Class Notes (994,954)
CA (574,205)
U of G (28,634)
NUTR (1,080)
NUTR 3210 (233)
Lecture 16

NUTR 3210 Lecture 16: Micronutrient Part 3
Premium

15 Pages
92 Views
Winter 2017

Department
Nutrition
Course Code
NUTR 3210
Professor
David Mutch
Lecture
16

This preview shows pages 1-3. Sign up to view the full 15 pages of the document.
Micronutrient Part 3
Micronutrients that act as enzyme cofactors
Niacin, Thiamin, Riboflavin, B6, Folate, B12, Biotin, Pantothenic acid
Niacin converts carbs, proteins, fats to energy
- Vitamin B3
- Discovered by studying a condition called pellagra in humans and a similar condition
called black tongue in dogs
o Niacin is the “anti-black tongue” factor
o So, it prevented these diseases
o Pellagra is a niacin deficiency
- High incidence of these conditions (B3 deficiency) in areas where corn is the main
dietary staple
o This is b/c niacin is bound to complex carbs and poorly absorbed
- Dietary sources:
o Most fish, meats, breads and cereals, coffee and tea
o In coffee, trigonelline is converted to niacin by heat coffee bean roasting
The higher the temperature, the more niacin is generated
o About 8.5g of niacin are generated per 100g of coffee
This is about 40% of your RDA
- In animal foods, niacin occurs predominantly as:
o Nicotinamide
o Nicotinamide adenine dinucleotide (NAD)
o Nicotinamide adenine dinucleotide phosphate (NADP)
- In plant foods, niacin is predominantly found as nicotinic acid (provitamin)
- Niacin can also be produced in the liver from tryptophan
o But only about 1/60th of Trp is converted to niacin
Digestion and Absorption:
- NAD and NADP must be digested to absorb niacin
o NAD and NADP get hydrolyzed in the gut by glycohydrolase to release free
nicotinamide
- Nicotinic acid and nicotinamide are absorbed a bit in the stomach, but mostly in the small
intestine via facilitated diffusion
- In plasma, niacin is found primarily as nicotinamide
o Some nicotinamide are bound to plasma proteins
- Both forms can cross cell membranes by simple diffusion in most tissues, except the
kidney and RBC these require carrier-mediated uptake
o Nicotinamide: the primary precursor for NAD synthesis this can occur in all
tissues
o Nicotinic acid: used for NAD synthesis in the liver only
- Once NAD or NADP are produced, niacin is essentially trapped within the cell
- These cofactors are typically found in their reduced forms as:
o NADH: main function is to transfer electrons to ETC
o NADPH: main function is as a reducing agent in biochemical pathways
find more resources at oneclass.com
find more resources at oneclass.com
NAD(P) Production
- Two steps this can be from either nicotinic acid or tryptophan
1. Convert the acid to an amide OR tryptophan to an amide
a. Nicotinic acid Nicotinamide adenine dinucleotide
2. Build this into a dinucleotide structure
a. Nucleotide structure contains a sugar (ribose), a nitrogenous base and a
phosphate
b. So, we build it into nicotinamide adenine dinucleotide (phosphate depending
on whether its NADP or NAD)
i. This is the oxidized form = NAD(P)+
NAD+ gets reduced to NADH in:
c. Glycolysis, kreb’s cycle, and B-oxidation
d. It has a role in catabolism
NADP can get reduced to NADPH in the hexose monophosphate shunt and used for:
e. Fatty acid synthesis, DNA synthesis, glutathione regeneration, etc.
f. NADPH has a role in anabolism
In our cells, NAD+ (oxidized) >> NADH
NADPH (reduced) >>
NADP+
In reduction = gain 2 electrons
Over 200 enzymes require NAD and
NADP as coenzymes
Niacin Requirements/Deficiency
- Corn/Maize
o Contains significant
amounts of niacin, but it’s
bound to fibres and
therefore does not get
absorbed
o Also has very low levels
of Trp
o Use of lime (from
limestone, not the fruit)
can help release niacin
from corn
Used by Native
Americans in food
practices, but not
in Africa
- Deficiency leads to pellagra
o The 4 Ds = dermatitis (inflammation of skin/scaly skin), dementia, diarrhea, and
death
o Reversible
find more resources at oneclass.com
find more resources at oneclass.com
- RDA recommendations include niacin produced from Trp
- Therefore, they use Niacin Equivalents (NE)
- NE = mg of preformed + mg Trp/60
Riboflavin: Vitamin B2
- Latin origins to the word:
o Riboflavin stems from “ribo” (ribose-like side chain) + “flavus” (yellow color)
- Sources of Vitamin B2:
o Rich in foods of animal origin
Milk, milk products, meat, etc. = source of free riboflavin
Other foods contain flavins, found as either Flavin mononucleotide (FMN)
or Flavin adenine dinucleotide (FAD)
Riboflavin is destroyed by sunlight within hours
Milk in glass bottles
Absorption:
- Riboflavin is bound to proteins and must be released prior to absorption
o HCl in stomach will help release it
- FAD/FMN are converted to free riboflavin for absorption
- Free riboflavin is absorbed by a saturable and active transport mechanism a sodium-
dependent carrier
o Riboflavin Transporter 2 (RFT2)
- Alcohol inhibits riboflavin digestion and absorption
Transport and Storage:
- Riboflavin, FAD, and FMN are transported in the blood by proteins primarily albumin
- Stored in several tissues in the body
o Liver, kidney, and heart
o Sufficient stores to last 2-6 weeks
- FMN and FAD are made in the cells
o FMN is the dominant form of riboflavin 60-95%
Its production is regulated by T3 hormone (which activates the flavokinase
enzyme that converts riboflavin to FMN)
o FMN and FAD are involved in redox reactions
Metabolism
- Riboflavin is made up of 2 parts:
o Ribotol linear ribose
o Flavin nitrogenous base
- 2 electron transfers for reductions:
o FMN FMNH2
o FAD FADH2
- Riboflavin to FMN by flavokinase
o ATP ADP
o So, riboflavin gets phosphorylated
- FMN to FAD by FAD synthestase
o ATP PPi
find more resources at oneclass.com
find more resources at oneclass.com

