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.) AGE
2.) SEX
3.) HEIGHT
4.) WEIGHT
5.) 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
Peristalsis

series of involuntary
wave-like muscle
contractions which
move food along the
digestive tract
Human Digestive Tract
Mouth – Ingestion occurs
Oral 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 swallowing
2. 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.
The Stomach
-
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
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.
2.
3.
Cecum
Colon
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
Digestive Homeostasis Disorders

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



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.