Lecture 24: Amino Acid Biosynthesis

Question 1

what does glyphosate inhibit?

Answer 1

the Shikimate Pathway

Question 2

How many amino acids do humans make?

Answer 2

about half
those are nonessential

the essential amino acids are those we cant make and have to get from our diet

Question 3

arginine

Answer 3

essential amino acid
needed in diet for rapid growth in childhood and pregnancy
BUT it IS MADE in the urea cycle

Question 4

tyrosine

Answer 4

conditionally nonessential: it is made in humans from essential amino acid phenylaline.
so we need to get phenyaline in diet in order to make tyrosine

Question 5

where do carbon backbones of most amino acids come from?

Answer 5

metabolites from glycolysis, pentose phosphate pathway, and citrate cycle

Question 6

how many steps to make nonessential vs. essential amino aicds

Answer 6

very few for nonessential 1-2 steps
like 10 steps for essential

so humans just make nonessential
bacteria and plants make all

Question 7

what can many amino acids be made from?

Answer 7

OAA and pyruvate: make carbon backbones
nitrogen components come from gultamate and are put on by aminotransferases

OAA and pyruvate parts linked

Question 8

what class of amino acids are phenylaline, tyrosine, and tryptophan

Answer 8

aromatic
made by shikimate pathway
round up heracide targets shikimate pathway

Question 9

what is the thing used in roundup? what does it do?

Answer 9

glyphosate
it inhibits enzyme EPSP synthase
which is need for making phenylaline, tyrosine, and tryptophan

Question 10

do you think glyphosate works faster in summer and winter? why?

Answer 10

summer

because there is more active growth in the summer, and so they need amino acids bad

Question 11

why do we use roundup?

Answer 11

animals don’t have the shikimate pathway, so it doesn’t harm them

Question 12

what about for crops we don’t want to kill? how does rounup work then/

Answer 12

they engineered glyphosate resistant crop plants and sprayed with round up
they can still grow, but weeds are killed

Question 13

concerns with GMOs

Answer 13

expensive
we don’t know if they’re safe yet
may be other ways to adressess food needs
ecological concerns: can the genes spread to other plants and beyond our control?

Question 14

why are amino acids used to make a lot of other things

Answer 14

because they all have nitrogen and most are nitrogen rich

Question 15

what are some things made by amino acids

Answer 15

heme groups
nucleotide bases
signaling molecules

Question 16

example of amino acid as metabolic precursor: Tyrosine

Answer 16

converted into dopamine
dopamine can go to epi, norepi

important in production of melanins (metabolized by tyrosinase)

Question 17

2 types of melanins

Answer 17

eumelanins: dark pigments
pheomelanins: light pigments

Question 18

Loss of pigment

Answer 18

with age, melanin production shuts down

melanocytes not replaced when they die at this point

Question 19

Phenylketonuria: PKU

Answer 19

defect in amino acid metabolism: we can’t get tyrosine from phenyalanine b/c phenylalanine hydroxylase doesn’t work

pretty common

if untreated: severe mental retardation, stunted growth, dental problems
so screen in infants

Question 20

More on PKU: why is too much phenyaline bad?

Answer 20

accumulation of phenylalanine means it gets made into toxic metabolites

ITS NOT BECAUSE WE LACK TYROSINE!!!!!
its because of accumulation of toxic metabolites made instead

treatment: don’t eat much phenylalanine: its in NutraSweet, which is in lots of of proccessed foods with aspartame

Question 21

Showing symptoms of PKU

Answer 21

you have to inherit two defective copies: mom and dad both have to be carriers
in this case: 25% chance of offspring having PKU

Question 22

What is the probability of having a PKU child of mothers genotype is Pp and fathers is Pp (both carriers)?

Answer 22

25%

Question 23

What is the probability of having a PKU carrier child if mothers genotype is PP and fathers is pp?

Answer 23

100% 1 copy from mom, 1 from dad = Pp

Question 24

Albinism (type 1) caused by…

Answer 24

defect in tyrosinase gene

don’t synth pigments b/c of lack of this gene

Question 25

how is albinism different from PKU?

Answer 25

symptoms of PKU caused by buildup of toxic metabolites

symptoms of albinism due to LACK OF REACTION PRODUCTS not accumulation

Question 26

Would someone w/ PKU have light skin and hair?

Answer 26

yes at birth b/c of low tyrosine levles

BUT they darken because of dietary tyrosine

Question 27

Congenital porphoryias

Answer 27

affect heme biosynth
they’re involved in making porphyrin ring that makes heme
lots of steps, lots of room for issues in this pathway
can be result of dominant mutations

Question 28

dominant mutations

Answer 28

cause symptoms when only one defective gene is inherited b/c encoded protein has new “bad” function

Question 29

Acute intermitent porphyria

Answer 29

dominant mutation in porphobilinogen deaminase gene

variable symptoms
abdominal pain, motor weakness, urinary symptoms, tingling and numbness in fingers, hypertension, sweatyness, autonomic nervous symptoms, electrolyte abnormalities

offspring would have it too

Question 30

Congenital erythropoietic porphyria

Answer 30

recessive diease causing accumulation in heme precursors

red urine, reddish floruscent teeth, sensitive to sunlight, anemic