1
Q
what are DNA and RNA made up of
A
monomers called nucleotides
2
Q
what is a nucelotide
A
contains a phosphat group, nitrogen-containibg organic base and pentose (either ribose/RNA or deoxyribose/ DNA)
3
Q
what are the two groups of organic bases
A
- pyrimidines- single ring
- purines- double ring
4
Q
what are the 4 nitrogenous bases found in DNA
A
- guanine (purine)
- cytosine (pyrimidine)
- adenine (purine)
- thymine (pyrimidine)
5
Q
what is different about the nitrogenous bases in RNA
A
thymine is replaced by uracil
6
Q
what does ATP stand for
A
adenosine triphosphate
7
Q
is ATP a nucleotide
A
yes
8
Q
what is the structure of ATP
A
a ribose sugar joined to the adrenine base with 3 phosphate groups attached
9
Q
how is energy released from ATP
A
- when the high energy bond between the 2nd and 3rd phosphate group is broken via hydrolysis by the enzyme ATPase
- adenosine diphospahte is formed (ADP)
10
Q
how much energy is released when ATP turns to ADP
A
30.6 KJ
11
Q
is ATP to ADP reversible
A
yes but it requires energy from respiration of glucose to reform bond
12
Q
ATP hydrolysis equation
A
ATP –> ADP+ pi (inorganic phosphate) + 30.6 KJ energy
13
Q
what is the structure of ADP
A
2 phosphates, ribose, adenine
14
Q
what are the advantages of ATP
A
- energy released quickly from one step and involves one enzyme
- energy is release in small amounts
- its universal currency- common source of energy
15
Q
what are the roles of ATP
A
- used in many anabolic reactions
- active transport
- muscle contraction
- nerve impulse transmission
16
Q
what is an exergonic reaction
A
can occur without energy
17
Q
what is an endergonic reaction
A
does require energy
18
Q
what is the structure of DNA
single strand
A
- two polynucleotide strands are arranged into a double helix
- first, a dinucleotide is formed when a condensation reaction occurs between two nucelotides
- the 5th carbon atom of the deoxyribose sugar joins to 3rd carbon arom of the deoxyribpse sugar above it via a phosphate moelcule - this builds a single DNA strand
19
Q
whats the structure of DNA double strand
A
-DNA is formed from two strands which run anti-parallel to eachother
- held together with hydrogen bonds between complementary bases
- forms a double helix
20
Q
which bases are complementary
A
guanine froms hydrogen bonds with cyosine
adenine form hydrogen bonds with thymine
21
Q
are the hydrogen bonds between bases strong
A
hydrogen bonds are weak but due to so mnay makes it very strong
22
Q
how do you extract DNA
A
- via grinding up cells with ice cold water and washing up liquid
- soap dissolves phospholipid membrane
- protease will digest remaining cellular enzymes and the histones that DNA is wound around
- add ethanol to salt present to cause DNA to precipitate out the solution
23
Q
what are the types of RNA in protein synthesis
A
mRNA
rRNA
tRNA
24
Q
what is mRNA
A
- a single stranded molecule typically 300-2000 nucleotides long
- produced in nucleus using one DNA strands as a template during transcription
25
what is rRNA
forms ribosomes with the addition of protein
26
what is tRNA
- small molecules that wind itself into a cloverleaf shape
- it has anticodons at one end and amino acids at the other
- it transfers the correct amino acid to the growing polypeptide during translation
27
what are the functions of DNA
- proteins synthesis- the sequence of bases in one strand caled the template strand, determines the order of amino acids in the polypeptide
- replication- when cells divide, a complete copy of DNA needs to be made. both DNA strands seperate and each strand acts as a template to synthesise a complementary strand
28
what are the theories for how DNA replicates
- conservative replication
- semi-conservative replication
- dispersive
29
what is conservative replication
original parent double-stranded moelcules is conserved and a new double stranded molecule synthesised from it
30
what is semi-conservative replication
parental strand separate and each strand acts as a template to synthesise a new strand. the new model consists of one original parent strand and one newly synthesied strand
31
what is dispersive
the newly synthesised molecules contain fragments from the original parent strand and newly synthesised DNA
32
what are the stages of semi-conservative DNA replication
1. DNA helicase breakes the hydrogen bonds bewteen the bases causing the double helix to unwind and seperate into 2 strands
2. the exposed bases bind to free floating nucelotides in the nucleoplasma
3. DNA polymerase binds the complementary nucelotides (forming the phosphodiester bond)
4. one strand acts as the template for the newly synthesised DNA contains one parent strand and a complementary newly synthesised strand
