the hydrogen bonds This means that organisms can use evaporation from sweating to cool down without losing too much water

Question 41

Why is water cohesive and when is this useful?

Answer 41

Because water is dipolar, the molecules tend to stick together which makes it easier got transporting substances in organisms (e.g. xylem) It also creates surface tension, which creates habitats for insects like pond skaters