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Terms in this set (225)

silent mutation.

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-If you chose 'Frameshift Mutation', this is incorrect. Errors that increase or decrease the number of nucleotides in a gene cause frameshift mutations. The insertion of an extra base or the removal of one of the bases will change which groups of three bases that the ribosome reads when it translates the message. This is said to 'shift' the 'reading frame' from the correct groups of three bases to different groups.

To visualize what a frameshift is, imagine you are given a string of letters and told to start at the beginning and read every group of three letters: CATDOGRATPIGAPE. You would get "cat dog rat pig ape". But if we add an extra letter, say CATDFOGRATPIGAPE, following our "read every group of three" rule, we would get "cat dfo gra tpi gap e". Shifting our 'reading frame' by adding one more letter completely changes what we read. This is similar to what happens with a frameshift mutation.

-If you chose 'Missense Mutation',this is incorrect. A single nucleotide change in the DNA (point mutation ) that changes a codon in the mRNA such that it codes for a different amino acid, changes one amino acid in the amino acid sequence of a protein. This is called a missense mutation. See Figure 1-19 in the Module 1 text for more information.

- If you chose 'Nonsense Mutation', this is incorrect. A single nucleotide change in the DNA (point mutation ) that changes a codon in the mRNA from one that codes for an amino acid into one that specifies the STOP signal is a nonsense mutation. The protein will terminate prematurely.

Background: When a point mutation (single nucleotide change) occurs it changes the mRNA codon (triplet sequence that codes for amino acid), however, it doesn't affect the amino acid it codes for. For example, if a point mutation caused UUU (codes for Phe) to change to UUC- this is a silent mutation as both codons (UUU and UUC) code for Phe.
2. Competitive inhibitors bind reversibly to the active site and do not change the enzyme tertiary structure; non-competitive inhibitors bind only irreversibly to the allosteric site and do not change the enzyme tertiary structure.

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Correct! Competitive inhibitors bind reversibly to the active site and do not change the enzyme tertiary structure; non-competitive inhibitors bind reversibly or irreversibly to the allosteric site and change the enzyme tertiary structure.
A competitive inhibitor is usually a molecule similar in structure to a substrate that can bind to an enzyme's active site even though the molecule is unable to react. This non-substrate molecule competes with the substrate for the active site. Enzymes can also be inhibited by substances called non-competitive inhibitors. Some non-competitive inhibitors attach to the enzyme at an allosteric site, which is a site other than the active site. competitive inhibitors bind to the active site.

Competitive inhibitors bind to the active site so that the substrate cannot, thereby inhibiting the reaction. The presence of the non-competitive inhibitor changes the shape of the enzyme enough to interfere with binding of the normal substrate. Some non-competitive inhibitors are used in the regulation of metabolic pathways, but others are poisons.

Non-competitive inhibitors distort the tertiary protein structure and alter the shape of the active site. Any enzyme molecule thus affected can no longer bind its substrate, so the enzyme cannot catalyze a reaction. Although some non-competitive inhibitors bind reversibly, others bind irreversibly and permanently inactivate the enzyme molecules, thereby greatly decreasing the reaction rate. In non-competitive inhibition, increasing the substrate concentration does not increase the reaction rate as it does in the presence of a competitive inhibitor.
1. The Beta bond connects the alpha carbon to the beta carbon and is broken during beta-oxidation.
3. The omega carbon at the end of the fatty acid.

The alpha carbon is found adjacent to the carboxylic acid group carbon. The correct answer is the beta bond, which connects the alpha carbon to the beta carbon. This is the bond that is broken during beta oxidation (which is why the pathway that breaks down fatty acids is called beta oxidation). The positions of carbons and bonds within the fatty acid chain are often named using Greek letters beginning at the carbon closest to the carboxylic acid. That is the alpha carbon, and its bond to the carbon of the carboxylic acid is called the alpha bond. Similarly, the next carbon in the chain is the beta carbon, and its bond to the alpha carbon is known as the beta bond. The carbon at the end of the fatty acid opposite the carboxylic acid group is the omega carbon.

If you chose the beta carbon, the answer is incorrect. Placement of a double bond in the carbon chain determines whether the fatty acid is an omega fatty acid; The carbon at the end of the fatty acid opposite the carboxylic acid group is the omega carbon.
The correct answer is the beta bond, which connects the alpha carbon to the beta carbon. This is the bond that is broken during beta oxidation (which is why the pathway that breaks down fatty acids is called beta oxidation). The positions of carbons and bonds within the fatty acid chain are often named using Greek letters beginning at the carbon closest to the carboxylic acid. That is the alpha carbon, and its bond to the carbon of the carboxylic acid is called the alpha bond. Similarly, the next carbon in the chain is the beta carbon, and its bond to the alpha carbon is known as the beta bond. The carbon at the end of the fatty acid opposite the carboxylic acid group is the omega carbon.