Nucleic acids Flashcards
What are the 2 purine bases
Adenine and guanine
What are the pyrimidine bases
cytosine and thymine/uracil
What is a nucleotide
monomer of nucleic acids with a pentose sugar a nitrogenous base and a phosphate group
What are the components of a nucleotide
a phosphate group
A nitrogenous base
Pentose sugar
what are chemoautotrophic organisms
Organisms that use energy from oxidation of electron donors eg bacteria
What is the structure of ATP
three phosphate groups
Base
Ribose sugar
What are the roles of ATP
metabolic processes like building proteins from amino acids
Movement - muscle contraction
Active transport -changing shape of carrier proteins
What are the advantages of ATP
only 1 enzyme is needed to release the energy in ATP
Releases energy in small amounts
Common source of energy in most chemical reactions
where does ATP transfer energy
from energy rich compounds e.g glucose to cellular reactions
what are the issues with energy transfer from glucose
energy transfers are inefficient so energy is lost through heat
energy release from glucose is uncontrollable so it would produce enough heat to destroy a cell
what is the structure of DNA
2 polynucleotide strands wound round each other to form a double helix
deoxyribose sugar and phosphate groups are on the outside of the molecule and form the backbone
the two strands are antiparalell
how many hydrogen bonds are between cytosine and guanine
3
how many hydrogen bonds are between adenine and thymine
2
why is DNA suited for its functions
it is a large molecule so it carries alot of genetic info
two strands can seperate as they are held together by hydrogen bonds
backbone protects the genetic information inside
what is the structure of RNA
a single polynucleotide
contains the sugar ribose
has uracil instead of thymine
what are the 3 types of RNA
messenger-mRNA
transport-tRNA
ribosomal-rRNA
What is mRNA
synthesised in the nucleus and carries genetic code from DNA to ribosomes in the cytoplasm
what is rRNA
found in cytoplasm and made up of large complex molecules
made up of proteins and ribosomal rna
site of translation of genetic code onto protein
what is tRNA
transfer RNA
small single stranded molecule that folds so that base sequences form complementary pairs
carries the anticodon
transports specific amino acids to the ribosomes in protein synthesis
what is an anticodon
groupf of three bases on a tRNA molecule that corellates with the specfic amino acid being carried
what is the functions of DNA
replication and protein synthesis
when is DNA replicated
during interphase in the nucleus
what is conservative replication
parental double helix remains intact and a whole new double helix is made
what is semi conservative replication
parental double helix seperates into 2 strands which each act as a template for a new strand
What is dispersive replication
two new double helicies contain fragments from both strands of the parental double helix
What is a gene
a section of DNA on s chromosone which codes for a specific polypeptide
What are the characteristics of the genetic code
three bases encode each amino acid so the code is a triplet code
Stop codons
Code is universal
Non overlapping because each base only occurs in one triplet
What is an Extron
coding region in the nucleotide sequence of DNA and pre-mRNA that remains present in the final nature mRNA after introns removed
What is an intron
non coding nucleotide sequence in DNA and pre mRNA that is removed from pre MRNA to produce mature mRNA
What happens in translation
the sequence of codons on the mRNA is is used to generate a specific sequence of amino acids forming a polypeptide
Where does translation occur
on a ribosome
What is each ribosome made up of
two subunits
Larger one has two sites of attachment of tRna molecules
Smaller subunit binds to mRNA
What are the three stages of translation
initiation
Elongation
Termination
what happens in initation
a ribosome attaches to start codon at one end of the mRNA molecule
what happens in elongation
the two amino acids are sufficiently close for a ribosomal enzyme to catalyse the formation of a peptide bonds between them
what happens in termination
sequence repeats until a stop codon is reached
what is amino acid activation
once tRNA is released from the ribosome it is free to collect another amino acid from the cytoplasm ,
energy from ATP is needed to attach the amino acid to the tRNA
what is post translational modification
polypeptides on the ribosome are are transported through the cytoplasm to the golgi and can be folded in to secondary, tertiary or quaternary structure
e.g haemoglobin- 4 polypeptides combined
what are the functions of proteins in living organisms
hormones, enzymes,antibodies
what is the difference between DNA and RNA
rna has uracil Instead of thymine
rna single stranded DNA double stranded
rna has ribose sugar DNA has deoxyribose
