CH.7: RNA to Protein

Codon

An mRNA sequence is decoded in a set of 3 nucleotides called a _____.

polyribosomes

Proteins are produced on ______. This means that for each mRNA strand, when translation has begun and proceeded along a certain length, another ribosome comes along to continue the job. Therefore, a series of ribosomes can simultaneously translate the same mRNA molecule.

UAA, UAG, UGA

The 3 stop codons are...

stop codons

The end of translation in both prokaryotes and eukaryotes is signaled by the presence of one of several codons, called the ______ in the mRNA.

polypeptide chain

The energy from the high energy bond produced by the linking of the AA to the tRNA us later used to link that AA covalently to the growing ________.

ribozyme

The ribosome is a _____, aka an RNA molecule capable of acting as an enzyme.

cytoplasm

There are a high abundance of ribosomes attached to the membranes of the ER, but they are also located in the ____ of eukaryotic cells.

release factors

Translation halts at a stop codon, where proteins known as _______ bind to any stop codon that reaches the A site on the ribosome. This binding alters the activity of the peptidyl transferase in the ribosome, causing it to catalyze the addition of a water molecule instead of an AA to the peptidyl RNA. The completed polypeptide is released, and the ribosome dissociates into its two separate subunits.

proteases

_____ are enzymes that degrade proteins by hydrolyzing their peptide bonds.

reading frames

_______ are one of the 3 possible ways in which a set of successive nucleotide triplets can be translated into protein, depending on which nucleotide serves as the starting point.

4, 80

A ribosome is a large complex which has a large subunit and a small subunit, which together contain _____ rRNAs and more than _____ small proteins.

rRNAs, proteins

A ribosome is a large macromolecule complex, composed of _____ and dozens of small ______, that translate a messenger RNA into a polypeptide chain. A typical eukaryotic cell contains millions of ribosomes

ribosome

Accurate and rapid translation of mRNA into protein requires a molecular machine that can latch onto an mRNA, capture and position the correct tRNA molecules, and then covalently link the amino acids that they carry to form a polypeptide chain. In both prokaryotes and eukaryotes, that machine is the ________.

controlled protein breakdown

After a protein is released from a the ribosome, a cell can control its activity and longevity in various ways. For example, __________ helps regulate the amount of each protein in a cell.

translation

After transcription, the next major step in the central dogma is ________, where the mRNA molecule produced in transcription directs the incorporation of amino acids into protein.

ribosome binding sites

Bacterial mRNAs have no 5' caps to tell the ribosome where to begin searching for the start of translation. Instead, each mRNA molecule contains a specific _______, ]located a few nucleotides upstream of AUG at which translation is to begin.

64

Because a codon consists of 3 nucleotides and there are 4 diffferent nucleotides, there are _____ possible codons which are redundant in nature.

5' cap, poly-A tail

Efficient protein translation also requires additional proteins that are bound at the ____ and ____ of the mRNA.

single protein

Eukaryotic mRNA usually carries the info for a ______, so it can rely on the 5' cap and the proteins that recognize it to position the ribsome for its AUG search.

A site, P site, E site

In addition to a binding site an mRNA molecule, each ribosome contains 3 binding sites for tRNA molecules called...

proteasomes

In eukaryotic cells, proteins are broken down by large protein machines called ______, which are present in both the cytosol and the nucleus.

antibiotics, translational

Inhibitors of prokaryotic protein synthesis can be used as ______. This is because they target/impede _______ processes of prokaryotes.

charged particle

Once aminoacyl-tRNA synthetase has attached the correct AA to the matching tRNA, the tRNA is now considered a __________.

recycled, discarded (in urine), recycled

Once the ubiquitized protein has been degraded by the proteasome... The ubiquitin is _____ for future use. The AAs will either be _____ or can be ______ if they are in a good state.

polyubiquitin chain

So, how do proteasomes select which proteins in the cell should be degraded? In eukaryotes, proteasomes act primarily on proteins that have been marked for destruction by the covalent attachment of a _______.

codons

Specific ______ in an mRNA sequence signal the ribsome where to start and to stop in protein synthesis.

aminoacyl-tRNA synthetase

Specific enzymes couple tRNAs to the correct AA. Recognition and attachment of the correct AA depend on enzymes called _______, which covalently couple each AA to the appropriate set or tRNA molecules. Because there are 20 amino acids, there are 20 of these enzymes. One for each AA.

charged tRNA, A site, anticodon base pairs

Step 1 of protein synthesis... A _______ carries the next amino acids to be added to polypeptide chain via the ______. The tRNA binds via ______ with the mRNA codon that is exposed there (enables specificity).

carboxyl, P site, peptide bond, large subunit.

