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A Level Biology Year 1 > Chapter 2 - Nucleic acids > Flashcards

Chapter 2 - Nucleic acids Flashcards

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1
Q

Name 5 useful properties of water

A 
It is an important metabolite
High latent heat of vaporisation
Buffers changes in temperature
Good solvent
Strong cohesion between water molecules
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2
Q

What makes water a good metabolite?

A

Many metabolic reactions involve a condensation or hydrolysis reaction (where water is produced as a new bond is formed or used to break an existing bond)

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3
Q

Why is it important that water is a good metabolite?

A

Amino acids are joined together to make polypeptides in condensation reactions

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4
Q

Why does water have such a high latent heat of vaporisation?

A

It takes a lot of energy to break the hydrogen bonds between water molecules
When water molecules evaporate from a body of water, they take a lot of energy with them
So the body of water cools down

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5
Q

Why is it important that water has such a high latent heat of vaporisation?

A

Animals can keep cool by sweating and plants cool down when water evaporates from leaves

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6
Q

Why does water have such a high specific heat capacity?

A

The hydrogen bonds between water molecules can absorb a lot of energy so it absorbs a lot of heat energy before a significant change in temperature occurs

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7
Q

Why is it important that water has such a high specific heat capacity?

A

It makes aquatic environments great habitats because the temperature is stable
Water buffers temperature changes inside our bodies so our internal body temperature is constant

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8
Q

Why is water such a good solvent?

A

Many compounds are ionic (they consist of one positively charged ion and one negatively charged one)
Because water is polar, the positive end of it will attach to the negative end of the compound and vice versa
This means the compound will get surrounded by water molecules and will eventually dissolve

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9
Q

Why is it important that water is such a good solvent? (2)

A

Many reactions inside the body can only happen when the reactants are dissolved in water
Dissolved substances like glucose can be transported around body

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10
Q

Why are water molecules so cohesive?

A

They are polar molecules so hydrogen bonds form between the differently charged ends of the molecule

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11
Q

Importance of water’s strong cohesion 2

A

Water flows so it is great for transporting substances

Surface tension means small insects can live on surface

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12
Q

Describe the structure of water

A

The shared hydrogen electrons are pulled to one side of the hydrogen atoms, leaving the other side with a slight positive charge
The unshared electrons on the oxygen give it a slight negative charge
These different charges make it a polar molecule
The slightly negative oxygen atoms join to the slightly positive hydrogen ones
These are called hydrogen bonds

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13
Q

What is one nucleotide made out of?

A

A pentose sugar
A phosphate group
A nitrogen-containing organic base

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14
Q

Function of DNA

A

It stores all the genetic information we need to grow and develop

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15
Q

Function of RNA

A

It transfers genetic information from the nucleus to the ribosomes

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16
Q

What are the four bases in DNA?

A

Adenine, Thymine, Guanine, Cytosine

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17
Q

What pentose sugar is found in DNA?

A

Deoxyribose

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18
Q

What are the four bases on RNA?

A

Adenine, Uracil, Guanine, Cytosine

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19
Q

What pentose sugar is found in RNA?

A

Ribose

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20
Q

What is a polynucleotide?

A

A polymer made of numerous nucleotides

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21
Q

How do the sugar, base and phosphate group join together?

A

A condensation reaction occurs between the sugar and phosphate group

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22
Q

How is a polynucleotide formed?

A

A condensation reaction occurs between the sugar of one DNA group and the phosphate group of another, forming a phosphodiester bond

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23
Q

What bond is formed when two nucleotides join?

A

Phosphodiester

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24
Q

How are the two strands of DNA held together?

A

Hydrogen bonds

25
Q

What are the complimentary base pairs?

A

Adenine - Thymine

Cytosine - Guanine

26
Q

How many hydrogen bonds form between A and T?

A

Two

27
Q

How many hydrogen bonds form between C and G?

A

Three

28
Q

What does antiparallel mean?

A

The two DNA strands run in opposite directions

29
Q

Why is DNA very stable?

A

The phosphodiester backbone protects the more reactive organic bases, and the hydrogen bonds between complimentary bases are strong

30
Q

Why is DNA said to be antiparallel?

A

The enzyme DNA polymerase can only attach nucleotides to the 3’ carbon on the DNA molecule

31
Q

What name is given to the current theory on DNA replication?

A

The Semi-Conservative model

32
Q

What does the enzyme DNA helicase do?

A

Breaks hydrogen bonds between the base pairs

33
Q

What does the enzyme DNA polymerase do?

A

Joins activated nucleotides together

34
Q

What is the Semi-Conservative model of DNA replication?

A

DNA helicase breaks the hydrogen bonds, so the strands of DNA split apart.
Each exposed strand then acts as a template for the new strand
Complimentary base pairing means that free-floating bases are attracted to their exposed complimentary bases on the template strand
DNA polymerase joins the two strands together in a condensation reaction, forming hydrogen bonds
Each new strand of DNA contains one strand from the original DNA molecule and one new strand`

35
Q

What is the structure of a molecule of ATP?

A

Contains adenine, ribose and a chain of three phosphate groups

36
Q

How does ATP store energy?

A

Between the three phosphate groups, there are weak bonds, with a low activation energy. When they are broken, a lot of energy is released in a hydrolysis reaction

37
Q

What is produced when ATP is hydrolysed?

A

ADP + P + energy

38
Q

Which enzyme catalyses the reaction of ATP to ADP?

A

ATP hydrolase

39
Q

What is special about the use of ATP?

A

It is reversible - energy can be used to add a phosphate to ADP to make ATP

40
Q

What enzyme is used to made ATP from ADP?

A

ATP synthase

41
Q

What can the phosphate group released when ATP releases energy be used for?

A

It can join to another compound to make it more reactive

42
Q

Why is ATP only a short-term energy source?

A

The bonds between phosphates are very unstable

43
Q

Why is ATP a better energy source than glucose? (2)

A

Energy is released in much smaller, more manageable amounts

The hydrolysis of ATP to ADP is a single reaction that releases immediate energy

44
Q

5 uses of ATP

A 
Metabolic processes
Movement
Active transport
Secretion
Actvation of molecules
45
Q

How is ATP used in metabolism?

A

It provides the energy to make larger molecules from their units

46
Q

How is ATP used in movement?

A

It provides the energy for muscle contraction

47
Q

How is ATP used in active transport?

A

It provides the energy for proteins to change shape

48
Q

How is ATP used in secretion?

A

It creates the lysosomes necessary for secretion

49
Q

How is ATP used to activate molecules?

A

The phosphate produced can make other molecules more reactive

50
Q

What did Meselson and Stahl do?

A

Provide evidence for semi-conservative DNA replication

51
Q

What was Meselson and Stahl’s experiment?

A

They grew two samples of bacteria - one in heavy and one in light nitrogen. When placed in a centrifuge, heavy nitrogen would settle at the bottom and light nitrogen would float. At the end of the experiment, the bacteria floated in the middle, showing they had taken DNA from both types of nitrogen

52
Q

What is an ion with a positive charge called?

A

A cation

53
Q

What is an ion with a negative charge called?

A

An anion

54
Q

What is special about an inorganic ion?

A

It doesn’t contain any carbon

55
Q

Where are iron ions found?

A

Haemoglobin

56
Q

What are hydrogen ions used for?

A

Determining pH

57
Q

What are sodium ions used for?

A

Co-transport

58
Q

What are phosphate ions used for?

A

Bonds between phosphates in ATP store up energy

A Level Biology Year 1 (21 decks)

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