Structure of Nucleotides Flashcards
What are nucleic acids?
Polymers made from monomers called nucleotides
What are all nucleotides made up of?
three parts which are combined by Phosphodiester bonds formed in condensation reactions
What are the components of nucleotides?
-phosphate group
-A pentose sugar (deoxyribose, or river sugar)
-An organic nitrogenous base
What are the two groups of organic nitrogenous base?
Pyrimidine skeleton and purine skeleton
What bases are pyrimidine (single ring)?
Thymine
Cytosine
uracil(replaced timing in RNA)
What bases are purine (double ring)?
Adenine
Guanine
What does DNA stand for?
Deoxyribonucleic Acid
What is DNA and where is it found?
-Very large and stable molecule
-Found as chromatin in the nucleus of eukaryotic cells, and small amounts are found in the mitochondria and chloroplasts
What are the functions of DNA?
-It carries is the genetic code for protein synthesis
-replicates in dividing cells
what does DNA consist of?
Two polynucleotide strands twisted into a double helix.
What does DNA contain?
A pentose sugar (deoxyribose) and one of four nitrogenous bases: Adenine, Guanine, Cytosine, Thymine (components)
Why are the two DNA strands said to be anti-parallel?
The two strands run in opposite directions
Within each polynucleotide strand, what are the nucleotides held together by and what does this mean?
Bonds between the phosphate group attached to the fifth carbon atom on one pentose sugar and the third carbon atom on another- means that one end of the strength finishes on carbon five, so it’s called carbon five prime end (5’)
The other finishes on carbon three and it’s called three prime end (3’)
What do the two sugar phosphate backbones in DNA do?
protect the genetic information, stored within a sequence of bases
What do the bases face each other within the double helix according to, and what they held together by?
-according to the complimentary base pair rule
-Held together by hydrogen bonds
What does guanine pair with?
cytosine (three h2 bonds)
What does RNA stand for?
ribonucleic acid
what is RNA and where is it found?
A short lived molecule (single-stranded polynucleotide), mainly found in the cytoplasm of the cell and also found in the nucleus
what do RNA nucleotides contain?
A different pentose sugar (ribose) one of 4 organic nitrogenous bases- AGCU
what is the function of RNA?
-It is involved in protein synthesis, and there are three types of RNA involved
What are the three types of RNA
mRNA
rRNA
tRNA
What is mRNA?
A 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?
-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 is rRNA?
this, together with protein forms a large complex molecule: ribosome
-Ribosomes translate the genetic code and joining amino acids together to form polypeptides
How do you compare DNA and RNA?
-the pentose sugar for DNA is deoxyribose, whereas for RNA it’s ribose
-The Purine bases in DNA and RNA are guanine and adenine
-the pyrimidine bases in DNA are thymine and cytosine, cytosine and uracil in RNA
-DNA double stranded, RNA single stranded
-DNA= long , RNA short
what are differences between DNA and RNA?
DNA is found in the nucleus bound to histone proteins whereas RNA is found in both the nucleus and the cytoplasm,
• DNA is a much longer-lived molecule than RNA and
• DNA always contains hydrogen bonds between complementary bases, whereas in RNA hydrogen bonds are only found in tRNA.
what codes for the sequence of amino acids (primary structure) in one polypeptide?
sequence of DNA nucleotides (a gene)
what 2 stages are involved in protein synthesis involve?
Transcription and translation
Where does transcription occur?
In the nucleus
What is transcription?
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?
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
what is ATP (Adenosine Triphosphate) and where is it found?
-And nucleotide found in all living organisms
What does ATP contain?
-three phosphate groups, a ribose sugar and the nitrogenous base adenine
What is chemical energy stored in?
carbohydrates or lipids (like glucose)
what does respiration do to glucose?
Oxidises it in a series of small reactions to release energy in the form of ATP
what is ATP?
-not an energy store but an energy currency; it is synthesised as it is required
what is ATP involved in?
Energy changes, carrying the energy where it is needed and releasing the energy when ATP is broken down
What are the uses of ATP?
-Active transport
-Nerve impulse transmission
-Secretion (packaging molecules into vesicles for exocytosis)
-Muscle contraction
-Synthesis of complex molecules from smaller simpler molecules e.g. Proteins/nucleic acids
What’s the formation of ATP?
The enzyme AT synthase combines ADP and P, (inorganic phosphate) in a condensation reaction. This requires an input of energy (30.6 kJ mol-1) in an endergonic reaction. The addition of this phosphate to ADP is called phosphorylation.
What is the hydrolysis of ATP?
The enzyme ATPase hydrolyses the terminal phosphate bond releasing a small packet of energy (30.6 kJ mol-1) in an exergonic reaction. This forms ADP and Pi.
What are the advantages of using ATP as an intermediate and providing energy compared with using glucose directly?
Glucose*
ATP
Many enzymes needed to release energy
Only one enzyme is needed to release energy through the breaking of one high energy bond*
Releases large quantities of energy that may not be needed, generating lots of heat.
Releases small packets of energy (30.6kJ) when and where it is needed*
Only releases energy through respiration.
Common source of energy for different chemical reactions - universal.*
Requires proteins to cross a membrane
Easily transported across membranes*
Why is ATP called the universal energy currency?
it provides energy for many metabolic reactions in all living organisms
what is ATP synthase?
The enzyme that synthesises ATP
what is ATPase?
The enzyme on that hydrolyses ATP
What is exergonic?
Reaction that releases free energy
what is endergonic?
Reaction that requires energy
