nucleic acids Flashcards
double helix
shape of DNA molecule,
due to coiling of the two sugar-phosphate backbone strands into a right-handed spiral configuration
nucleotide
molecule consisting of a pentose (five-carbon) sugar, a phosphate group and a nitrogenous base
monomer
molecule when repeated makes up a polymer.
nucleotides are the monomers of nucleic acids
polynucleotide
large molecule containing many nucleotides
DNA polymerase
enzyme that catalyses formation of DNA from activated deoxyribose nucleotides, using single-stranded DNA as a template
this forms the sugar-phosphate backbone and hydrogen bonds between bases
strands twist to form a double helix
helicase
enzyme that catalyses the breaking of hydrogen bonds between the nitrogenous pairs of bases in a DNA molecule
helix unzips to form two single strands
semi-conservative replication
how DNA replicates, resulting in two new molecules, each of which contains one old strand and one new strand.
one old strand is conserved in each new molecule
gene
a length of DNA that codes for a polypeptide or for a length of RNA that is involved in regulating gene expression
polypeptide
a polymer made of many amino acids joined together by peptide bonds
insulin is a polypeptide of 51 amino acids
protein
a large polypeptide of 100 or more amino acids
however, the terms are often used synonymously, and insulin may be described as a small protein
transcription
the process of making messenger RNA from a DNA template
mRNA copy of a gene is made in the nucleus
translation
formation of a protein, at ribosomes, by assembling amino acids into a particular sequence
according to the coded instructions carried from DNA to the ribosome by mRNA
base triplet
a triplet of bases n a DNA molecule
codon
a triplet of bases on a length of mRNA
anticodon
a triplet of bases on a tRNA molecule, complementary to the mRNA codon
DNA functions (3)
- coding biologically useful information via transcription and therefore acting as a blueprint for building cells and bodies
- ensuring continuity within a multicellular organism and between generations through semi-conservative replication
- allowing evolution to occur by generating variation through mutation.
DNA molecule
—DNA molecule is composed of two strands.
contains two polynucleotide chains made up of nucleotides joined together
mutation
a change to the DNA base sequence
they can alter the sequence of amino acids in a protein
which elements do nucleotides contain?
C, H, O, N and P
Importance of nucleotides
-monomers that make up DNA and RNA (types of nucleic acid)
DNA
-used to store genetic information-the instructions an organism needs to grow and develop
RNA
used to make proteins from the instructions in DNA
uses of ADP and ATP
to store and transport energy in cells
deoxyribose
pentose sugar in a DNA molecule
purine base
contains two carbon-nitrogen rings joined together
Adenine and guanine
pyrimidine base
only has one carbon-nitrogen ring
smaller than a purine base
Cytosine and thymine
ribose
the sugar in RNA
RNA structure
uracil (pyrimidine) replaces thymine as a base
made up of a single polynucleotide chain
how to Phosphorylate a nucleotide?
you add one or more phosphate groups to it
ADP structure
contains the base adenine, the sugar ribose and two phosphate groups
ATP structure
contains the base adenine, the sugar ribose and three phosphate groups
ATP
provides energy for chemical reactions in the cell
synthesised from ADP and inorganic phosphate using energy breakdown of glucose in respiration
ADP is phosphorylated to form ATP and a phosphate bond is formed
polynucleotides
when nucleotides join between phosphate group of one nucleotide and the sugar of another
this forms a phosphodiester bond consisting of the phosphate group and two ester bonds
sugar-phosphate backbone
the chain of sugars and phosphates
hydrogen bonding between?
bases of two DNA polynucleotide strands
complementary base pairing
each base can only join with one particular partner
Adenine with thymine (A-T)
Cytosine with guanine (C-G)
Number of hydrogen bonds between A and T?
2
number of hydrogen bonds between C and G?
3
how DNA double-helix is formed?
when two antiparallel polynucleotide strands twist
Self-Replication
DNA can copy itself
gene
sequence of DNA nucleotides that codes for a polypeptide
messenger RNA (mRNA)
made in the nucleus
three adjacent bases are called a codon
it carries the genetic code from the DNA in the nucleus to the cytoplasm, where it’s used to make a protein during translation
transfer RNA (tRNA)
found in the cytoplasm
it has an amino acid binding site at one end and a sequence of three bases at the other end called an anticodon
it carries the amino acids that are used to make proteins to the ribosomes during translation
ribosomal RNA (rRNA)
forms the two subunits in a ribosome (along with proteins)
the ribosomes move along the mRNA strand during protein synthesis
the rRNA in the ribosome helps to catalyse the formation of peptide bonds between the amino acids
genetic code
- non-overlapping
- degenerate
- universal
the sequence of base triplets (codons) in DNA or mRNA, which codes for specific amino acids
each base triplet is read in sequence, separate from the triplet before and after it
transcription
RNA polymerase attaches to DNA double-helix at the beginning of a gene
hydrogen bonds in gene break, separating the strands and DNA molecule uncoils
one strand is used as a template to make an mRNA copy
T is replaced by U in RNA joined together forming an mRNA
hydrogen bonds reform and strands coil back into a double-helix
translation
amino acids are joined together to make a polypeptide chain
mRNA attaches to a risosome and tRNA carries amino acids to the ribosome
