NUCLEIC ACIDS (2.1.3) Flashcards
1
Q
What elements are found nucleotides
A
- Carbon
- Hydrogen
- Oxygen
- Nitrogen
- Phosphorus
2
Q
What is a nucleotide
A
- type of biological molecule
Can be: - monomers of Nucleic acids (DNA, RNA)
- stores of energy (ATP, ADP)
3
Q
describe the structure of a DNA nucleotide
A
- phosphate group
- deoxyribose sugar
- nitrogenous base
4
Q
State the 4 nitrogenous bases present within DNA
A
- Adenine
- Thymine
- Cytosine
- Guanine
5
Q
What is the purpose of DNA
A
- stores genetic information
- contains the instructions for an organisms growth
6
Q
Describe an RNA nucleotide
A
- phosphate group
- ribose pentose sugar
- nitrogenous base
7
Q
State the 4 nitrogenous bases present within RNA
A
- Adenine
- Uracil
- Cytosine
- Guanine
8
Q
What is the purpose of RNA
A
Used to make proteins from genetic information stored within DNA
9
Q
- describe the structure of a purine
- state the nitrogenous bases that are purines
A
- 2 carbon-nitrogen rings joined together
- larger
- Adenine
- Guanine
10
Q
- describe the structure of pyrimidine
- state the nitrogenous bases that are pyrimidines
A
- 1 Carbon-nitrogen ring
- smaller
- Cytosine
- Thymine
- Uracil
11
Q
Describe how polynucleotides are formed
A
- condensation reaction
- phosphodiester bonds connect phosphate group on one nucleotide and the sugar on another nucleotide
12
Q
Describe the structure of the Nucleic acid, DNA
A
DOUBLE HELIX STRUCTURE
- 2 polynucleotide strands
- anti parallel to each other
- joined by hydrogen bonds between complementary bases
- large molecule
13
Q
State the complementary bases
A
Adenine - Thymine (2 hydrogen bonds)
Cytosine - Guanine (3 hydrogen bonds)
14
Q
Describe the structure of the Nucleic acid, RNA
A
- single stranded polynucleotide
- smaller
15
Q
Compare DNA and RNA’s size with reasons
A
- DNA is large, as it contains genetic information for an entire organism
- RNA is smaller, as it needs to leave the nucleus to make proteins from DNA’s “instructions”
16
Q
Describe the structure of ATP (Adenine Triphosphate)
A
- 3 phosphate groups
- ribose pentose sugar
- adenine (nitrogenous base)
17
Q
Describe the structure of ADP (Adenine Diphosphate)
A
- 2 phosphate groups
- ribose (pentose) sugar
- adenine (nitrogenous base)
18
Q
Explain what ATP is used for
- state 3 examples that require it
A
A store of chemical energy, necessary for
- synthesis/anabolic reactions
- transport
- movement (muscle contractions AND nerve impulses)
19
Q
- describe how ATP is made
- state the enzyme that catalyses the reaction
A
- condensation reaction
- ADP is phosphorylated (gains a phosphate ion)
- reaction catalysed by ATP synthase (enzyme)
20
Q
Why must ATP be made instead of leaving glucose as a form of energy
A
- plants + animal cells cannot get energy directly from glucose
- require photosynthesis/respiration to release energy, which is used to make ATP
- ATP can then provide energy needed
21
Q
- how is ATP used
- state the enzyme that catalyses the reaction
A
- hydrolysis reaction
- phosphate bond between 2nd and 3rd phosphate ion is broken
- releases energy stored in bond
- catalysed by ATP hydrolyse enzyme
22
Q
What is the purpose of DNA replication
A
- to ensure each new cell produced from cell division has the full amount of DNA
- necessary to pass genetic information through generations
23
Q
Which enzyme breaks hydrogen bonds during DNA replication
A
DNA helicase
24
Q
State the enzyme responsible for forming phosphodiester bonds during DNA replication
A
DNA polymerase
25
Outline the stages of DNA replication
1. Hydrogen bonds between polynucleotide strands broken (DNA helicase), causing DNA to unwind
2. Free DNA nucleotides form hydrogen bonds with complementary bases on each “template” strand of DNA
3. Phosphodiester bonds formed between free nucleotides (DNA polymerase)
4. Sugar phosphate backbone on new strands are formed
5. Strands form double helix with a 1 old strand and 1 new strand
26
Why is DNA replication considered as “semi-conservative”
Half the strands in each new DNA molecule are old, the other half are new
