Download 2. Digestion

Topic 12
I. Nutrition
A. Types of Nutrition
 1. Autotrophic nutrition - organisms make their
own food through the process of photosynthesis or
chemosynthesis - includes plants and algae
 2. Heterotrophic nutrition - organisms take food
from their environment - can’t make their own food
II. Heterotrophic Nutrition
A. Processes of Heterotrophic nutrition
 1. Ingestion - taking in of food from the
environment
 2. Digestion - breakdown of large molecules into
smaller molecules
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a. extracellular digestion - digestion that occurs outside
of the cells
b. intracellular digestion - digestion that occurs inside of
cells in vacuoles
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c. mechanical digestion - food is broken down into
smaller pieces to increase surface area - the chemical
composition is not changed at all
d. chemical digestion - food is broken down chemically
into different materials by the action of digestive
enzymes
e. hydrolysis - food molecules are broken down by the
addition of water
 3. Egestion - the removal, or elimination, of
undigested or indigestible materials - it is not
excretion which is the removal of wastes produced
inside the tissues of an organism by its metabolic
activities
 B. Adaptations for heterotropic nutrition in fungi
 1. Rhizoids - filaments that go into the food source
 2. Digestive enzymes are secreted by the rhizoids
which allows for extracellular digestion which is
then absorbed into the cells of the rhizoids
 C. Paramecium
 1. Ingestion - cilia (tiny hairs) bring food into the
oral groove
 2. Digestion - the food is brought into a food
vacuole which combines with a lysosome that
contains digestive enzymes
 3. Egestion - undigested material goes out through
the anal pore
Anatomy of the paramecium
 D. Ameba
 1. Ingestion - pseudopods (false feet) surround the
food and enclose it in a food vacuole through a
process known as phagocytosis
 2. Digestion - ingested food is taken into a food
vacuole which joins with a lysosome that contains
digestive enzymes
 3. Egestion - undigested materials are released
through the cell membrane
Anatomy of the Ameba
 E. Hydra
 1. Ingestion - food is brought in through the mouth
by the tentacles into the digestive cavity - has a two
way digestive system
 2. Digestion
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a. extracellular - specialized cells in the lining of the
digestive cavity secrete digestive enzymes into the cavity
b. intracellular - some food particles are engulfed by
phagocytosis and digested intracellularly
 3. Egestion - with a two way digestive system wastes
travel out through the same opening that the food
came in to so wastes travel out through the mouth
Anatomy of the Hydra
F. Earthworm
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1. Type of digestive system - has a one way digestive
system - food enters one opening and wastes exit
through a different opening - is a tube within a tube
2. Organs
 a. mouth - food enters and goes into the esophagus
 b. crop - food is stored here
 c. gizzard - mechanical digestion occurs here
 d. intestine - chemical digestion occurs here
 e. anus - wastes leave
Anatomy of the Earthworm
 G. Grasshopper
 1. Type of digestive system - tube like digestive
system similar to the earthworm – includes a
mouth, esophagus, crop, gizzard, stomach and
intestines
 2. Auxillary organs
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a. mouth parts - mechanical breakdown
b. salivary glands – secrete enzymes
c. gastric caeca - release enzymes into the stomach for
chemical digestion
Anatomy of the Grasshopper
III. Human Nutrition
A. Human foods
 1. Nutrients - substances in food that the human
body can digest, absorb, and use for its metabolism
- there are six kinds of nutrients: carbohydrates,
proteins, lipids, vitamins, minerals and water
 2. Roughage(fiber) - can’t be digested - used for the
proper functioning of the digestive system and to
help eliminate wastes
 3. Digestion of nutrients - vitamins, minerals and
water are small enough that they can be absorbed,
however; carbohydrates, proteins, and lipids must
first be digested then absorbed
 4. Nutritional needs vary with age, sex, and physical
activity
IV. Human Digestion
A. human digestive system - gastrointestinal tract
- food moves by the action of peristalsis
 B. Mouth (oral cavity)
 1. Structures - teeth, tongue, openings to salivary
glands
 2. Functions
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a. teeth - break pieces of food mechanically into smaller
pieces to expose a larger surface area
Human Anatomy
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b. salivary glands - secrete saliva which contains the
enzymes salivary amylase which starts the chemical
digestion of starch(carbohydrate)
c. tongue-helps to mix the food with saliva and move it to
the back of the mouth for swallowing
 C. esophagus
 1. Structure - muscular tube that connects the
mouth to the stomach
 2. Function - moves food to the stomach
 3. peristalsis – muscular contractions that move
food throughout the digestive system
 4. epiglottis – prevents food from entering the
trachea
 D. stomach
 1. Structure - muscular sac - has gastric glands that
secrete enzymes (pepsin for the breakdown of
proteins) and hydrochloric acid
 2. Functions - mix the food with digestive juices enzyme gastric protease begins the digestion of
proteins - HCl gives the proper pH for gastric
protease
 3. pepsinogen (zymogen of pepsin) – inactive form
of pepsin made by the stomach cell – it is activated
by HCl and turned into pepsin (gastric protease)
 E. small intestine
 1. Structure - long, coiled tube of small diameter contains intestinal glands that secrete digestive
enzymes into the intestine - receives food from the
stomach
 2. Accessory organs
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a. liver - secretes bile which is stored in the gall bladder
b. pancreas - secretes pancreatic juice
 3. Digestive functions
 a. bile - emulsify fats
 b. pancreatic juice contains proteases (trypsin and
chymotrypsin), lipases, and amylases (starch digestion) –
pancreatic proteases are produced and stored as inactive
forms called zymogens
 c. intestinal juice contains aminopeptidases (polypeptide
digestion), lipases, and dissacharidases – bulk of the
digestion occurs here
 4. Absorption
 a. Structures - lining of the intestine has tiny fingerlike
projections known as villi - help increase the surface area
for absorption
 b. absorption of end products of digestion
 (1) fatty acids and glycerol - end products of fats
(chylomicrons) are absorbed by the villi and transported
to the circulatory system – the chylomicrons are taken
into the lacteals inside of the villi and transported to
lymph vessels before they enter the veins
 (2) monosaccharides and amino acids - transported by
the blood to the liver where they are stored until needed
 F. large intestine
 1. Structure - tube of larger diameter and shorter
length than the small intestine - undigested food
travels from small intestine to the large intestine
 2. Functions - excess water is absorbed back into the
body - remaining wastes go to the rectum and form
feces - leave through the anus
V. Disorders of the Digestive
system
A. ulcers – when stressed, excess HCl is produced
which eats the lining of the stomach or small
intestine
B. constipation – too much water is absorbed in
the large intestine
C. diarrhea – too little water is absorbed in the
large intestine