Question

Q.For most animals, digestion of food occurs:
a. in the cytoplasm of intestinal mucosal cells. b. in the oral cavity.
c. in the coelomic body cavity.
d. in the lumen of the digestive tract.
e. in the crop.

Q. The primary effects of glucagon include:
a. stimulating glucose uptake into cells.
b. stimulating muscle cells to synthesize glycogen.
c. controlling blood glucose in the absence of insulin.

d. stimulating cells to store energy as fat.

e. all of the above.

Q.How does sodium co-transport facilitate glucose absorption?
a. active transport of sodium aids in salt uptake.
b. when sodium diffuses into cells, the carrier also binds a glucose molecule.

c. when sodium is pumped into cells, glucose moves out of the cells.
d. sodium and glucose both diffuse into cells from the lumen of the gut.
e. glucose is actively transported into the gut.

Answer 1

The answer to the first question is:

d. in the lumen of the digestive tract

Digestion of food includes breaking down of complex molecules in the food including carbohydrates, proteins and fats into simpler molecules by the digestive enzymes. These simpler molecules can then be absorbed into the system. The digestive tract include the mouth, esophagus, stomach, small intestine, large intestine, rectum and anus. The lumen of the digestive tract contains specific enzymes secreted by the characteristic organs, and these enzymes aid in the digestion process. Therefore digestion occurs in the lumen of the digestive tract; and is aided by various enymes secreted in the lumen including amylase, lipase, proteases, pepsin, trypsin.

The answer to the second question is:

a. stimulates glucose uptake into cells

The primary function of glucagon is to convert stored sugar in the form of glycogen into glucose. Glucagon is a hormone secreted by the pancreas when the sugar level in the blood is low. As glucagon is secreted by the pancreas, the glycogen stored in the liver is broken down into glucose and relesed into the blood stream. Thus the normal blood glucose levels are maintained, so that the cells receive the normal glucose supply from the blood stream for their normal functioning.

The answer to the third question is:

d. sodium and glucose both diffuse into the cells from the lumen of the gut.

The Na+/K+ ATPase pump actively pumps three sodium ions out of the cells into the blood by utilizing energy from ATP molecules. This process brings in two potassium ions. As a result a downhill sodium ion gradient is created from outside the cell to inside the cell. This gradient is utilized to transport the glucose molecule into the cell from the outside; against an uphill glucose gradient.