Nucleic acids

Question 1

What do RNA and DNA stand for?

Answer 1

Ribonucleic acid (RNA)

Deoxyribonucleic acid (DNA)

Question 2

What is the structure of a nucleotide?

Answer 2

• Pentose sugar
• Phosphate group
• A Nitrogen-containing organic base. Which are (C)ytosine, (T)hymine, (U)racil,(A)denine and (G)uanine.

Question 3

What joins the components of a nucleotide?

Answer 3

The phosphate group, pentose sugar and organic base are joined by condensation reactions.

Question 4

Whats a mononucleotide?

Answer 4

Mononucleotide: A single nucleotide.

Question 5

How do nucleotides bond? And what is formed?

Answer 5

Nucleotides bond via their phosphate and pentose sugar groups.

One nuclotides phosphate joins to one nucleotide’s pentose sugar.

Forms a phosphodiester bond and creates a di-nucleotide.

Question 6

How are polynucleotides formed?

Answer 6

Linking of mononucleotides.

Question 7

What is RNA?

Answer 7

A single, short polynucleotide chain.

Question 8

What are RNA’s organic bases?

Answer 8

(A)denine, (G)uanine, (C)ytosine, (U)racil

Question 9

What is RNA’s pentose sugar it always has?

Answer 9

Ribose (hence ribo)

Question 10

Who discovered DNA?

Answer 10

James Watson and Francis Crick.

Question 11

What are the organic bases of DNA?

Answer 11

(A)denine, (T)hymine, (G)uanine, (C)ytosine

Question 12

What is the pentose sugar of DNA?

Answer 12

Deoxyribose is the pentose sugar (hence deoxyribo)

Question 13

What is DNA?

Answer 13

Two long polynucleotide chains, joined by hydrogen bonds on certain bases.

Question 14

What are always the base pairs in DNA?

Answer 14

Adenine-Thymine

Guanine-Cytosine

Question 15

What rule do base pairs share regarding quantity?

Answer 15

Adenine and Thymine are always the same quantity

Guanine and Cytosine are always the same quantity.

Question 16

What supports the DNA molecules?

Answer 16

The double helix.

Question 17

Why is DNA a stable molecule?

Answer 17

• Phosphodiester bond backbone, protects reactive organic bases between them from external forces.
• Hydrogen bonds between bases form strength and stability between strands. E.g. 3 hydrogen bonds between C and G.

Question 18

How is DNA adapted for its function?

Answer 18

• Very stable so can easily pass between generations of offspring and rarely mutate.
• Joined by hydrogen bonds which can seperate during DNA replication and protein synthesis.
• Deoxyribose-phosphate molecule backbone protects genetic info from external chemicals and forces.
• Base pairing allows DNA replication and then information transfer as mRNA.

Question 19

How do carbon atoms in the pentose molecule influence how nucleotides are arranged?

Answer 19

Carbon atoms in the pentose molecules are (3-prime) and (5-prime) carbon atoms.

3’ has a hydroxyl group

5’ has a phosphate group

So as they bond nucleotides they run down the strands 3-5-3-5

The two strands in DNA run in opposite directions in this way so are called antiparallel

Question 20

Why is DNA replication required?

Answer 20

So daughter cells have identical genetic information.

Question 21

What is universally accepted as how DNA replication takes place?

Answer 21

Semi-Conservative Replication.

Question 22

What are the requirements for for semi-conservative replication.

Answer 22

• Four types of nucleotide with either A, G, C or T bases present.
• Both DNA strands so they can act as templates.
• Enzyme, DNA polymerase
• Chemical energy source e.g. ATP

Question 23

What is the process for Semi-Conservative replication?

Answer 23

1. DNA helicase breaks hydrogen bonds between two polynucleotides of DNA.
2. The two strands unwind due to this.
3. Exposed strands work as a template for external free nucleotides to bind to complimentary bases.
4. DNA polymerase makes polymer by condensing the new nucleotides together making two new strands.
5. Each DNA molecule has one original strand, so original DNA is incorperated into both DNA molecules.
6. Called Semi-conservative replication.

