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Biology OCR A - A-level > Nucleotides and nucleic acids And Enzymes > Flashcards

Nucleotides and nucleic acids And Enzymes Flashcards

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1
Q

What is a nucleotide made from?

A

Pentose sugar, nitrogenous base and a phosphate group

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2
Q

What are ATP and ADP and what are they used for?

A

Nucleotides used to store and transport energy in cells

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3
Q

What are the 2 purines?

A

Adenine and Guanine

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4
Q

What are the 3 pyrimidines?

A

Cytosine, Thymine and Uracil

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5
Q

What base does uracil replace?

A

Thymine

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6
Q

What is an RNA molecule made up of?

A

A single polypeptide chain

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7
Q

How do you phosphorylate a nucleotide?

A

Add one or more phosphate to it

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8
Q

What is ATP made from?

A

Adenine, ribose and 3 phosphates

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9
Q

What is ADP made from?

A

Adenine, ribose and 2 phosphates

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10
Q

How is energy in ATP/ADP released?

A

Bonds are broken

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11
Q

What do nucleotides form when joined together?

A

Polynucleotides

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12
Q

How is a phosphodiester bond formed?

A

Phosphate and sugart from different nucleotides form via a condensation recation

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13
Q

What does a chain of polynucleotides form?

A

A sugar-phosphate backbone

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14
Q

How do polynucleotides join?

A

Hydrogen bonds between bases

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15
Q

How many hydrogen bonds does C and G have?

A

3

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16
Q

How many hydrogen bonds does A and T have?

A

2

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17
Q

What does DNA helicase do? (Step 1)

A

Breaks hydrogen bonds and unzips DNA into 2 stands

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18
Q

How does the DNA sequence act as a template? (Step 2)

A

Free-floating nucleotides join exposed bases

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19
Q

How are the new DNA strands joined together with the original strands? (Step 3)

A

DNA polymerase

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20
Q

What is semi-conservative replication?

A

DNA replication where the final DNA molecule contains one original DNA strand and one new DNA strand

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21
Q

What is a gene?

A

A sequence of DNA nucleotides that code for a polypeptide

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22
Q

Where is mRNA made?

A

In the nucleus

23
Q

what does mRNA carry?

A

Genetic code

24
Q

Where is tRNA found?

A

Cytoplasm

25
Q

What is an anticodon?

A

Three bases on the end of a tRNA molecule opposite to the amino acid

26
Q

What does rRNA do?

A

Catalyses the formation of peptide bonds in amino acids

27
Q

What does degenerate mean?

A

A codon can be used more than once with other codons to produce a different amino acid

28
Q

What does the genetic code being universal mean?

A

The same base triplets code for the same amino acids in all living things

29
Q

Outline the stages of transcription.

A

1) RNA polymerase attaches to DNA at beginning of gene
2) hydrogen bonds break
3) RNA polymerase lines up free nucleotides alongside template
4) U replaces T in complementary base pairing
5) mRNA formed
6) hydrogen bonds reform once RNA polymerase has passed
7) mRNA leaves through nuclear paws and attaches to ribosomes

30
Q

Outline the stages of translation.

A

1) tRNA carries amino acids to a ribosome
2) TRA with anticodon complementary to start codon attaches to mRNA
3) second tRNA attaches to next codon
4) rRNA catalyses formation of peptide bonds
5) third tRNA Binds to next codon, and second tRNA MOVES AWAY
6) process continues
7) polypeptide chain moves away

31
Q

What are enzymes?

A

Biological catalysts that speed up reactions

32
Q

What does intracellular mean?

A

Within cells

33
Q

What does extracellular mean?

A

Outside of cells

34
Q

What is an example of an intracellular enzyme?

A

Catalase works inside cells to catalyse the breakdown of hydrogen peroxide

35
Q

What is an example of an extracellular enzyme?

A

Amylase catalyses the breakdown of starch into maltose in the mouth

36
Q

What type of protein are enzymes?

A

Globular

37
Q

Define the lock and key model.

A

The substrate fits into the enzyme in the same way that a key fits into a lock

38
Q

Defined the induced fit model

A

The enzyme alters the shape of its active site to fit the substrate more closely

39
Q

Which theory is better, lock and key or induced fit?

A

Induced fit

40
Q

What are the factors that affect enzyme activity?

A

• temperature
• pH
• enzyme concentration
• substrate concentration

41
Q

How does temperature affect enzyme activity?

A

High temperatures means there’s more kinetic energy so there are more frequent collisions. If it gets too hot, the enzyme will denature

42
Q

How does pH affect enzyme activity?

A

Above and below the optimum pH can break ionic and hydrogen bonds

43
Q

How does enzyme concentration affect enzymes?

A

High concentration means more collisions

44
Q

How does substrate concentration affect enzymes?

A

High concentration means more collisions

45
Q

What a non-protein substance allows some enzymes to work

A

Cofactors

46
Q

What do inorganic cofactors do?

A

Only help the enzyme and the substrate to bind together

47
Q

What do organic cofactors do? What are they called?

A

Coenzymes that participate in the reaction and act as a second substrate

48
Q

What is an enzyme inhibitor?

A

Molecules that bind to the enzyme and stop it from functioning

49
Q

What is competitive inhibition?

A

They have a similar shape to the substrate and compete to bind to the active site

50
Q

What is non-competitive inhibition?

A

Molecules bind to the allosteric site and change the shape of the active site, so the substrate cannot bind

51
Q

What determines if an inhibitor can be reversed?

A

If it has a strong covalent bond, it cannot be reversed, if they have weaker hydrogen bonds, they can be reversed

52
Q

How do anti-viral drugs stop viruses?

A

Reverse transcript, inhibitors prevent replication of the viral DNA

53
Q

What is the metabolic pathway?

A

A series of connected metabolic reactions where the product of the first reaction takes part in the second reaction and so on

54
Q

What is product inhibition?

A

Where the enzyme is inhibited by the product they produce

Biology OCR A - A-level (24 decks)

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