Transcript No Slide Title

Biology 188 General Biology II
March 31, 2003
Obtaining & Processing Nutrients
&
Relation of Animal Body Evolution to Digestion
Kenneth L. Campbell
Professor of Biology
University of Massachusetts at Boston
This presentation is made possible
by a grant entitled
“Shortcourses in Endocrinology at
Minority Undergraduate Institutions”
from the
National Institute of General Medical
Sciences (NIGMS)
to
The Minority Affairs Committee of the
Endocrine Society
Obtaining & Processing
Nutrients
What are nutrients?
Why are they being extracted?
Nutrients are those parts of food that provide
sources of energy, molecular building blocks,
or ions and small molecules needed to
support biochemical functions.
•Amino acids
•Fats
•Sugars
•Nucleic Acid Components
•Minerals
•Vitamins
Where does this occur?
Teeth: break food into smaller particles & mix in saliva
Saliva: adds water, buffer salts & often enzymes that
begin sugar digestion
Stomach: adds HCl & pepsin, a proteolytic enzyme
Apocrine pancreas & bile: add enzymes & detergents
for degrading protein, fats, sugars, & nucleic acids
Small intestine: absorbs simple sugars, amino acids,
fats, nucleosides, vitamins, & ions
Cecum: often acts as a fermenter allowing bacteria to
break down complex sugars
Large intestine: absorbs water, ions, & small molecules
Colon: absorbs water, stores feces
Review:
What do
each of
these
organs
do?
Teeth
Saliva
Pancreas
& Bile
Large
Intestine
Cecum
Stomach
Small
Intestine
Colon
Mucosa:
HCl & pepsin
Small
Intestine
Histology
www.iun.edu/~biologyn/
P262%20Web%20Pages/
EX-14%20Digestive%
20Histology/aa.GIF
Smooth
muscle
layers
www.le.ac.uk/pathology/teach
/ va/anatomy/case6/gi4.gif
Stomach
Histology
www.uoguelph.ca/zoology/devobio/ miller/013634fig8-24.gif
Fats are often broken down after being
absorbed by the small intestine. They are
moved as complexes wrapped in specific
proteins. The earliest complexes have the
most fat relative to protein and are the
least dense.
hsc.usf.edu/2005/ lipoprotmet.jpg
The Liver is Central to Processing of Sugars.
Converts many simple sugars, several amino
acids, acetate & glycerol to glucose ( =
gluconeogenesis) then secretes it into blood.
Stores glucose as a macromolecule, glycogen, &
hydrolyzes glycogen to glucose.
Makes fat from fatty acids & glycerol, & breaks fat
down to acetate & glycerol.
Stores amino acids as protein, & can break
proteins down to amino acids.
Glucose Homeostasis
The body must control glucose levels because
all cells use glucose to make ATP, the energy
currency of cells. Some tissues like brain
almost never burn any other fuel molecule. But
too much glucose damages cells by getting
attached to certain proteins and changing their
function. Key tissues in this balancing act are:
Liver
Fat
Muscle
Brain
Pancreas (endocrine cells)
After meals glucose
from liver is mainly
stored as glycogen in
liver & muscle & as fat
in fat cells. When
more energy is
needed between
meals, glycogen, fat &
protein (last) are
broken down & liver
uses the parts to
make glucose.
Hormones (insulin,
glucagon, adrenalin,
cortisol) signal the
change from storage
to synthesis.
Hormones Control the
Islets of Langerhans
Glucose Balance
http://medlib.med.utah.edu/WebPath/jpeg4/ENDO039.jpg
Pancreas
Insulin acts on body cells
to allow them to take in
circulating glucose.
Insulin levels rise when
glucose rises.
Glucagon
Insulin
Adrenaline, cortisol, &
growth hormone also
make blood glucose
Glucagon acts on liver to
stimulate glucose production rise. But insulin-like& release, & on fat to cause
growth factor I acts
fat breakdown. Glucagon
like insulin.
rises when glucose falls.
Relation of Animal Body
Evolution to Digestion
Evolutionary Adaptations for Digestion
Shape & arrangement of teeth:
From Wessells & Hopson, Biology, (Random House:1988), 817, 822, 819.
Carnivore
Omnivore
Herbivore
Contents of saliva:
Contains amylases in cloven hoofed animals, rodents,
rabbits, dogs, & primates.
High content of HCO3 -2 & PO4 -3 in herbivores.
Venoms & proteases in some reptiles & invertebrates.
Form & function of the gut.
Digestive Tracts of Carnivores:
Simple
stomach,
short small
intestine,
simple,
short large
intestine for
extraction of
high quality
foods.
Digestive Tracts of Herbivores:
Ruminants, efficiently extract nutrients from low quality
foods by symbiosis with bacteria in complex stomach.
On similar
feed, equids
extract easily
digested
materials in
foregut, &
get more
calories by
fermentation
in complex
hindgut.
Digestive Tracts of Omnivores:
These are
hybrid,
systems:
simple
stomachs,
moderately
long small
intestines,
& welldeveloped,
but simple,
large
intestines.
Summary:
Digestion is an extraction &
breakdown process optimized to
provide metabolic building blocks
& energy source molecules.
Evolutionary adaptations match
each animal’s anatomy & physiology
to it’s food sources & quality.