Structure of Nucleotides Flashcards
What are nucleic acids
Polymers made of monomers called nucleotides
What are nucleotides?
- phosphate group
- a pentose sugar (deoxyribose = DNA, ribose = RNA + ATP)
- a organic nitrogenous base
What are the two types of nitrogenous base?
Pyrimidine (single ring)
- thymine
- cytosine
- uracil
Purine (double ring)
- adenine
- guanine
What is DNA?
Deoxyribose nucleic acid
A very stable and large molecule that is found in the chromatin in the nucleus of eukaryotic cells, and in small amounts in mitochondria, chloroplasts, and prokaryotes
What are the functions of DNA?
- carries the genetic code for protein synthesis
- replicates in dividing cells
What is the structure of DNA?
One pentose sugar (deoxyribose), one phosphate group, and one organic nucleotide (T, A, C, G)
These are arranged in two polynucleotide strands twisted into a double helix structure that run in opposite directions (antiparallel)
Nucleotides are held together by phosphate bonds attached by the 5C on one side and the 3C on the other so when the bond breaks, there is the 5’ end, and the 3’ end
Guanine and cytosine are attached by three hydrogen bonds, and adenine and thymine/uracil are attached by two hydrogen bonds
Two sugar phosphate backbones protect the genetic information stored within the sequence of bases, which face each other within the double helix
What is RNA?
Ribonucleic acid
- short lived molecule
- found mainly in the cytoplasm of the cell
- also found in the nucleus
- single stranded polynucleotide
- one phosphate group, ribose sugar, and one of 4 nitrogenous bases (adenine, uracil, guanine, cytosine)
What are the functions of RNA?
RNA is involved in protein synthesis in 3 ways:
mRNA: single stranded molecule that carries the DNA for a specific protein from DNA in the nucleus to the ribosome in the cytoplasm
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
rRNA: alongside protein, forms a large complex molecule (a ribosome) that translates the genetic code and joins the amino acids together to forms polypeptides
What are the differences between DNA and RNA?
- pentose sugar: DNA= deoxyribose, RNA= ribose
- purine bases: guanine, adenine in both
- pyrimidine bases: DNA = thymine, cytosine, RNA = uracil, cytosine
- strands: DNA= 2 + double stranded, RNA= 1 + single stranded
- length: DNA= long, RNA= short
- location: DNA= in the nucleus bound to histone proteins, RNA= both the nucleus and the cytoplasm
- lifespan: DNA is much longer lived
- H-bonds: DNA always contains hydrogen bonds between complementary bases, whereas RNA only contains hydrogen bonds in tRNA
What is ATP?
Adenine triphosphate= a nucleotide found in all living organisms
Contains 3 phosphates, a ribose sugar, and the nitrogenous base adenine
Energy currency that is synthesised as required
Respiration oxidises glucose in a series of small reactions to release energy in the form of ATP
Why is ATP the universal energy currency?
Universal:
- used as a source of energy in all cells in all organisms
- used in all enzyme reactions inside cells
Energy
- ATP supplies energy released as small packets immediately in usable amounts
- one enzyme (ATP hydrolase) needed to release energy from ATP
- the energy is transferred from 1 molecule only (ATP) directly to an energy-requiring reaction
What are some uses of ATP?
- active transport
- muscle contraction
- nerve impulse transmission
- secretion (packaging molecules into vesicles for exocytosis)
- synthesis of complex molecules from smaller simpler molecules
How is ATP formed?
ATP synthase combines ADP and Pi (inorganic phosphate) in condensation reaction
Requires an input of energy (30.6 kJmol-1) in an endergonic reaction
Addition of Pi is called phosphorylation
What is hydrolysis of ATP?
ATPase hydrolyses the terminal phosphate bond to release a small packet of energy (30.6 kJmol-) in an exergonic reaction to form ADP and Pi
What is an exergonic reaction?
A reaction that releases free energy
What is an endergonic reaction?
A reaction that requires energy
What are the advantages of using ATP?
- only one enzyme is needed to release energy through the breaking of one high energy bond
- releases small packets of energy when and where it is needed
- common sense of energy for different chemical reactions (universal)
- easily transported across membranes
