Nucleic Acids And ATP Flashcards
What is the structure of a nucleotide
Phosphate group, Pentose sugar, nitrogen containing base
Function of DNA
Holds genetic information which codes for polypeptides
What is DNA Pentose sugar
Deoxyribose
What is the function of RNA
Transfer genetic info from DNA to ribosomes
How are polynucleotides formed
● Condensation reactions, removing water molecules
● Between phosphate group of one nucleotide and deoxyribose / ribose
● Forming phosphodiester bond
When nucleotides join together what type of bond does it form
Phosphodiester bond
In a polynucleotide what are the chain of sugars known as
Sugar phosphate backbone
Compare the structure of DNA and RNA
DNA- double helix- 2 polynucleotide strands
Pentose sugar= deoxyribose
Nitrogen contains base= thymine
Longer
RNA- single helix
Nitrogen containing base is uracil
Pentose sugar= ribose
Shorter
What are the complementary base pairs of DNA
2 hydrogen Bonds with adenine and thymine
3 hydrogen bonds between guanine and cytosine
What are the complementary base pairs of RNA
2 hydrogen bonds between adenine and uracil
3 hydrogen bonds between guanine and cytosine
How does the structure of DNA relate to its function
● Two strands → both can act as templates for semi-conservative replication
● Hydrogen bonds between bases are weak → strands can be separated for replication
● Complementary base pairing → accurate replication
● Many hydrogen bonds between bases → stable / strong molecule
● Double helix with sugar phosphate backbone → protects bases / hydrogen bonds
● Long molecule → store lots of genetic information (that codes for polypeptides)
● Double helix (coiled) → compact
Describe the structure of (messenger) RNA
● Polymer of nucleotides (polynucleotide)
● Each nucleotide formed from ribose, a phosphate
group and a nitrogen-containing organic base
● Bases - uracil, adenine, cytosine, guanine
● Phosphodiester bonds join adjacent nucleotides
● Single helix
Why is semi conservative replication important
Ensures genetic continuity between generations of cells
Why is semi conservative replication described as semi conservative
-strands from DNA acts as a template
-new DNA molecule contains one old and one new strand
What is the semi conservative process breifly review
- DNA helicase breaks hydrogen bonds between complementary bases, unwinding the double helix
- Both strands act as templates
- Free DNA nucleotides attracted to exposed bases and join by specific complementary base pairing
- Hydrogen bonds form between adenine-thymine and guanine-cytosine
- DNA polymerase joins adjacent nucleotides on new strand by condensation reactions
- Forming phosphodiester bonds
What is a phosphodiester bond
2 ester bonds in a polynucleotide
Which scientist validated Watson and Crick of the structure of DNA and the theory of semi conservative replication
Meleson and stahl
Describe the work of Meselson and Stahl in validating the Watson-Crick model of semi-conservative DNA replication
- Bacteria grown in medium containing heavy nitrogen so nitrogen is incorporated into DNA bases
○ DNA extracted & centrifuged → settles near bottom, as all DNA molecules contain 2 ‘heavy’ strands - Bacteria transferred to medium containing light nitrogen and allowed to divide once
○ DNA extracted & centrifuged → settles in middle, as all DNA molecules contain 1 original ‘heavy’ and 1 new ‘light’ strand - Bacteria in light nitrogen allowed to divide again
○ DNA extracted & centrifuged → half settles in middle, as
contains 1 original ‘heavy’ and 1 new ‘light’ strand; half settles near top, as contains 2 ‘light’ strands
What is the nucleotide ATP deprived from
A molecule of ribose, adenine and 3 phosphate groups
What is ATP known as
Adenosine triphosphate
Describe how ATP is broken down
● ATP (+ water) → ADP (adenosine diphosphate) + Pi (inorganic phosphate)
● Hydrolysis reaction, using a water molecule
● Catalysed by ATP hydrolase
Give two ways in which the hydrolysis of ATP is used in cells
● Coupled to energy requiring reactions within cells (releases energy) ○ eg. active transport, protein synthesis
● Inorganic phosphate released can be used to phosphorylate
(add phosphate to) other compounds, making them more reactive
Describe how ATP is resynthesised in cells
● ADP + Pi → ATP (+ water)
● Condensation reaction, removing a water molecule
● Catalysed by ATP synthase (enzyme)
● During respiration and photosynthesis
what are 2 similarities of RNA and DNA
Both important information carrying molecules
both are polymers of nucleotides
how is the sugar phosphate backbone made in a polynucleotide
series of condensation reactions between the deoxyribose sugar and the phosphate group making a polynucleotide and a phosphodiester bond
the DNA polymer occurs in pairs and is joined by what
hydrogen bonds between bases leading to the double helix
Use your knowledge of enzyme action to suggest why DNA polymerase moves in opposite directions along DNA strands
● DNA has antiparallel strands
● So shapes / arrangements of nucleotides on two ends are different
● DNA polymerase is an enzyme with a specific shaped active site
● So can only bind to substrate with complementary shape
Name the two scientists who proposed models of the chemical structure of DNA and of DNA replication
Watson and Crick
what is the last step of semi conservative replication
DNA polymerase in the condensation reaction that joins adjacent nucleotides.
Describe the work of Meselson and Stahl in validating the Watson-Crick
model of semi-conservative DNA replication
- Bacteria grown in medium containing heavy nitrogen (15N) so
nitrogen is incorporated into DNA bases
○ DNA extracted & centrifuged → settles near bottom, as all
DNA molecules contain 2 ‘heavy’ strands - Bacteria transferred to medium containing light nitrogen (14N)
and allowed to divide once
○ DNA extracted & centrifuged → settles in middle, as all DNA
molecules contain 1 original ‘heavy’ and 1 new ‘light’ strand - Bacteria in light nitrogen (14N) allowed to divide again
○ DNA extracted & centrifuged → half settles in middle, as
contains 1 original ‘heavy’ and 1 new ‘light’ strand; half settles
near top, as contains 2 ‘light’ strands
Why did many scientists initially doubt that DNA carried the genetic code?
The relative simplicity of DNA - chemically simple molecule with few components
Suggest how the properties of ATP make it a suitable immediate source of
energy for cells
● Releases energy in (relatively) small amounts / little energy lost as heat
● Single reaction / one bond hydrolysed to release energy (so immediate release)
● Cannot pass out of cell
