Nutrition and Digestion
CHAPTER 20
• Everything that lives needs food, in order to
carry out all of life’s functions.
• Food contains complex organic and simple
molecules that can supply both energy and
raw materials.
Nutrients
The complex substances and simpler
substances that are used in life processes.
Nutrients
• Food is composed of 3 major organic
molecules & their building blocks.
• Polymer-Large molecule (ex. Protein)
• Monomer-Smallest building block (ex.
Amino Acids)
1. Carbohydrates
• Polysaccharides( Starch) are digested into
monosaccharides.
2. Proteins
• Proteins are digested into Amino Acids.
3. Lipids (Fats)
• Fats are digested into fatty acids & glycerol.
Human nutrition
Do water, vitamins and minerals
need to be digested?
Why not?
Digestion
• Digestion is the process of converting
complex organic molecules (Polymers) into
smaller ones (Monomers) so they can be
absorbed through the cell membrane.
Autotrophs
• produce their organic molecules in the
process of photosynthesis.
• Do plants carry out digestion? _______
• Why or why not?
• Do plants carry out digestion? __NO_____
• Why or why not? They build their own organic
substances by using water, carbon dioxide, and
minerals absorbed from surrounding.
Photosynthesis- makes sugars
Sugars can be built into more complex sugar
molecules or combined with minerals to form
lipids and amino acids.
Heterotrophs
• obtain their organic molecules by eating.
• Do heterotrophs carry out digestion?
_YES____
• Why or why not? Chunks of food have to
be broken down into smaller particles
until in form of molecules small enough to
pass through cell membrane.
Do all nutrients need to be
digested before entering the
blood stream?
NO!
• Water, Vitamins, and
Minerals readily pass across
cell membrane with little or
no need for digestion.
DIGESTION IN HETEROTROPHS
• Intracellular digestion
Digestion that takes
place inside a cell.
• Protozoans use food
vacuoles & lysosomes
to digest the food.
Food Vacuoles in Paramecium
Intra or Extracellular?
• Sponges have flagella
that draw the water
(containing plankton)
in & digest the food in
individual cells
Extracellular Digestion
• Digestion that takes
place in a cavity
surrounded by cells.
• Hydra is a chunkfeeder, taking in large
particles & digesting
them in its
gastrovascular cavity.
• 2-Way traffic-1
opening!
Filter Feeding-Pass food thru a part of their
body that strains out microscopic plankton.
• Sessile or slow
moving animals like
sponges & bivalves
filter the water.
• Sponges have flagella
that draw the water in
& digest the food
intracellular.
1-Way Traffic A complete mouth-anus digestive
tract is present in many animals. Much more
efficient as digestive is divided into stages.
Earthworm digestion
• Complete digestive
tract-Mouth-Anus
Bivalves
• Filter Feeders
• Have a true digestive
tract-strain food on
mucus covered gills.
• Incurrent & Excurrent
siphons.
http://www.youtube.com/watch?
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http://www.youtube.com/watch?
v=uO4lkvjLRs&feature=channel&safety_
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Pharynx
Muscular-helps to “suck in” soil
Crop
Stores the food
Gizzard
An organ filled with sand that grinds
the food.
Intestine
Chemical digestion and absorbs
nutrients.
• Intestine
Human Digestive System
Video of digestive system
http://www.youtube.com/watch?v=uFX-MOLSGaU
Beginning of Digestion
• Mechanical &
Enzymatic digestion
begin in the mouth• Food is masticated to
increase surface area
for Enzymatic
digestion
.
Human Salivary glands
Secrete Saliva-Water, Salivary amylase
that digests starch (enzymatic)
Peristalsis
• Peristaltic waves of
esophagus muscles
move food along the
digestive tract
stimulating the
opening of the
cardiac sphincter.
3 layers of muscle in stomach
Stomach
• The stomach’s rugae
continue to churn
(mechanical) the
food, acts as a
storage area for the
food and..
• Chemical digestion
also takes place…
Gastric Juice
• Gastric juice is
secreted which
contains HCL,
mucus & Pepsin
which will digest
proteins.
• Chyme then leaves
the stomach thru the
pyloric sphincter.
Small Intestine-Several organs secrete
digestive juices into the duodenum thru various
ducts.The gall bladder adds bile-stored from the liver
Pancreas
• The Pancreas adds
enzymes to digest all 4
groups of organic
molecules.
• Intestinal Juice acts on
the disaccharides in
the small intestine.
Enzymes in digestion
Final steps in Digestion
The complete breakdown & absorption of organic
molecules occurs in the jejunum & ileum.
Villi & Microvilli
• The lining of the small
intestine is folded to
increase the surface
area to absorb the max
amount of nutrients.
• The absorbed nutrients
travel in the blood to
the liver to be sorted
out by the Liver.
Large Intestine (Colon)
Water is absorbed as solid feces are formed
until they exit through the rectum
Large intestine
What occurs in
the large
intestine?
Why should
you eat yogurt
when you take
antibiotics?
What can be
dangerous
about having
diarrhea?
Colonoscopy
/http://www.insidestory.iop.org/insidestory_fl
ash1.html
A- Salivary Glands/Mouth
B- Esophagus
C- Stomach
D- Pancreas
E- Large Intestine (Colon)
F- Appendix
G- Small Intestine
H- Gallbladder
I- Liver
J- Rectum/Anus
Vestigial structure, once used to aid in
carbohydrate digestion
APPENDIX
Releases bile into small intestine- helps digest fats
GALL BLADDER
Adds enzymes like trypsin to digest organic
molecules (proteins amino acids) into small
intestine
PANCREAS
Mechanical and chemical digestion
(amylase break down carbs). Chew up
food to increase surface area for enzymes to
digest
Mouth/Salivary Glands
Produces bile (helps digest fats) and sorts
out nutrients.
LIVER
Water reabsorption
LARGE INTESTINE
Mechanical (churning and mixing) and
chemical digestion. Gastric Juices- HCl,
pepsin, mucus start to break down proteins
changing food into chyme.
SMALL INTESTINE
tubular passageway leading into stomach
peristalsis- toothpaste squeezing movement
of food.
ESOPHAGUS
Where solid feces are stored and then released.
RECTUM/ANUS
Complete breakdown and absorption of organic
molecules. Villi (and microvilli) increases the
surface area so the max. amount of nutrients can
be absorbed into the bloodstream to be transported
to liver.
SMALL INTESTINE
Digestive disorders
•
•
•
•
•
•
•
Gall bladder disease
Lactose intolerance
Irritable bowel syndrome
Crohn’s Disease
Heartburn/esophageal reflux disease
Diabetes
Hyper/hypoglycemia
Importance of good nutrition
• Why the saying “you are what you eat?”
• What should you eat before a game or a
run?
• What should you eat after weight-lifting?
• What foods should you avoid?
• What is the best way to maintain a healthy
body composition (lean/fat balance,
weight)?
Which type of organism do you
think would have a longer
digestive tract?
An herbivore or a carnivore….
Hmmmmm…….
Carnivores vs Herbivores
Why?