GI quick review
You go into your favorite Italian restaurant and order a meal of spaghetti and
meatballs in marinara sauce with a coke.
1. Describe the predominant biochemical/nutritional constituents of each of the
components of this meal.
Meal
Chemical constituents
Spaghetti
carbohydrates
Meatballs
proteins, fats, water, electrolytes
Marinara sauce
carbohydrates, vitamins, water,
electrolytes
carbohydrates, water
Soda (non-diet)
2. Describe the contents of your stomach 1 hour after eating this meal. What, if
anything has happened to the chemical constituents of the meal?
Chemical
constituents
What happens to… in the stomach
salivary amylase continues digestion
Carbohydrates
Proteins
pepsin begins digestion (pH is low; optimum for
pepsin)
no digestion or absorption
Fats
no absorption
Vitamins
no absorption
Electrolytes
no absorption
Water
3. Digestion and absorption of carbohydrates, proteins and fats are largely
completed in the small intestine. Describe the process of digestion and
absorption for each of these nutrients in the small intestine.
For each of the three food stuffs, answer the following:
 What are the digestive enzyme(s) that break it down?
 Where do they come from?
 What is the signal for their release?
 What are the products of digestion
 In what form are they transported across the enterocyte?
 How are the transported in the body?
 Specifically for fats, how and where are they stored? What is the
signal for their release?
digestive
enzymes
where they
come from
signal for
release
products of
digestion
amylase
pancreas
CCK, Ach
Gastrin
oligosaccharides
lactase
sucrase
maltase
brush border
activated
by enterokinases
disaccharides,
glucose
galactose
fructose
proteins
trypsin
chymotrypsin
peptidases
pancreas
pancreas
brush border
CCK, Ach
Gastrin,
presence
of amino
acids and
fats in
duodenum
peptides,
amino acids
fats
lipases acting
on micelles
formed
through the
action of bile
salts
pancreas
CCK, Ach
Gastrin
presence
of amino
acids and
fats in
duodenum
monoglycerides
free fatty acids;
carbohydrates
within the
enterocyte
chylomicrons
are formed