33
what is apart of the code
the sequence of nucleotide bases
34
what is a triplet code/codon
each code has three letters which codes for a specific amino acid
35
what is a degenerate code
that different codons can code for the same amino acid
36
what is a one gene
starts the DNA transcription
37
where does transcription and translation happen in protein synthesis
- transcription- nucleus
- translation- ribosomes
- post translational modification- gologi body
38
what is transcription
DNA acts as a template for the production of mRNA
39
what is the process of transcription
1. DNA helicase breaks H bonds between complementary bases in the gene to be transcribed.
2. RNA polymerase binds to the template strand. Free RNA nucleotides bind with H bonds to their exposed complementary bases
3. MRNA produced is complementary to the template strand
4. DNA rewinds
5. The mRNA molecule leaves though nuclear pore into the cytoplasm where it attached to ribosomes
40
what happens in eukaryotes after the mRNA leaves the nucelus in transcription
- introns are present within many genes so are also transcribed producing mRNA
- the coding regions are exons
- the pre-mRNA is spliced to remove the non-coding regions before passing to the ribosomes
41
what happens in prokaryotes after the mRNA leaves the nucelus in transcription
- the DNA doesnt contain introns so the mRNA is produced directly from the DNA template
42
what is translation
involves converting the codons on the mRNA into a sequnence of amino acids called polypepetides
43
what is the structure of tRNA
- at one end of tRNA, there are 3 exposed bases called anticodons, these are complementary to the mRNA codom
- at the opposite end of tRNA, is an amino acid attachment site where the relevent amino acid is found. the attachment is called amino acid activation and needes ATP
44
what is the process of translation
1. initatin- ribosome attcahes to the start codon
2. tRNA molecule with a complementary anticodon to the first codon binds to the first attachment sit of ribsosome
3. a second tRNA molecule joins to the second attachment site and a ribosomal enzyme catalyses the formationof a peptide bond between the two amino acids. this is elongation
4. the first tRNA molecules is released and the ribosome now moves one codon long the mRNA which exposes a free attcahment sire and another tRNA moelcule joins and process in repeated
5. this repeats until a stop codon is reached when the polypeptide is released-called termination
6. usually ribosomes bind to single mRNA strand at the same time- called polysome
45
why is post translation modification needed
to produce a protein with a secondary, tertiary, quaternanry structure
- occurs in golgi body
- modifciations also occur to produce molecules such as glycoproteins, lipoproteins and complex quaternary structures like haemoglobin
46
how does haemoglobin formed
2 alpha chains and 2 beta chains need to be assembled together with iron as a prosthetic group
47
what is a polysome
a group of ribosomes bound to an mRNA molecule like “beads” on a “thread”
48
what is the function of a polysome
allow for the synthesis of several polypeptides concurrently on the same mRNA molecule.
49
What organism did the meselson and stahl experiment use
Ecoli
50
What’s the method for the Meselson and Stahl experiment
1. Grow E-Coli in a test tube containing heavy nitrogen (N15) for several generations. This incorporates N15 into the DNA, making it denser than normal DNA which contains N14
2. They then extract the DNA and separate it using a centrifuge. This produces a single band of DNA at a high density
3. Transfer the bacteria to a test tube containing only N14 and allow them to replicate for one round
4. After the first round of replication, extract the DNA and centrifuge it. The DNA will form an intermediate-density band, indicating that each DNA molecule has one old (^15N) strand and one new (^14N) strand
5. After a second round of replication in ^14N, centrifuge the DNA again. This time, two bands are observed: one at the light density (all ^14N) and one at intermediate density (one strand ^15N, one strand ^14N).
51
What were the results of the Meselson and Stahl experiment
- After one replication round in ^14N: All the DNA had one heavy strand and one light strand (intermediate density).
- After two replication rounds in ^14N: Half the DNA molecules were light (both strands ^14N), and half were intermediate (one strand ^15N, one strand ^14N).
The results supported the semi-conservative model of DNA replication. This means that during replication, each new DNA molecule consists of one old (parental) strand and one newly synthesized strand.
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