Nucleotides And Nucleic Acids :). Flashcards
1
Q
What’s a nucleotide made up of?
A
A pentose sugar (sugar with 5 carbon atoms)
A nitrogenous (nitrogen-containing) base
Phosphate group
2
Q
What elements do all nucleotides contain?
A
CHONP
3
Q
Why are nucleotides really important?
A
They’re monomers that make up DNA and RNA both types of nucleic acid
4
Q
DNA is used for
A
To store genetic information
The instructions an organism needs to grow and develop
5
Q
RNA used for?
A
To make proteins from instructions in DNA
6
Q
What are ADP and ATP?
A
Special types of nucleotide
Used to store and transport energy in cells
7
Q
What is the pentose sugar in a DNA nucleotide
A
Deoxyribose
8
Q
DNA
A
Deoxyribonucleic acid
9
Q
What does each DNA nucleotide contain the same?
A
The same sugar and a phosphate group
The base on them varies
10
Q
What are the four DNA bases?
A
Adenine and thymine
Cytosine and guanine
11
Q
What type of base are adenine and guanine?
A
A type of base called purine
12
Q
What type of base are cytosine end thymine?
A
Phyrimidine
13
Q
A purine base contains
A
Two carbon-nitrogen rings joined together
14
Q
Pyrimidine base
A
Only had one carbon-nitrogen ring
Pyrimidine base is smaller than a purine base
15
Q
What does a molecule of DNA contain?
A
Two polynucleotide chain
Each chain is made up of lots of nucleotides joined together
16
Q
RNA
A
Ribonucleic acid
17
Q
What does a RNA contain?
A
A nucleotide with a ribose sugar
18
Q
How are RNA and DNA nucleotides similar?
A
Have phosphate group
One of four different bases
19
Q
Difference between RNA and DNA
A
RNA uracil (pyrimidine) DNA thymine (pyrimidine)
20
Q
What does a molecule of RNA contain?
A
Made up of single polynucleotide chain
21
Q
What type of nucleotide are ADP and ATP?
A
Phosphorylated nucleotides
22
Q
What do to phophorylate a nucleotide?
A
Add one or more phosphate groups in it
23
Q
ADP
A
Adenosine diphosphate
24
Q
ATP
A
Adenosine triphosphate
25
ADP contains
Base adenine
Sugar ribose
Two phosphate groups
26
ATP contains
Base adenine
Sugar ribose
Three phosphate groups
27
ATP provides what
Energy for chemical reactions in the cell
28
ATP synthesised from what?
ADP and inorganic phosphate using energy from an energy-releasing reaction
E.g. Breakdown of glucose in respiration
ADP is phosphorylated to form ATP and phosphate bond is Forbes
29
How is energy stored in phosphorylated nucleotides?
Stored in phosphate bond
When energy needed by a cell
ATP is broken down into ADP and inorganic phosphate
Energy is released from phosphate bonds and used by the cell
30
What is a nucleotide
A type of biological molecule
31
Where do nucleotides join up?
Between phosphate group of one nucleotide and the sugar of another
32
What do nucleotides form?
A phosphodiester bond (consisting of the phosphate group and two ester bonds)
33
What are the sugars and phosphates known as?
Sugar- phosphate backbone
34
What can polynucleotides be broken down into?
Nucleotides again breaking the phosphodiester bonds
35
How do 2 DNA polynucleotides join together?
By hydrogen bonding between bases
36
What can each base join?
Complementary base pairing
Join with one particular partner
Complementary base pairing
37
Base pairs?
Adenine and thymine
| Cytosine and guanine
38
What are the purine bases?
Adenine and guanine
39
What are the pyrimidine bases?
Thymine and cytosine
40
A purine base always pairs with a?
Pyrimidine
41
How can bonds between adenine and thymine?
Two hydrogen bonds
42
How many bonds between cytosine and guanine?
Three hydrogen bonds
43
What does Antiparallel mean?
Running in opposite directions
44
What do two Antiparallel polynucleotide strand do?
Twist to form the DNA double-helix
45
What can you use to investigate structure of DNA and other nucleic acids?
