Nucleic Acids

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What is the monomer unit of a nucleic acid called?
A nucleotide
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What are the 3 components of a nucleotide?
1. Pentose sugar 2. Organic base 3. Phosphate group
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What type of reaction causes the 3 components of a nucleotide to join together?
A condensation reaction
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Two mononucleotides may join together from a condensation reaction between the pentose sugar of one mononucleotide and the phosphate group of another. What is the bond that is formed called? and what is the new structure called?
A phosphodiester bond. A dinucleotide
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If there is a continued linking of mononucleotides what is this new structure called?
Polynucleotides.
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What are the organic bases of DNA and what are their pairs?
Adenine and Thymine. Guanine and Cytosine
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What are the organic bases of RNA and what are their pairs?
Adenine and Uracil. Guanine and Cytosine.
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What is the difference between RNA and DNA?
Ribonucleic acid is a polymer of nucleotides. It is a short polynucleotide chain where the pentose sugar is always ribose. It has an organic base of uracil instead of thymine.
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What is the pentose sugar of DNA?
Deoxyribose
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What makes the structure between RNA and DNA, if RNA is just a single short polynucleotide chain?
DNA is made up of two strands of polynucleotides. Each of which are extremely long.
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How are the two strands of the DNA joined together?
By hydrogen bonds between the complementary strand of each base.
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Why is DNA a stable molecule?
1. The phosphodiester backbone protects the more chemically reactive organic bases inside the helix. 2. Hydrogen bonds link the organic base pairs forming bridges between the phosphodiester uprights. The more C-G the more stable due to 3 H bonds
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What are some of the functions of the DNA?
It is the hereditary material responsible for passing genetic information from cell to cell and generation to generation.
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How is a DNA molecule adapted to carry out its functions?
1. It is very stable 2. Its 2 separate strands are joined with only hydrogen bonds, which allows them to separate during replication. 3. It is a very large molecule and carries an immense amount of genetic info
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How is a DNA molecule adapted to carry out its functions? (part 2)
4. By having the base pairs within the helical cylinder of the deoxyribose-phosphate backbone, the genetic info is protected from being corrupted by outside forces. 5. Base pairing leads to DNA being able to replicate & transfer info as mRNA
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What is semi-conservative replication?
It describes the mechanism by which DNA is replicated in all known cells. It suggests that each strand of the double helix would serve as a template for synthesis of a new strand. It would allow each daughter strand to associate w/ the template stran
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What are the 4 requirements for semi-conservative replication?
1. The 4 types of nucleotide 2. Both strands of the DNA molecule act as a template 3. The enzyme DNA polymerase 4. A source of chemical energy to drive the process.
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What is the first stage of semi-conservative replication?
The enxyme DNA Helicase breaks the hydrogen bonds between the organic base pairs.
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What is the second stage of semi-conservative replication?
The double helix separates into 2 strands and unwinds
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What is the third stage of semi-conservative replication?
Each exposed polynucleotide strand then acts as a template to which complementary free nucleotides bind by specific and complementary base pairing.
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What is the fourth stage of semi-conservative replication?
Nucleotides are joined together in a condensation reaction by the enzyme DNA polymerase to form the missing polynucleotide strand on each of the two original polynucleotide strands of the DNA.
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What is the fifth stage of semi-conservative replication?
Each of the new DNA molecules contain one of the original DNA strands. Half the the original DNA is built into the new DNA molecule.
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What is ATP?
Both plants and animals oxidise organic molecules to make adenosine triphosphate (ATP0 which is the main energy source to carry out processes within cells
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What is the structure of ATP?
Adenine, ribose and phosphates.
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How does ATP store energy?
ATP is a nucleotide and has three phosphates. The bonds between the phosphates are unstable and so have a low activation energy. This means they are easily broken. When they are broken down they release a lot of energy.
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What is the equation for the breaking down of ATP?
ATP + H20 -> ADP + Phosphate + Energy
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What type of reaction is use when breaking down ATP?
Hydrolysis
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The breakdown of ATP is reversible. This mans we can add a phosphate to ADP to reform ATP. What enzyme is needed for this condensation reaction?
ATP synthase
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What examples are there of the synthesis of ATP?
1. in chlorophyll-containing plant cells during photosynthesis 2. in plant and animal cells during respiration 3. in plant and animal cells when phosphate groups are transferred from donor molecules to ADP
