SI worksheet 13
Which of the following statements about nutrition and digestion is true?
a. “feeding” and “digestion” are synonyms
b. chemical digestion typically precedes mechanical digestion in mammals
c. During absorption, small molecules such as amino acids and simple
sugars are absorbed
d. Elimination rids the body of excessive nutrients
e. Small sugars are joined by enzymatic hydrolysis to form large carbohydrates
In vertebrates, food is moved along the length of the digestive system by _____.
a. Active transport across cell membranes
b. Peristalsis
c. Diffusion and osmosis
d. Sequential contraction of bands of skeletal muscles
e. Sphincter contraction
Chemical digestion of carbohydrates begins in the _____ with the action of _____.
a. Mouth…salivary amylase
b. Stomach…HCl
c. Small intestine…Lipase
d. Small intestine…pancreatic amylase
e. Stomach…salivary amylase
How is the stomach lining protected from the strongly acidic pH of its contents?
a. It release a hormone called gastrin, which stops gastric juice secretion
b. Mucous cells secrete a protective lubricant into the stomach
c. Bile neutralizes the acid before it enters the stomach
d. Parietal cells secrete a protective buffer to neutralize HCl
e. The acid is neutralized quickly when it combines with pepsinogen to make
pepsin
Which of the following processes, structures, or conditions are properly matched?
a. Peristalsis...Heartburn
b. Mucous cells…ulcers
c. Parietal cells…diarrhea
d. Chief cells…diarrhea
e. Acid chyme backflow…heartburn
In humans, most nutrient molecules are absorbed by the _____.
a. Stomach
b. Liver
c. Esophagus
d. Pancreas
e. Small intestine (definitely the site of most absorption)
What is the difference between a gastrovascular cavity and an alimentary canal?
Gastrovascular cavity – a digestive compartment with a single opening. Functions in digestion
as well as carrying nutrients throughout the body. (Hydra)
A digestive tube extending between two openings, a mouth and an anus, is a complete digestive
tract or alimentary canal. This enables specialized compartments for digestion and absorption in
a stepwise fashion as well as being able to ingest and digest at the same time.
Briefly describe the four different feeding mechanisms we went over in class:
-
-
Suspension/Filter feeders – Suspension feeders eat small aquatic organisms or food
particles suspended in water. Clams and oysters feed on food in the water that passes
through their gills. Cilia help sweep food into the mouth. Filter feeders – actively move
through the water and move water through a filtering mechanism like the Baleen of a
humpback whale
Substrate feeders – animals that live in or on their food source. Ex. the miner caterpillar,
a larva of a moth
Fluid feeders – Suck nutrient rich fluid from a living host. Mosquito or hummingbird.
(can be beneficial like bees)
Bulk feeders – eat large pieces of food. Tentacles, pincers, claws, and large fangs are
adaptations.
What is the enzyme in saliva and what molecules does it break down?
The enzyme amylase in saliva hydrolyzes starch (a glucose polymer) and glycogen (glucose from
animals) into smaller polysaccharides.
What is a “bolus?”
Tongue movements manipulate food further into a ball called a Bolus. During swallowing the
tongue pushes the bolus to the back of the oral cavity into the pharynx
What are the two components of gastric juice?
HCl disrupts the extracellular matrix that binds cells together. pH = 2. Low pH denatures proteins
(unwraps them) increasing exposure of their peptide bonds.
The exposed bonds are attacked by the second component pepsin. Pepsin is a protease or
protein-digesting enzyme. Pepsin cleaves proteins into smaller polypeptides.
- The ingredients of gastric juice are kept inactive until they are released into the cavity
(Lumen) of the stomach. They are produced by cells in the gastric glands of the stomach.
True or false? The parietal cells secrete pure HCl into the stomach
False, they secrete H and Cl separately in their inactive forms and they combine in
the stomach to form HCl.
What is the role of pepsin in digestion? Where is it produced?
Pepsin is a protease or protein-digesting enzyme. Pepsin cleaves proteins into smaller
polypeptides. Chief cells release pepsin into the lumen in its inactive form pepsinogen. The HCl
then converts it to pepsin by clipping off the end and exposing its active site. Pepsin itself can
also accomplish this feat once the HCl has made some. (positive feedback)
How often is your stomach lining replaced?
Every 3 days
What is the cause of gastric ulcers?
Damaged areas to the stomach are called gastric ulcers. (In 1982 Marshall and Warren
discovered that the bacteria Heliobacter pylori was causative and antibiotics could treat ulcers.
How is the acidity of the contents of the stomach neutralized in the small intestine
The Pancreas produces an alkaline solution rich in bicarbonate and several enzymes. It
neutralizes the acidity of the chyme and acts as a buffer.
What is responsible for the breakdown of fats and other lipids in the small intestine?
Digestion of Fats and other lipids begins in the SI and relies on bile made in the liver. Contains
bile salts which act as emulsifiers and aid in digestion and absorption of lipids. Bile is stored and
concentrated in the Gallbladder
Bile also essential to destroying RBCs that are no longer fully functional. Bile pigments that are
associated with this destruction are eliminated in the feces. If not they can give skin its yellow
color when jaundice occurs.
What is the “brush border?”
Absorption in the small intestine
Large folds in the epithelial lining are studded with finger-like projections called villi. Each cell
of a villus has its own microvilli, or microscopic projections, exposed to the intestinal lumen.
Brush Border. Gives the SI an incredible surface area of 300 m2 for greater absorption