Question 24

What evidence is there against Semi-conservative replication?

Answer 24

Conservative model

Suggests original DNA molecule stays intact and seperate daughter DNA was built from deoxyribose, phosphate and organic bases.

Question 25

What evidence is there for Semi-conservative replication?

Answer 25

_Semi-conservative model._ Original DNA molecule split into two seperate strands which are then replaced by pairs. So two molecules are made each with one new and one old strand of Mononucleotides.

Question 26

What does ATP stand for?

Answer 26

Adenosine triphosphate.

Question 27

What is ATP's structure?

Answer 27

Adenine - _organic base containing nitrogen_ Ribose - _A pentose sugar_ Phosphates - A _chain of three phosphate groups_

Question 28

How does ATP store energy?

Answer 28

* Bonds between phosphate groups are unstable so easily broken. * When they break they release a considerable amount of energy.

Question 29

How does ATP go to ADP and AMP and vice versa?

Answer 29

Water converts ATP to ADP to AMP _via hydrolysis_ with the help of _ATP hydrolase._ _ATP is reformed_ with _water_ in _condensation_ and _ATP synthase_.

Question 30

How are phosphate molecules added to ADP?

Answer 30

* In chlorophyll containing cells in photosynthesis. * Cells during respiration. * Cells when phosphate molecules are transferred to ADP from donor molecules.

Question 31

Why does ATP work as an immediate energy source for cells?

Answer 31

* Less energy is released from ATP than from glucose but its released more frequently. * Breaking down glucose takes longer as its much larger. *

Question 32

What processes need energy from ATP and why?

Answer 32

* _Metabollic processes_, ATP energy to make polymers from monomers. * _Movement_, ATP energy for muscle contraction. * _Active transport_, ATP energy to change carrier protein shape, allowing molecules or ions to move against concentration gradient. * _Secretion_, ATP energy to form cell's lysosomes * _Activasion of molecules_, ATP's phosphate molecules can be used to reduce other compounds.

Question 33

What's the structure of a water molecule?

Answer 33

Two hydrogen molecules. One oxygen molecule. (H₂O)

Question 34

Water is dipolar, explain why.

Answer 34

Water has _positive and negative poles_. Oxygen has a slightly negative charge. Hydrogen has a slightly positive charge.

Question 35

Why is water cohesive?

Answer 35

Water is cohesive because negative charges attract to positive charges and vice versa. So the positive pole of one water molecule will be attracted to the negative pole of another and vice versa. These are called hydrogen bonds. Lots of hydrogen bonds make water cohesive.

Question 36

Water can act as a buffer for sudden temperature change. Explain why?

Answer 36

Due to cohesion of hydrogen bonds lots of kinetic energy is required to break up the water molecules.

Question 37

What is the latent heat of vaporisation?

Answer 37

The energy required to evaporate one gram of water.

Question 38

What is water used for in metabolism?

Answer 38

* Used for hydrolysis * Used for chemical reaction locations * Raw material in photosynthesis.

Question 39

What dissolves in water?

Answer 39

* Oxygen and CO₂ gases * Wastes * Inorganic ions and small hydrophillic molecules * Enzymes that catalyse in solution

Question 40

Give three examples of benefits to organisms water brings.

Answer 40

* Evaporation cools organisms for temperature control. * Not easily compressed so good for hydrostatic skeleton of animals * Transparent so aquatic plants can photosynthesize.

Question 41

Give four functions of inorganic ions related to their properties.

Answer 41

* Iron ions in haemoglobin for oxygen transportation. * Phosphate ions for DNA. * Hydrogen ions to control PH of solutions. * Sodium ions for transport of glucose and amino acids across plasma membranes.