Computer modelling
46
How can you purify DNA?
Using a precipitation reaction
47
Putrifying DNA using precipitation reaction step 1?
Break up cells in your sample. You can use a blender to do this
48
Putrifying DNA using precipitation reaction step 2?
Make up a solution of detergent (dilute washing-up liquid will do), salt (sodium chloride and distilled water)
49
Putrifying DNA using precipitation reaction step 3?
Add broken-up cells to a beaker containing detergent solution. Incubate beaker in water bath at 60 degrees for 15 minutes
50
Putrifying DNA using precipitation reaction step 4?
Once incubated, put beaker in an ice bath to cool the mixture down. When cooled, filter the mixture. Transfer a sample of your mixture to a clean boiling tube
51
Putrifying DNA using precipitation reaction step 5?
Add protease enzyme to the filtered mixture. These will break down some proteins in the mixture, e.g. Proteins bound to DNA. Adding RNase enzyme will break down any RNA in the mixture
52
Putrifying DNA using precipitation reaction step 6?
Slowly dribble some cold ethanol down the side of the tube so it forms a layer on top of the DNA-detergent mixture
53
Putrifying DNA using precipitation reaction step 7?
If you leave the tube for a few minutes the DNA will form a white precipitate (solid) which can remove from tube using a glass rod
54
Why did the solution in step 3 involve detergent, salt and a water bath?
The detergent in the mixture breaks down the cell membrane. The salt bonds to the DNA and causes it to clump together. The temperature of the water bath should stop enzymes in the cells from working properly and breaking down the DNA
55
When does DNA copy itself?
Before cell division so that each new cell has the full amount of DNA.
56
How does DNA copy itself step 1?
DNA helicase (enzyme) breaks down the hydrogen bonds between two polynucleotide DNA strands. The helix unzips to form two single strands.
57
How does DNA copy itself step 2?
Each original strand acts as a template for a new strand. Free-floating DNA nucleotides join to the exposed bases on each original template strand by complementary base pairing
58
How does DNA copy itself step 3?
Nucleotides of new strand are joined together by enzyme DNA polymerase forming sugar-phosphate backbone. Hydrogen bonds form between the bases on the original and new strand. The strands twist to form a double-helix
59
How does DNA copy itself step 4?
Each new DNA molecule contains one strand from the original DNA molecule and one new strand
60
What is the sort of copying involved in DNA copying itself called?
Semi-conservative replication because half of its strands in each new DNA molecule are from the original piece of DNA (i.e. The new molecule contains one old strand and one new strand)
61
What is DNA replication?
Accurate it has to be to make sure genetic information is conserved (stays the same) each time the DNA in a cell is replicated
62
What happens every so often in DNA replication?
A random, spontaneous mutation occurs
63
What's a mutation
Any change to the DNA sequence.
64
Explain effects of mutations
Don't always have an effect
Can alter sequence of amino acids in a protein causing an abnormal protein to be produced. The abnormal protein may function better than normal protein or it may not work at all
65
What is a gene?
A sequence of DNA nucleotides that codes for a polypeptide
66
What does the sequence of amino acids in a polypeptide do?
Form the primary structure of a protein
67
Different proteins have?
Different number and order of amino acids
68
What's does the order of the nucleotides based in a gene determine?
The order of amino acids in a particular protein
69
What is each amino acid coded for by?
A sequence of three bases (triplet) in a gene
70
Different sequences of bases code for what?
Different amino acids. So the sequence of bases in a section of DNA is a template that's used to make proteins during protein synthesis
71
Why can't protein synthesis happen in the nucleus?
DNA molecules are in the nucleus but other organelles that make protein are found in the cytoplasm
72
Why can't DNA leave the nucleus and how is the information going to the cytoplasm as a result?
