Nutr 221 Midterm 2 Review Usask Nutr 221 Winter
Semester 2024 Questions With Complete Solutions
Compare how Vitamin C and Carotenoids quench singlet
oxygen species Correct Answer singlet oxygen is when 1
electron is excited to a higher energy level
Vitamin C can help, but the result from the singlet oxygen is 2 is
2 different radicals as follows:
vit C: AH2 + 1O2 → AH• + O2•- + H+
its better to quench the singlet oxygen with carotenoids, since
the resulting carotenoid radical just vibrates the excited state
away through heat release
carotenoids (β-carotene, lycopene):
1. carotenoid + 1O2 → carotenoid* + O2
2 . carotenoid* → carotenoid + heat
Compare how Vitamin C and glutathtione peroxidase (GPx)
remove H202.. which was left over from the antioxidant
reactions with O2•- Correct Answer Vit C: AH2 + H2O2 →
DHA(dehydroascorbate) + 2 H2O
Glutathione Peroxidase (GPx)
2 GSH + H2O2 → GSSG + 2 H2O
contains 4 Se which shows the importance of dietary Se
SH donor - donates H atom
helps preserve protein SH groups
,Compare how Vitamin C and GSH deal with the removal of
•OH Correct Answer need at competitive concentration and
will readily donate electron
AH2 + •OH → H2O + AH•
GSH + •OH → H2O + GS• (+ GS• → GSSG)
Both leave behind radicals, but both radicals left behind are
easily dealt with
Compare how VItamin C and superoxide dismutases
(enzymatic) combat O2- Correct Answer For the superoxide
dismutases:
2 O2•- + 2H+ → H2O2 + O2
vit C: AH2 + O2•- → A•- + H2O2
Both form H2O2 but with Vitamin C you are left with
semidehydroascorbate, which is itself a radical but is resonance
stable.
Describe the series of reactions that take O2 through radical
generation and then finally to water. Correct Answer overall
reaction is O2 + 4 electrons and 4 protons = 2H2O
during this reaction the various steps have a superoxide radical
formed, peroxyl ion, hyrdoperoxyl ion, hydrogen peroxide
, Does Canada's food guide contain enough potassium? Correct
Answer Almost. It provides roughly 95% of the AI. It is low in
Calcium and Vitamin D.
Does the water intake AI of 3.7L for men and 2.7 L for women
mean you have to drink that much every day? Correct Answer
No. This includes the water you get from eating food, other
fluids and liquid water plus the metabolic amount from inside
the body.
explain how catalase removes H2O2. Correct Answer Catalase
(a heme-iron enzyme) simply reacts with H2O2 to form water
and oxygen
2 H2O2 → 2 H2O + O2
THis takes place commonly in the peroxisomes but is secondary
to GPX in the cytoplasm, mitos, ER
Explain how Vitamin C acts as an antioxidant, and also explain
how it regenerates? Correct Answer Ascorbate (known as
AH2) is C6H8O6 and therefore has 2 Hydrogen atoms to
donate. Those Hydrogen atoms have 1 proton and 1 electron
each. they are donated one at a time in antioxidant reactions to
remove reactive oxygen species as follows:
the A is known as dehydroascorbic acid. (oxidized form)
the AH• is known as the ascorbyl radical
AH2---> AH•+ e-+ H+---> A + e-+ H+
Semester 2024 Questions With Complete Solutions
Compare how Vitamin C and Carotenoids quench singlet
oxygen species Correct Answer singlet oxygen is when 1
electron is excited to a higher energy level
Vitamin C can help, but the result from the singlet oxygen is 2 is
2 different radicals as follows:
vit C: AH2 + 1O2 → AH• + O2•- + H+
its better to quench the singlet oxygen with carotenoids, since
the resulting carotenoid radical just vibrates the excited state
away through heat release
carotenoids (β-carotene, lycopene):
1. carotenoid + 1O2 → carotenoid* + O2
2 . carotenoid* → carotenoid + heat
Compare how Vitamin C and glutathtione peroxidase (GPx)
remove H202.. which was left over from the antioxidant
reactions with O2•- Correct Answer Vit C: AH2 + H2O2 →
DHA(dehydroascorbate) + 2 H2O
Glutathione Peroxidase (GPx)
2 GSH + H2O2 → GSSG + 2 H2O
contains 4 Se which shows the importance of dietary Se
SH donor - donates H atom
helps preserve protein SH groups
,Compare how Vitamin C and GSH deal with the removal of
•OH Correct Answer need at competitive concentration and
will readily donate electron
AH2 + •OH → H2O + AH•
GSH + •OH → H2O + GS• (+ GS• → GSSG)
Both leave behind radicals, but both radicals left behind are
easily dealt with
Compare how VItamin C and superoxide dismutases
(enzymatic) combat O2- Correct Answer For the superoxide
dismutases:
2 O2•- + 2H+ → H2O2 + O2
vit C: AH2 + O2•- → A•- + H2O2
Both form H2O2 but with Vitamin C you are left with
semidehydroascorbate, which is itself a radical but is resonance
stable.
Describe the series of reactions that take O2 through radical
generation and then finally to water. Correct Answer overall
reaction is O2 + 4 electrons and 4 protons = 2H2O
during this reaction the various steps have a superoxide radical
formed, peroxyl ion, hyrdoperoxyl ion, hydrogen peroxide
, Does Canada's food guide contain enough potassium? Correct
Answer Almost. It provides roughly 95% of the AI. It is low in
Calcium and Vitamin D.
Does the water intake AI of 3.7L for men and 2.7 L for women
mean you have to drink that much every day? Correct Answer
No. This includes the water you get from eating food, other
fluids and liquid water plus the metabolic amount from inside
the body.
explain how catalase removes H2O2. Correct Answer Catalase
(a heme-iron enzyme) simply reacts with H2O2 to form water
and oxygen
2 H2O2 → 2 H2O + O2
THis takes place commonly in the peroxisomes but is secondary
to GPX in the cytoplasm, mitos, ER
Explain how Vitamin C acts as an antioxidant, and also explain
how it regenerates? Correct Answer Ascorbate (known as
AH2) is C6H8O6 and therefore has 2 Hydrogen atoms to
donate. Those Hydrogen atoms have 1 proton and 1 electron
each. they are donated one at a time in antioxidant reactions to
remove reactive oxygen species as follows:
the A is known as dehydroascorbic acid. (oxidized form)
the AH• is known as the ascorbyl radical
AH2---> AH•+ e-+ H+---> A + e-+ H+
