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Biology > B2 - Nucleic acids, ATP, water and inorganic ions > Flashcards

B2 - Nucleic acids, ATP, water and inorganic ions Flashcards

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1
Q

What does deoxyribonucleic acid (DNA) do?

A

Stores genetic information and contains all the instructions for the growth and development of all organisms

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2
Q

What does ribonucleic acid (RNA) do?

A

Transfers the genetic code in DNA out of the nucleus, carries it to the ribosomes in the cytoplasm

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3
Q

What is the monomer that makes the polymers DNA and RNA?

A

Nucleotides

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4
Q

What makes up a nucleotide?

A

A pentose sugar, a nitrogen containing base, a phosphate group

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5
Q

What is the difference between DNA and RNA on carbon 2?

A

DNA has a Hydrogen (H)
RNA has a hydroxyl group (OH)

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6
Q

What are the 4 bases in DNA?

A

Adenine (A)
Cytosine (C)
Thymine (T)
Guanine (G)

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7
Q

What are the 4 bases in RNA?

A

Adenine (A)
Cytosine (C)
Uracil (U)
Guanine (G)

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8
Q

What are the 2 types of bases and the example of each

A

Purines - Adenine + Guanine - double ring structure
Pyrimidines - Cytosine + Thymine + Uracil - single ring structure

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9
Q

How do nucleotides join together?

A

A condensation reaction between the phosphate group of one nucleotide and the pentose sugar of the next nucelotide. This forms a phosphodiester bond. Many nucleotides form a polynucleotide chain with a sugar phosphate backbone.

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10
Q

What is the structure of DNA?

A

DNA molecules are made up of two polynucleotide strands lying side by side, running in opposite directions - they are antiparallel
Each DNA polynucleotide strand has a 3 carbon end and a 5 carbon end

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11
Q

How are the 2 antiparallel strands held together?

A

They are held together by hydrogen bonding between complementary DNA base pairs
The purine adenine (A) always pairs with the pyrimidine thymine (T) by two hydrogen bonds
The purine guanine (G) always pairs with the pyrimidine cytosine (C) by three hydrogen bonds

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12
Q

What is the structure of RNA?

A

Made up of one polynucleotide strand which is shorter than DNA

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13
Q

What are ribosomes?

A

They are the site of protein synthesis and are formed from Ribosomal RNA (rRNA) which has enzyme properties, and proteins.

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14
Q

Why did scientists doubt the newly discovered DNA in the 1800s?

A

They doubted it could carry the genetic code because of the relatively simple chemical composition of DNA

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15
Q

How does DNA enable variation?

A

Through the use of the triplet code

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16
Q

What is semi-conservative replication?

A

When one DNA strand, from the original DNA molecule, is copied. This ensures there is genetic continuity between generations of cells as new cells inherit all their genes from parent cells

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17
Q

What is the process of semi-conservative replication?

A
  1. DNA Helicase catalyses the unwinding of the double helix, by breaking the hydrogen bonds between complementary base pairs causing the strands separate. (Like a zip)
  2. Free nucleotides are attracted to the exposed bases on each strand by complimentary base pairing
  3. Nucleotides are then joined together by DNA Polymerase, this catalyses the formation of phosphodiester bonds between adjacent nucleotides
  4. Original & new strands are joined together through hydrogen bonding between complimentary base pairs
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18
Q

What direction does DNA polymerase work in?

A

It can only build new strands in the 5’ to the 3’ direction.

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19
Q

What is a leading strand?

A

The template strand that the DNA polymerase attaches to. The strand where DNA polymerase can synthesise the new strand continuously (5’ to 3’)

20
Q

What is a lagging strand?

A

DNA polymerase moves in the opposite direction (3’ to 5’) so the strand is synthesised in short fragments

21
Q

What is the difference between conservative and semi-conservative replication?

A

Conservative was when a whole new double helix was produced from an original DNA that was not broken up
Semi-conservative is when a strand from an original DNA is copied to produce 2 identical new DNA helices

22
Q

How was the semi-conservative replication proved?

A

2 samples used, 1 with N14 and the other with N15. The bacteria took up the nitrogen to make new nucleotides so was incorporated into their DNA. A sample of each was centrifuged, the DNA in the heavy nitrogen settled lower than the light nitrogen did. The DNA in heavy nitrogen broth was replicated again but in the light nitrogen. When centrifuged, it settled in the middle showing that it kept a strand of the old DNA and created a new strand with the light nitrogen. Therefore, the DNA replicated semi-conservatively.

