Nucleic Acids

Question 1

What is DNA

Answer 1

DNA is made out of deoxyribonucleic acid and it contains genetic material

Question 2

What is the structure of DNA

Answer 2

Has 2 phosphate backbones held together by bases in a double helix structure with a deoxyribose sugar

Question 3

What are the DNA bases

Answer 3

Thymine, adenine, guanine, cytosine

Question 4

How are the DNA bases paired

Answer 4

Adenine has a double hydrogen bond to thymine
ctyosine has a triple hydrogen bond to guanine

Question 5

What is RNA

Answer 5

sugar is ribose not deoxyribose, it is single strand not double stranded. 2 types of RNA, mRNA and tRNA

Question 6

What is the RNA base pairings

Answer 6

Thymine is replaced by uracil, all of the other bases are the same

Question 7

What type of replication do does DNA go through

Answer 7

Semi conservative- one parent strand, one new daughter strand

Question 8

Steps of DNA replication

Answer 8

1. DNA helicase unwinds by breaking thr hydrogen bonds between the nucleotides to separate the 2 strands
2. Each original strands acts as a template for new strand. Free DNA nucleotides are attracted to the exposed bases through complementary base pairing.
3. The free nucleotides are joined by a condensation reaction and is catalysed by DNA polymerase which form hydrogen bonds between the 2 bases.

Question 9

How does DNA polymerase work

Answer 9

Each DNA strand has a dstructures structure due to the end of each strand being either sugar that’s attached to the 5th carbon 5’ end or a hydroxyl group attached the 3’ end. DNA polymerase is only complimentary to the 3’ end of the template strand so it can only move along the template strand and add nucleotides in the 3’ and 5’ direction. The strand is build in a 5’ 3’ direction as it is antiparallel. Leading strand is continuously built and lagging is built in sections.

Question 10

Evidence for semi-conservative replication

Answer 10

Meselson and Stahl- two isotopes of nitrogen, 14N(light) and 15N(heavy). Bacteria grown in 15N is transferred into a broth of 14N. If replication was semi conservative the line on the test tube would be in between the line of heavy nd light nitrogen. This is what they found in the first generation.

Question 11

What is ATP

Answer 11

ATP provides energy

Question 12

What is the structure of ATP

Answer 12

It contains a ribose sugar, an adenine base and 3 phosphate groups.

Question 13

How is energy stored

Answer 13

Energy is stored in the phosphate bonds and when they are hydrolysed, the energy is released

Question 14

What is the phosphate the us separated from the ATP used for

Answer 14

It can be used to phosphorylate other molecules in cells to make them more reactive

Question 15

What is ATP that goes through a condensation reaction called

Answer 15

It is called ADP (adenine diphosphate) and a Pi group (an inorganic phosphate group) is catalysed by bt the enzyme ATP hydrolase.

Question 16

Why is water considered a polar molecule

Answer 16

Water is considered a polar molecule as the hydrogen molecules have a slight positive charge and the oxygen has a slight negative charge. Slight negative oxygen is attracted to the slight positive hydrogen molecules.

Question 17

What happens when water molecules get close together

Answer 17

When the water molecules get close together, the opposite charged parts of the molecules attract each other, forming hydrogen bonds, called cohesion. At room temperature water forms a lattice.

Question 18

What are the properties of water dependent on

Answer 18

The properties depend on the polar nature of the water molecule and on the hydrogen binding between water molecules

Question 19

What is water useful for

Answer 19

.It is a good solvent
.Attracted to other substances that are also polar
.Water molecules cluster around charged parts of the solute molecule or ions and help to stay apart dissolved and solution can be formed
.hydrogen bonds pull water molecules towards each other causing cohesion
.high surface tension as hydrogen bonds pull the molecules inwards at the surface
.high heat capacity
.strong cohesion between water molecules so supports tube like transport cells of plants

Question 20

Role of hydrogen ions and ph

Answer 20

A high concentration ognhydrogen ions yield a low pH, whereas a low level of hydrogen ions result in a high pH.

Question 21

Iron ions and haemoglobin

Answer 21

Iron ions are the central part of the haem group in haemoglobin allowing red blood cells to transport O² and CO²

Question 22

Role of Sodium ions in the co-transport of glucose

Answer 22

Sodium binds to co-transported proteins to allow glucose and amino acids to be transport as it binds to the other molecule that needs transporting

Question 23

The roles of phosphate ions as components of DNA

Answer 23

It creates the phosphate backbone to provide structure to the DNA