2 Nucleic acids

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  • Created by: sydjow17
  • Created on: 04-12-19 16:49
Describe the difference in functions of DNA and RNA.
DNA carries the genetic information and RNA transfers the genetic information from DNA to ribosomes.
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What are ribosomes formed from?
rRNA and proteins.
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What is a DNA nucleotide composed of?
Deoxyribose, a phosphate group, and one of the organic bases adenine, cytosine, guanine or thymine.
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What is an RNA nucleotide composed of?
Ribose, a phosphate group, and one of the organic bases adenine, cytosine, guanine or uracil.
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How is a polynucleotide formed?
Through the series of condensation reactions between mononucleotides, with the formation of phosphodiester bonds between them.
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Which components of nucleotides are involved in a phosphodiester bond?
The pentose sugar of one mononucleotide and the phosphate group of another.
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Describe the general structure of a DNA molecule.
A double helix with two polynucleotide chains held together by hydrogen bonds between specific complementary base pairs.
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Describe the specific base pairing.
Adenine always pairs with thymine and cytosine always pairs with guanine.
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What is meant by the structural backbone of the DNA molecule?
The winding around of one another of the uprights of phosphate and deoxyribose to form a double helix.
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How many hydrogen bonds between adenine and thymine?
Two.
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How many hydrogen bonds between cytosine and guanine?
Three.
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What is the function of DNA?
It is the hereditary material responsible for passing genetic information from cell to cell and generation to generation.
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Which of the carbon atoms in the pentose molecule are of particular significance?
The 3' (3-prime) and 5' (5-prime) carbon atoms.
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What does the 5' carbon have attached?
A phosphate group.
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What does the 3' carbon have attached?
A hydroxyl group.
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Describe the term antiparallel.
The term used to describe the arrangement of the two strands in the DNA molecule. One strand runs in the 5' to 3' direction while the other runs the opposite way - in the 3' to 5' direction.
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In which direction only can nucleic acids synthesised? Why?
In the 5'-to-3' direction, because DNA polymerase can only attach nucleotides to the hydroxyl group on the 3' carbon molecule.
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What are the two main stages of cell division?
Nuclear division and cytokinesis.
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Define nuclear division, and state its two types.
The process by which the nucleus divides. The two types are mitosis and meiosis.
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Define cytokinesis.
Follows nuclear division and is the process by which the whole cell divides.
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What must happen before a cell divides? Why?
DNA replication. To ensure that all the daughter cells have the genetic information to produce the enzymes and other proteins that they need.
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Why is DNA replication termed 'semi-conservative replication'?
One strand of the parent double helix is conserved in each new DNA molecule (with the addition of a newly formed strand).
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Name the two enzymes involved in DNA replication.
DNA helicase and DNA polymerase.
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What is the role of DNA helicase in DNA replication?
It breaks the hydrogen bonds linking base pairs of DNA, causing the double helix to separate into its two strands and unwind.
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What is the role of DNA polymerase in DNA replication?
It joins nucleotides together in a condensation reaction. It attaches nucleotides to the hydroxyl group on the 3' carbon molecule.
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What is ATP and what are its three components?
ATP is a phosphorylated macromolecule made up of adenine, ribose and a chain of three phosphate groups.
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How does ATP store energy?
The bonds between the phosphate groups are unstable and so have a low activation energy, which means they are easily broken. When they do break they release a considerable amount of energy.
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What type of reaction is involved in the breaking down of ATP?
Hydrolysis.
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Name the enzyme that catalyses ATP hydrolysis.
ATP hydrolase.
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What is ATP hydrolysed into?
ADP and an inorganic phosphate.
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Name the enzyme that catalyses ATP synthesis.
ATP synthase.
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Describe why ATP is only an immediate energy source.
ATP releases its energy very rapidly in a single step, and is transferred directly to the reaction requiring it. The instability of the phosphate bonds means it is too unstable to be a long term store.
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Explain how ATP can make an enzyme-catalysed reaction take place more readily.
ATP provides a phosphate that can attach to another molecule, making it more reactive and so lowering its activation energy. As enzymes work by lowering activation energy they have less 'work' to do and so function more readily.
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Give 5 roles of ATP.
In metabolic processes building up macromolecules; in movement; in active transport (in changing the shape of carrier proteins); in secretion (to form lysosomes); in activation of molecules.
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Suggest why the vase pairings of adenine with cytosine and guanine with thymine do not occur.
The bases are linked by hydrogen bonds. The molecular structures could be such that hydrogen bonds do not form between non-complementary bases.
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Define amphipathic.
(of a molecule, especially a protein) having both hydrophilic and hydrophobic parts.
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Card 2

Front

What are ribosomes formed from?

Back

rRNA and proteins.

Card 3

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What is a DNA nucleotide composed of?

Back

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Card 4

Front

What is an RNA nucleotide composed of?

Back

Preview of the front of card 4

Card 5

Front

How is a polynucleotide formed?

Back

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