2.1.3 nucleotides and nucleic acids Flashcards
(55 cards)
1
Q
2 nucleic acids
A
RNA, DNA
2
Q
Nucleic acid monomer
A
nucleotide
3
Q
3 components of a nucleotide
A
- phosphate group
- pentose sugar
- nitrogenous base
4
Q
purine
A
- 2 rings
- adenine and Guanine
5
Q
pyrimidine
A
- 1 ring
-2 cytosine, thymine and uracil
6
Q
Differences in RNA and DNA
A
RNA IS
- non helical
- single stranded
- shorter than DNA
- ribose sugar
- URACIL instead of thymine
7
Q
why is RNA shorter than DNA
A
only contains the small portion of the genetic code necessary for its function
8
Q
3 types of RNA
A
- mRNA (carries gene out of nucleus and to ribosomes)
- tRNA (transports amino acids to ribosomes)
- rRNA (makes up the ribosome)
9
Q
structure of DNA
A
- 2 polynucleotide strands of nucleotide monomers
- lie in opposite antiparallel directions
- double helix
- 2 strands held together by CBP - (purine to pyrimidine)
10
Q
H bonds between A and T (or U)
A
2
11
Q
H bonds between C and G
A
3
12
Q
gene
A
sequence of DNA nucleotides that code for a protein
13
Q
why cant DNA itself leave the nucleus
A
- too big to fit through the small pores in the nuclear envelope
14
Q
evidence for CBP
A
- similar amounts of A and T , then C and G
15
Q
HOW ARE PHOSPHODIESTER BONDS FORMED
A
condensation
16
Q
bonds between nucleotides
A
phosphodiester
17
Q
how to break a phosphodiester bond
A
hydrolysis
18
Q
ADP and ATP are …
A
phosphorylated nucleotides
19
Q
structure of ADP and ATP
A
- pentose sugar (ribose)
- nitrogenous base (adenine)
- 2 or 3 inorganic phosphates
20
Q
STEPS OF DNA REPLICATION (7)
A
- double stranded molecule untwists and molecule UNZIPS (H bonds between complementary bases break) catalysed by DNA helicase
- 2 chains separate, exposing the bases, creating a Y shaped replication fork. each strand is used as a template to make 2 new double strands
- Free phosphorylated nucleotides from nucleoplasm bond to bases by CBP (a,t , c,g ) phosphodiester bonds , catalysed by DNA POLYMERASE
- DNA polymerase also Proofreads
- 2 daughter dna stranfs
21
Q
how does the structure of DNA allow replication
A
- double stranded helix (2 antiparallel strands)
- BOTH act as a template
- weak H bonds between complementary base pairs easy to break
- purins ONLY bind to pyrimidines due to their different sizes
- 2 bonds A-T. 3 bonds C-G
22
Q
mutatin in DNA leads to different tertiary structure
A
- change in base sequence (different primary structure)
- R groups interact differently (ionic bonds, h bonds etc)
- THIS DETERMINES tertiary structure, which is 3D shape
23
Q
describe how the polypeptide chains are held together
A
- phosphodiester bonds between sugar and phosphate group forms sugar phosphate backbone
- H bonds between bases
- 2 H bonds A-T, 3 between C-G
- purine only to pyrimidine as different sizes
24
Q
how is the sugar phosphate backbone formed
A
- DNA polymerase
- condensation between phosphate and sugar of adjacent nucleotides
25
how is dna organised in eukaryotes?
