4.2 PROTEIN SYNTHESIS

TRANSCRIPTION:

1. DNA helicase breaks H bonds.

2. Only one DNA strand acts as template

3. Free RNA nucleotides align by complementary base pairing;

4. U relapces T.

5. RNA polymerase catalyses join adjacent nucleotides.

6. By phosphodiester bonds.

7. Mature RNA with five prime end.

8. pre-mRNA spliced to remove introns.

Hot thick cocktails under Paris is messy.

HOW IS A POLYPEPTIDE FORMED BY THE TRANSLATION OF mRNA?

1. mRNA attaches to ribosomes.

2. Ribosome moves to find start code (AUG)

3. Idea of two codons / binding sites

4. tRNA anticodons bind to complementary mRNA codons.

5. tRNA brings a specific amino acid.

6. Amino acids join by peptide bonds held by tRNA (condensation).

7. With the use of ATP.

8. tRNA released after amino acid joined to polypeptide.

9. The ribosome moves along the mRNA to next codon to form the polypeptide. (ATP)

After cocktails the books start prowling all june mondays.

ANSWER FOR DNA, mRNA, AND tRNA?

1. HOW MANY POLYNUCLEOTIDE CHAINS?

2. WHICH IS THE LARGEST AND SMALLEST?

3. SHAPE?

4. WHAT IS THE PENTOSE SUGAR?

5. BASES?

6. WHERE IS TI FOUND?

7. IS IT CHEMICALLY STABLE?

1. DNA has double, others have single.

2. DNA largest and tRNA smallest.

3. Double helix, single helix, clover.

4. DNA has deoxyribose, others have ribose.

5. DNA has ATCG, others have AUGC.

6. DNA - nucleus, mRNA (manufactures in nucleolus) - found throughout cell, tRNA - cytoplasm.

7. DNA stable, mRNA least stable.

ADVANTAGE OF mRNA BEING BROKEN DOWN QUICKLY?

Allows the cell to regulate protein synthesis efficiently, so proteins are only produced when needed, preventing waste of resources.

DIFFERENCES BETWEEN tRNA AND mRNA

tRNA is 'clover leaf shape', mRNA is linear.

tRNA has hydrogen bonds, mRNA does not.

tRNA has an amino acid binding site, mRNA does not.

tRNA has anticodon, mRNA has codon.

tRNA has less nucleotides.

tRNAs are all similar / same length, mRNAs have different lengths/

DIFFERENCES BETWEEN mRNA AND pre-mRNA? (2)

mRNA fewer nucleotides Pre-mRNA more nucleotides

mRNA has no introns/has (only) exons

mRNA is shorter

(Because of) splicing;

DESCRIBE HOW mRNA IS PRODUCED FROM AN EXPOSED TEMPLATE STRAND OF DNA (DON’T MENTION DNA HELICASE OR SPLICING)? (3)

Free RNA nucleotides form complementary base pairs

Phosphodiester bonds form

By (action of) RNA polymerase;