PROTEIN SYNTHESIS

Protein Synthesis

The basic concepts behind protein synthesis is that a gene in

the DNA is

TRANSCRIPTION (p. 242)1. The DNA molecule unzips and the enzyme _______________

attaches to one side of the DNA (______________________), attracted to a particular section of DNA by a special DNA base sequence called a _________________________

2. A complimentary daughter strand is assembled using RNA nucleotides

3. Once the RNA polymerase reaches a ____________________, the new RNA strand, called the ________________________, separates from the DNA strand, and the DNA zips back up

TRANSCRIPTION (p. 242)

Template strand

Coding strand

RNA Primary Transcript

TRANSCRIPTION (cont’d)4. Modifications are done to this primary transcript before it can

leave the nucleus:

5. The RNA strand, now called mRNA transcript , migrates out of the nucleus into the cytoplasm to attach to a ribosome

TRANSLATION (p. 250)1. Once the mRNA strand is in the cytoplasm it

attaches onto the smaller subunit of the ribosome

2. A______, with the appropriate _________ binds to the mRNA and the larger subunit of the ribosome attaches to the smaller part, putting the tRNA in the _________

• the first ________ (group of 3 bases on the mRNA) is always _______, which codes for the amino acid _____________________

• the first _______________ (3 exposed bases of the middle loop of tRNA) is ________

• there are _____________different codons

TRANSLATION (cont’d)

3. A second _______ binds to the mRNA at the ______of the ribosome, starting the __________________.

4. An enzyme, _______________________, attaches the methionine to the amino acid of the tRNA in the A site, forming a ____________________, and releases the tRNA from the P site.

5. The ___________________three bases down the mRNA strand, __________________________________, leaving the A site for the next tRNA with the appropriate anticodon.

TRANSLATION (cont’d)6. Once the appropriate amino acid sequence

(________________) is made, the last codon on the mRNA molecule codes for a _______________

• there are 3 _________________that code for a _______________instead of an amino acid:

7. The release factor causes an _______ group to bind to the last amino acid, completing the carboxyl end, and causes the ________________________, the ____________________and the ___________ to all come apart

6. The mRNA strand then finds another ribosome to begin the sequence

Translation:

OH

Summary

http://www.youtube.com/watch?v=4PKjF7OumYo

http://www.veoh.com/browse/videos/category/entertainment/watch/v192834509Hece6df

http://www.youtube.com/watch?v=983lhh20rGY

Regulation of Protein SynthesisEukaryotic Cells: there are 4 levels of control of gene expression

a)Transcriptional: regulates which genes are transcribed (housekeeping genes)

b)Post-transcriptional: capping and tailing, and excising of introns

c)Translational: controls how often and how rapidly mRNA transcripts will be translated

into proteins

d)Post-translational a number of control mechanisms affect the rate at which a protein becomes active and the time it remains functional

Regulation of Protein Synthesis (cont’d)

Prokaryotic Cells: there are two types of control mechanisms that these cells use: enzyme inducers and enzyme repressors

• Operon is the general name of these control mechanisms

•Lac operon is an example of an inducer operon

•Trp operon is an example of a repressor operon

• Operons are made up of a cluster of genes under the control of a promoter and an operator

LAC OPERON– in bacteria, the LacZ, LacY, and LacA genes code for enzymes that break down lactose

No lactose present -The repressor molecule (Lacl protein) is active and binds onto the operator site-RNA polymerase cannot bind to the operator-The genes are not transcribed(no lactose present, no need for protein that breaks it down!)

Lactose present:-Lactose binds to the lactose site on the repressor, deactivating it -mRNA polymerase can bind to the operator-the genes are transcribed

The presence of lactose ACTIVATES it; therefore, promoter operon

TRP OPERON– in bacteria, there are 5 genes that code for enzymes necessary to make the amino acid tryptophan

*Inhibitor; presence of the thing (trp) inhibits it

No tryptophan present:-the repressor is inactive, and nRNA polymerase can bind to the operator-the genes that code for the making of more trytophan are transcribed

Trytophan presentTryptophan binds to the site on the repressor molecule, activating it, causing it to bind to the operator-mRNA polymerase cannot bind to the operator-the genes are not transcribed

Questions: Page 258REALLY GOOD QUESTIONS!! Do them, faggot~