Exam 2 (Ch. 14- proteins) Flashcards
inborn errors of metabolism
- alkaptonuria
- phenylketonuria
archibald garrod’s work
Garrod provided the 1st published account of a case of recessive inheritance in humans: called ___
Alkaptonuria
worked on mutants of the fungus Neurospora crassa (a mold) leading to their groundbreaking discovery that genes provide the instructions for making proteins
Beadle and Tatum (1941)
Beadle and Tatum’s Experiment –> one gene:
later updated to:
- one gene:
one enzyme hypothesis (genes are responsible for encoding an enzyme);
one polypeptide hypothesis
when phenylalanine is blocked by an enzyme called phenylalanine hydroxylase, results in excess phenylalanine converting into __
phenylpyruvic acid
if there is no phenylketonuria block then phenylalanine can convert to
tyrosine
the 1st case of recessive inheritance that would connect the genes and proteins (and the function of proteins)
Alkaptonuria block (homogentisic acid oxidase)
Garrod contribution to errors in metabolic pathways were caused by 2 main blocks
- Phenylketonuria block (newborn PKU test)
- Alkaptonuria block (recessive inheritance)
- A physician that studied alkaptonuria & phenylketonuria and how they were inherited in families. He concluded that hereditary information controls chemical reactions in the body. “unit factors” aka genes –> “ferments” aka enzymes. (1902)
- Provided the first published account of a case of recessive inheritance in humans & attributed a biochemical role to genes
Archilbald Garrod
Cannot metabolize the alkapton 2,5 dihydroxyphenylacetic acid known as homagentistic acid. This acid accumulates in cells an tissues and is excreted in urine.
- Arthritis and urine turns black when exposed to air, dark skin in ears and nose.
Alkaptonuria
a disorder related to a defective recessive gene on chromosome 12 that prevents metabolism of phenylalanine (UUU)
Phenylketonuria (PKU)
protein synthesis requires the translation of
mRNA
each polypeptide is properly folded and placed at the correct cellular or extracellular location/ and assume higher order structures, and they may interact with other polypeptides.
What happens after translation?
4 levels of structure in proteins
- Primary
- Secondary
- Tertiary
- Quaternary
amino acid sequence of a protein
primary structure
Alpha-helix and beta-pleated sheets, stabilized by the formation of hydrogen bonds between atoms located in the polypeptide backbone
secondary structure of protein
A coiled region constituting one form of the secondary structure of proteins, arising from a specific pattern of hydrogen bonding between atoms of the polypeptide backbone (not the side chains).
alpha helix
secondary structure found in proteins in which “pleats” are formed by hydrogen bonding between atoms on the backbone of the polypeptide chain
beta-pleated sheet (β-pleated)
protein structure is formed when the twists and folds of the secondary structure fold again to from a larger 3D structure
- final folding
- structure determined by hydrophobic & ionic interactions; also hydrogen bonds & Van der Waals interactions
tertiary structure of protein
protein structure that is a protein consisting of more than one folded amino acid chain
- This is formed when the various polypeptides associate with one another to make a functional protein
quaternary structure of a protein
- isolated from diseased and normal individuals differ in their rates of electrophoretic migration.
- This was the result of a single amino acid change
- Studies established that one gene encodes one polypeptide
hemoglobin
iron-containing structures on hemoglobin, the sites of oxygen binding
heme group
a genetic disorder that causes abnormal hemoglobin, resulting in some red blood cells assuming an abnormal sickle shape, transport of hemoglobin is blocked
sickle cell anemia
one single amino acid change causes sickle cell anemia: substitution from __ –> __ in position 6 of the beta-chain
Valine (hydrophobic) for glutamic acid (hydrophilic)