23
Q

What does ATP stand for?

A

Adenosine triphosphate

24
Q

What is the structure of ATP?

A

An adenine nitrogenous base, a ribose (pentose sugar) and 3 phosphate groups

25
Q

What is the name for the adenine + pentose sugar?

A

Adenosine

26
Q

What is ATP hydrolysis?

A

Turning ATP to ADP and an inorganic phosphate group (Pi), which is catalysed by the enzyme ATP hydrolase (ATPase). This releases energy for energy requiring reactions

27
Q

What is ATP synthesis?

A

It is when ATP is formed from ADP and an inorganic phosphate (Pi) group by the enzyme ATP synthase. This is an energy-requiring reaction, water is released as a waste product

28
Q

What are the benefits of ATP?

A

Releases a sufficient amount of energy
It is a stable molecule
Can be recycled
Hydrolysis is quick
Soluble, so can move within cell

29
Q

How is the hydrolysis of ATP used in cells?

A

To provide energy for other reactions
To add phosphate to other substances and make them more reactive/change their shape

30
Q

How does water work in cells?

A

It is the solvent in which all metabolic reactions take place
A reactive metabolite (product) in many reactions (e.g., condensation and hydrolysis reactions)
The sharing of the electrons is uneven between the oxygen and hydrogen atoms, this forms a dipole or polar molecule. This is what allows hydrogen bonds to form between water molecules

31
Q

What properties does water’s polarity and its ability to form hydrogen bonds contribute to?

A

An excellent solvent
A relatively high specific heat capacity
A relatively high latent heat of vaporisation
Water is less dense when a solid
Water has high surface tension and cohesion
It acts as a reagent
Metabolite in many reactions

32
Q

Why is water a good solvent and why is this good?

A

It is a good solvent as it is a dipole
Many ions and covalently bonded polar substances will dissolve in water
Allows chemical reactions to occur as molecules become more reactive
Allows efficient transport of metabolites

33
Q

Why does water have a high specific heat capacity and why is this good?

A

A lot of energy is required to break H-bonds so temperature of water doesn’t change greatly, this provides a suitable habitat for organisms and maintains optimal temperatures for enzyme activity and heat transfer in the blood plasma

34
Q

Why does water have a high latent heat of vaporisation and why is this good?

A

Large amounts of energy is required to break the many hydrogen bonds in water & change its state this means there is a cooling effect so organisms can lose a great amount of heat, without loosing too much water E.g. sweat through the skin

35
Q

Why does water have cohesion and why is this good?

A

Hydrogen bonds between water molecules allows for strong cohesion between water molecules, this allows column of water to move through the xylem of plants & through blood vessels in animals

36
Q

Why does water have adhesion and why is this good?

A

Water is also able to hydrogen bond to other molecules, such as cellulose, which is adhesion, this also enables water to move up the xylem due to transpiration

37
Q

What is the name of a positive ion?

A

Cation

38
Q

What is the name of a negative ion?

A

Anion

39
Q

What is an inorganic ion?

A

An ion that does not contain carbon, they occur in solution with some in high and others in very low concentrations

40
Q

What are H+ ions important for?

A

Concentration of H+ in a solution determines the pH (inversely proportional)
Metabolic processes
Enzyme structure & activity

41
Q

What are iron ions (Fe2+/Fe3+) important for?

A

Essential for transporting oxygen around the body
Fe2+ in Haemoglobin binds to oxygen → forms oxyhaemoglobin
Myoglobin (in muscles) is a similar protein, but is only made up of one polypeptide chain
Iron is also necessary for electron transport in respiration/photosynthesis

42
Q

What are sodium ions (Na+) important for?

A

Required for the transport of glucose and amino acids across cell-surface membranes
Glucose and amino acid molecules can only enter cells, through carrier proteins, alongside Na+ - this is known as co-transport
Na+ is also required for the transmission of nerve impulses

43
Q

What are magnesium ions (Mg2+) important for?

A

Photosynthesis

44
Q

What are nitrate ions (NO3-) important for?

A

Protein synthesis

45
Q

What are phosphate ions (PO4,3-) important for?

A

They attach to other molecules → form phosphate groups - essential components of: DNA, RNA, ATP, Phospholipids
Phosphorylates other compounds making them more reactive

46
Q

What are calcium ions (Ca2+) important for?

A

Essential in the movement of organisms
Stimulate muscle contraction
Help to regulate protein channels → affects the permeability of cell membranes
Enzymes are often activated by calcium ions
Calcium ions are also a clotting factor

Biology (17 decks)

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