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Biology HL IB 2020-22 > 7.3 Translation (HL) > Flashcards

7.3 Translation (HL) Flashcards

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1
Q

What does the ribosome structure consist of?

A
  • Large subunit
  • Small subunit
  • 3 tRNA binding sites (Large subunit)
  • mRNA + mRNA binding site (Small subunit)
  • Growing polypeptide chain
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2
Q

tRNA molecule: What is the function of the acceptor stem?

A

Carries amino acid to combine with the growing polypeptide

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3
Q

tRNA molecule: Function of hydrogen bonds

A

Holds the bases and molecule together into an L shaped tertiary structure

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4
Q

tRNA molecule: Function of anticodon

A

Associates with mRNA codon via complementary base pairing

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5
Q

tRNA molecule: Function of T arm + which side is it on?

A
  • Associates with ribosome via E, P, A binding sites

- On the right side

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6
Q

tRNA molecule: Function of D arm + side it is on

A
  • Left side

- Associates with the tRNA activating enzyme

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7
Q

Function of tRNA activating enzyme

A

It adds the amino acid to the acceptor stem

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8
Q

Why is there more than one type of tRNA activating enzyme

A
  • Each tRNA molecule has different chemical properties

- Each amino acid is recognized by a specific enzyme although one enzyme may recognize multiple due to degeneracy

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9
Q

How is tRNA activated?

A
  1. Enzyme binds ATP to amino acid to form amino acid-AMP complex linked by high energy bond
  2. Amino acid is coupled to tRNA and AMP is released
  3. tRNA is now charged and ready for use
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10
Q

Use of the energy transferred to charged tRNA molecule by ATP

A

Energy is transferred and stored energy will provide effort required for peptide bond formation during translation

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11
Q

3 stages of translation

A

Initiation
Elongation
Termination

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12
Q

What happens during initiation?

A

Mature mRNA binds to small ribosomal subunit and large subunit joins to complete assembly

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13
Q

What is the first tRNA called and what does mRNA have to combine with it?

A

It’s called initiator tRNA and mRNA has a start codon (AUG) to link with it

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14
Q

What happens during elongation?

A

A repeated cycle to create a growing polypeptide chain

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15
Q

What is the A site and what happens?

A
  • Aminoacyl tRNA binding site

- Incoming tRNA with attached amino acid binds to chain

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16
Q

What is the P site and what happens?

A
  • Peptidyl-tRNA binding site
  • Where tRNA from A site moves after amino acid forms peptide bond with chain.
  • Where the tRNA holding the chain is found
17
Q

What is the E site and what happens?

A
  • Exit site
  • Where tRNA moves after transferring amino acid
  • Where it readies to detach from ribosome
18
Q

What happens in termination?

A

Once termination codon is reached, release factor binds in A site and causes disassembly of components of translation complex. . i.e. ribosomal subunits, tRNA can all be reused

19
Q

Why does translation occur immediately after transcription in prokaryotes?

A
  • Prokaryotes don’t have nuclear membrane so ribosomes directly bind to mRNA rather than wait for relocation to cytoplasm
  • In eukaryotes, mRNA is spliced and processed to create mature mRNA
20
Q

Polysome

A

Structure that consists of multiple ribosomes attached to single mRNA

21
Q

Purpose of polysome

A

Translates mRNA simultaneously to quickly create multiple copies of required protein

22
Q

How do polysomes in prokaryotes differ from eukaryotes?

A
  • Prokaryotes: Chromosome may have numerous polysomes attached directly
  • Eukaryotes: Polysomes occur separately in cytoplasm or on ER as ribosomes attach to mRNA as it is being translated
23
Q

What are bound ribosomes attached to?

A

Endoplasmic reticulum

24
Q

Where do proteins synthesized by bound ribosomes go?

A
  • Outside the cell
  • ER
  • Golgi apparatus
  • Lysosomes
  • Plasma membranes
25
Q

Bound ribosomes: What does beginning of the polypeptide contain?

A

Signal sequence that is recognized by SRP (Signal recognition particle)

26
Q

Bound ribosomes: What happens after SRP binds to recognition protein on ER membrane?

A

After binding on ER, polypeptide enters rER as it grows

27
Q

Bound ribosomes: What happens when translation ends?

A
  • Complex disassembles

- Signal peptide is removed and whole protein is taken into rER

28
Q

Bound ribosomes: What happens after protein is taken into rER?

A

Post-translational modifications and sorting of protein takes place in lumen of ER

29
Q

What type of proteins do free ribosomes synthesize for?

A
  • Proteins that are destined for mitochondria, chloroplasts, cytoplasm or nucleus of the cell
30
Q

Difference between bound vs. free proteins

A

Bound proteins are meant for secretion or use in lysosomes while free proteins are mostly for intracellular use

31
Q

Primary structure of protein

A

Protein is maintained by peptide bonds between subunits

32
Q

Secondary structure of protein

A
  • Folds back onto itself in beta-pleated sheets or alpha helices
33
Q

Bonds in secondary structure

A

Stabilized by hydrogen bonds between -NH groups and C=O groups on different peptides in the same chain

34
Q

Tertiary structure of protein

A

Further folding such that hydrophilic amino acids are outside and hydrophobic in the center

35
Q

Bonding in tertiary structure

A
  • Stabilized by interaction between R groups
  • Polar R groups have ionic interactions between acidic/basic groups or H bonding
  • Covalent bonds form between R groups with sulfur
36
Q

Quaternary structure in proteins

A

More than one polypeptide chain where each chain is a subunit. Joined by similar bonds to tertiary

37
Q

Conjugated protein

A

Quaternary structure which may have a prosthetic group that attaches to polypeptides

38
Q

Properties of R groups

A
  • Polar/hydrophilic
  • Non-polar/ hydrophobic
  • Positively/negatively charged
  • Some may contain sulfur

Biology HL IB 2020-22 (24 decks)

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