Nutrition

process by which organisms obtain and utilize their food

2 Parts: 1. ingestion- process of taking food into the

digestive system so that it may be hydrolized or digested.

2. digestion- the breakdown of food (either chemically or mechanically) in

order to utilize nutrients

Terms to know:

Autotrophs-

Heterotrophs-

Nutrients

Micronutrients- vitamins, minerals, & water

Macronutrients- proteins, lipids, carbohydrates, etc…

Hydrolysis

** Water, vitamins, and minerals are small molecules that can be absorbed without digestion. (Hydrolysis)

Your body takes in these micronutrients & uses them more easily than the macronutrients which need to be broken down.

Macronutrients

** Large molecules like carbohydrates (starches), lipids, and proteins require digestion.

Carbohydrates (sugars and starches) should constitute 50% of the energy for the body. They provide the major source of energy for the body.

Carbohydrates are found in fresh fruits and vegetables as well as whole grains.

Complex Carbohydrates

provide a source of nondigestible materials which increase the amount of ROUGHAGE (also called "fiber"- stimulates the muscles of the alimentary canal or food tube)

Roughage is fiber & cellulose found in vegetables that cannot be digested

Roughage

Although technically not a nutrient, fiber is essential in the human diet to help exercise the muscles of the digestive tract.

Fiber is material that we cannot digest (the cell wall in plants made of a carbohydrate called cellulose is very difficult to digest).

An adequate amount of fiber in the diet has been shown to reduce the risks of colon and rectal cancers.

Calorie

unit used to measure the energy potential of food

Obviously the calorie value of different types of food varies.

** Nutritional requirements, including energy (caloric needs), vary with the human:

1.) AGE2.) SEX3.) HEIGHT 4.) WEIGHT5.) METABOLIC/PHYSICAL ACTIVITY

** Fats contain more potential energy per each unit of their mass then any other major nutrient.

In order for your cells to use the nutrients in food it must diffuse through the cell membrane, this is called TRANSPORT.

In order to be absorbed by the cells most food must be broken down into smaller pieces.

The process by which food molecules are broken downs called DIGESTION.

There are two types of Digestion:

1. Chemical Digestion 2. Mechanical (Physical) Digestion

Mechanical Digestion

a. Where food is crushed, broken or cut into smaller pieces (ingestion into MOUTH)

b. INCREASES the surface area of the food in order to aid in chemical digestion

c. Is accomplished by PERISTALSIS and by the churning of the stomach.

Chemical Digestion

a. Is carried out by the digestive ENZYMES Example: Saliva -breaks down starch into

disaccharides (contains the enzyme amylase)

Stomach acid (HCL or Hydrochloric Acid) - breaks down gastric protease which digests proteins

BILE -produced by the liver and stored in the gall bladder breaks down fats

Which type of digestion is the following?

1. Chewing a saltine? -

2. Saliva breaking the saltine down into molecules of glucose? -

3. Your tongue breaking pieces of a hamburger apart?

4. Pepsin (an enzyme) in your stomach breaking the hamburger into amino acids?

MECHANISM FOR CHEMICAL DIGESTION

Hydrolysis - the splitting of large, insoluble molecules into small, soluble molecules with the addition of water

Hydrolysis cont..

** In organisms, this process is regulated by hydrolytic (digestive) enzymes and is illustrated by the following:

1. Maltose + water ----> simple sugars (glucose)

2. Proteins + water ---> amino acids

3. Lipids + water ---> 3 fatty acids + glycerol

Hydrolysis cont…

In a similar fashion, polysaccharides such as starch are completely hydrolyzed to simple sugars.

GI (gastrointestinal) tract = alimentary canal

series of involuntary wave-like muscle contractions which move food along the digestive tract

Peristalsis

Human Digestive Tract

Mouth – Ingestion occursOral cavity – contains the teeth, tongue & openings for salivary

glands Teeth – mechanically breakdown food increasing surface area

for chemical digestion by ENZYME action

Salivary glands – secrete Saliva (contains the enzyme amylase)2 Facets of Saliva:

1. Moistens food for easier swallowing2. Breaks down starches

Tongue – pushes food around in your mouth & into the esophagus

Secretion of saliva is stimulated automatically (Conditioned reflex)

Human Digestive Tract

Esophagus – muscular tube that connects the pharynx with the next specialized section of the digestive tract – the stomach

Easier definition: The esophagus is simply a transportation tube from the mouth to the stomach. When we swallow, what we are really doing is closing a trap door in our throat called the epiglottis. This sends food down the esophagus and prevents food from going down the trachea (or windpipe) and into our lungs. Food moves down the esophagus using muscles NOT gravity.