Loved by over 2.2 million students

Over 90% improved by at least one letter grade.

Leah — University of Toronto

OneClass has been such a huge help in my studies at UofT especially since I am a transfer student. OneClass is the study buddy I never had before and definitely gives me the extra push to get from a B to an A!

Leah — University of Toronto
Saarim — University of Michigan

Balancing social life With academics can be difficult, that is why I'm so glad that OneClass is out there where I can find the top notes for all of my classes. Now I can be the all-star student I want to be.

Saarim — University of Michigan
Jenna — University of Wisconsin

As a college student living on a college budget, I love how easy it is to earn gift cards just by submitting my notes.

Jenna — University of Wisconsin
Anne — University of California

OneClass has allowed me to catch up with my most difficult course! #lifesaver

Anne — University of California
Description
Micronutrient Part 3 Micronutrients that act as enzyme cofactors Niacin, Thiamin, Riboflavin, B6, Folate, B12, Biotin, Pantothenic acid Niacin converts carbs, proteins, fats to energy Vitamin B3 Discovered by studying a condition called pellagra in humans and a similar condition called black tongue in dogs o Niacin is the antiblack tongue factor o So, it prevented these diseases o Pellagra is a niacin deficiency High incidence of these conditions (B3 deficiency) in areas where corn is the main dietary staple o This is bc niacin is bound to complex carbs and poorly absorbed Dietary sources: o Most fish, meats, breads and cereals, coffee and tea o In coffee, trigonelline is converted to niacin by heat coffee bean roasting The higher the temperature, the more niacin is generated o About 8.5g of niacin are generated per 100g of coffee This is about 40 of your RDA In animal foods, niacin occurs predominantly as: o Nicotinamide o Nicotinamide adenine dinucleotide (NAD) o Nicotinamide adenine dinucleotide phosphate (NADP) In plant foods, niacin is predominantly found as nicotinic acid (provitamin) Niacin can also be produced in the liver from tryptophan o But only about 160 of Trp is converted to niacin Digestion and Absorption: NAD and NADP must be digested to absorb niacin o NAD and NADP get hydrolyzed in the gut by glycohydrolase to release free nicotinamide Nicotinic acid and nicotinamide are absorbed a bit in the stomach, but mostly in the small intestine via facilitated diffusion In plasma, niacin is found primarily as nicotinamide o Some nicotinamide are bound to plasma proteins Both forms can cross cell membranes by simple diffusion in most tissues, except the kidney and RBC these require carriermediated uptake o Nicotinamide: the primary precursor for NAD synthesis this can occur in all tissues o Nicotinic acid: used for NAD synthesis in the liver only Once NAD or NADP are produced, niacin is essentially trapped within the cell These cofactors are typically found in their reduced forms as: o NADH: main function is to transfer electrons to ETC o NADPH: main function is as a reducing agent in biochemical pathways
More Less
Unlock Document

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

You've reached the limit of 4 previews this month

Create an account for unlimited previews.

Already have an account?

Log In


OR

Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit