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Biology > Section 1- Nucleic acids > Flashcards

Section 1- Nucleic acids Flashcards

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1
Q

What is the semi-conservative model in DNA replication?

A

Original DNA molecule splits into 2 separate stands

Strands acted as templates

1 old strand, 1 new strand

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2
Q

Who proposed the evidence for the semi-conservative model?

A

Watson and Crick

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3
Q

What was the Meselson and Stahl experiment into semi-conservative replication?

A

Used 2x Nitrogen isotopes

  1. Grew E.Coli for several generations in each isotope
  2. DNA isolated and centrifuged
    DNA formed separate bands according to densities
  3. E.Coli from 15N moved with 14N
    After 1 generation band in between space formed
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4
Q

What are individual nucleotides made up of?

A

Pentose sugar
Phosphate group
Nitrogen-containing organic base

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5
Q

What reaction occurs to produce a nucleotide?

A

Condensation reaction

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6
Q

What bond is formed between nucloetides?

A

Phosphodiester bond

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7
Q

What is the sugar in RNA?

A

Ribose sugar

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8
Q

What bond joins 2 DNA strands?

A

Hydrogen bond

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9
Q

In 1953, what did Watson and Crick discover?

A

Structure of DNA

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10
Q

Why is DNA a stable molecule?

A

Phosphodiester backbone protects more chemically reactive organic bases inside double helix.

3 Hydrogen bonds between C-G, the higher proportion of G-C pairings, the more stable the DNA molecule.

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11
Q

How is a DNA molecule adapted to carry out its functions?

A

Very stable structure which passes from generation to generation without significant change

Hydrogen bonds allow separation during DNA replication

Extremely large so carries large amount of genetic material

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12
Q

Why can nucleic acids only be synthesised in the 5’-to-3’ direction?

A

DNA polymerase can only attach nucleotides to the hydroxyl group on the 3’ carbon molecule.

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13
Q

What is the pentose sugars in DNA & RNA?

A

DNA: deoxyribose

RNA: ribose

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14
Q

What is the role of DNA in living cells?

A

Base sequence of genes codes for functional RNA & amino acid sequence of polypeptides.

Genetic information determines inherited characteristics

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15
Q

Which bases are purine and which are pyrimidine?

A

A & G = 2-ring purine

T & C & U = 1-ring pyrimidine

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16
Q

What is the process of semi-conservative DNA replication?

A
  1. DNA helicase breaks H-bonds between base pairs.
  2. Each strand acts as a template.
  3. Free nucleotides attach to exposed bases by complementary base pairing.
  4. DNA polymerase catalyses condensation reactions that join adjacent nucleotides on new strand.
  5. Hydrogen bonds form.
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17
Q

Why is the process of DNA replication described as semi-conservative?

A

Half the original DNA is built into the new DNA strand

18
Q

If an inhibitor of DNA polymerase were introduced into a cell, what would the effect on DNA replication be?

A

Linking together of new nucleotides could not take place.

19
Q

What is the structure of ATP?

A

Adenine
Ribose
3 phosphates

20
Q

What is the role of ATP in cells?

A

ATP hydrolase catalyses ATP into ADP + Pi

Energy released is coupled to metabolic reactions

Phosphate group phosphorylates compounds to make them more reactive.

21
Q

How is ATP resynthesised in cells?

A

ATP synthase catalyses condensation reaction between ADP + Pi

During photosynthesis and respiration.

22
Q

Why is ATP suitable as the ‘energy currency’ of cells?

A

High energy bonds between phosphate groups

Small amounts of energy released at a time = less waste

Single-step hydrolysis = energy available quickly

Readily resynthesised

23
Q

What are the 3 ways a phosphate molecule is added to ADP to make ATP?

A

In chlorophyll containing plant cells during photosynthesis (photophosphorylation)

In plant and animal cells during respiration (oxidative phosphorylation)

In plant and animal cells when phosphate groups are transferred from donor molecules to ADP

24
Q

Why is ATP a better immediate energy source than glucose?

A

Each ATP molecule releases more energy than each glucose molecule

The hydrolysis of ATP to ADP is a single reaction that releases immediate energy.
Breakdown of glucose is long series of reactions.

25
Q

What processes is ATP in cells used for?

A

Metabolic processes

Movement

Active transport

Secretion

Activation of molecules

26
Q

Why is ATP referred to as an ‘immediate energy source’?

A

ATP releases its energy very rapidly.

Energy is released in a single step and is transferred directly to the reaction requiring it.

27
Q

How can ATP make an enzyme-catalysed reaction take place more readily?

A

ATP provides a phosphate that can attach to another molecule, making it more reactive and so lowering its activation energy.

Enzymes have less ‘work’ to do and so function more readily.

28
Q

What are 3 roles of ATP in plant cells?

A

Building up macromolecules

Active transport

Secretions

Activation of molecules

29
Q

Why is water a polar molecule?

A

O is more electronegative that H so attracts the electron density in the covalent bond more strongly.

30
Q

What are 4 biologically important properties of water?

A

Metabolite- used for hydrolysis reaction

Solvent for chemical reaction in the body - readily dissolves other substances

High specific heat capacity

High latent heat of vaporisation

Cohesion between molecules

31
Q

Why is water significant to living organsims?

A

Solvent for polar molecules during metabolic reactions

Enables organisms to avoid fluctuations in core temperature

Cohesion-tension of water molecules in transpiration stream

32
Q

What are inorganic ions and where are they found in the body?

A

Ions that do not contain carbon atoms

Found in cytoplasm

May be in high or very low concentrations

33
Q

What is the role of hydrogen ions in the body?

A

High concentration of Hydrogen ions = low pH

Hydrogen ions interact with Hydrogen bonds & ionic bonds in tertiary structure of proteins which can cause them to denature

34
Q

What is the role of iron ions in the body?

A

Iron ions bond to porphyrin ring to form haem group in haemoglobin

35
Q

What is the role of sodium ions in the body?

A

Involved in co-transport of absorption of glucose and amino acids

36
Q

What is the role of phosphate ions in the body?

A 
Component of:
DNA
ATP
NADP
cAMP
37
Q

Why is having a high latent heat of vaporisation important in living organisms?

A

Cooling effect by evaporation

38
Q

What are 2 ways in which the properties of ATP make it a suitable source of energy in biological processes?

A

Energy released in small amounts

Soluble

Involves a single reaction

39
Q

Apart from respiration, what are uses of ATP?

A

Active transport

To produce glycogen

Exocytosis

Cell division

DNA synthesis

40
Q

What is the role of DNA polymerase in DNA replication?

A

Joins nucleotides

41
Q

How does ice floating on the top of a pond help organisms to survive?

A

Ice is less dense as molecules spread out

Molecules form lattice

Causes an insulating layer

Water doesn’t freeze so organisms can still move

42
Q

How does water acting as a solvent for ions such as nitrates, help organisms to survive in ponds?

A

Ions are polar which interact with water

Plants uptake minerals for amino acids

Biology (25 decks)

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