Structures Of Nucleotides Flashcards
What are the 3 components of a nucleotide?
- a phosphate group
- a pentose sugar
- an organic nitrogenous base
What are the two types of organic nitrogenous base?
- Pyrimidine (single ring)
- Purine (double ring)
Name the pyrimidines
- Thymine
- Cytosine
- Uracil
Name the purines
- Adenine
- Guanine
Where is DNA found?
It’s found as chromatin in the nucleus of eukaryotic cells, and small amounts are found in mitochondria and chloroplasts
What are the functions of DNA?
- It carries the genetic code for protein synthesis
- It replicates in dividing cells
What does DNA consist of?
Two polynucleotide strands twisted into a double helix
What do DNA nucleotides contain?
Deoxyribose, a phosphate group and one of 4 organic nitrogenous bases: adenine, thymine, guanine, cytosine
What are the 2 strands of DNA said to be?
Antiparallel
What do the 2 sugar-phosphate backbones do?
They protect the genetic information stored within the sequence of bases
How are bases held together in DNA?
Hydrogen bonds
What are the complementary base pairs in DNA and how many hydrogen bonds do they form?
Guanine+Cytosine - 3 hydrogen bonds
Adenine+Thymine - 2 hydrogen bonds
Where is RNA found?
Mainly in cytoplasm. Also in nucleus.
How many strands does RNA consist of?
RNA is a single stranded polynucleotide
What pentose sugar does RNA contain?
Ribose
What are the 4 organic nitrogenous bases found in RNA?
Adenine, cytosine, guanine, uracil
What is the function of RNA?
Involved in protein synthesis
What does mRNA do?
Carries the genetic code for a specific protein from DNA in the nucleus to ribosomes in the cytoplasm
What does tRNA do?
This transfers specific amino acids to the ribosome. A single RNA strand forms a cloverleaf shape held together by hydrogen bonds between certain base pairs.
What does rRNA do?
Together with a protein, forms a ribosome. Ribosomes translate the genetic code and join amino acids together to form polypeptides.
What is protein synthesis?
A sequence of DNA nucleotides codes for the sequence of amino acids (primary structure) in one polypeptide.
What are the 2 stages involved in protein synthesis?
Transcription and translation
What is transcription and where does it occur?
Occurs in the nucleus
DNA is read by enzymes and used to make a single stranded mRNA molecule. This then leaves the nucleus through a nuclear pore and travels to a ribosome in the cytoplasm or rough endoplasmic reticulum.
What is translation and where does it occur?
Occurs at a ribosome
mRNA attaches to the ribosome and a tRNA molecule brings a specific amino acid. Ribosomal enzymes catalyse the formation of peptide bonds between adjacent amino acids to form the primary structure of a new polypeptide.
