structure of nucleotides Flashcards
define purine
a double ringed organic nitrogenous base
(adenine, guanine)
define pyramidine
a single-ringed organic nitrogenous base
(thymine, cytosine, uracil)
define tRNA
transfer RNA
a clover leaf-shaped single RNA strand which transfers specific amino acids to a ribosome in translation
define mRNA
messenger RNA
a single stranded RNA molecule which is a copy of one gene formed in transcription
define rRNA
ribosomal RNA
makes up a ribosome (along with some protein)
define universal energy currency
ATP is described as this because it provides energy for many metabolic reactions in all living organisms
define ATP synthase
the enzyme that synthesises ATP
define ATPase
the enzyme that hydrolyses ATP
define exergeonic
a reaction that releases free energy
define endergonic
a reaction that requires energy
what does DNA stand for?
deoxyribose nucleic acid
what are nucleotides composed of?
- phosphate group
- a pentose sugar (deoxyribose sugar or ribose sugar)
- organic nitrogenous base
what are the two type of organic nitrogenous bases?
- pyramidine
- purine
what bases are pyramidine and what bases are purine?
purine : adenine, guanine
pyramidine : cytosine, thymine, uracil
describe pyrimidine
single ring
describe purine
double ring
what are the functions of DNA?
- it carries the genetic code for protein synthesis
- it replicates in dividing cells
why is DNA said to be anti-parallel?
the two DNA strands run in opposite directions
if the strand finishes on the fifth carbon atom, what is it called?
5 prime end
what do the two sugar-phosphate ‘backbones’ do?
protect the genetic information stored within the sequence of bases which face each other within the double helix.
what bond holds the bases together?
hydrogen bonds
what bases pair together?
guanine and cytosine
adenine and thymine
what doe RNA stand for?
ribose nucleic acid
describe RNA
a short-lived molecule
found mainly in the cytoplasm of the cell - also found in the nucleus
single stranded polynucleotide
what are the four organic nitrogenous bases in RNA?
- adenine
- guanine
- cytosine
- uracil
in what process is RNA involved in?
protein synthesis
what are the 3 types of RNA?
- mRNA
- tRNA
- rRNA
what is mRNA?
single stranded molecule that carries the genetic code for a specific protein from DNA in the nucleus to ribosomes in the cytoplasm
what is tRNA?
this transfers specific amino acids to the ribosome
A single RNA strand forms a clover-leaf shape held together by hydrogen-bonds between certain base pairs
what is rRNA?
this, together with protein, forms a large complex molecule : a ribosome.
ribosomes translate the genetic code and join amino acids together to form polypeptides
state the differences between DNA and RNA?
DNA - deoxyribose sugar
RNA - ribose sugar
DNA - adenine, guanine,cytosine, thymine
RNA - adenine, guanine, cytosine, uracil
DNA - double stranded
RNA - single stranded
DNA - longer in length
RNA - shorter in length
where is DNA is found?
the nucleus bound to histone protein
what is protein synthesis?
a sequence of DNA nucleotides codes for the sequence of amino acids in one polypepetide chain
in how many stages does protein synthesis occur, and what are these stages called?
two stages
1. transcription
2. translation
describe transcription
- occurs in nucleus
- DNA is read by enzymes and is used to make single stranded mRNA.
- this leaves the nucleus through a nuclear pore
- this travels to a ribosome in the cytoplasm or rough endoplasmic reticulum
describe translation
- occurs at a ribosome
- mRNA attatches to the ribosome, and a tRNA molecule brings a specific amino acid
- ribosomal enzyme catalyse the formation of peptide bonds adjacent amino acid to form the primary structure of a new polypeptide
what does ATP stand for?
adenine triphosphate
what is ATP composed of?
- three phosphate groups
- a ribose sugar
- the nitrogenous base adenine
what is ATP described as and why?
energy currency
BECAUSE…
it is a source of energy for many metabolic reactions in all living organisms
what are some uses of ATP?
- muscle contraction for movement
- synthesis of complex molecules (e.g protein, DNA)
- active transport
- nerve impulse transmission
how is ATP formed?
the enzyme ATP synthase combines ADP and P i in a condensation reaction
this is a endergonic reaction
the addition of this phosphate to ADP is called phosphorylation
how is ATP broken down?
the enzyme ATPase hydrolyses the terminal phosphate bond releasing a small packet of energy in an exergonic reaction.
this forms ADP and P i
what are the advantages of using ATP as an intermediate in providing energy, compared with using glucose directly?
ATP - only one enzyme needed to release energy through the breaking of one high energy bond
GLUCOSE - many enzymes needed to release energy
ATP - releases small packets of energy (30.6kJ) where it is needed
GLUCOSE - releases large quantities of energy that may not be needed, generating lots of heat
ATP - common source of energy for different chemical reactions
GLUCOSE - only releases energy through respiration
ATP - easily transported across membrane
GLUCOSE - requires a specific carrier protein for transport across membrane
what does tRNA consist of ?
hydrogen bonds
amino acid attachment site
anti-codon
