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AQA A-Level Biology > Chapter 2 - Nucleic Acids > Flashcards

Chapter 2 - Nucleic Acids Flashcards

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1
Q

What is the structure of a nucleotide?

A

•phosphate group
•pentose sugar
•nitrogenous bases (C/A/T/G/U)
These three components join together by condensation reaction forming a mononucleotide and two molecules of water

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2
Q

What does a mononucleotide +mononucleotide form?

A

Dinucleotide + H20

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3
Q

What bond does a dinucleotide have?

A

Phosphodiester bond

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4
Q

Complete the sentence:

Polynucleotide forms ……………….

A

The bases of DNA

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5
Q

What is the purine?

A
  • Guanine

* Adenine

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6
Q

What is a pyrimidine?

A
  • cytosine
  • thymine
  • uracil
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7
Q

What base goes with cytosine?

A

Guanine

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8
Q

What base goes with adenine?

A

Thymine (uracil)

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9
Q

Describe a ribonucleic acid (RNA)

A
  • polymer of nucleotides
  • ribo sugar attaches to phosphate group and nucleotide
  • contains A/U/C/G
  • NO T
  • shorter than DNA
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10
Q

What are the three types of RNA? And describe each type

A
  • mRNA - messenger RNA carries DNA code from nucleus to ribose
  • tRNA - transfer RNA carries amino acid across cytoplasm
  • rRNA - ribosomal RNA makes up tinosomes
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11
Q

Describe a deoxyribonueic acid (DNA)

A
  • Made up of deoxyribose/phosphate group/nucleotide bases
  • contains A/T/C/G
  • made up of two strands
  • longer than RNA
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12
Q

Describe complimentary base pairing

A 
•To DNA polynucleotide strands join by hydrogen bonds
•can only pair to specific
-A/T (two hydrogen bonds)
-G/C (three hydrogen bonds)
•always equal amounts
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13
Q

Describe how the DNA is stable

A
  • Phosphodiester backbone protects the more chemically reactive organic bases - You would have to And why the double helix to expose the DNA
  • The hydrogen bonds form bridges between nucleotide bases
  • There are three hydrogen bonds between C and G – the more C and G bonds the more stable helix
  • Anti-parallel arrangement - 5’ to 3’ - nucleic acids can only synthesised in this direction
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14
Q

What are the two main stages of cell division?

A
  • nuclear division

* cytokinesis

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15
Q

Before the first stage of cell division what takes place?

A

Semi-conservative replication

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16
Q

What is semi-conservative replication?

A

DNA makes exact copies of itself by undermining the double helix so that each chain acts as a template for the next.

DNA Replication

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17
Q

What are the four requirements for DNA replication?

A
  • Four types of nucleotides (constant supply)
  • Strands to act as a template
  • DNA polymerase-> catalyse reaction
  • source of chemical energy
18
Q

Describe the process of DNA replication

A
  • Enzyme DNA helicase breaks down hydrogen bonds linking pairs
  • As a result double helix unwinds into two strands
  • each exposed polynucleotide strands acts as a template to which complimentary nucleotides are attracted
  • Energy used to activate these nucleotides
  • activated nucleotides are joined together by enzyme DNA polymerases
  • each of the new DNA molecules contain one of the original DNA strands
19
Q

What is pentose sugar is found in DNA?

A

Deoxyribose

20
Q

What is the nitrogen and carbon containing molecules compromising to ring structures?

A

Purine

21
Q

What is the nitrogen and carbon containing molecules containing molecule comprising a one ring structure?

A

Pyrimidine

22
Q

What are the strong bonds formed between adjacent to nucleotides in a polynucleotide?

A

Phosphodiester

23
Q

What is the general name for five carbon sugar?

A

Pentose

24
Q

What are the following enzymes used for?
•DNA Polymerase:
•DNA Helicase:

A
  • joins the free nucleotides together forming hydrogen bonds

* breaks the hydrogen bonds

25
Q

What is the structure of ATP?

