2B Flashcards
Name the monomers that make DNA and RNA
Nucleotides
Describe the basic structure of a nucleotide
A phosphate group, a pentose sugar and a base
What do A, T, G, C and U stand for?
Adenine, cytosine, thymine, guanine, uracil
How do DNA and RNA nucleotides differ?
RNA has a ribose sugar whereas DNA has a deoxyribose sugar. RNA has a uracil base whereas DNA has Thymine
Describe the structure of RNA
Single polynucleotide strand of RNA nucleotides.
Describe how nucleotides join to form polynucleotides?
By condensation reactions between the sugar and phosphate groups to form phosphodiester bonds and a sugar phosphate backbone.
Which bases form complementary base pairs in DNA and RNA?
Adenine with Thymine (Uracil in RNA). Cytosine with Guanine.
Briefly outline the two main stages involed in protein synthesis.
- Transcription; reads DNA sequence and produces mRNA.
- Translation; reads mRNA sequence and orders amino acids to form polypeptide.
Describe the process of transcription.
DNA uncoils (DNA helicase) into two strands with exposed bases. One used as a template. Free RNA nucleotides form hydrogenn bonds with complementary bases. Nucleotides are joined together by RNA polymerase forming phospodiester bonds between the sugar and phosphate groups in a condensation reaction.
What happens to mRNA after transcription?
It moves out of the nucleus into the cytoplasm and attaches to a ribosome, ready for translation.
Describe the process of translation.
The anti-codon of tRNA attaches to complementary bases on the mRNA codons.
Amino acids bonded to tRNA form peptide bonds in a condensation reaction, continuing to form a polypeptide chain until a stop codon is reached.
This process requires ATP.
Explain how bases code for amino acids
Three bases code for one amino acid
Identify features of the genetic code
A triplet of bases codes for a particular amino acid.
Non-overlapping=each triplet is only read once.
Degenerate=more than one triplet codes for the same amino acid (64 possible triplets for 20 amino acids).
What is a gene?
A sequence of bases on a DNA molecule that codes for a specific sequence of amino acids in a polypeptide chain.
Define dipeptide
Two amino acids joined by a peptide bond
Define polypeptide
Two or more amino acids joined together by peptide bonds
How are polypeptides formed from their monomers?
Amino acids join together in condensation reactions, forming a peptide bond.
What is meant by the primary structure of a protein?
Primary = basic amino acid sequence.
What is meant by the secondary structure of a protein?
Secondary = whether the polypeptide chain is arranged into a helix or pleated sheet. Held together by H bonds.
What is meant by the tertiary structure of a protein?
Tertiary = 3D folding of the secondary structure into a complex shape held together by bonds between R groups of different amino acids e.g. ionic, hydrogen, disulfide bonds as well as hydrophobic and hydrophillic interactions.
What is meant by the quarternary structure of a protein?
When more than one polypeptide chain in a tertiary structure bonds together
How does the primary structure affect the tertiary (3D) structure?
Different amino acid sequence therefore different R groups that produce different bonds in the tertiary structure.
Describe how the structure of fibrous proteins relates to their function.
Long polypeptide chains. Very little tertiary structure. Strong cross-linkages between polypeptide chains. Hydrophobic groups on outside. This makes them insoluble, and useful for providing structure.
Give an example of a fibrous protein and explain how its properties relate to its use.
Collagen. Three polypeptide chains form a triple helix which creates fibres held together by strong crosslinks. This makes it useful in bones, cartilage and
other connective tissue.