Step 2 of protein synthesis... Looking at the preceding charged tRNA, The ______ end of the polypeptide chain is uncoupled from the tRNA at the _____. At the same time on the subsequent tRNA, the AA on the tRNA in the A site forms a ______ to the free amino group. This reaction is carried out by a catalytic site in the _____.

translocates

Step 3 of protein synthesis... The large subunit _______, therefore moving the two bound tRNAs in the E and P sites of the large subunit.

3, ejects, resets

Step 4 of protein synthesis... The small subunit moves exactly _____ nucleotides along the mRNA molecule, bringing it back to its original position relative to the large subunit. This movement _____ the spent tRNA and _____ the ribosome with an empty A site. *this cycle is repeating with step 1 again but with an incoming charged tRNA to the A site.

polysictronic, several different proteins

Such ribosome-binding sequences are necessary in bacteria, as prokaryotic mRNA are often _______, that is they encode ________ on the same mRNA molecule. There is a separate ribosome-binding site for each protein coding sequence.

E site

The ____ is the location in the ribosome where discharged tRNAs leave the ribosome as the AA is now part of the growing peptide chain during protein synthesis.

P site (peptide forming site)

The _____ is the location in the ribosome which holds the tRNA which is linked to the growing polypeptide chain during protein synthesis.

A site (acceptor site)

The ______ is the location in the ribosome that the t-RNA binds during the protein synthesis process.

small subunit

The ______ of a ribosome has about 33 ribosomal proteins and 1 rRNA molecule.

large subunit

The ______ of a ribosome has about 49 ribosomal proteins and 3 rRNA molecules.

anticodon

The ________ is the sequence of three bases of a tRNA molecule that pairs with the complementary three-nucleotide codon of an mRNA molecule during protein synthesis.

aminoacyl-tRNA synthetases, tRNAs

The genetic code is translated by both ______ and _____ are equal in importance in the decoding process because it is the combined action of the synthatases and tRNAs that allow each codon in the mRNA molecule to be correctly matched to its AA.

Fold, stabalize, catalytic site

The main purpose of the proteins in the ribosome molcule seems to be to help ____ and ____ the RNA core. However, the rRNA portions of the ribosome act as the _______ for peptide bond formation.

genetic code

The set of rules by which the nucleotide sequence of a gene, through an intermediary mRNA molecule, is translated into the amino acid sequence of a protein is known as the ______.

hydrolysis of ATP, 2 pyrophosphate

The synthetase-catalyze reaction that attaches the AA to the 3' end of the tRNA is one of many reactions in cells that is coupled to the energy-releasing ________ by releasing _____. This reaction produces a high-energy bond between the charged tRNA and the amino acid.

AUG, initiator tRNA, methionine (MET), P site

The translation of an mRNA begins with the start codon_____, for which a special charged tRNA is required. This first tRNA is referred to as the _______, and it always carries the AA _______, and it is always loaded into the ______ of the ribosome.

tRNAs.

The translation of mRNA into protein depends on the adapter molecules that bind to a codon with one part of the adapter, and to an AA with another. They adapters in this context consist of a set of small RNA molecules known as ________.

5' G-cap, f-methionine, AUG, mRNA-small subunit complex, P site, A site

To begin translation... 1. The mRNA binds to the small subunit of the ribosome via the ______ to from a mRNA-small subunit complex. 2. The ______ tRNA binds to the "start" codon which has the reading frame _____. 3. The large subunit of the ribosome binds with the ______ in step 1. 4. The very first tRNA of a new polypeptide chain is place in the ______. 5. All subsequent tRNAs are deposited in the ______ as the chain grows.

four step cycle

Translation takes place in a ________, which is repeated over and over during the synthesis of a protein.

serveral nucleotides

Unlike a eukaryotic ribsome, a prokaryotic ribosome can readily bind directly to a start codon that lies in the interior of an mRNA, as long as the ribosome-bidning site precedes it by ________.

amino acid, anticodon loop, anticodon

tRNAs fold into a 3D "cloverleaf" shape which provides it's function for transferring an AA. On the 3' of the folded tRNA is the attached ______. In the middle of the sequence, is a ________ which contains the _____.