Topic 6 Nucleic Acids and Protein Synthesis. Flashcards
What are the two key features of a DNA molecule in terms of its abilities?
- The ability to store information: the information needed is a set of instructions for controlling the behaviour of cells.
- The ability to copy itself accurately: whenever a cell divides it must pass on exact copies of the ‘genetic molecule’ to each of its daughter cells so no information is lost.
What is DNA and RNA?
DNA (which stands for deoxyribonucleic acid) and RNA (which stands for ribonucleic acid) are polynucleotides (polymer), made up of long chains of nucleotides (monomer).
What is the name of the bond that connects adjacent monomers after condensation?
What is the bond that links adjacent base pairs?
The bond between adjacent monomers after condensation is called a phosphodiester bond (a type of covalent bond).
The bond between adjacent base pairs in DNA is called a hydrogen bond.
What is a nucleotide?
A molecule consisting of a nitrogen-containing or nitrogenous base, a pentose sugar molecule (which is a five carbon sugar and can be either ribose in RNA or deoxyribose in DNA) and a phosphate (PO₄³⁻) group.
The phosphate (PO₄³⁻) group is negatively charged, making DNA and RNA negatively charged molecules.
How are polynucleotides formed?
Polynucleotides are formed through the process of polymerisation, where individual nucleotides are joined together during condensation reactions forming long chains.
This process is catalyzed by enzymes known as DNA polymerases or RNA polymerases, depending on whether DNA or RNA is being synthesised.
The nucleotides are linked together through phosphodiester bonds, which connect the sugar of one nucleotide to the phosphate group of the next, forming a backbone for the polynucleotide chain.
What is a phosphodiester bond?
A phosphodiester bond is a bond joining two nucleotides together. The phosphate group involved now has two ester bonds, one of each of the sugars it is connected to.
What are the four different nitrogen-containing/ nitrogenous bases found in DNA?
In DNA the bases are:
- Adenine.
- Guanine.
- Thymine.
- Cytosine.
What are the four different nitrogen-containing/ nitrogenous bases found in RNA?
In RNA the bases are:
- Adenine.
- Guanine.
- Uracil.
- Cytosine.
What are purines and pyrimidines?
Adenine and guanine contain double ring structures and are classified as purine bases.
Thymine, uracil and cytosine contain single ring structure and are classified and pyrimidines.
NOTE THAT: Purine always binds with pyrimidine.
What are the main structural differences between DNA and RNA?
-
Strands:
- DNA is typically double-stranded, forming a double helix structure.
- RNA is usually single-stranded. -
Sugar:
- DNA contains deoxyribose sugar.
- RNA contains ribose sugar (contains 1 oxygen atom more than deoxyribose). -
Nitrogenous Bases:
- DNA has A, T, C, and G.
- RNA has A, U, C, and G.
What is adenosine triphosphate (ATP)?
Adenosine triphosphate (ATP) is an energy-carrying molecule found in the cells of all living things formed from the process of cellular respiration in the mitochondria of a cell and is released it to fuel other cellular processes.
What is the structure of ATP?
Adenosine can also be combined with 1 and 2 phosphate groups. Name them.
ATP or adenosine triphosphate is a nucleotide that consists of three main structures: the nitrogenous or nitrogen-containing base (adenine), the pentose sugar (ribose) and a chain of three phosphate groups.
Adenosine monoposphate, adenosine diphosphate respectively.
What are three functions of ATP?
- Metabolic reactions.
- Transporting substances across membranes against their concentration gradients such as in active transport.
- Energy needed for mechanical work in cells such as cell motility.
Describe the structure of DNA and RNA.
- DNA and RNA have a sugar-phosphate backbone. In DNA, the sugar is deoxyribose, while in RNA, it is ribose. The sugar molecule has a five-carbon structure.
- Each sugar is attached to a phosphate group, which connects to the next sugar in the chain through a phosphodiester bond (strong covalent bond). This bond forms when the hydroxyl group of the sugar reacts with the phosphate group.
In DNA only:
- The antiparallel nature of DNA means that its two strands run in opposite directions, with one strand going from 5’ to 3’ and the other from 3’ to 5’.
Explain the complementary base pairs in DNA and RNA, focusing on the number of hydrogen bonds formed?
Complementary base pairing occurs between opposite strands.
The number of hydrogen bonds between complementary base pairs is as follows:
- A and T are connected by 2 hydrogen bonds.
- C and G are connected by 3 hydrogen bonds.
- In RNA, A pairs with U through 2 hydrogen bonds.
This difference in hydrogen bonding contributes to the stability of the DNA double helix, with C-G pairs being stronger due to the three bonds compared to the A-T pairs.