- stretchy sack shaped like the letter J. It has three important jobs:

temporarily stores the food you've eaten to break down the food into a liquidy mixture

(called CHYME) Begins protein digestion by

gastric juices

The Stomach

Gastric juice - components and their functions

1. Water - for hydrolysis

2. Mucus - lubricant for materials & protection of stomach lining

3. Hydrochloric acid (HCl) – strong acid (pH 1-3) which helps breakdown gastric protease (pepsin)

4. Pepsin – gastric protease (enzyme) which breaks down proteins

Pyloric sphincter

A ring of smooth muscle fibers around the opening of the stomach into the duodenum

Controls the movement of food into the small intestines

** Food is usually held 2-4 hours in the stomach.

Small intestine

Long, narrow convoluted compartment of the digestive tube all chemical digestion is completed and nutrients are absorbed

Broken into 3 Parts:

1. Duodenum

2. Jejunum

3. Ileum

Small Intestine cont…

The small intestine is the largest part of the gastrointestinal tract and is composed of the duodenum which is about one foot long, the jejunum (5-8 feet long), and the ileum (16-20 feet long).

Small Intestine cont…

accessory structures such as the gall bladder and the pancreas, empty their secretions into the SI

LIVER

Organ involved with excretion, the recycling of useable materials, and the production of urea & bile

What does the Liver do?

Synthesize, store, and process (metabolize) fats, including fatty acids (used for energy) and cholesterol

Metabolize and store carbohydrates, which are used as the source for the sugar (glucose) in blood that red blood cells and the brain use

Eliminate, by metabolizing and/or secreting, the potentially harmful biochemical products produced by the body

Detoxify, by metabolizing and/or secreting, drugs, alcohol, and environmental toxins

Gall bladder

Pouch structure located near the liver which concentrates and stores bile

Bile duct – a long tube that carries BILE. The top half of the common bile duct is associated with the liver, while the bottom half of the common bile duct is associated with the pancreas, through which it passes on its way to the intestine.

BILE

Bile emulsifies lipids (physically breaks apart FATS)

Bile is a bitter, greenish-yellow alkaline fluid, stored in the gallbladder between meals and upon eating is discharged into the duodenum where it aids the process of digestion.

Pancreas

An organ which secretes both digestive enzymes (exocrine) and hormones (endocrine)

** Pancreatic juice digests all major nutrient types.

Nearly all digestion occurs in the small intestine & all digestion is completed in the SI.

Intestinal glands

simple tubular glands that open to the intestinal lumen between the base of the villi.

Absorption in the SI

Much absorption is thought to occur directly through the wall without the need for special adaptations

Almost 90% of our daily fluid intake is absorbed in the small intestine.

Villi - increase the surface area of the small intestines, thus providing better absorption of materials

VILLI

Large Intestine

Specialized compartment of the digestive tube designed to collect undigested materials and reabsorb water

Prepares waste (feces) to be expelled from the body

Broken into 3 main parts:1. Cecum2. Colon3. Rectum

Appendix

Sac-like structure in humans found below the junction of the small and large intestine

Large Intestines cont…

** Undigested food and water enter the large intestine where water is absorbed.

Strong peristaltic action forces feces out through the rectum and the anus.

Defecation

the act or process by which organisms eliminate solid or semisolid waste material from the digestive tract.

Waves of muscular contraction known as peristalsis in the walls of the colon move fecal matter through the digestive tract towards the rectum.

Undigested food may also be expelled this way; this process is called egestion

Digestive Homeostasis Disorders

ULCERS – erosion of the surface of the alimentary canal generally associated with some kind of irritant

CONSTIPATION – a condition in which the large intestine is emptied with difficulty.

Too much water is reabsorbed and the solid waste hardens

Digestive Homeostasis Disorders

Digestive Homeostasis Disorders

DIARRHEA – a gastrointestinal disturbance characterized by decreased water absorption and increased peristaltic activity of the large intestine.

This results in increased, multiple, watery feces.

This condition may result in severe dehydration, especially in infants

Digestive Homeostasis Disorders

APPENDICITIS – an inflammation of the appendix due to infection

Common treatment is removal of the appendix via surgery

Digestive Homeostasis Disorders

GALLSTONES – an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder

Can either be “passed” (OUCH!!) or surgically removed

Digestive Homeostasis Disorders

ANOREXIA NERVOSA - a psychological condition where an individual thinks they appear overweight and refuses to eat.

Weighs 85% or less than what is developmentally expected for age and height

Young girls do not begin to menstruate at the appropriate age.

Digestive Homeostasis Disorders

HEART BURN – ACID from the stomach backs up into the esophagus.