Chapter 8 - Nutrition

8-1 The Process of Nutrition

• includes all activities of obtaining and processing food

• furnishes nutrients for energy, growth, repair, and regulation

autotrophic nutrition

- makes organic
    compounds from
    inorganic materials
 
 
 
 
 

- "autotrophs":
        most plants
        some monerans
        protists (including all
                        algae)

- two types:
        photosynthesis -most
                        common
        chemosynthesis

heterotrophic nutrition

- can NOT make organic
    compounds from
    inorganic materials

-must obtain organic
    materials from other
    living organisms or their
    products

- "heterotrophs":
        all animals
        most fungi, protozoans,
        and bacteria
 
 

HUMAN NUTRITIONAL NEEDS
 

• nutritional needs vary  depending on age,   gender, and physical activity

• substances that can be digested,               absorbed and used for metabolism

• needed to provide energy, growth,                  repair, and regulation

• six kinds:
• carbohydrates
• proteins
• lipids (fats)
• vitamins
• minerals
• water

• indigestible material in foods

• passes through digestive tract                      chemically unchanged

• needed for proper functioning                                   of muscles in tract

• can be absorbed without                           digestion:
• vitamins
• minerals
• water
• must be digested to be used:
• carbohydrates
• lipids
• proteins

ENERGY CONTENT OF FOOD

• chemical energy that can be                           obtained from food is                                measured in units called calories

8-2 Adaptations for Nutrition
      and Digestion
 

HETEROTROPHIC NUTRITION
1. Ingestion
    - taking in food from
        environment

2. Digestion
    - break down of insoluble
       or large food molecules
       into smaller, soluble
       molecules so they can
       pass through cell
       membrane
    - extracellular - if
       digestion occurs
        outside of cell
    - intracellular - food
        enclosed inside
        vacuoles in cells,
        then digested
    - end products diffuse
        through membrane
        and enter cytoplasm
    a. Physical Changes -
        cutting, grinding,
        tearing into smaller
        pieces
       - this increased surface
         area so chemical
         agents can work better
    b. Chemical Changes
            - food broken down
                chemically with
                digestive enzymes
            - produces soluble
                end products

3. Egestion
        -removal or elimination
         of undigested or
         indigestible materials
        - different from
          excretion, which is
          removal of waste
          products produced by
          metabolic activities

Fungi
-heterotrophs
-food supply may be living
 organisms or the decaying
 remains of organisms

Adaptations:
1. rhizoids-filaments which
     penetrate food source
2. digestive enzymes are
    secreted by the rhizoids
    causing extracellular
    digestion; digested
    nutrients then absorbed
    into cells of the rhizoids
 
 

NUTRITION OF
REPRESENTATIVE
ORGANISMS
 

paramecium
[see Fig. 8-8, p 156 Tiger Book]
1. Ingestion
        - by motion of cilia
        - ingests food through
          opening at base of
          oral groove

2. Digestion
      - food ingested in food
       vacuole that forms at
       the base of oral
       groove
     - merges with lysosomes
       which contains
       digestive enzymes
     - end products absorbed
       into cytoplasm

3. Egestion
    - undigested material in
        food vacuole is carried
        to anal pore, released
        to environment
 
 

ameba
[see Fig. 8-7, p 156 Tiger Book]
1. Ingestion
    - surrounds food with
        pseudopods
    - merge and enclose food
        in a food vacuole
        (called phagocytosis)

2. Digestion
    - occurs in food vacuole
    - absorption occurs in
        food vacuole
    - food vacuole merges
       with lysosomes
        (as with paramecium)

3. Egestion
    - undigested material in
        food vacuole is
        released when
       vacuole touches cell
       membrane
    - forms an opening and is
       released to outside
 
 
 
 
 
 

hydra
[see Fig. 8-9, p 157 Tiger Book]

1. Ingestion
    - has sac-type digestive
        cavity, with single
        opening
    - food ingested through
      this opening
   - tentacles help
      manipulate

2. Digestion
    extracellular
        (outside of cell)
      - cells line cavity that
        secrete enzymes
    intracellular
        (inside of cell)
        - occurs in cells in the
          inner lining of cavity
        - food is engulfed by
            phagocytosis
        - food is digested
            intracellularly

