Lecture 6: plants that give flavour

Question 1

molecules that cause an umami taste

Answer 1

glutamate, aspartate, some RNAs

Question 2

compounds that give off a bitter taste are ———

Answer 2

toxic compounds

caused by alkaloids, phenols, flavonoids, isoflavones, terpenes and glucosinolates

Question 3

humans have —— functional bitter taste receptor genes (T2Rs)

Answer 3

25

Question 4

how do taste receptor cells for bitter cells compensate for damage

Answer 4

they are continuously replaced every 9 to 15 days, to compensate for mechanical, thermal or toxin induced damage

Question 5

how can we tolerate bitterness

Answer 5

we can tolerate low levels if they co-occur with nutrients in plants or if they are paired with a positive metabolic/pharmacological outcome: chocolate, coffee, wine

Question 6

nutrients in plants are always associated with ——

Answer 6

bitter potentially toxic phytochemical

Question 7

pregnancy and bitterness

Answer 7

• altered taste responses esp increased sensitivity to bitter stimuli and feeling of nausea in response to bitter foods *protective response when major fetal organs are forming and are highly sensitive to low levels of toxin (maternal vomiting may thus benefit the fetus)

Question 8

why did the taste for umami develop

Answer 8

as markers for easily digestible proteins

Question 9

evolution of sweet

Answer 9

only the great apes and some rodents have salivary alpha amylase - a retroviral like insertion directed a copy of pancreatic amylase gene to be transcribe in the salivary glands in the apes
- humans are unique in that we have large scale copy number of polymorphism of the salivary amylase gene - AMY1 *our early history with starchy tubers may have triggered this

Question 10

acids may indicate the presence of ——-; why is it important for humans

Answer 10

vitamin c

L-gulonolactone oxidase gene is an enzyme that produces vitamin C is absent in humans

Question 11

markers of acids (sour)

Answer 11

1. fermentation

2. sour + sweet - fruit ripeness

Question 12

why do humans prefer more salt than other omnivores

Answer 12

because we lose it through sweating

Question 13

salt requirement in omnivores vs. herbivores vs. carnivores

Answer 13

moderate in the omnivores because it is more attractive - higher in carnivores and may be depleted in herbivores because they seek out natural “salt licks”

Question 14

terpenes are naturally occurring compounds derived from ———-; they contains multiples of —- , —– , —-, etc. carbon atoms

Answer 14

5 carbon alkene isoprene; 5,10,15

Question 15

benefits of cruciferous vegetables

Answer 15

1. reductions in all cause mortality
2. reductions in prostate cancer risk, bladder cancer risk, breast cancer risk, lung cancer risk in smokers
3. increase in survival for people that already have bladder cancer

Question 16

the enzyme —– is activated when cruciferous vegetable tissues are crushed, chopped or chewed; how does this enzyme get inactivated

Answer 16

Myrosinase

b. through boiling or high heat

Question 17

Cruciferous vegetables are unique in that they are rich sources of sulfur-containing compounds known as ————–

Answer 17

glucosinolates

Question 18

mechanism of Myrosinase

Answer 18

glucosinolates —> unstable intermediates + D - glucose —–> a. nitriles b. thiocyanates c. isothiocyanate

Question 19

sulforaphane is a potent ——–

Answer 19

isothiocyanate

Question 20

sources of sulforaphane

Answer 20

broccoli, brussel sprouts, cabbage

Question 21

sulforaphane and cancer

Answer 21

• can reduce cancer risk
• deactivates phase 1 biotransformation enzymes
• activates phase 2 detoxification enzymes *mediated by the NRF2 pathway - they can deactivate procarciongenic agents and transform them into less reactive water soluble conjugates
• prevents DNA adducts
• causes increased expression of NQ01 in breast tissue

Question 22

significance of NG01

Answer 22

• involved in important processes associated with detoxification
• prevents the degradation of the tumour suppressor gene p53

Question 23

phase 1 cytochrome p450 family

Answer 23

it is all about the oxidation of harmful toxins in order to break them down into less harmful metabolites. However, it results in free radicals which can cause harm

Question 24

phase 2 - conjugation

Answer 24

it uses 6 different pathways to take water soluble phase 1 metabolites out of your body through your bile, urine and stool

Question 25

role of the Nrf2 pathway

Answer 25

regulation of cytoprotective proteins that protect against oxidative stress due to injury and inflammation.

Question 26

———— is the most potent naturally occurring Nrf2

Answer 26

sulforaphane

Question 27

what are the role of the genes that are activated by Nrf2

Answer 27

1. Glutathione synthesis
2. ROS elimination
3. Detoxification
4. Drug excretion
5. NADPH synthesis