- nucleus
- each large DNA molecules wound around HISTONE proteins. 1 chromosome = 1 molecule of DNA
26
where does the energy to make phosphodiester bonds come from
- hydrolysis of activated nucleotides
- to release the extra phosphate groups
27
how to extract DNA
- macerate tissue using a pestle and mortar
- add detergent
- att ethanol so DNA precipitates out
28
gene
short section of DNA that codes for a protein
29
4 examples of where tertiary structure is important for protien
1. enzyme active site complementary to substrate
2. variable region of antibody complementary to antigen
3. receptor on cell membrane shape complementary to cell signalling molecule
4. ion channel protein has HPO AA on the inside and LIPOPHILIC aa on the outside
30
nature of genetic code (3)
1. near UNIVERSAL (same triplet of bases codes for same AA)
2. DEGENERATE (more than one base triplet for each AA) reduces harm of mutation
3. NON-OVERLAPPING
31
transcription steps (5)
1. gene unwinds and unzips
2. H bonds between cbp break
3. RNA POLYMERASE catalyses the formation of phosphodiester bonds between bases, after H bonds between RNA nucleotides and the complementary bases, on the TEMPLATE STRAND
4. free nucleotides use CBP to produce the coding strand (comp to the template RNA strand)
5. mRNA passes out of nucleus, through nuclear envelope to a ribosome
32
how are ribosomes made
- in nucleolus in 2 smaller subunits
- pass separately out of nuclear envelope pores and then bind together helped by MAGNESIUM IONS
33
2 susbunits of ribsosome
- ribosomal RNA
- protein
34
Translation
- mRNA attached to ribosome
- ribosome 'reads' codon
- tRNA brings amino acids, complementary anticodon temperarily H bonds to complementary codon on mRNA
- ribosome moves along the mRNA, synthesising a peptide bond between
- ENERGY NEEDED
- PPC assembled, folds into tertiary 3d structure
- mRNA breaks down and molecules can be recycledf into new mRNA
35
tRNA
- made in nucleolus
- single strand PPC
- at one end is a trio of bases that recognises and attaches to a specific amino acis. (amino acid binding site)
- also has another triplet of bases (ANTICODON) complementary to a specific codon of bases on the mRNA
36
methyl green pyronin stain
DNA = green
RNA = red
37
why ight there be a triplet which doesnt have an amino acid
STOP CODON: protein finished
38
purpose of crushing tissue before extracting DNA
break cell walls
39
purpose of using detergent in experiment
break down PHOSPHOLIPID BILAYAER
40
enzyme that should be used in DNA experiment
-protease
-break down histones
41
whats it called when the white layer of DNA forms?
precipitation
42
why no need to crush animal cells
no cell wall
43
purpose of adding salt and ethanol in DNA experiment
- precipitate out the DNA from the aqueous solution
44
similarities DNA and ATP (4)
- pentose sugar
- adenine base
- phosphodiester bond
- contain phosphate
45
differences DNA and ATP (2)
- ATP has 2 additional phosphates
- ATP has ribose sugar instead of deoxyribose
46
differences DNA and ADP (2)
- ADP has ribose whereas DNA has deoxyribose
- ADP has 2 phosphates whereas DNA has 1 phosphate
47
why is only a small proportion of your mass ATP at the end of the day despite loads being made?
- ATP Broken down
- used to provide energy for metabolic reactions
48
similarities DNA replication and transcription (7)
- DNA unwinds and unzips
- helicase to unzip
- template DNA
- CBP
- hydrogen bonds
- free activated nucleotides
- polymerase enzymes
49
differences DNA replication and transcription
- only a small section of DNA unzipped in transcirption
- BOTH strands are templates in replication
- RNA vs DNA free nucleotides
- RNA vs DNA polymerase
- one strand produced in RNA, 2 in DNA
- mRNA leaves nucleus, but DNA strand remains bound to the template strand
50
why are enzymes essential to all organisms (2)
- catalysts: speed up reactions by lowering activation energy, allowing reactions to take place at lower body temperatures
- the hgih temperatures needed otherwise would denature proteins
51
why is replication semi-conservative?
- contains one old strand and one new strand
- EACH dna strand acts as a template strand
52
importance of TRANSCRIPTION
- translation must take place at ribosome
- DNA transcribed to mRNA
- as DNA is too large to leave through the small pores in the nuclear envelope
53
purpose of salt in that experiment
helps DNA precipitate out (with ethanol)
54
phosphodiester bond is between phosphate group and carbon ...
3
55
in DNA replication bOTH STRANDS ARE
template strands
