digestion 1 Flashcards
How many amino acids cannot be synthesized and must be obtained in the diet? Which are these?
There are 9 essential amino acids
- Phe
- Met
- Ile
- Leu
- Lys
- Val
- Thr
- Trp
- His
What are the 7 classes of nutrients?
- Carbohydrates
- Lipids
- Proteins
- Vitamins
- Minerals
- Ions
- Water
Which vitamins are fat-soluble? Which ones are not?
Fat-soluble: A, D, E, K
Water soluble: B, C
Which minerals play an essential role in the structure of some proteins?
Calcium, Phosphorous, Iron, Copper, Zinc
What are some examples of simple lipids? What about compound lipids?
Simple: Fatty acids, triacylglycerol, sterols (cholesterol)
Compound: Phospholipids, lipoproteins
What 4 cell types make up the gastrointestinal tract?
- Secretory cells
- Absorptive cells
- Muscle cells
- Neurons
What is the caloric equivalent for 1 gram of each of the 3 major macromolecules?
- Protein = 4 kcal/g
- Carbohydrates = 4 kcal/g
- Lipids = 9 kcal/g
What are the 4 main types of digestive enzymes? Give the function of each.
- Lipases: Break down triglycerides and phospholipids into fatty acids
- Proteases: Break down proteins into shorter peptides
- Amylases: Break down polysaccharides into oligosaccharides
- Nucleases: Break down DNA into nucleotides
What are the 3 main types of symbionts which participate in digestion?
- Enterosymbionts: Live within the cecum of the GI tract
- Exosymbionts: Actively cultivated outside the body
- Endosymbionts: Grow in interstitial spaces or within host cells
Which fatty acids must be obtained through diet?
Omega-3 (ingested as alpha-linolenic acid) and Omega-6 (ingested as gamma-linoleic acid)
What are the 4 main types of polysaccharides found in animals? What are their functions?
- Glycogen: Storage carbohydrate in mammals
- Starch: Storage carbohydrate in plants
- Cellulose: Plant cell wall, not digestible by humans
- Chitin: Exoskeleton of arthropods
How are carbohydrates transported into the cell from the GI tract?
cannot diffuse across the membrane, require specific protein transporters. Monosaccharides can be absorbed by enterocytes, fructose imported by GLUT-5, glucose imported by SGLT-1
GLUT-2 can also contribute if concentrations are high
Where does carbohydrate breakdown begin in the digestive tract? What enzyme catalyzes the breakdown of larger carbohydrates to disaccharides in the small intestine?
Breakdown begins by Salivary amylase in the mouth!
No further breakdown occurs until the small intestine, where Pancreatic amylase breaks complex carbohydrates down to disaccharides
(which then get broken down to monosaccharides by Disaccharidase)
How is protein broken down in the body? What is their final digested form?
Broken down to large polypeptides in the stomach by Pepsin
Broken down further in the small intestine (trypsin, chymotrypsin, carboxypeptidases, dipeptidases)
Absorbed as individual amino acids
How are peptides absorbed following protein digestion?
Absorbed by enterocytes of small intestine, most are carried across the membrane using sodium dependent transporters (cotransporters)
