2.1.3 Nucleotides and nucleic acids Flashcards
what is a nucleotide
a monomer from which nucleic acids are made of
what is a nucleic acid
the functional molecule made of one or more polynucleotide chains
eg DNA, RNA
what is the structure of nucleotide
made of three components
- a pentose sugar - contains 5 carbon atoms
- a nitrogenous base - contains carbon and nitrogen
- a phosphate group - contains phosphate
what is the difference between RNA and DNA nucleotides
-DNA has a deoxyribose sugar and RNA has a ribose sugar
-DNA has the bases A,T,C,G
-RNA has the bases A,U,G,C
-DNA is long and RNA is relatively short
-DNA has 2 strands RNA has 1 strand
what is a purine
- a class of nitrogenous bases which are made up of two rings.
- adenine and guanine
what is a pyrimidine
a class of nitrogen bases which are made up of a single ring
- cytosine, thymine and uracil
describe the complementary base pairings between the different bases
always a pyrimidine with a purine
adenine pairs with thymine via 2 hydrogen bonds A-T
cytosine pairs with guanine via 3 hydrogen bonds C-G
what is RNA
it is a type of nucleic acid that uses information from DNA to synthesis proteins
describe the synthesis and breakdown of polynucleotides
- nucleotides are joined together via condensation reactions to form polynucleotides
- the phosphate group of one nucleotide forms a covalent bond with the sugar of another nucleotide
- this forms a phosphodiester bond
- many nucleotides can join this way to create a chain of phosphates and sugars known as the sugar-phosphate backbone
- phosphodiester bonds can be broken via hydrolysis reactions
what is DNA
a type of nucleic acid that contains instructions needed to make proteins
what are some features of DNA
- sugar-phosphate backbone - protect the coding bases on the inside of the helix
- double stranded - allows strands to act as templates in DNA replication
- Large molecule - it stores lots of information
- double helix - makes the molecule more compact
- complementary base pairing - allows accurate DNA replication
- Weak hydrogen bonds- allows strands to separate in DNA replication
what is ATP
it is a phosphorylated nucleotide that provides energy for many process inside living cells
what is the structure of ATP
- ATP contains ribose, adenine and three phosphate groups
how does ATP go to form ADP
when ATP is hydrolysed it forms ADP and one phosphate molecule
- the process is catalysed by ATP
what is the structure of ADP
- ADP contains a ribose sugar adenine and 2 phosphate groups
what is the structure of DNA (deoxyribonucleic acid)
- contains deoxyribose ( a pentose sugar)
- A,T,C,G base
- a phosphate group
- hydrogen bonding between the complimentary base pairs on two antiparallel DNA nucleotides forms a DNA molecule
- the twisting of DNA produces the double-helix shape
how is DNA copied
a process called semi-conservative replication
explain the process of DNA replication
- DNA is unwounded by the gyrase enzyme
- The bonds between the DNA strands are pulled apart by the enzyme helicase, to break the hydrogen bonds
- Both strands act as a template for DNA replication
- free nucleotides pairs with the template strands complementary bases
- the enzyme DNA polymerase joins the free nucleotides together via condensation reaction in the 5’ to 3’ direction.
- the other strand known as the lagging strand is done after the first strands is replicated and is replicated in the 3’ to 5’ direction by the DNA polymerase enzyme
- two identical copies of DNA are made, each copy is made of one original DNA strand and one new DNA strand
what is a mutation
- changes to the DNA base sequence
what are some errors during DNA replication which leads to mutations
- bases inserted into the complimentary strand in the wrong order
- an extra base being inserted
- a base being left out
these mistakes occur at random and are spontaneous ( they do not have any particular case)
explain the importance of conserving genetic information with accuracy
- retaining one original DNA strand maximise accuracy during DNA replication as each DNA strand is created from an existing template
- each new cell will contain the same genetic information as its parent so genetic continuity is ensured between generations of cells.
- this is important as cells in our body is replaced regularly and the new cells needs to carry out the same roles as the parent cells
what is genetic code
- the order of bases on DNA consisting of triplets/codons of bases.
- each triplet codes for a particular amino acid known as a codon
what are the features of genetic code
- universal - each DNA triplet codes for the same amino acid in all organisms
2.non-overlapping - each base in the DNA is only read once
- degenerate - most amino acids are coded for by more than one triplet
what is a gene
a short section of DNA that codes for a polypeptide ( a protein)
how does a gene determine the sequence in a polypeptide ( primary structure of a protein)
- a codon codes for an amino acid
- the amino acids in a polypeptide chain are bonded by peptide bonds.
- the gene is a sequence of bases on a DNA molecule which forms multiple amino acids to make a polypeptide chain/ protein.
what is the non-codon section of DNA
- a section of DNA which doesn’t code for a protein
what is the two stages of protein synthesis
- transcription
- translation
where does transcription and translation occur
transcription - nucleus
translation - cytoplasm
explain the process of transcription
- in the nucleus, the gyrase enzyme uncoils the DNA strand and helicase enzyme breaks the hydrogen bonds
- RNA polymerase enzyme allows for the nucleotides to bind weakly to the complementary DNA nucleotides on template strand to form the messenger RNA
- the mRNA is an exact copy of the coding strand and has the bases (A,U,C,G)
- mRNA leaves the nucleus via nuclear pores into the cytoplasm and bind to ribsome
explain the process of translation
- ribosome moves along mRNA three bases at a time
- at each mRNA codon, a transfer RNA (tRNA - made in the nucleolus) with complementary anti-codon lines up and carries an amino acid.
- the amino acids join by peptide ponds to for a polypeptide and this folds into a 3D protein
