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52 Cards in this Set
- Front
- Back
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What is the most important biological compound?
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protein
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Name as many of the eight roles of protein that you can:
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- structure
- catalysis - movement - transport - hormones - protection - storage - regulation |
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What are the two major types of proteins, their solubility and their basic use?
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- fibrous proteins, insoluble, are used for structural purposes
- globular proteins, -/+ soluble, are used for nonstructural purposes |
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How many amino acids commonly occur in nature?
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20
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What is an alpha amino acid?
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An amino acid in which the amino group is linked to the carbon atom next to the -COOH carbon.
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Amino acids are classified into four groups regarding their polarity:
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- nonpolar
- polar but neutral - acidic - basic |
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Nonpolar side chains on amino acids are _____, whereas polar but neutral, acidic and basic side chains are _____.
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_____ side chains on amino acids are hydrophobic, whereas _____, _____ and _____ side chains are hydrophilic.
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Of the 20 amino acids, which one does not fit the basic structure? How does it differ?
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Proline, it also has a bond between the R and the N.
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All 20 amino acids are chiral except for which one?
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Glycine
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Which enantiomer is most common for the amino acids?
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The L-isomer.
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List the eight nonpolar amino acids:
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- Leucine (Leu, L)
- Alanine (Ala, A) - Proline (Pro, P) - Valine (Val, V) - Methionine (Met, M) - Phenylalanine (Phe, F) - Tryptophan (Trp, W) - Isoleucine (Ile, I) |
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List the seven polar but neutral amino acids:
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- Glycine (Gly, G)
- Asparagine (Asn, N) - Serine (Ser, S) - Glutamine (Gln, Q) - Threonine (Thr, T) - Tyrosine (Tyr, Y) - Cysteine (Cys, C) |
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List the two acidic amino acids:
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- Aspartic acid (Asp, D)
- Glutamic acid (Glu, E) |
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List the three basic amino acids:
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- Lysine (Lys, K)
- Histidine (His, H) - Arginine (Arg, R) |
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For proline (Pro, P), is the alpha amino group primary, secondary or tertiary?
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It is secondary, the amino group is bound to two carbons.
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Which two amino acids have two stereocenters?
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Isoleucine (Ile, I) and Threonine (Thr, T)
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What is a zwitterion?
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A compound that has a positive charge on one atom and a negative charge on another.
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What happens if a strong acid (H3O) is added to a solution containing a zwitterion of an amino acid (RCH(NH+3)COO-)?
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A proton is donated to the COO- group making the zwitterion a positive ion (RCH(NH+3)COOH).
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What happens if a strong base (OH-) is added to a solution containing a zwitterion of an amino aicd (RCH(NH+3)COO-)?
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A proton is donated to the OH- group making the zwitterion a negative ion (RCH(NH2)COO-).
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What is the isoelectric point (pI)?
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A pH at which a sample of amino acids or protein has an equal number of positive and negative charges.
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What is special about cysteine when compared to the other amino acids?
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Cysteine contains a sulfhydryl group which is easily oxidized to a disulfide (R-S-S-R).
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What is different about the structures of tryptophan, phenylalanine, and tyrosine?
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They have aromatic rings in their side chains.
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Tryptophan is associated with which neurotransmitter(s)? What is/are the effect(s)?
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Tryptophan is converted to serotonin, which has a calming effect. Low levels of serotonin are associated with depression, while high levels are associated with manic states.
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What neurotransmitter(s) are associated with tyrosine?
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Tyrosine (along with phenylalanine) is converted to catecholamines which includes epinephrine and norepinephrine. Tyrosine also converts to L-dopa, which is associated with Parkinson's in low levels.
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What neurotransmitter(s) are associated with phenylalanine?
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Along with tyrosine, phenylalanine is associated with epinephrine and norepinephrine.
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What is a peptide bond?
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An amide bond that links two amino acids.
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Describe how a peptide bond links two amino acids:
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The carboxyl (RCOO-) of one amino acid bonds to the amino (NH+3R) of another amino acid, yielding a dipeptide (RCO-NH2R) and H2O.
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Explain how dipeptides have constitutional isomers:
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Each amino acid in the bond has its own COO- and NH+3, leaving two different possibilities for bonding. These two different results are constitutional isomers.
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What is a dipeptide?
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Two amino acids joined by a peptide bond.
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What is a tripeptide?
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Three amino acids joined by a peptide bond.
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What is a protein?
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A biological macromolecule containing at least 30 - 50 amino acids joined by peptide bonds.
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What is the C-terminus in a polypeptide?
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It is the amino acid at the end of the peptide that has the free alpha-carboxyl (COO-) group.
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What is the N-terminus in a polypeptide?
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It is the amino acid at the end of the peptide that has the free alpha-amino (NH+3) group.
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In which directions are proteins synthesized?
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From the N-terminus to the C-terminus (from left to right as written).
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Proteins are _____ soluble in water at their isoelectric point.
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Proteins are least soluble in water at their ___ ___.
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Explain why proteins are most easily precipitated from their solutions at their isoelectric point:
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When they have a net positive or a net negative charge (high pH or low pH), the like charges cause the protein molecules to repel one another. At their isoelectric point, there are no repulsive forces and they clump together, reducing their solubility.
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What is the primary structure of a protein?
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It is the sequence of amino acids in that protein.
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What is the secondary structure of a protein?
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A repetitive conformation of the protein backbone. Proteins can fold or align themselves in such a manner that certain patterns repeat themselves.
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What are the three types of secondary structure?
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- alpha-helix
- beta-pleated sheet - random coil |
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Where does the hydrogen bonding take place in secondary structures?
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Between the backbone C=O
or H-N groups. |
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Explain the beta-pleated sheet configuration:
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A secondary protein structure in which the backbone of the two protein chains in the same or different molecules is held together by hydrogen bonds.
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Give an example of a protein that consists of primarily alpha-helix configuration:
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hair, fingernails, horns, wool
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Give an example of a protein that contins mainly the beta-pleated sheet configuration:
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silkworm silk and spider silk
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Where is the extended helix most commonly found?
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In collagen, which forms bone, cartilage, tendons, skin, etc).
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Explain the tertiary structure of a protein:
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It is the complete three-dimensional arrangement of the atoms in a protein.
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List five ways tertiary structures are stabilized:
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- covalent bonds
- hydrogen bonds - salt bridges - hydrophobic interactions - metal ion coordination |
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Explain the quaternary structure of proteins:
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The spatial relationship and interactions between subunits in a protein that has more than one polypeptide chain.
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In what three ways are individual chains held together in quaternary structures?
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- salt bridges
- hydrogen bonds - hydrophobic interactions |
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Proteins that contain non-amino acid portions are called _____ proteins.
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Proteins that contain ___-___ ___ portions are called conjugated proteins.
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The non-amino acid portion of the conjugated protein is called a ___ ___.
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The non-amino acid portion of the ___ ___ is called a prosthetic group.
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What is tropocollagen and where is it found?
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It is the triple helix unit of collagen and can be found only in fetal or young connective tissue.
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What is denaturation?
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The loss of the secondary, tertiary and quaternary structures of a protein by a chemical or physical agent that leaves the primary structure intact.
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