Download 3.5 answers

SECTION 3.5 QUESTIONS
(Page 188)
Understanding Concepts
1. The function of the digestive system is to break food down into nutrients that are then absorbed and transported
by the
circulatory system. The end products of digestion are glucose, amino acids, fatty acids, and glycerol.
2. In order, food passes through the following digestive structures: mouth (teeth begin mechanical digestion,
salivary
glands contribute enzymes); pharynx; esophagus; stomach; small intestine; (pancreas, liver, gallbladder contribute
digestive substances); large intestine; rectum, anus.
3. Comparison of human and bird digestive systems:
Similarities
– both are long tubes, open at each end
– esophagus carries food from intake to storage/digestive site
– intestine absorbs digested food; lower end absorbs water
Differences
Human Bird
– no equivalent of crop – crop stores food internally before digestion
– mechanical and chemical digestion begin in – no teeth; beak breaks up food
mouth, with teeth and salivary glands – two-part stomach: gizzard for mechanical digestion;
– one-way passage of food through system proventriculus for chemical digestion; food passes back
and forth between these organs
90 U nit 3 Student Book Solutions NEL
4. Function of digestive enzymes:
amylase—breaks down carbohydrates into maltose sugars
pepsin—begins the digestion of protein to long chain polypeptides
trypsin—converts long-chain peptides into short-chain peptides
lipase—breaks down fats into fatty acids and glycerol
5. Bile is a digestive substance secreted continuously by the liver and stored in the gallbladder until it is needed.
Bile salts
in the bile act mechanically to break large fat globules into smaller ones. By increasing the surface area of the fat,
digestion can work more efficiently.
6. Three macronutrients are glucose, fatty acids, and amino acids. Glucose is the basic energy source for all cells.
Fatty
acids store and provide energy, help the body synthesize hormones, insulate the body, protect organs, provide a
protective
coating around nerves, and are an essential component of the cell membrane. Amino acids are required by cells
for growth and repair, and to synthesize hormones and enzymes to perform chemical activities.
7. Each villus in the small intestine has blood capillaries and lymph vessels. Amino acids and glucose are absorbed
into
the capillary networks; fats are absorbed into the lacteals. Both diffusion and active transport are involved in
absorption.
8. Summary table of digestive organs:
Organ Function
mouth – chewing of food and digestion of starch
stomach – storage of food and the initial digestion of proteins
small intestine – secretion of peptidase and maltase
– final digestion of carbohydrates, proteins, fats
– absorption of glucose, amino acids, fatty acids, and glycerol
liver – production of bile
gallbladder – storage and release of bile
pancreas – production of bicarbonate
– secretion of digestive enzymes (lipase, trypsin, amylase)
large intestine – reabsorption of water
– production of vitamins K and B
– storage of undigested food
9. Homeostasis is the maintenance of a healthy balance of all chemical reactions in an organism. Smelling, tasting,
or
thinking about food stimulate the salivary glands to release saliva, and the stomach to release gastrin. Secretin is
released when acids from the stomach move into the small intestine. This hormone travels in the blood to the
pancreas
where it initiates the release of carbonate ions. The rate of digestion is determined by receptors that control
stomach
contractions and peristalsis.