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

Biological molecules 2 Flashcards

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?

A

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

25
Q

What is the function of DNA ligase?

A

Catalyses the formation of new phosphodiester bonds between the two strands of DNA

26
Q

Where does translation take place?

A

The surface of the ribosomes

27
Q

What is a triplet code?

A

The code of three bases, giving 64 possible combinations

28
Q

What is the definition of a gene?

A

A sequence of bases on a DNA molecule coding for a sequence of amino acids, that affect the phenotype

29
Q

What is a codon?

A

A sequence of three bases on the DNA or RNA

30
Q

How did scientists work out the codons of DNA?

A

Using mRNA as it is a complementary strand to the DNA acting as a reverse image of the original DNA sequence

31
Q

how is the code non-overlapping?

A

Each base in a gene is only part of one triplet of bases that codes for one amino acid

32
Q

What is an advantage of a non-overlapping code?

A

If point mutation occurs, It will only affect one codon and therefore one amino acid

33
Q

How is the code degenerate?

A

The genetic code contains more information than is needed, there are 64 combinations.

34
Q

What is the advantage of a degenerate code?

A

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
Q

What is the structure of RNA?

A

Single helix

36
Q

What are the three main functions of RNA in the process of protein synthesis?

A

-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
Q

Where does mRNA form a template?

A

On the antisense strand of the DNA

38
Q

What does mRNA code for?

A

One polypeptide

39
Q

What is the function of DNA-directed RNA polymerase (RNA polymerase)?

A

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
Q

How does mRNA allow protein synthesis to take place?

A

-Passes through the nuclear pores into the cytoplasm
-Moves to the surface of the ribosomes where protein synthesis takes place

41
Q

What is the function of Transfer RNA (tRNA)?

A

Picks up particular amino acids from the cytoplasm and transports them to the surface of a ribosome to align with mRNA

42
Q

What is an anticodon?

A

Sequence of three bases on tRNA that are complementary to the bases in a mRNA codon

43
Q

What is the function of Ribosomal RNA (rRNA)?

A

To hold together the mRNA and tRNA and act as enzymes controlling the process of protein synthesis

44
Q

What are polysomes?

A

Groups of ribosomes, joined by a thread of mRNA, that can produce mass amounts of a particular protein

45
Q

What is transcription?

A

DNA information copied to mRNA

46
Q

What is translation?

A

mRNA information translated into specific sequence of amino acids

47
Q

What is mutation?

A

A permanent change in the DNA of an organism

48
Q

What is point/gene mutation?

A

A change in one or a small number of nucleotides affecting a single gene

49
Q

What are the three types of point mutation?

A

-Substitution
-Deletion
-Insertion

50
Q

What is a substitution?

A

One base in a gene is substituted for another

51
Q

What is a deletion?

A

Where a base is completely lost in the sequence

52
Q

What is an insertion?

A

When an extra base is added, either a replication or a new base completely

53
Q

What are chromosomal mutations?

A

A change in the positions of genes within chromosomes

54
Q

What is whole-chromosome mutations?

A

When an entire chromosome is either lost during meiosis, or duplicated in one cell

55
Q

What chromosome causes Down syndrome?

A

chromosome 21, 3 copies instead of two

56
Q

How can mutations be advantgeous?

A

Could result in the production of a new and superior protein, giving an organism a reproductive advantage

57
Q

What happens in sickle cell disease?

A

Haemoglobin molecules stick together to form rigid rods that give red blood cells a sickle shape

58
Q

What mutation happens in sickle cell disease?

A

Point mutation, affects the protein chains making up haemoglobin

59
Q

What happens to blood flow in sickle cell disease?

A

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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