Chapter 3: 3.8 Flashcards
Nucleic acids (23 cards)
What is the structure of nucleic acids like?
They are large polymers formed from many nucleotides linked together in a chain.
What is an individual nucleotide made up of?
- a pentose monosaccharide (sugar), containing 5 carbon atoms
- a phosphate group that is inorganic, acidic and negatively charged (PO4{2-])
- a nitrogenous base - a complex organic molecule containing 1 or 2 carbon rings in its structure as well as nitrogen.
How are nucleotides linked together?
Condensation reactions to form a polymer called a polynucleotide.
How is a phosphodiester bond formed?
The phosphate group at the 5th carbon of the pentose sugar of 1 nucleotide forms a covalent bond with the hydroxyl (OH) group at the 3rd carbon of the pentose sugar of an adjacent nucleotide.
Forms a long, sugar-phosphate backbone with a base attached to each sugar.
How are the phosphodiester bonds broken?
Hydrolysis - reverse of condensation. Releases individual nucleotides.
What does deoxyribonucleic acid (DNA) contain?
Contains the sugar deoxyribose. The nucleotides in DNA each have 1 of 4 different bases. This means there are four different DNA nucleotides, which can be divided into 2 groups: pyrimidines and purines.
What are pyrimidines?
The smaller bases, which contain single carbon ring structures - thymine (T) and cytosine (C).
What are purines?
The longer bases, which contain double carbon ring structures - adenine (A) and guanine (G).
The double helix in DNA
- Can range in length
- Made up of 2 polynucleotide strands coiled into a helix.
- Held together by H-bonds between the bases
- Two strands run anti-parallel, arranged so that they run in opposite directions
- Base pairing allows DNA to be copied and transcribed: key properties required of the molecule of heredity.
What are the rules for base pairing?
- Adenine and Thymine are both able to form 2 H-bonds and always join with each other
- Cytosine and Guanine form 3 H-bonds and also only bind to each other [in complementary base pairing]
- Small pyrimidine base always bind to large purine base
- DNA always contains equal amount of Adenine & Thymine and Cytosine & Guanine due to Complementary Base Pairing
What role does ribonucleic acid (RNA) play?
- Transfer of genetic information from DNA to the proteins that make up the enzymes and tissues of the body
Why can’t DNA leave the nucleus?
- The DNA of each eukaryotic chromosome is a very long molecule, formed from many hundreds of genes
What ways does DNA use in order to leave the nucleus?
- The relatively short section of the long DNA molecule corresponding to a single gene is transcribed into a similarly short messenger RNA (mRNA) molecule
- Each individual mRNA is therefore much shorter than the whole chromosome of DNA.
Do DNA and RNA form polymers in the same way?
Yes - by the formation of phosphodiester bonds in condensation reactions.
What happens to RNA after protein synthesis?
The RNA molecules are degraded in the cytoplasm. The phosphodiester bonds are hydrolysed and the RNA nucleotides are released/reused.
What elements make up nucleic acid?
Carbon Hydrogen, Oxygen, Nitrogen Phosphorus.
How do you carry out DNA extraction?
1) You will grind the sample in a motar and pestle - which breaks down the cell wall
2) Mix the sample with detergent - which breaks down the cell membrane, releasing cell contents into solution
3) Add salt that breaks the hydrogen bond between DNA and water molecules
4) Add pro-tease enzyme - which breaks down the proteins associated with the DNA in the nuclei
5) Layer of alcohol is then added on top of the sample - alcohol causes the DNA to precipitate out of solution
6) DNA can then be seen as white strands forming between layer of the sample and layer of alcohol
DNA is then picked up by spooling onto a glass rod
What does DNA store?
DNA stores all genetic information needed by an organism, which is then passed from generation to generation
What mRNA made up of?
: it is a polymer composed of many nucleotide monomers
What is the role of nucleic acid?
They are responsible for the storage and transfer of genetic information and the synthesis of polypeptides (proteins)
The two types of nucleic acid?
DNA and RNA
What are the differences between RNA and DNA?
RNA has a pentose sugar that is ribose rather than deoxyribose
Has uracial base rather than a thymine base
How is RNA and DNA similar>
Uracil form 2 hydrogen bonds with adenine similar like thymine in DNA
RNA nucleotide bind to DNA following the base pairing rules
