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25 Cards in this Set
- Front
- Back
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Function of DNA and RNA |
To carry cellular information |
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Structure of a nucleotide |
Pentose sugar joined to a nitrogen-containing base and a phosphate group via a phosphodiester bond |
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DNA pentose sugar and bases |
Deoxyribose and adenine, thymine, cytosine and guanine |
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Pentose sugar and bases in RNA |
Ribose and uracil, thymine, cytosine and guanine |
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Main RNA function |
To transfer genetic info from DNA to ribosomes to make proteins |
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Detailed structural features of DNA |
A-T has 2 hydrogen bonds, C-G has 3 hydrogen bonds Two antiparallel polynucleotide strands twist to form double helix |
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RNA structural features |
Relatively short single polynucleotide strand |
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What does semi-conservative replication mean? |
There is genetic continuity between generations of cells because half of the strands in each new DNA molecule are from the original DNA molecule |
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Outline the events in semi-conservative replication |
DNA helipads breaks hydrogen bonds between bases to unwind double helix into 2 single strands Each original strand is a template, free floating DNA nucleotides are attracted to complementary exposed bases DNA polymerase forms hydrogen bonds between the new and old bases |
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How does DNA polymerase work? |
The active site is only complementary to the 3’ end of DNA so only adds nucleotides at 3’, so works in opposite ways along the antiparallel DNA strands |
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What evidence is there for semi-conservative replication? |
Meselson and Stahl grew bacteria DNA in light and heavy nitrogen so settle in different places in centrifuge tube, then added heavy DNA to light for one replication cycle, then the DNA settled in the middle - one strand had heavy one light |
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Why is water being a metabolite important? |
It is involved in condensation and hydrolysis reactions, e.g. releasing energy from ATP, joining amino acids to make a polypeptide |
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Why does water having a high latent heat of vaporisation make it important? |
It means it takes a lot of heat energy to break hydrogen bonds, which means a lot of energy is used up through evaporation - means can use water loss to cool down, e.g. sweat |
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Why can water be a buffer? |
High specific heat capacity (takes a lot of energy to heat it up) so that means aquatic environments don’t experience rapid temperature changes - good as stable for organisms living there to maintain a constant internal body temperature |
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Why is water a good solvent? |
Many metabolic reactions involve ions, and since water is polar it can surround the ions and dissolve them |
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Why does water’s strong cohesion matter? |
Cohesion = strong attraction between 2 same molecules Strong cohesion can help in transporting substances, e.g. through xylem, and also means water has a high surface tension so pond skaters can walk on the surface |
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What is the function of ATP? |
Immediate source of energy in a cell |
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What is the structure of ATP? |
An adenine based joined to a ribose sugar and 3 phosphate groups joined together |
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How is energy released from ATP? |
Via a hydrolysis reaction of 1 or 2 of the phosphate group bonds using enzyme ATP hydrolase - makes ADP + Pi |
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What enzyme re-synthesises ATP? |
ATP synthase using a condensation reaction adding on Pi |
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What is an inorganic ion? |
An atom with an electric charge that doesn’t contain carbon. Positive charge = cation, negative charge = anion |
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Function of iron ions |
In Haemoglobin - each of 4 polypeptide chains joined together in Hb has an iron ion in the centre which binds to oxygen to transport it in blood |
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Function of hydrogen ions |
Determine pH - more H+ the lower the pH, the more acidic. Enzyme-controlled reactions affected by pH |
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Function of sodium ions |
Helps transport glucose and amino acids across membranes in co-transport |
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Function of phosphate ions |
Essential component of ATP and DNA, the phosphate groups store energy in ATP and in DNA and RNA allow nucleotides to join up to form polynucleotides |