It is too big so a section is copied into messenger RNA (transcription). Messenger RNA leaves nucleus and joins with ribosome in cytoplasm where it can be used to synthesise a protein (translation)
73
RNA remember is
Single polynucleotide strand containing uracil as a base instead of thymine. Uracil is always paired with adenine during protein synthesis
74
Three types of RNA
```
Messenger RNA (mRNA)
Transfer DNA (tRNA)
Ribosomal RNA (rRNA)
```
75
Describe messenger RNA
Made in nucleus
Three adjacent bases are a codon
Carries genetic code from DNA in nucleus to cytoplasm where it's used to make a protein during translation
76
Transfer RNA?
Found in cytoplasm
Has amino acid binding site at one end and a sequence of 3 bases at the other and a sequence of three bases at the other end is called an anticodon
Carries amino acids that are used to make proteins to ribosomes during translation
77
Ribosomal RNA?
Forms two subunits in a ribosome (along with proteins)
Ribosomes move along mRNA strand during protein synthesis. rRNA in ribosomes helps to catalyse formation of peptide bonds between the amino acids
78
Three adjectives for genetic code?
Non-overlapping
Degenerate
Universal
79
What is genetic code?
Sequence of base triplets (codons) in DNA or mRNA which codes for specific amino acids
80
How is each base triplet read in genetic code?
In sequence separate from triplet before it and after it. Base triplets don't share their bases so code is non-overlapping
81
Why is genetic code degenerate?
More possible combinations of triplets than there are amino acids (20 amino acids but 64 possible possible triplets). This means that some amino acids are coded for by more than one base triplet e.g. Tyrosine can be coded for UAU or UAC
82
How does the cell know when to start or stop production of protein?
Some triplets are used to tell the cell when to start and when to stop production of a protein-these are called start and stop signal (start or stop codons) found at the beginning and the end of a gene e.g. UAG is a stop signal
83
What are codons and anticodons sometimes referred to as?
Triplets
84
How is genetic code universal?
Same specific base triplets code for the same amino acids in all living things e.g. UAU codes for tyrosine in all organisms
85
What is the first stage of protein synthesis?
Transcription
86
When does transcription start?
When the RNA polymerase (an enzyme) attaches to DNA double-helix at the beginning of a gene
87
What's stage 2 of transcription?
Hydrogen bonds between the two DNA strands in the gene break, separating the strands and the DNA molecule uncoils at that point
88
Stage 3 of transcription
One of the strands is then used as a template to make mRNA copy
89
Stage 4 transcription
The RNA polymerase lines up free RNA nucleotides alongside the template strand. Complementary base pairing means that the mRNA strand ends up being a complementary copy of the DNA template strand (except base T is replaced with U in RNA)
90
Step 5 transcription
Once the RNA nucleotides have paired up with their specific bases on the DNA strand they're joined together forming an mRNA molecule
91
Transcription stage 6
The RNA polymerase moves along the DNA separating the strands and assembling the mRNA strand
92
Transcription stage 7
The hydrogen bonds between the RNA polymerase has passed by and the strands coil back into a double-helix
93
Where does translation happen?
At the ribosomes in the cytoplasm
94
What's the goal of translation?
Amino acids are joined together to make a polypeptide chain (protein) following the sequence of codons carried by the mRNA
95
Stage 1 translation
mRNA attached itself to a ribosome and transfer RNA molecules carry amino acids to the ribosomes
96
Stage 2 translation?
A tRNA molecule with anticodon that's complementary to the start codon of mRNA attached itself to the mRNA by complementary base pairing
97
Stage 3 translation?
A second tRNA molecule attracted to itself to the next codon on the mRNA in the same way
98
Step 4 translation
Ribosomal RNA in the ribosome catalyses the formation of a peptide bond between two amino acids attached to the transfer RNA molecules. This joins the amino acids together. The first tRNA molecules moves away, leaving its amino acid behind
99
Step 5 translation?
A third tRNA molecule binds to the next codon on the mRNA. Its amino acid binds to the first two and second tRNA molecule moves away
100
Translation stage 6?
This process continues producing a chain of linked amino acids (a polypeptide chain) until there's a stop codon on the mRNA molecule
101
Last stage of translation?
The polypeptide chain moves away from the ribosomes and translation is complete
102
What is protein synthesis also called?
Polypeptide synthesis as it makes a polypeptide
