Nucleotides and Nucleic Acid Flashcards
1
Q
What abilities do nucleic acids have?
A
- The ability to carry out instructions
- The ability to be copied
2
Q
DNA and RNA are …; the individual … are the … that build up the …
A
- polymers
- nucleotides
- monomers
- polynucleotides
3
Q
What does DNA stand for?
A
deoxyribonucleic acid
4
Q
What does RNA stand for?
A
ribonucleic acid
5
Q
What are nucleotides made up of?
A
Three smaller components:
- Nitrogen-containing base
- Pentose sugar (it has 5 carbon atoms)
- Phosphate group
6
Q
List the bases found in DNA
A
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
7
Q
List the bases found in RNA
A
- Adenine (A)
- Uracil (U)
- Cytosine (C)
- Guanine (G)
8
Q
What are the base pairings in DNA?
A
A - T
C - G
9
Q
What are the base pairings in RNA?
A
A - U
C - G
10
Q
What bases are purines?
A
A and G
11
Q
Are purines larger or smaller than pyrimidines
A
Larger
12
Q
What ring structure do purines have?
A
Double ring structure (Carbon and Nitrogen atoms)
13
Q
What bases are pyrimidines?
A
T, U and C
14
Q
What ring structure do pyrimidines have?
A
Single ring structure (Carbon and Nitrogen atoms)
15
Q
How many hydrogen bonds are in base pairings in DNA?
A
A - T has two hydrogen bonds
C - G has three hydrogen bonds
16
Q
What reaction are nucleotides linked by?
A
Condensation reaction
17
Q
What is the polymer of nucleotides known as?
A
Polynucleotide
18
Q
Alternating … and … groups join
A
Sugars
Phosphate group
19
Q
What type of bond is formed at the 5th carbon of the pentose layer with the OH group 3 carbon of adjoining nucleotides?
A
Phosphodiester bond
20
Q
What reaction are the phosphodiester bonds broken by?
A
Hydrolysis
21
Q
What does the hydrolysis of phosphodiester bonds release?
A
Individual nucleotides
22
Q
DNA strands are said to be antiparallel, which means
A
The DNA strands are side-by-side run in opposite directions
23
Q
What type of bond is in between bases in DNA?
A
Hydrogen bonds
24
Q
What is the fact that hydrogen bonds can be broken relatively easily important for?
A
Protein synthesis
DNA replication
25
What does tRNA do?
Brings amino acids to the ribosome
26
What does mRNA do?
Allows the transfer of genetic information from the nucleus to a ribosome
27
What does rRNA do?
Responsible for translation, they read the order of the amino acids and link the amino acids together
28
How do RNA nucleotides bond (is it the same as DNA)?
Bond in the same way as DNA - phosphodiester bonds formed in condensation reactions
29
What is the difference between RNA and DNA?
Deoxyribose has one less oxygen atom than ribose
30
When a cell divides, what must the daughter cell receive?
An exact copy of the genetic material from the parent cell
31
For the daughter cell to receive an exact copy of the genetic material, what must happen?
The DNA in the parent cell must first be replicated
32
How is DNA replicated?
- DNA Helicase is responsible for unwinding DNA and allows strands to separate by breaking hydrogen bonds
- Complementary base pairing occurs as free nucleotides in the nucleoplasm are attracted to the complementary bases on the two sugar-phosphate backbones
- Once in place, the activated nucleotides are joined together by DNA polymerase using strong covalent bonds, forming the sugar-phosphate backbone
- The result is that there is two DNA molecules, each with one newly synthesised strand of DNA and one strand from the original DNA
33
What is the lagging strand in DNA replication?
DNA polymerase is moving away from the replication fork. As DNA polymerase is moving away from helicase it must constantly return to copy newly separated stretches of DNA. This means that the lagging strand is copied as a series of short fragments (Okazaki fragments)
34
What are the short fragments called on the lagging strand?
Okazaki fragments
35
Why is there a lagging strand when copying DNA?