27
- what is meant by a gene
- why effect do they have on protein synthesis
- sequence of bases that code for a polypeptide
- the order of codons determine the order of amino acids
- this determines the proteins primary structure
28
What is meant by a codon
3 nitrogenous bases that code for an amino acid
29
- what is meant by the genetic code
- why is it “non-overlapping”
- why is it degenerate
- sequence of codons in which code for specific amino acids
- each triplet is separate, bases are not shared
- some codons code for the same amino acid, some are STOP or STARY signals
30
Which enzyme breaks bonds between bases on DNA during transcription
DNA helicase
31
Which enzyme forms phosphodiester bonds between free RNA nucleotides during transcription
RNA polymerase
32
Outline the stages of transcription
1. Bonds between DNA bases broken (DNA helicase)
2. Free RNA nucleotides form H bonds with complementary bases on the DNA “template” strand
3. (RNA polymerase) forms phosphodiester bonds between them
4. RNA polymerase detaches from DNA once it has reached a STOP codon - it has made the mRNA strand
5. DNA recoils into double-helix
6., mRNA leaves through a nuclear pore, into the cytoplasm
33
Outline the stages of translation
1., mRNA attaches to a ribosome
2., tRNA molecules carry amino acids to the ribosome
3., tRNA have anti-codons, complementary to an mRNA codon
4., rRNA catalyses the joining of 2 amino acids with a peptide bond
5., first tRNA molecule is released
6. Ribosome moves down mRNA strand, repeating the process
7. Polypeptide strand moves away, proteins primary structure is made
34
- describe the structure of messenger RNA (mRNA)
- describe its function
- single polynucleotide
- made in nucleus (transcription)
- moves genetic information from DNA outside the nucleus to a ribosome
35
- describe the structure of ribosomal RNA (rRNA)
- describe its function
- forms 2 sub units in a ribosome (large and small)
- catalyses formation of peptide bonds between amino acids
36
- describe the structure of transfer RNA (tRNA)
- describe its function
- single polynucleotide folded into a clover
- anti-codon on one side, amino acid binding site on the other
- carries amino acids to ribosomes during translation
37
Outline the method to gain a sample of purified DNA from a sample of peas
1. Crush/grind a sample of peas, breaking them up
2. Add washing up liquid to distilled water and salt to make a solution
3. Add broken pea cells to beaker, containing the solution
4. Place beaker in 60DEGREE C water bath for 15 minutes
5. Cool mixture in ice bath for 5 minute
6. Use filter paper to filter the mixture into a boiling tube
7. Add 2-3 drops of protease enzyme to test tube
8. Dribble ice cold ethanol down the side to form a layer of DNA
38
Why is washing up liquid added to the sample of peas
- dna purification practical
- breaks down phospholipid bị layer and nuclear membranes
- releases DNA
39
Why is salt added to the pea sample
- dna purification practical
- salt binds to DNA
- DNA clumps together
40
Why is the sample of peas and solution placed in a 60DEGREE C water bath for 15 minutes
- dna purification practical
- denatures any enzymes
- stops them from digesting DNA
41
Why is the sample of peas and solution cooled/placed in an ice bath for 5 minutes after the water bath
- dna purification practical
- lower temperature prevents DNA itself breaking down
- DNA breaks down at high temperatures
42
- why is the pea sample and solution filtered
- what does the filtrate contain
DNA PURIFICATION PRACTICAL
- filtering removes cel debris and membrane fragments
- the filtrate contains only DNA and associated proteins
43
Which enzyme is added to the pea filtrate and why
- dna purification practical
- protease enzyme
- breaks down histones/proteins that are bound to the DNA in the mixture
- this leaves just DNA in the sample
44
Why is ice cold ethanol added to the sample of peas
- dna purification practical
- Nucleic acids are insoluble in ice-cold ethanol
- DNA precipitates out of the sample on top of the mixture
