3.8 Nucleic acids Flashcards
What is a nucleic acid? (2 marks)
Large polymers formed by many nucleotides linked together, that were discovered in cell nuclei.
Name the two types of nucleic acid. (1 mark)
RNA
DNA
What elements do nucleic acids contain? (2 marks)
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus
Describe the structure of a nucleotide. (3 marks)
Pentose sugar bonded to:
A phosphate group
And a nitrogenous base
How are nucleotides linked together? (2 marks)
Condensation reactions between the phosphate group on the 5th carbon and the hydroxyl group on the 3rd carbon.
What are the covalent bonds between nucleotides called? (1 mark)
Phosphodiester bonds.
Nucleotides joined by condensation reactions are sometimes referred to as a strong s_____-p__________ b_______. (1 mark)
Strong sugar-phosphate backbone
What does DNA stand for? (2 marks)
Deoxyribonucleic acid
Wat pentose sugar does DNA contain? (1 mark)
Deoxyribose
What four bases can each nucleotide in DNA contain? (4 marks)
Thymine
Cytosine
Adenine
Guanine
Bases can be divided into two groups depending on what?
How many carbon rings they have.
What are the two categories of base? (2 marks)
Pyrimidines
Purines
How many carbon rings do pyrimidines have? (1 mark)
One
How many carbon rings do purines have? (1 mark)
Two
Name the two bases in DNA with two carbon rings. (2 marks)
Adenine
Guanine
Name the two bases in DNA with one carbon ring. (2 marks)
Thymine
Cytosine
Name the bases in DNA that are pyrimidines. (2 marks)
Thymine
Cytosine
Name the two bases in DNA that are purines. (2 marks)
Adenine
Guanine
What is a DNA molecule made up of? (2 marks)
Two strands of polynucleotides coiled into a helix, known as a double helix.
What are the two strands in a DNA molecule held together by? (1 mark)
Hydrogen bonds between bases.
The two strands in a DNA molecule are a_____________ because they run in o__________ d_____________.
The two strands in a DNA molecule are anti-parallel because they run in opposite directions.
What does the pairing between bases allow for DNA? (1 mark)
Allows DNA to be copied and transcribed.
What are the complementary base pairings? (2 marks)
Adenine-thymine
Cytosine-guanine
Why is it important that a small base always binds with a larger base? (2 marks)
Maintains a constant distance between the DNA backbones, resulting in parallel polynucleotide chains.
What carries the genetic information of an organism in the form of code (1 mark)
The sequence of bases along a DNA strand.
What pentose sugar is in RNA? (1 mark)
Ribose
What does RNA stand for? (2 marks)
Ribonucleic acid
Why can DNA not leave the nucleus, why is this a problem, and how is this problem be solved? (4 marks)
DNA cannot supply the information directly to the sites of protein synthesis.
Short sections of the long DNA molecule (corresponding to a single gene) is transcribed into a short messenger RNA (mRNA), this can leave the nucleus.
Which base is different in RNA in comparison to DNA? (1 mark)
No thymine
Uracil instead
Is uracil a pyrimidine or a purine? (1 mark)
Pyrimidine
What happens to the RNA molecules after protein synthesis? (2 marks)
They are degraded in the cytoplasm- the phosphodiester bonds are hydrolysed and the RNA nucleotides are released and reused.
Describe how DNA can be extracted from plant material. (6 marks)
- Grind sample using a mortar and pestle
- Mix sample with detergent
- Add salt
- Add protease enzyme
- Add a layer of alcohol on top of the solution
- The DNA forms white strands between the layer of sample and layer of alcohol, ‘spool’ with a glass rod to pick them up.
When extracting DNA from plant material, what does grinding the sample do? (1 mark)
Break down the cell walls.
When extracting DNA from plant material, what does mixing the sample with a detergent do? (1 mark)
Breaks down the cell membrane, releasing the cell contents.
When extracting DNA from plant material, what does adding salt to the sample do? (1 mark)
Breaks hydrogen bonds between the DNA and water molecules.
When extracting DNA from plant material, what does adding protease enzyme do? (1 mark)
Break down the proteins associated with the DNA in the nuclei.
When extracting DNA from plant material, what does adding a layer of alcohol on top of the sample do? (1 mark)
Causes the DNA to precipitate out of solution.
Is RNA single or double stranded? (1 mark)
Single