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What is ATP a source for the cell of?
It is an immediate source of energy for the cell.
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Why is the cell not storing large quantities of ATP, not a problem?
ATP is rapidly re-formed from ADP and inorganic phosphate so little goes a long way.
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Why is ATP a better source of energy than glucose?
1. The energy for reactions is released in smaller and more manageable amounts. 2. The hydrolysis of ATP to ADP is a single reaction that releases immediate energy. The breakdown of glucose is a long series of reactions so energy release is longer.
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ATP cannot be stored so is continuously made within the mitochondria within the cell. What does this mean for cells such as muscle fibres?
They will need to possess many large mitochondria as these cells require a lot of energy.
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How is ATP used in metabolic processes?
ATP provides the energy needed to build up macromolecules from their basic units.
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How is ATP used in movement?
ATP provides the energy for muscle contraction. ATP provides the energy for the filaments of muscle to slide past one another and shorten the overall length of the muscle fibre.
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How is ATP used in active transport?
ATP provides the energy to change the shape of carrier proteins in plasma membranes. This allows molecules or ions to be moved against a concentration gradient.
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How is ATP used in secretion?
ATP is needed to form the lysosomes necessary for the secretion of cell products.
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How is ATP used in activation of molecules?
The inorganic phosphate released in the hydrolysis of ATP can be used to phosphorylate other compounds in order to make them more reactive, thus lowering the activation energy in enzyme-catalysed reactions.
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Why is water described as dipolar?
The oxygen atoms has slight negative charge while the hydrogen atoms have a slight positive charge. The water molecule has both negative and positive poles.
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The opposite charge of the poles of the water molecule are attracted to each other. The attractive force between the opposite charges is called what?
A hydrogen bond.
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Why are hydrogen bonds considered important forces?
Each bond is fairly weak, together they cause the water molecules to stick together, giving water its unusual properties.
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Why does water have a higher melting point then expected of its structure?
Because the hydrogen bonds allow the water molecules to stick together so it require quite a bit of energy to separate them to a gas.
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What is latent heat of vaporisation?
Hydrogen bonding between water molecules means that it requires a lot of energy to evaporate it. This energy is called latent heat vaporisation.
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What is cohesion? Does water have a large or small cohesive force?
The tendency for molecules to stick together. Water has a large cohesive force.
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What is surface tension?
It means that the water surface acts as like a skin and is strong enough to support small organisms like pond skaters. Water molecules tends to be pulled back into the body of water rather than escaping from it.
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What is the importance of water in metabolism?
1. Water is used to break down molecules by hydrolysis. 2. Chemical reactions take place in an aqueous medium 3. Water is a major raw material in photosythensis
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What is the importance of water as a solvent?
Water readily dissolves other substances: oxygen and carbon dioxide, wastes such as ammonia and urea, inorganic ions and small hydrophilic molecules such as amino acids, monosaccharides and ATP, enzymes, whose reactions take place in solution.
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What are some other important features of water?
1. Its evaporation cools organisms & allows them to control their temp. 2. It is not easily compressed & provides support 3. It is transparent, therefore aquatic plants can photosynthesise, also light rays can penetrate the fluid in the eye to retina
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Where are inorganic ions found?
In organisms where they occur in solution in the cytoplasm of cells and in body fluids and as well as part of larger molecules.
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What are some examples of inorganic ion uses?
1. Iron ions are used in haemoglobin where they play a role in the transport of oxygen 2. The phosphate ions that form a structural role in DNA molecules and a role in storing energy in ATP molecules
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What are some examples of inorganic ion uses? (part2)
3. Hydrogen ions are important in determining the pH of solutions and therefore the functioning of enzymes 5. Sodium ions are important in the transport of glucose and amino acids across plasma membranes.
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Card 2

Front

What are the 3 components of a nucleotide?

Back

1. Pentose sugar 2. Organic base 3. Phosphate group

Card 3

Front

What type of reaction causes the 3 components of a nucleotide to join together?

Back

Preview of the front of card 3

Card 4

Front

Two mononucleotides may join together from a condensation reaction between the pentose sugar of one mononucleotide and the phosphate group of another. What is the bond that is formed called? and what is the new structure called?

Back

Preview of the front of card 4

Card 5

Front

If there is a continued linking of mononucleotides what is this new structure called?

Back

Preview of the front of card 5
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