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Cell and Molecular Bio > Translation-14 > Flashcards

Translation-14 Flashcards

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1
Q

What is translation?

A

process by which ribosomes read the genetic message in the mRNA and produce a protein product according to the message’s instruction

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2
Q

What components does Translation require?

A 
mRNA
tRNA 
Ribosomes 
Translation factors 
-most cells use a substantial amount of energy on translation
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3
Q

What are the different types of RNA included in translation?

A

Messenger RNA (mRNA): carries the genetic instructions for protein synthesis from DNA in the nucleus to the ribosomes in cytoplasm

Ribosomal RNA (rRNA): major component of the ribosomes; protein synthesis

Transfer RNA (tRNA): brings amino acids to ribosomes for protein synthesis

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4
Q

What is mRNA?

A

messenger RNA which carries the genetic information from nucleus to cytoplasm for protein synthesis

Each group of 3 nucleotides in the mRNA is a “codon”, which codes for 1 amino acids

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5
Q

Where are ribosomes and rRNA made?

Where are rRNA found?

A

They are synthesized in the nucleolus and shipped out of nucleolus through the nuclear pores to cytoplasm in eukaryotic cells

rRNA are found in the ribosomes and account for 80% of the total RNA present in the cell

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6
Q

Sub units in the Ribosome:

A

There are 2 pieces or subunits to every ribosome-large subunit and small subunit

Each subunit is made up of one or more rRNA and a variety of ribosomal proteins and act as the site of proteins synthesis

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7
Q

Ribosome and their binding sites:

A

Each ribosome has an mRNA binding site and 3 tRNA binding sites

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8
Q

What are the 3 binding sites? tRNA

A

facilitate coupling of tRNA anticodon to mRNA codon

  1. A site (aminoacyl-tRNA site)
    - holds tRNA carrying next amino acid to be added to a polypeptide chain
  2. P site (peptidyl-tRNA site)
    - holds tRNA carrying growing polypeptide chain
  3. E site (exit site)
    - empty tRNA leaves ribosome from exit site
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9
Q

What are the characteristics of tRNA? How many bases make up the anticodon?

A

Transfer RNA (tRNA) are short RNAs that fold into a characteristic cloverleaf pattern

Each tRNA has 3 bases that make up the anticodon
-these base pair with the 3 bases of the codon on mRNA during translation

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10
Q

What is the function of tRNA?

A

tRNA brings amino acids to the ribosome for protein production

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11
Q

What does Aminoacyl-tRNA synthetase catalyze?

A

Catalyzes the attachment of amino acids to tRNA
-one for each different amino acids

Reactions result in tRNA with amino acid attached or charged tRNA or aminoacyl tRNA

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12
Q

How do we code for amino acids with only 4 bases?

A

Nucleotide bases exist in triplets for a codon

3 bases=1 codon=1 amino acid

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13
Q

Genetic code, what is the start codon (first base 5’ end)?

A

AUG
methionine
(met)

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14
Q

Genetic code, what is the stop codon (third base 3’ end)?

A

UAA
UAG
UGA

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15
Q

What are the 3 stages of translation?

A

Initiation
-mRNA, first tRNA and ribosomal subunits assemble

Elongation
-Synthesis from start codon to stop codon

Termination
-Complex disassembles at stop codon releasing completed polypeptide

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16
Q

What occurs during Initiation, what starts binding here?

A

1- Ribosome binding site on mRNA binds to complementary sequence on small subunit of ribosome, with the help of proteins called initiation factors

2- Initiator tRNA brings in the first amino acid “methionine (Met)” and binds to mRNA’s start codon,
AUG”

3-Large subunit of ribosome binds -> placing initiator tRNA in the (P-site -holds tRNA carrying growing polypeptide chain)

Elongation starts (step 4)

17
Q

What occurs during Elongation, what starts binding here?

A

4- Incoming tRNA binds to the codon in the A site-(holds tRNA carrying next amino acid to be added to a polypeptide chain) via complementary base pairing between anticodon and codon

5- Amino Acid in the P site:

  • breaks the bond with its tRNA
  • forms a peptide with the amino acid in the A site

6- Translocation

  • Ribosome moves down to the next codon on mRNA
  • tRNAs shift over one spot
  1. Repeat the Cycle
    - Incoming tRNA enters the A site
    - peptide bond formation (with adjacent amino acid)
    - translocation
18
Q

What occurs during the termination stage of Translation?

A
  1. Occurs when a stop codon is revealed in A site-> A protein called a release factor enters the A site
  2. Release factor promotes the hydrolysis of the bond linking the tRNA in the P-site with its polypeptide-. releases polypeptide and tRNAs
  3. Ribosomal subunits, mRNA and protein release factor all separate from one another
19
Q

How are amino acids joined together to make a polypeptide?

A

Amino acids join together through a condensation reaction forming peptide bonds where water is removed and is made a product

20
Q

Each mRNA molecule is simultaneously translated by many……

A

ribosomes, all reading the mRNA from 5’ to 3’ and synthesizing the polypeptide

21
Q

Relationship between nucleic acids and proteins, What determines the sequence of amino acids in a protein?

A

Sequence of bases in DNA determines sequence of amino acids in a protein

22
Q

Relationship between nucleic acids and proteins, What does the sequence of amino acid determine?

A

Sequence of amino acids determines a protein’s structure and function

23
Q

Small changes in the DNA doesn’t cause that much of a difference in the protein (true/false)

A

False, Small changes in the DNA may cause large changes in a protein

24
Q

What makes proteins in the cell?

A

Free floating ribosomes

25
Q

What makes proteins that are secreted outside the cell?

A

Ribosomes attached to ER (RER)

26
Q

DNA point Mutation, What occurs during Translation which causes the change in the functioning of hemoglobin?

A

The changed codon in m RNA is coded to produce a different amino acid.

Instead of glutamate, valine is inserted in the poly-peptide chain, this amino acid causes a change in the functioning of the hemoglobin, so that it cannot bind to oxygen

Sickle cells cause anemia

27
Q

DNA summary definition:

A

DNA base sequence (triplets) of the gene codes for synthesis of a particular polypeptide chain

28
Q

What is a polypeptide?

A

Amino acid sequence of the polypeptide chain

Cell and Molecular Bio (13 decks)

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