Helicase is moving in the opposite direction so unzipped parts of DNA is now being copied but DNA polymerase has to wait to copy them
36
What is the process of semi-conservative replication?
- Replication starts at a specific sequence on the DNA molecule, which is called the origin of replication
- DNA helicase unwinds and unzips the DNA molecule, breaking the hydrogen bonds that join the base pairs, and forms two separate strands of DNA
- The new DNA molecules are built up from the four nucleotides (A, C, G, T) that are abundant in the nucleoplasm.
- These nucleotides attach themselves to the bases on the old strands by complementary base pairing
- DNA polymerase joins the new nucleotides to each other by strong covalent bonds, forming the new sugar-phosphate backbone
- The two new DNA molecules are identical to the old molecule, and each has one strand of DNA from the original DNA molecule
37
How are mutations caused?
Sequences of bases are not always matched correctly, such errors are random and spontaneous, which leads to a change in the DNA sequence called a mutation
38
What is the sequence of bases on DNA called?
A code
39
What is meant by 'the code is universal'
It is used in all organisms
40
How are the four bases read?
In triplets (codons)
41
Are triplets overlapping?
No, they are non-overlapping
42
How many possible base triplets are there?
64
| A combination of 4 letters in groups of 3, gives 64 possible base triplets
43
What do the 64 codons code for?
The 20 amino acids
44
Why is the DNA code called degenerate?
More than one triplet will code for each amino acid
45
What gives rise to the huge variety of proteins?
Combinations of the 20 amino acids
46
What amino acid do all polypeptides start with?
Methionine
47
What is the conservative hypothesis?
The complete parent DNA molecule acts as a template for the new daughter molecule, which is assembled from new nucleotides. The parent molecule is unchanged
48
What is the semi-conservative hypothesis?
The parent DNA molecule separates into its two component strands, each of which acts as a template for the formation of a new, complementary strand. The two daughter molecules, therefore, contain half the parent DNA and half new DNA
49
How did Meselson and Stahl in 1958, prove the semi-conservative hypothesis?
- They grew E. coli with different isotopes of nitrogen
- Bacteria were exposed to N15, for several generations until it was exposed to a lighter N14
- Scientists could then distinguish between the different DNA densities by centrifuging them
50
What did Meselson and Stahl know before they proved the semi-conservative hypothesis?
- All the bases in DNA contain nitrogen
- Nitrogen bases have two forms: Heavy (N15) and Light (N14)
- Bacteria will incorporate nitrogen from their growing medium into any new DNA they make
51
What is the function of DNA?
- To code for proteins
| - Not all of the DNA molecule code for proteins, the functional parts that do are called genes
52
What is the function of RNA?
- Different genes are instructions to build different proteins
- The DNA that contains the genes can't leave the nucleus, so a copy of the gene must be made, which is mRNA, a type of nucleic acid
53
How is RNA structured differently to DNA?
- Uracil instead of thymine
- Ribose instead of deoxyribose
- Single strand
54
Where is transcription done in eukaryotes?
In the nucleus
55
Is DNA directly involved in transcription and why?
Yes, it is being matched with complementary RNA bases
56
Is RNA involved in transcription, and why?
Only mRNA, as it makes a template for protein synthesis through translation
57
Where is translation done?
On a ribosome (in the cytoplasm in eukaryotes)
58
Is DNA directly involved in translation and why?
No, as it stays in the nucleus
59
Is RNA involved in translation and what does it do?
tRNA and rRNA are involved, they make a sequence of amino acids
60
What are the similarities between DNA and RNA
- Both are nucleic acids
| - Both contain the bases: guanine, cytosine, adenine
61
What are the features of DNA?
- Only found in the nucleus of eukaryotes cells, except during mitosis, where the nucleus is temporarily disassembled
- Arranged as a double helix
- Has the base thymine
Has the sugar deoxyribose
62
What are the features of RNA?
- Can travel out of the nucleus to a ribosome in eukaryotes
- Single-stranded
- Has the base uracil
- Has the sugar ribose
63
What the three types of RNA?