3. Egestion
    - undigested material is
        released through the
        same opening it was
        ingested through

earthworm
[see Fig. 8-11, p 158 Tiger Book]
1. Type of Digestive System
    - one-way, tube-like
    - opening at each end
    - food passes through
        specialized organs

2. Organs
    - food ingested through
        mouth and esophagus
    - stored temporarily in
       crop
    - enters gizzard -
        mechanical
        breakdown occurs here
    - chemical digestion
       occurs in the intestine,
        end products are
        absorbed here
    - undigested materials
      egested through the
      anus

Fig. 3 - earthworm digestion

grasshopper
[see Fig. 8-12, p 159 Tiger Book]
1. Type of Digestive System
    - tube-like
    - similar to earthworm

2. Auxiliary Organs
    - food broken down
        mechanically by mouth
        parts
    -also has gastric caeca,
     which secretes digestive
     enzymes into tract for
     chemical digestion

Fig. 4 - grasshopper digestion

 
 
 
 

• one-way passage for ingested                     food-called the                                          gastrointestinal tract                                              (or the GI tract)
• GI tract is hollow tube with an                              opening at each end
• accessory organs assist in                         digestive functions
• peristalsis are muscular                         contractions that move food                             along the GI tract

THE ESOPHAGUS
1. structure.
    -muscular tube that
    connects mouth to
    stomach

2. function.
    -swallowing moves food
        into esophagus
    -Peristalsis of muscular
       walls moves food down
       to stomach
 
 

THE STOMACH
1. structure.
    -muscular sac
    - lining contains gastric
        glands
    - glands secrete
        enzymes and
        hydrochloric acid (HCl)
(Gastr-Greek refers to belly)

2. function.
    -mix food with digestive
        juices
    -enzyme gastric protease
        begins digestion of
        protein
    -HCl provides proper pH

THE SMALL INTESTINE
[see Fig. 8-16, p 164 Tiger Book]
1. structure.
    -long, coiled tube of
        small diameter
    -lining contains intestinal
        glands
    -glands secrete digestive
        enzymes into intestine
    -partially digested food
        enters from stomach

2. Accessory functions.
   a. -liver secretes bile
       -bile stored in gall
        bladder, passes
        through duct into the
        intestine
    b.pancreas secretes
        pancreatic juice

3.Digestive functions.
    a. bile- mechanically
        breaks down fats into
        small droplets
    b. pancreatic juice-
        contains proteases,
        lipases (digest lipids),
        and amylases
    c. intestinal juice-
        contains proteases,
        lipases, and
        disaccharidases                                                   (digests disaccharides;
 e.g. maltase digests                                         "maltose"--a disaccharide)

4. Absorption.
a. Structures for absorption.
    villi-along lining (s. villus)
        -increase the surface
         area of small intestine
        -most absorption
         occurs through villi
         walls
        -inside each villus are
        lacteals-small vessels
        of the lymphatic
        system--and
        cappillaries of the
        circulatory system.

b. Absorption of end
    products of digestion
 (1) Fatty acids and gylcerol
   -absorbed through the
    villi into the lacteals
   -transported by the lymph
    to the circulatory system
 (2) Monosaccharides and
        amino acids
    -absorbed through villi
        into cappillaries
    -transported by blood to
        liver, where stored
        until needed

THE LARGE INTESTINE
1. structure.
    -tube of large diameter,
        much shorter that sm.
        intestine
    -undigested food passes
        here from sm. intestine

2. functions.
    -excess water is
        absorbed here
    -wastes are moved by
        peristalsis into rectum
    -these semi-solid wastes
        are called feces
    -feces is egested
        through an opening
        called anus
 

CHEMICAL DIGESTION
1. Organs &their secretions.
[see HANDOUT-"SECRETIONS OF THE
   HUMAN DIGESTIVE SYSTEM."]

2. Hydrolysis.
    -breaking large
        molecules down to
        smaller molecules by
        addition of water
    -most digestion occurs
        by this process
    -reverse of dehydration
        synthesis

3. Polysaccaride digestion.
   -digestive enzymes break
    them down into simple
    sugars, such as glucose,
    by hydrolysis
 

4. Digestion of proteins.
    -broken down by
        digestive enzymes into
        amino acids by
        hydrolysis of peptide
        bond

5.Digestion of lipids (fats).
    - digestive enzymes
    called lipases break into
    fatty acids and glycerol
    by hydrolysis