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Chp 20 Proteins
| Question | Answer |
|---|---|
| What is a protein? | a protein is a naturally occurring, UNBRANCHED polymer in which the monomer units are amino acids. |
| How much does protein account for in the cell’s overall mass? | proteins account for 15% of the cell’s over all mass. |
| All proteins contain the elements? The presence of _______ element sets proteins apart from carbohydrates and lipids | carbon, hydrogen, oxygen, and nigtrogen, most also contain sulfur. CHON. The presence of Nitrogen set them apart from carbs and lipids. |
| What is an amino group? | -NH2 |
| What is a carboxyl group? | -COOH |
| What is an amino acid? | is an organic compound that contains both an amino (-NH2) group and a carboxyl (-COOH) group. |
| The amino acids found in proteins are always Alpha or Beta amino acids? | alpha-amino acids. |
| What are alpha-amino acids? | is an amino acid in which the amino group and the carboxyl group are attached to the alpha-carbon atom. |
| What is a standard amino acid? | is one of the 20 alpha-amino acids normally found in protein. |
| What are the four categories of amino acids? SEE TABLE 20.1 on pg 585 | 1) nonpolar amino acids 2) polar neutral amino acids 3) polar acidic amino acids 4) polar basic amino acids. |
| What is a nonpolar amino acid? | is an amino acid that contains one amino group, one carboxyl group, and a nonpolar side chain. When incorporated into a protein these amino acids are hydrophobic! |
| What is a polar neutral amino acid? | is an amino acid that contains one amino group, one carboxyl group, and a side chain that is POLAR but NEUTRAL (neutral pH. Cannot be acidic or basic). They are more soluble in water than nonpolar amino acids. |
| What is a polar acidic amino aicd? | is an amino acid that contains one amino group and TWO carboxyl groups, the second carboxyl group being part of the side chain. |
| What is a polar basic amino acid? | is an amino acid that contains TWO amino groups and one carboxyl group. The second amino group being part of the side chain. |
| How many naturally occurring amino acids are there? | 20 |
| What are essential amino acids? | ones that can NOT be synthesized by an organism. Must be in diet. |
| What is a complete protein? | contain all essential amino acids. Meat, fish, milk, egg, sobybean, potatoes. |
| What are complimentary proteins? | you have to combine foods. Most famous of these are beans and rice, beans and barely… |
| In standard amino acids, how many possess a chiral center? | 19 out of the 20 standard amino acids possess chiral centers. |
| With frew exception the amino acids found in nature and in proteins are D or L isomers? | L isomers. |
| Are amino acids charged or uncharged? | they are charged. |
| In neutral solutions, amino GROUPS tend to do what? | in neutral solutions amino acids tend to accept a proton (+H), producing a positively charged species. The –COOH group donates a proton to NH2. |
| What is a zwitterions? | it is an atom that has a positive and negative side. There is NO net charge. |
| In an acidic solution, the zwitterions does what? | it accepts a proton (+H) to form a positively charged ion. |
| In a basic solution the zwitterions does what? | it loses a proton (+H) to make it negative. |
| What is the acid/base scale? | if below 7 it is acidic, if above 7 it is basic. |
| What is the isoelectric point? | is the PH at which an amino acid exists primarily in its zwitterions form. Neutral. |
| What is unique about the standard amino acid Cysteine? | it is the only standard amino acid that contains a sulfhydryl group (-SH group). |
| What is a dimer? | a dimer is a molecule that is made up of two like subunits. |
| What is a peptide? | it is an unbranched chain of amino acids. Amino acid-amino acid-amino acid-amino acid-amino acid-amino acid. |
| What is a dipeptide? | contains two amino acids. |
| What is a tripeptide? | contains 3 amino acids. |
| The name oligopeptide is loosely used to refer to peptides with how many amino acid residues? | 10-20 amino acid residues. |
| What is a polypeptide? | is a LONG UNBRANCHED chain of amino acids. |
| In a pentapeptide, how many peptide bonds are there? | there are four. Amino acid-amino acid-amino acid-amino acid-amino acid. |
| What is a peptide bond? | it is a covalent bond between the carboxyl group of one amino acid and the amino group of another amino acid. |
| What is an amino acid residue? | is the portion of an amino acid structure that remains, after the release of H2O, when an amino acid participates in peptide bond formation as it becomes part of a peptide chain. |
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organismalbiology