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Edexcel Biology B A-level > Biological molecules 2 > Flashcards

Biological molecules 2 Flashcards

(59 cards)

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1
Q

What are nucleotides made up of?

A

-5 carbon pentose sugar
-Nitrogen-containing base
-Phosphate group

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2
Q

What are the functions of nucleotides?

A

-Energy currency for a cell (ATP)
-Building blocks for DNA and RNA

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3
Q

How many nitrogen-containing rings does a purine base have?

A

Two

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4
Q

How many nitrogen-containing rings does a pyrimidine base have?

A

One

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5
Q

What the two most common purine bases?

A

Adenine and guanine

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6
Q

What the three most common pyrimidine bases?

A

Cytosine, thymine and uracil

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7
Q

What makes nucleotides carry a negative charge?

A

The phosphate group

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8
Q

How is the sugar, base and phosphate group joined together?

A

Condensation reaction

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9
Q

How many phosphate groups does ATP have?

A

Three

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10
Q

What happens when energy is needed in a cell?

A

-The third phosphate bond is broken by a hydrolysis reaction

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11
Q

What enzyme breaks down ATP?

A

ATPase

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12
Q

What product is formed from the breakdown of ATP?

A

Adenosine diphosphate (ADP)

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13
Q

What are nucleic acids made up of?

A

Many nucleotide monomer units

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14
Q

What is the function of nucleic acids?

A

Carries all the information needed to form new cells

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15
Q

How are nucleic acids made?

A

Condensation reaction

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16
Q

What are the bonds in nucleic acids?

A

Phosphodiester bonds

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17
Q

What bases are present in RNA?

A

C, G, A and U

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18
Q

What bonds hold together bases?

A

Hydrogen bonds

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19
Q

How many bonds are between C and G?

A

Three bonds

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20
Q

How many bonds are between A and T?

A

Two bonds

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21
Q

What happens in semi-conservative replication?

A

The DNA unwinds and new nucleotides align along each strand

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22
Q

What happens in conservative replication?

A

The double helix remains intact and new strands form

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23
Q

Which enzyme catalyses the unwinding of DNA?

A

DNA helicase

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24
Q

What is the function of DNA polymerase?

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A

Lines up and catalyses the linking up of the nucleotides along the template strand

25
What is the function of DNA ligase?
Catalyses the formation of new phosphodiester bonds between the two strands of DNA
26
Where does translation take place?
The surface of the ribosomes
27
What is a triplet code?
The code of three bases, giving 64 possible combinations
28
What is the definition of a gene?
A sequence of bases on a DNA molecule coding for a sequence of amino acids, that affect the phenotype
29
What is a codon?
A sequence of three bases on the DNA or RNA
30
How did scientists work out the codons of DNA?
Using mRNA as it is a complementary strand to the DNA acting as a reverse image of the original DNA sequence
31
how is the code non-overlapping?
Each base in a gene is only part of one triplet of bases that codes for one amino acid
32
What is an advantage of a non-overlapping code?
If point mutation occurs, It will only affect one codon and therefore one amino acid
33
How is the code degenerate?
The genetic code contains more information than is needed, there are 64 combinations.
34
What is the advantage of a degenerate code?
If the final base in the triplet is changed, the mutation could still produce the same amino acid with no effect on the organism
35
What is the structure of RNA?
Single helix
36
What are the three main functions of RNA in the process of protein synthesis?
-Carries instructions for a polypeptide from the DNA to the ribosomes -Picks up specific amino acids from the protoplasm and carried them to the ribosome -Makes up the bulk of ribosomes
37
Where does mRNA form a template?
On the antisense strand of the DNA
38
What does mRNA code for?
One polypeptide
39
What is the function of DNA-directed RNA polymerase (RNA polymerase)?
Allow parts of the DNA molecule to transcribe onto strands of mRNA -catalyses the formation of phosphodiester bonds between the sugars and phosphate groups of the bases to form a strand of mRNA
40
How does mRNA allow protein synthesis to take place?
-Passes through the nuclear pores into the cytoplasm -Moves to the surface of the ribosomes where protein synthesis takes place
41
What is the function of Transfer RNA (tRNA)?
Picks up particular amino acids from the cytoplasm and transports them to the surface of a ribosome to align with mRNA
42
What is an anticodon?
Sequence of three bases on tRNA that are complementary to the bases in a mRNA codon
43
What is the function of Ribosomal RNA (rRNA)?
To hold together the mRNA and tRNA and act as enzymes controlling the process of protein synthesis
44
What are polysomes?
Groups of ribosomes, joined by a thread of mRNA, that can produce mass amounts of a particular protein
45
What is transcription?
DNA information copied to mRNA
46
What is translation?
mRNA information translated into specific sequence of amino acids
47
What is mutation?
A permanent change in the DNA of an organism
48
What is point/gene mutation?
A change in one or a small number of nucleotides affecting a single gene
49
What are the three types of point mutation?
-Substitution -Deletion -Insertion
50
What is a substitution?
One base in a gene is substituted for another
51
What is a deletion?
Where a base is completely lost in the sequence
52
What is an insertion?
When an extra base is added, either a replication or a new base completely
53
What are chromosomal mutations?
A change in the positions of genes within chromosomes
54
What is whole-chromosome mutations?
When an entire chromosome is either lost during meiosis, or duplicated in one cell
55
What chromosome causes Down syndrome?
chromosome 21, 3 copies instead of two
56
How can mutations be advantgeous?
Could result in the production of a new and superior protein, giving an organism a reproductive advantage
57
What happens in sickle cell disease?
Haemoglobin molecules stick together to form rigid rods that give red blood cells a sickle shape
58
What mutation happens in sickle cell disease?
Point mutation, affects the protein chains making up haemoglobin
59
What happens to blood flow in sickle cell disease?
The sickle cells may block blood vessels They don't carry oxygen very efficiently

Edexcel Biology B A-level (13 decks)

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