1-2 Nucleic acid, water & ATP

Question 1

What are the 5 adaptations of a DNA molecule?

Answer 1

• stable structure
• h bonds easily break
• large molecule
• protective backbone
• base pairing for RNA

Question 2

Which direction is the strand joined up?

Answer 2

5’-3’

Question 3

Why is ATP better than glucose?

Answer 3

• released in small manageable amounts

- the hydrolysis of ATP to ADP is a single reaction

Question 4

What are the three ways in which ADP -> ATP?

Answer 4

• photophosphorylation
• substrate level phosphorylation
• respiration - oxidative phosphorylation

Question 5

How does water support an organism’s metabolism?

Answer 5

• raw material for photosynthesis
• hydrolysis
• aqueous chemical reactions

Question 6

What are nucleotides made of?

Answer 6

A pentose sugar (has 5 carbon atoms)
A phosphate group

A nitrogen-containing organic base (includes Cytosine, Thymine, Uracil, Adenine and Guanine)
These parts are joined by a condensation reaction

Question 7

How do you join two nucleotides together?

Answer 7

A condensation reaction between a deoxyribase sugar and a phosphate group
For each mole of dinucleotide formed, one mole of water is formed

Called a dinucleotide
Joined by a phosphodiester bond

Question 8

What are the types of RNA?

Answer 8

tRNA: Transfers information from DNA to the ribosomes
mRNA: Makes up ribosomes alongside protein

Involved in protein synthesis

Question 9

What is the structure of DNA?

Answer 9

The two polynucleotide chains wind around eachother to form a double helix which forms the structural backbone
Pentose sugars are anti-parallel (in the opposite direction)

Question 10

What breaks up a dinucleotide?

Answer 10

A hydrolysis reaction

Question 11

How does DNA’s structure relate to its function?

Answer 11

Very stable structure: rarely mutates
Two strands: allows it to seperate during DNA replication and protein synthesis

Extremely large molecule: carries an immense amount of genetic information
Base pairs within the helical cylinder: genetic information is partly protected from being corrupted by outside chemical/physical forces
Base pairing: DNA can replicate and transfer information as mRNA

Question 12

When does the synthesis of DNA occur?

Answer 12

In mitosis during interphase

Question 13

What are the steps of the semi-conservative method?

Answer 13

1. DNA helicase (an enzyme) unwinds the double helix by breaking the hydrogen bonds and splitting the helix into two strands
2. Free nucleotides which have been activated bind to the complimentary bases on the seperate strands- parental strand acts as a template for the synthesis of a new strand
3. DNA polymerase makes phosphodiester bonds and hydrogen bonds are naturally formed between the bases
4. Two identical polynucleotide chains are formed
5. This is called the semi conservative method because half the DNA is from the original DNA molecule

Question 14

What are the steps of the Meselson and Stahl experiment?

Answer 14

1. Grew E. coli in a nutrient broth containing 15N
2. E.coli took it up and used it to build their DNA
3. After many generations they had pure strands of 15N bacteria and 14N bacteria
4. They measured the density of the DNA using density gradient centrifugation (seperating molecules based on density by spinning it, allows for small changes in density)

Question 15

What were the results of the Meselson and Stahl experiment?

Answer 15

G0: 100% heavy
G1: 100% mixed, single band

G2: 50% mixed, 50% light, two strands
G3: 25% mixed, 75% light ^
G4: 12.5% mixed, 87.5% light ^

Question 16

How did the conservative and semi-conservative methods differ?

Answer 16

The conservative method predicted that there would always be one band of heavy and one of light, without any mixing of densities

Question 17

Why does the breakdown of ATP release so much energy?

Answer 17

The bonds are broken which requires very little energy
The bonds formed between H20 and the two phosphate groups releases large amounts of energy

H goes to the larger molecule and OH goes to the phophate that is leaving ADP
Therefore the net release of energy is large

Question 18

What are the uses of ATP?

Answer 18

Metabolic processes: building macromolecules from basic units
Movement: energy for muscle contraction

Secretion: formation of lysosomes for secreting cell products
Activation of molecules: phosphate released can go on to form other molecules
Energy: for any active processes within the cell

Question 19

What are the uses of phosphate in the body?

Answer 19

To make RNA
To make DNA;

To make ATP/ADP
To make membranes
For phosphorylation

Question 20

What is the structure and bonding of water?

Answer 20

Two atoms of hydrogen and one atom of oxygen
Dipolar molecule

Hydrogen = positive, oxygen = negative
Hydrogen bonding is the attractive force between molecules
Covalently bonded so don’t conduct electricity

Question 21

What are the properties of water which aid life? (No explanation)

Answer 21

Dipolar
Has hydrogen bonding

Covalently bonded
High boiling point due to hydrogen bonding
High specific heat capacity
High latent heat of vaporisation
Cohesion
Not easily compressed
Transparent

Question 22

How do the properties of water aid life?

Answer 22

High boiling point: buffer against sudden temperature changes
High latent heat of vaporisation: sweating provides an effective cooling effect

Cohesion: xylem can transport water
Not easily compressed: provides support for organisms
Transparent: light can reach aquatic plants

Question 23

How is water used in the metabolism?

Answer 23

Used to break down many complex molecules by hydrolysis
Chemical reactions take place in an aqueous medium

Water is a major raw material in photosynthesis

Question 24

How is water used as a solvent?

Answer 24

It readily dissolves some substances including gases, wastes, inorganic ions, small hydrophilic molecules and enzymes

Question 25

Which base complements guanine?

Answer 25

Cytosine

Question 26

Which base complements thymine?

Answer 26

Adenine