Topic 1 B

Question 1

What is DNA called?

Answer 1

Deoxyribonucleic acids

Question 2

What is the role of DNA?

Answer 2

To store the genetic information

Question 3

What is RNA called?

Answer 3

Ribonucleic acid

Question 4

What is the role of RNA?

Answer 4

Transfer genetic info from DNA to ribosomes

Question 5

What is DNA made from?

Answer 5

Nucleotides

Question 6

What is the structure of a nucleotide?

Answer 6

Phosphate group, pentose sugar and a nitrogen base

Question 7

What is a polynucleotide?

Answer 7

Many nucleotides joined together via a condensation reaction forming and ester bond between the phosphate group and the sugar. (phosphidiester bond= phosphate and two sugars)

Question 8

What does the sugar and phosphate group make?

Answer 8

Sugar-phosphate backbone

Question 9

What is the difference between DNA structure and RNA structure?

Answer 9

DNA RNA
Double stranded Single stranded
Thymine base Uracil base
Longer Shorter
Deoxyribose sugar Ribose sugar

Question 10

What are the 4 bases in DNA?

Answer 10

Thymine, Adenine, Cytosine and Guanine

Question 11

How are the complementary bases joined together?

Answer 11

By hydrogen bonds

Question 12

What does the DNA carry?

Answer 12

The genetic code

Question 13

How is DNA replicated?

Answer 13

DNA helicase breaks apart the hydrogen bonds causing the strands to unwind. Each strand acts as a template and the free floating Bases line up with their complementary on the template strand. Nucleotides are joined via a condensation reaction catalysed by DNA polymerase. The hydrogen bonds form between strands. Each new molecule has a copy of the original strand and a new strand.

Question 14

What are the two ends of DNA?

Answer 14

3’ and 5’ (‘=prime)

Question 15

Which end is the active site of DNA polymerase complementary to?

Answer 15

3’ of the newly forming strand (only add bases at 3’)

Question 16

Which direction does DNA polymerase move along the new strand?

Answer 16

5’ to 3’

Question 17

Which direction does DNA polymerase move down the template strand?

Answer 17

3’ to 5’

Question 18

What are the strands of the double helix?

Answer 18

Antiparallel

Question 19

Which direction does the DNA polymerase work on each strand?

Answer 19

Opposite

Question 20

What is semi-conservative replication?

Answer 20

When DNA replicates using the original strand and forming a new one

Question 21

How did Meselston and Stahl prove semi-conservative replication?

Answer 21

They had two samples of bacteria growing in a broth, one with 15N (heavy nitrogen) and one with 14N (light nitrogen). They bacteria took up the N from the broth to make new nucleotides. Took a sample of DNA from each bacteria and spun in a centrifuge. The DNA with heavy nitrogen settled lower in the centrifuge tube than light nitrogen. They then put the bacteria from the heavy broth into the light broth and left it for one round of DNA replication. A sample was taken and spun in a centrifuge. The DNA settled in the middle showing that it contained a mixture of heavy and light DNA.

Question 22

What does ATP stand for?

Answer 22

Adenosine triphosphate

Question 23

What is ATP made of?

Answer 23

Adenine base, ribose sugar and three phosphate groups

Question 24

What is ATP broken down into?

Answer 24

ADP and Pi and energy is released

Question 25

What catalyses the breakdown of ATP?

Answer 25

ATP hydrolase

Question 26

What can happen to the phosphate?

Answer 26

Can be added to another compound (phosphorylation) making it more reactive>

Question 27

What catalyses the synthesis of ATP?

Answer 27

ATP synthase

Question 28

What is the structure of water?

Answer 28

Negatively charged oxygen atom and two positively charged hydrogen atoms. (forms hydrogen bonds)

Question 29

Why is water an important metabolite?

Answer 29

Many metabolic reaction involve water e.g hydrolysis and condensation

Question 30

Why is water a good solvent?

Answer 30

Many important substances are ionic (one positively charged and one negatively charged atom). the slightly positive side of water will be attracted to the negative ion and vice versa, meaning it completely surrounds the ions.

Question 31

Why does water have a high latent heat of vaporisation?

Answer 31

A lot of energy is needed for the hydrogen bonds to break between water molecules. Lots of heat energy is used to change from a liquid to a gas. Use this to cool down without losing too much water as it will carry away the heat energy from the surface.

Question 32

How can water buffer changes in temp?

Answer 32

High specific heat capacity, lots of energy needed to break bonds so less to increase water temp. Allows organism to keep a stable temp and makes good habitats.

Question 33

How is water very cohesive?

Answer 33

Stick together due to polarity. Helps water flow, good fro transport e.g in xylem. High surface tension with air, sweat forms and evaporates cooling us down.

Question 34

What are ions?

Answer 34

An atom or group of atoms with an electric charge

Question 35

What is an ion with a positive charge called?

Answer 35

A cation

Question 36

What is an ion with a negative charge called?

Answer 36

An anion

Question 37

What is an inorganic ion?

Answer 37

An ion that doesn't contain carbon

Question 38

What are some example of inorganic ions?

Answer 38

Iron ions in haemoglobin- (FE2+) used to bind oxygen to carry it around the body (FE3+ until O is released) Hydrogen ions- pH calculated based on conc of H ions. More present, lower pH. pH affects enzymes