28 Biochemical Pathways Flashcards
mutation
change in the DNA
Why are not all mutations bad?
- they are the source of new alleles - can provide variability in the population - can provide an advantage in a particular environment - can allow adaptation to a changing environment
alkaptonuria
- black urine - due to build-up of homogentisic acid in cartilage, urine, skin, and nails - leads to joint problems, heart valve problems, and hearing loss
Who proposed alkaptonuria was genetic?
Archibald Garrod
One of the first disease phenotypes correlated with a genotype
alkaptonuria
alkaptonuria is caused by…
- absence of homogentisate oxidase - this enzyme is important to phenylalanine metabolism - leads to the metabolite before the blocked step - homogentisic acid - accumulating - an inborn error of metabolism
PKU
phenylketonuria - due to missing phenylalanine hydroxylase - the phenylalanine cannot enter its normal pathway and is instead converted to phenylpyruvic acid which builds up in brain leading to intellectual disabilities an inborn error of metabolism
record, restrict, replace
- motto for PKU - phenylalanine is an essential amino acid so individuals with PKU still need some phe, just not too much
why is diet soda a restricted item for individuals with PKU?
it contains aspartame which is a derivative of phenylalanine and can be converted to it in the body
PKU and alkaptonuria are blocks on…
a degradative pathway as phenylalanine is being degraded
albinism
- no melanin pigment - vision problems - autosomal recessive
why do people with albinism have vision issues?
melanin is found in the retina
issues with a biosynthetic pathway in phenylalanine metabolism
- albinism - typically, phenylalanine is converted to tyrosine - some of this tyrosine is converted to melanin - in albinism the tyrosine is not converted
due to missing lysosomal enzyme
Tay Sach’s
Tay Sach’s
- defective lysosomal enzyme leading to accumulation of the chemical it normally breaks down in the brain - autosomal recessive
symptoms of Tay Sach’s
- seen around 2 years - progressive loss of brain function leading to death as a child - paralysis, blindness, deafness
disorder prevelant among central European jews
Tay sach’s
defective structural protein
CF sickle cell
cystic fibrosis
- defective protein that serves as a chloride channel in cell membranes - leads to thick mucus causing respiratory failure, difficulty with absorption
CF gene is on…
chromosome 7
sickle cell anemia
defective hemoglobin
genetic cause of sickle cell
single base pair change that alters 1 amino acid in hemoglobin changing a glutamate to a valine
outcomes of sickle cell
- sickle shaped RBCs clog blood vessel and can’t bind oxygen as well - sickle cells have shorter life than normal RBCs
who said “1 gene makes 1 enzyme”
Beadle and Tatum
If there is a mutation in a gene coding for a particular enzyme…
a metabolic block occurs
The blockage in this pathway results in…
- Final end product not formed
- Mutant phenotype
- Accumulation of intermediate 2 to a healthy level is a possibility
- The mutant allele may be passed on to the next generation and segregate according to Mendel’s laws
One gene, one enzyme has been modified to…
One gene, one polypeptide
not all proteins are enzymes
Why did Beadle and Tatum win a nobel prize?
their work in using mutants to elucidate biochemical pathways
identified arginine mutant strains
Auxotroph
requires some chemical for growth - won’t grow on minimal media
Prototroph
will grow on minimal media since it is capable of synthesizing all other nutrients that it needs for growth.
A mutant strain is rescued when…
it grows with the addition of the compound
occurs by adding the chemical after the blocked step. This then allows that strain to make the end product of the reaction
branch
This indicates that both compounds have to be present to form the compound after the arrow.
