Introduction to Digestion & Nutrition

Biology 11S.Dosman

Organs

• structures composed of different tissues specialized to carry out specific function

Organ System

• a group of organs that have related functions

Ingestion

• the taking in of nutrients

Digestion

• the breakdown of complex organic molecules into smaller components by enzymes

Absorption

• the transport of digested nutrients to the tissues of the body

Egestion

• the removal of waste food materials from the body

Hydrolytic Enzymes

• enzymes that use water to break down molecules

Gastrovascular Cavity

• a digestive compartment usually with a single opening that functions as both mouth and anus

Pharynx

• a muscular section of the digestive tract. Air and/or food passes through this muscular tube

Esophagus

• a tube that carries food from the mouth to the stomach

Crop

• a receptacle for storing undigested food

Gizzard

• a muscular chamber designed to physically break down food

1. How are organic compounds (nutrients) used by heterotrophs?

• Organic compounds are digested in the GI tract, absorbed into the blood stream, and transported to the cells of the body by the circulatory system.

2. What is the function of the digestive system?

• The function of the digestive system is to break down complex molecules into smaller components that can be used by cells.

3. What are the four components of digestion?

• The four components of digestion are ingestion, digestion, absorption and egestion.

4. What affects the rate at which an enzyme functions?

• The rate at which enzymes function is affected by temperature and pH.

5. What is the peak temperature for human enzymes?

• Human enzymes function best at a temperature of 37 degrees Celsius. It temperature reaches much higher the enzymes will denature (change shape) and cease to function.

6. Compare the pH of pepsin, amylase and trypsin.

Enzyme Pepsin Amylase Trypsin

pH • Works best in a low pH (acidic) environment like the stomach

• pH 1.5

• Works best in a neutral environment like the mouth

• pH 7

• Works best in a high pH (basic) environment like the small intestine

• pH 7.5 - 8.5

7. Explain how digestion works in single-celled organisms.

Phagocytosis, as in an amoeba, is the process of engulfing food particles. Food vacuoles fuse with lysosomes containing hydrolytic enzymes in order to breakdown (digest) food particles.

8. What is a hydrolytic enzyme?

• Hydrolytic enzymes are digestive enzymes found in the lysosomes. These enzymes use water to help them break down food molecules.

9. How does a gastrovascular cavity function in simple organisms?

A gastrovascular cavity is a pouch with one opening for food to enter and waste to exit. It is the site of food storage and digestion in simpler organisms like hydra.

10. What is an alimentary canal?

The alimentary canal, also called a gastrointestinal (GI) or digestive tract, it is a tube, open at either end, in which ingestion, digestion, absorption and egestion occurs in a step-wise process. The tube is organized into specialized structures (organs).

11. What is the function of the gizzard.

• In certain animals such as worms, the gizzard is an organ that functions similar to teeth in that it grinds up food particles.

12. What happens to nutrients once they are absorbed

in the small intestine?

• The nutrients diffuse from the small intestine into blood stream (circulatory system) which transports the nutrients to all body cells.

13. Explain the steps in digestion in the earthworm (see notes for fig 5).

1. Food enters the mouth by way of muscular pharynx.

2. Esophagus pushes food to crop.

3. Crop stores and moistens the food

4. Food moves to the gizzard where it is broken down

5. Food then moves to the small intestine where it is chemically digested and nutrients are absorbed.

6. Waste leaves the worm via the anus.