3.1.8 Protein Synthesis Flashcards Preview

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Flashcards in 3.1.8 Protein Synthesis Deck (38)
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1

When is mRNA made?

During transcription

2

Describe the structure of mRNA

It's a single polynucleotide strand (& has groups of 3 adjacent bases)

3

What are 3 adjacent bases called?

Codons (or sometimes called triplets or base triplets)

4

What does mRNA do?

Carries genetic code from DNA to ribosomes & is then used to make a protein during translation

5

What does tRNA do?

Carries amino acids that are used to make proteins to ribosomes

(involved in translation)

6

Describe the structure of tRNA

It's a single polynucleotide strand that's folded into clover shape

7

How does tRNA stay in a clover shape?

H-bonds between specific base pairs hold it in shape

8

What does every tRNA molecule have? (2x)

  • Anticodon at one end - specific sequence of 3 bases 
  • An amino acid binding site at other end

9

What is the main thing that happens in transcription?

mRNA copy of gene is made from DNA

10

In eukaryotic cells, where does transcription takes place?

Nucleus

11

Describe the stages in transcription

  1. DNA helicase (in eukaryotes) breaks H-bonds between 2 DNA strands (in beginning of a gene)
  2. Only one DNA strand acts as a template (to make mRNA copy)
  3. Free bases in RNA nucleotides are attracted to exposed bases 
  4. Attraction occurs according to complementary base pairing (∴ mRNA strand becomes a complementary copy of DNA template strand)
  5. RNA nucleotides are joined together by RNA polymerase
  6. (In eukaryotes) mRNA moves out through nuclear pore

12

Where does transcription take place in prokaryotes?

Cytoplasm

13

When does the RNA polymerase stop making mRNA and detachs from DNA in transcription? 

When RNA polymerase reaches a particular sequence of DNA called stop signal

14

Where does translation occur in both eukaryotes and prokaryotes?

At ribosomes in cytoplasm

15

What is the main thing occuring during translation?

Amino acids are joined together to make polypeptide chain, following the sequence of codons (triplets) carried by mRNA

16

Describe the stages in translation

  1. mRNA moves into cytoplasm & attaches to ribosome
  2. tRNA carry amino acids to it
  3. Specific tRNA molecule for specific amino acid
  4. Anitcodon of tRNA binds to complementary codon on mRNA (attaches by specific base pairing)
  5. Peptide bond forms between amino acids
  6. tRNA detaches and collects another amino acid
  7. Ribosome moves along mRNA = forming a long polypeptide chain

17

What determines how the folded protein structure of protein will be?

Position of R groups in polypeptide chain

18

What issue can happen as polypeptide chains are formed on a ribosome?

  • Regions where amino acids have hydrophobic R groups can to clump together or join with other hydrophobic molecules spontaneously
  • Leads to forming a non-functional, 'mis-folded' protein & many of them = disease

19

What do cells produce to ensure the polypeptide chains made on ribosomes are folded correctly?

Chaperone proteins

20

Describe the role of chaperone proteins (3)

 

  • Chaperone proteins bind to hydrophobic groups (on the secretory proteins)
  • Prevent incorrect hydrophobic interactions
  • Allows protein to be correctly folded

21

Where are chaperone proteins are found?

In endoplasmic reticulum

22

What is the genetic code?

Sequence of base triplets (codons) in mRNA which code for specific amino acids

23

Name 3 qualities of the genetic code

  1. Non-overlapping
  2. Degenerate
  3. Universal

24

Describe how genetic code is non-overlapping

Each base triplet is read in sequence only once

25

Describe how genetic code is degenerate

Some amino acids are coded by more than one base triplet

e.g. tyrosine can be coded for by UAU or UAC

26

Describe how genetic code is universal

Same specific base triplets code for same amino acids in all living things

e.g. UAU codes for tyrosine in all organisms

27

What are start/stop signals (or codons)?

Triplets that tell the cell when to start/stop production of a protein

28

Transcription Makes _______ Products in Eukaryotes and Prokaryotes

Different

29

What does transcription make in eukaryotes?

pre-mRNA

30

What is pre-mRNA?

mRNA strands containing introns and exons

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