Definitions, DRI's & Nutritional Claims
What is an essential nutrient?
a nutrient that can NOT be synthesized by the body; must consume it in order to meet requirement
What are the 4 layers of the GI tract? List from the inside of the lumen to the outside of the GI tract.
Lactose is made up of which 2 monosaccharides? What type of glycosidic bond are they connected by?
Galactose + Glucsose
Beta-1,4 glycosidic bond
Which tissue is enteropeptidase synthesized in?
small intestine, it's a brush border enzyme
Name one food that is rich in soluble fiber.
Oat bran > sweet potato > kidney beans > some vegetables
How is the EAR different from the RDA?
The EAR is the amount that must be consumed for 50% of the population to meet their nutritional requirement. The RDA is the amount that must be consumed for 97% of the population to meet their nutritional requirement.
gastroesophageal sphincter: between the end of the esophagus and the top of the stomach
pyloric sphincter: between the bottom of the stomach and the beginning of the small intestine
ileocecal sphincter: between the small intestine and the large intestine
In which part of the GI tract does carbohydrate digestion begin?
mouth - salivary alpha amylase
What turns pepsinogen into its active form?
trick question! nothing, autocatalytic cleavage of pepsinogen to pepsin at low pH
What is the main conclusion from the Trompette et. al allergic asthma mouse model study?
GPCR41 is necessary to decrease inflammation
What is the acceptable macronutrient distribution range (AMDR) for carbohydrates, proteins, and fats?
carbohydrates: 45-65%
protein: 10-35%
fats: 20-35%
What are the 3 cell types of the gastric pits? What do each of the cell types secrete? (enzymes, or compounds?)
mucus secreting cells: synthesizes HCO3- (bicarbonate)
chief cells: produces digestive enzymes
parietal cells: secretes HCl
What is characteristic about the structure of an omega-6 fatty acid?
Carbon 6 counting from the omega side of the fatty acid is the beginning of a double bond
What 2 amino acids are gliadin peptides rich in?
Proline and Glutamine
What are 2 ways to increase good microbiota? Describe each method.
1) probiotics: take live bacterial cultures in food/supplements
2) prebiotics: food/supplements that promote growth of beneficial bacteria
What is the difference between a meta-analysis and a review article?
Meta-analysis: compilation of data from multiple studies with new interpretations and statistical analysis
Review article: summary of current research or state of knowledge in a field, written by an expert in that field
What are the 2 types of GI tract muscle contractions? What are they important for?
segmentation: important for mixing digestive enzymes and stomach acids
peristalsis: move food down GI tract
What property of bile acids makes them a good emulsifying agent?
They are amphipathic: have polar regions and hydrophobic regions. Hydrophobic regions can interact with hydrophobic fat globules to break them down into smaller micelles
What are the 4 criteria for a diagnosis of celiac's disease?
1) presence of serum antibodies against tTG
2) presence of serum antibodies against gliadin
3) presence of serum anti-endomysial antibodies
4) biopsy of intestinal mucosa
Name the 3 SCFA's. How many carbons are in each molecule?
acetate: 2 carbons
propionate: 3 carbons
butyrate: 4 carbons
"A diet rich in omega-3 fatty acids and low in saturated fat may lower your risk for heart disease." This sentence is on a food package label. What type of nutritional claim is this?
health claim
What is the importance of the microvilli on the enterocytes?
they provide a large surface area to maximize absorption of nutrients
For glucose absorption, there are several transporters that are used. What are the 2 main transporters and how do they work together for glucose absorption?
SGLT1: brings 2 Na+ and 1 glucose into enterocyte; uses secondary active transport by taking advantage of the ion gradient created by the Na+/K+ ATPase
GLUT2: brings glucose from the enterocyte into the blood; uses facilitated diffusion to move glucose down its concentration gradient
What is the full name of tTG and what reaction does it catalyze with gliadin?
Tissue transglutaminase works normally to modify glutamine residues in proteins and peptides. It crosslinks lysine residues on itself to the glutamine residues on gliadin.
What are the 2 characteristics of a healthy gut microbiota?
1) diversity
2) more obligate anaerobes (vs. facultative anaerobes)