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Grade 12 Biology > Protein Synthesis > Flashcards

Protein Synthesis Flashcards

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1
Q

What is mRNA?

A

Messenger RNA.

It carries the coded message for protein building from DNA to the ribosomes.

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2
Q

What is tRNA?

A

Transfer RNA. It transports amino acids to the mRNA at the ribosomes.

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3
Q

How big is mRNA?

A

It varies in length, but is always much shorter than DNA. (1%)

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4
Q

How big is TRNA?

A

Very short, 70-90 bases only.

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5
Q

What is rRNA?

A

Ribosomal RNA. It binds the large and small subunits to form a functional ribosome.

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6
Q

How big is rRNA?

A

It varies in length, but is shorter than mRNA.

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7
Q

What is transcription?

A

The process of making mRNA from copying the information from a piece of DNA.

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8
Q

What are the steps in transcription?

A

Initiation, Elongation, Termination, and Post-transcriptional modifications.

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9
Q

What happens in initiation?

A

RNA polymerase binds to an AT rich section of DNA. It then unwinds it.

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10
Q

What happens in elongation?

A

RNA polymerase H bonds free-floating nucleotides to their complementary bases. DNA snaps back together behind RNA polymerase causing the created mRNA to hang free off the side by a few base pairs.

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11
Q

What happens in termination?

A

RNA polymerase encounters a terminator sequence at the end of the gene, causing RNA polymerase and a primary transcript to be released.

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12
Q

What happens in post-transcriptional modifications for prokaryotes?

A

5’ cap is added, 3’ poly-a-tail is added, mRNA transcript becomes ready for release from nucleus.

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13
Q

For eukaryotes, what else happens in post-transcriptional modifications?

A

Spliceosomes remove introns and ligate exons, forming mature mRNA transcript.

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14
Q

What is an intron?

A

A non-coding region.

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15
Q

What is an extron?

A

A coding region.

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16
Q

What is the purpose of a 5’ cap?

A

To protect the mRNA from cytoplasmic enzymes.

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17
Q

What is a poly-A-tail?

A

200 or more adenines.

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18
Q

What adds poly-A-tail to mRNA?

A

poly-A-polymerase.

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19
Q

How many enzymes are involved in transcription?

A

ONE

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20
Q

What kind of bonds are formed in transcription?

A

H bonds and covalent bonds.

21
Q

What amount of the DNA is copied in transcription?

A

A small piece only

22
Q

Which strands are copied in transcription?

A

Only the template strand.

23
Q

How is the message on mRNA written?

A

In 3-letter triplets called CODONS.

24
Q

How many possible codons are there?

A

4^3 (64)

25
Q

Which are the two amino acids with a unique code?

A

UGG (trp) and AUG (met)

26
Q

Which is the start code?

A

AUG

27
Q

Why are UAA, UAG, and UGA stop codes>

A

BEcause there is no amino acid that is coded by these codons.

28
Q

What happens at a stop code?

A

The protein breaks.

29
Q

WHat adheres to the active ribosome?

A

The 5’ [CAP region]

30
Q

In which direction will the ribosome move the mRNA through it?

A

5’ to 3’

31
Q

What kind of structure does tRNA have?

A

A cross-like structure with an anticodon at its base. It also has an acceptor site at its 3’ end, that holds the amino acid.

32
Q

What is an anticodon?

A

The compliment of the codon on the mRNA

33
Q

WHat is the anticodon of AUG?

A

UAC

34
Q

amino acid + 1 ATP + correct tRNA =

A

amino-acyl tRNA

35
Q

How many ATP does it require to bond an amino acid to the correct tRNA?

A

1 ATP

36
Q

How many possible tRNA are there for 20 amino acids?

A

61

37
Q

How many enzymes does a cell need for the aa?

A

61

38
Q

STEP 1 Protein synthesis:

A

mRNA, rRNA, tRNA, 40s, and 60s are drifting around the cytoplasm

39
Q

STEP 2 Protein synthesis:

A

mRNA leaves nucleus and encounters 40s (attaches).

40
Q

STEP 3 Protein synthesis:

A

rRNA attaches 60s to 40s (attached to mRNA). Using 1 ATP, tRNAs are activated by the attachment of an amino acid.

41
Q

STEP 4 Protein synthesis:

A

tRNA with Met attached randomly enters Psite. It is held in place because its anti-codon matches the codon in the P-site.

42
Q

Where are mRNA, rRNA, tRNA transcribed from?

A

DNA in the nucleus.

43
Q

Where is the P-site?

A

on the ribosome

44
Q

STEP 5 Protein synthesis:

A

tRNA for next amino acid moves into Asite.

45
Q

STEP 6 Protein synthesis:

A

tRNA that first brought Met is now released, since Met has bonded to Pro.
mRNA is moved through ribosome until tRNA Met-Pro is in the P-site. Now the tRNA for the next code fits into the A-site.

46
Q

STEP 7 Protein synthesis:

A

steps 5 and 6 are repeated until a stop code reaches the A-site.
The amino acids have now been bonded into a polypeptide chain (connected to the last tRNA in the P-site).

47
Q

What level of protein structure is a polypeptide chain (step 7)?

A

Primary!

48
Q

STEP 8 Protein synthesis:

A

There was no tRNA to match UAG (stop code). The polypeptide chain is released. RIBOSOME FALLS APART AND MRNA IS BROKEN DOWN.

Grade 12 Biology (8 decks)

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