2.1.3 Nucleotides and nucleic acids Flashcards
What makes up a nucleotide?
- Pentose sugar
- Nitrogenous base
- Phosphate group
What bond forms between nucleotides?
Phosphodiester bonds
How many hydrogen bonds between T and A base pairs?
Two
How many hydrogen bonds between C and G base pairs
Three
What does a deoxyribose sugar (DNA) have on carbon 2’?
Hydrogen
Which nitrogenous bases are found on DNA?
Adenine
Cytosine
Guanine
Thymine
What shape is DNA?
Double stranded (double helix)
What does a ribose sugar (RNA) have on carbon 2’?
Hydroxyl group (OH)
Which nitrogenous bases are found on RNA?
Adenine
Cytosine
Guanine
Uracil
What shape is RNA?
Single stranded
What property does the OH group on RNA give?
More susceptible to hydrolysis so is a transport molecule whereas DNA is a storage molecule
What are the pyrimidines?
Smaller bases which contain single carbon ring structures
- Thymine
- Cytosine
- Uracil
What are the purines?
Larger bases which contain double carbon ring structures
- Adenine
- Guanine
P_____ pair with P_______
Purines
Pyrimidines
What is energy needed for?
- Anabolic reactions
- Movement
- Muscle contraction
- Conduction of nerve impulse
What makes up adenosine monophosphate (AMP)?
- Adenine base
- Ribose
- One phosphate group
What makes up adenosine diphosphate (ADP)?
- Adenine base
- Ribose
- Two phosphate groups
What makes up adenosine triphosphate (ATP)?
- Adenine base
- Ribose
- Three phosphate groups
How does ATP release energy?
- Releasing a phosphate group through hydrolysis reaction
- Hydrolysed to ADP + phosphate ion
What enzyme hydrolyses ATP?
ATPase
Why is ATP not a good long term store of energy?
Instability of phosphate bonds as the negative phosphate ions repel each other
Why is ATP a good immediate energy store?
Cellular respiration forming ATP is constantly occurring in living cells
How is ATP reformed?
By reattaching phosphate group to ADP through a condensation reaction
Outline the steps for DNA purification
1) Grind sample
2) Add detergent
3) Add salt
4) Add protease enzyme
5) Add ice cold ethanol
What is the purpose of grinding the sample in DNA purification?
Breaks down cell walls
What is the purpose of adding detergent to the sample in DNA purification?
Breaks down cell membrane by disrupting the phospholipids, releasing cell contents
What is the purpose of adding salt to the sample in DNA purification?
Breaks hydrogen bonds between DNA and water molecules
What is the purpose of adding protease enzyme to the sample in DNA purification?
Breaks down histone proteins associated with DNA in the nuclei
What is the purpose of adding ice cold ethanol to the sample in DNA purification?
Causes DNA to precipitate out of solution and form as white strands between the layer of sample and layer of ethanol
What is semi-conservative replication?
DNA is composed of one original strand and one newly formed one
Why is semi-conservative replication important?
Ensures there is genetic continuity so that the cells which are replaced regularly are exactly the same as the old cells
Outline the stages of DNA replication?
1) Helicase unwinds DNA helix by breaking hydrogen bonds between base pairs to form single strands (unzipping)
2) Free nucleotides pair up with complementary base pairs on original DNA strand acting as the template
3) DNA polymerase joins nucleotides together on new strand of DNA through condensation recations
How is the genetic code universal?
All organisms use the same codons but in different sequences
How is the genetic code non overlapping?
Each base is only read once in the codon it is part of
How is the genetic code degenerate?
Multiple codons can code for the same amino acid