A
  • phosphorylated macromolecule
  • adenine – nitrogen – containing organic base
  • ribose – pentose sugar acting as backbone
  • phosphate – chain of three phosphate group
26
Q

How does ATP store energy?

A

•ATP is a nucleotide
• phosphate bonds are important:
– They are unstable (low activation energy)
– Releases a decent amount of energy

27
Q

What are the products of a hydrolysed ATP?

A

ADP + P + E

Catalysed by the enzyme ATP hydrolase

28
Q

What synthesises ATP?

A
  • Chlorophyll – contained in plant cells
  • respiration
  • substrate-level phosphorylation -> phosphate groups are transferred from donor molecules
29
Q

What is the role of ATP?

A
  • ATP is an immediate energy source – it releases less energy than glucose molecules (hydrolysis is a single reaction was glucose is much longer)
  • ATP cannot be stored – continuously made in the mitochondria
30
Q 
List five ways ATP energy is required:
•
•
•
•
•
A
  • metabolic processes – energy needed to build up macromolecules from basic units
  • movement – energy for muscle construction provides energy for the filaments of muscles to slide past one another
  • Active transport – changes the shape of carrier proteins in plasma membrane allowing molecules/ions to move against a concentration gradient
  • secretion – needed to form lysosomes necessary for secretion of cell products
  • activation of molecules – inorganic phosphate is released during hydrolysis of ATP can be used to phosphorylate other compounds
31
Q

What is the structure of water?

A
  • covalent bond
  • polar molecule – electrons not evenly distributed across molecule
  • attraction between these charges from hydrogen bonds between water molecules
32
Q

What are the five properties of water?

A
  • High heat capacity
  • Large latent heat of vaporisation
  • Strong cohesion between water molecules
  • am important solvent
  • A metabolic in many reactions
33
Q

Describe high heat capacity in water

A
  • heat needed to raise the temperature of 1 kg of water by 1 °C in terms of specific heat capacity
  • Large specific heat = absorb large amounts of heat energy before temperature rate is a significant amount
34
Q

How is high heat capacity important to living organisms?

A
  • body = mostly water
  • water = absorbs a lot of heat without temperature rising too much
  • water ‘buffers’ heat changes
  • Advantageous for aquatic organisms – don’t change temperature quickly
35
Q

How is large latent heat of vaporisation important to living organism?

A
  • animals can sweat = keep cool as water evaporates off surface
  • plants cool = water evaporates from leaves
36
Q

Describe large latent heat of vaporisation in water

A
  • Body = some water molecules move faster - kinetic energy - some have enough energy to move into the air and evaporate
  • evaporated molecules take energy causing the water to cool as energy decreases
37
Q

Describe the strong cohesion between water molecules in water

A

The polarity - Water molecules are attracted to each other forming hydrogen bonds. The bonds hold the water together allowing the continuous stream known as mass flow

38
Q

How is the strong cohesion between water molecules important to living organisms?

A
  • plants – water moves up the xylem vessels as a mass flow (roots to leaves)
  • Water cohesion = surface tension - water behaves as if there is a skin where the water meets the air allowing small animals to survive on the surface of water
39
Q

Describe the water as an important solvent

A
  • solvent = liquid that other substances can dissolve
  • positive/negative charges of water attract other molecules – they separate from each other
  • substance are dissolved in water - free to move and react
40
Q

How is the water being an important solvent important to living organisms?

A
  • metabolic reaction that happened - only happens in water where reactants are dissolved
  • dissolved substance can be transported around body
41
Q

Describe the water as a metabolite in many reactions

A

Water can be dissolved in chemical reactions directly
•condensation - water released (small to large)
•hydrolysis - water is added (large to small)

42
Q

How is water being a metabolite important living organisms?

A
  • hydrolysis allows digestion

* condensation allows synthesis of important molecules e.g protein

AQA A-Level Biology (22 decks)

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