- messenger RNA (mRNA)
- transfer RNA (tRNA)
- ribosomal RNA (rRNA)
64
Define energy
The ability to do work
65
What is energy needed for?
- Metabolism/catabolism
- Movement
- Active transport
- Maintenance, repair and division of cells
- Production of substances
- Maintenance of body temperature
- Nerve impulse conduction
66
When is light energy converted into chemical energy in plants?
During photosynthesis
67
What energy is converted into ATP and during when?
Chemical energy from photosynthesis (in the form of organic molecules) is converted into ATP during respiration
68
What is ATP used for?
Used by cells to perform useful work
69
What does ATP stand for?
adenosine triphosphate
70
What is ATP made up of?
- Adenine (base)
- Ribose (sugar)
- Three phosphate groups
71
What are the 3 phosphate groups joined together by?
2 high energy bonds
72
How does ATP release a large amount of energy?
It can be hydrolysed to break a bond
73
What catalyses the hydrolysis of ATP to ADP?
The enzyme ATPase
74
What is the equation for the hydrolysis of ATP?
ATP + H2O --> ADP + P1 (+ energy = 30KJmol-1)
75
How can ATP be reformed from ADP + P1?
In phosphorylation
76
What type of reaction is phosphorylation?
Condensation reaction as water is released
77
Is the energy released from the splitting of ATP into ADP is released as large, unmanageable bursts?
No, it is released in small, manageable bursts
78
What is are the advantages of the hydrolysis of ATP to ADP rather than the breakdown of glucose?
- The energy released from the splitting of ATP into ADP is released as small, manageable bursts
- The hydrolysis of ATP to ADP is a single reaction, whereas the breakdown of glucose requires a long series of reactions
79
What are the disadvantages of the hydrolysis of ATP to ADP?
- Instability of bonds means ATP isn't good for long term storage of energy
- Instability means cells do not store large amounts of it, so the production of ATP needs to be constantly occurring in all living cells
80
What are the roles of ATP?
- ATP is an immediate energy source. It is made when required by reforming from ADP +P1. It is only stored for a matter of seconds
- Less energy produced than glucose, so more manageable
- ATP to ADP is a single reaction so it is very quick
81
What is ATP a source of energy for?
- Metabolic reactions
- Active transport
- Movement
- Secretion
- Activation of molecules
82
Which of the following bonds occur in a molecule of DNA?
a. Ionic
b. Hydrogen
c. Phosphodiester
d. Covalent
A. All of the above
B. None of the above
C. b, c and d
D. b and c
C
83
Complete the following passage with the most appropriate terms from the list below
anti-parallel B-pleated sheet Covalent Double helix
Hydrogen Parallel Polypeptide Ribose Sugar-phosphate
DNA is found in the nucleus. The molecule is twisted into a 1 2. in which each of the strands are 3. It has two 4 backbones attached to one another by complementary bases. These bases pair in the centre of the molecule by means of 5 bonds.
```
1 Double helix
2 Polypeptide
3 Anti-parallel
4 Sugar-phosphate
5 Hydrogen
```
84
State the components of a DNA nucleotide
Deoxyribose sugar
Phosphate group
Nitrogenous bases
85
Describe how the structure of RNA differs from that of DNA
RNA has the sugar ribose, instead of deoxyribose
RNA has the base uracil instead of thymine
RNA is single-stranded
86
State what a gene codes for
A sequence of amino acids
| Protein
87
Suggest how changing the sequence of DNA nucleotides could affect the final product the DNA codes for
The mutation may change how the bonds interact in a protein, so it doesn't fold into its' specific shape so it has a different function
88
Suggest why DNA is not able to leave the nucleus
Too large to fit through the nuclear pores
89
Explain why the mRNA molecule is shorter than a DNA molecule
Only the exons/coding parts of the DNA is included in the mRNA, so the non-coding parts of DNA are not included
DNA has more genes
