Transcript Lecture 10 - Nutrition

Biology 103 - Main points/Questions
1. Why do you need to eat?
2. What does your body do with this food?
3. What is in plant food?
What do you remember about
human circulation?
1. Name the
structure
2. Where is blood
in this structure
headed?
3. Blood in this
structure has
just come from
where?
1. Aorta
2. Blood is headed
out to the body
3. Blood here is
returning from
the body (this is
the right atrium)
Organisms’ two basic needs
Source of organic molecules
• Either build your own (autotrophs)
• Or take from other organisms (heterotrophs)
Energy source
• Either chemical (called chemotrophs)
• Or light (called phototrophs)
Most organisms are chemoheterotrophs
(Fungi, animals, many protists & bacteria) or
photoautotrophs (plants, many protists & bacteria)
We are Chemoheterotrophs so…
• We get energy and complex carbon
molecules (monomers) from other
organisms
• But often we actually get polymers – what
are these?
Polymers are chains built of smaller
“monomer” pieces
• These polymers are specific to the organism
that made them but the monomers are more
generic.
• How can we break these polymers apart to
get access to the monomers?
Hydrolysis
Your digestive
system frees up
monomers from
food (hydrolysis).
In vertebrates
these monomers
are moved
throughout body by
circulatory system.
As always…
exchange happens
between cells and
the interstitial fluid
that surrounds
them!
Molecules come in 4 categories… do
you remember them? (macromolecules)
• Carbohydrates
• Nucleic acids
• Proteins
• Lipids
Their jobs are…
Molecules come in 4 categories… do
you remember them? (macromolecules)
• Carbohydrates
 Energy storage (short, medium,
long) & structure
• Nucleic acids
 Information storage, short term
energy storage (ATP)
• Proteins
• Lipids
 Structure, enzymes, receptors,
signaling
 Long term energy storage, barriers,
signaling
The food pyramid and
other dietary
guidelines...
sparingly
milk, yogurt,
cheese
2–3 servings
vegetables
3–5 servings
bread, cereal,
rice,
pasta
6–11 servings
meat, poultry,
fish, beans, eggs,
nuts
2–3 servings
fruits
3–5 servings
Fig. 31.1
... try to make
sure people are
getting the
essential
nutrients they
need but not to
many calories.
Nutrition Labels provide
important information like...
Number of Calories per serving
% of various
macromolecules
And % of some the the key
vitamins and minerals
So how do animals process food?
Four stages of digestion
• Ingestion
Ingestion in a python! (chew your food!)
Four stages of digestion
• Ingestion
• Digestion (mechanical and chemical)
– Mechanical allows more surface area for...
– Chemical - the actual breakdown of polymers
into monomers (this is hydrolysis!)
Four stages of digestion
• Ingestion
• Digestion (mechanical and chemical)
• Absorption
– Once digested into monomers and other
nutrients you must absorb the molecules your
body needs
Four stages of digestion
• Ingestion
• Digestion (mechanical and chemical)
• Absorption
• Elimination - indigestible or unwanted
material is eliminated from the digestive
tract... nuff said
Small
molecules
Pieces
of food
Mechanical
digestion
Chemical digestion
Nutrient
(enzymatic hydrolysis) molecules
enter body
cells
Undigested
material
Food
1 Ingestion
2 Digestion
3 Absorption
4 Elimination
In simple
animals
digestion occurs
in one large
cavity and there
is only one
opening
(meaning only
one meal at a
time)
These organisms
have no
specialized
regions for
different digestion
and rely on
diffusion to
spread nutrients
around
• Complete tracts allow specialization
• Food passes each region in order
• Multiple meals at once ok
The digestive
system must also
interact with other
systems to move
nutrients from the
site of digestion to
the site of need.
These organisms
use a circulatory
system to move
fluids throughout
the organism.
Although cells still
use diffusion over
short distance (the
local environment)
The human
digestive system
has several
specialized
regions
Each one with a
specialized
function
We will look at several specialized
regions of the digestive tract in
humans including:
Mouth
Esophagus
1. Mouth
2. Esophagus
Stomach
Small
intestine
Large
intestine
Rectum
Anus
3. Stomach
4. Small & Large Intestine
Salivary
glands
Mouth
We will also look at several
specialized “helper”
organs/structures:
Esophagus
1. Salivary glands
Gallbladder
Liver
Pancreas
2. Liver
Stomach
Small
intestine
Large
intestine
Rectum
Anus
3. Pancreas
4. Gall bladder
Tour of the Digestive system:
Start in the mouth
Fig. 31.8 Diagram of generalized vertebrate dentition
Tour of the Digestive system:
Start in the mouth
• Lots of mechanical digestion (chewing)
• Add saliva – moisten/dissolve food
• Saliva includes amylase – what is this?
• Starts carbohydrate digestion
• What happens when you swallow?
We us the same tube for
breathing and eating at first
(the pharynx).
Food we swallow must pass
over the opening to the
trachea (the glottis)
A flap of tissue (the epiglottis)
covers the glottis as we
swallow to prevent choking.
food
pharynx
epiglottis
glottis
esophagus
larynx
(a) Before swallowing
epiglottis
(folds over)
food
(enters
esophagus)
larynx
(moves up)
(b) During swallowing
Tour of the Digestive system:
Next stop is the esophagus
• Muscular tube that transports food to
stomach
• What kind of muscle do you think?
Contraction of the
muscle lining (called
peristalsis!) pushes
food down the tube
Figure 31.12 The
esophagus and peristalsis
Tour of the Digestive system:
Next stop is the stomach
More smooth muscle
causes stomach to
“churn” food (more
mechanical digestion)
• Food is converted to an acidic soup called
chyme by the churning and the addition of
gastric juice from cells that line the stomach
• Protein digestion starts here as enzymes
secreted into the chyme start hydrolyzing
the proteins you eat
Tour of the Digestive system:
Next stop is the small intestine
• Controlled by a sphincter
• First part is called the duodenum
– Mixes chyme with other secretions from:
– Pancreas, Liver, Gall bladder and the intestine
itself
Digestion in the Small Intestine
• The small intestine is the longest section
of the digestive system
• It is the major organ of both chemical
digestion and absorption
• Each class of macromolecule needs
different digestive enzymes
Digestion takes place
in several different
places depending on
the type of molecule.
Carbohydrate digestion
Oral cavity,
pharynx,
esophagus
Polymers
Disaccharides
(starch, glycogen)
(sucrose, lactose)
Salivary amylase
Smaller polysaccharides,
maltose
Stomach
Polymers
Lumen of
small
intestine
Epithelium
of small
intestine
(brush
border)
Pancreatic amylases
Maltose and other
disaccharides
Disaccharidases
Monosaccharides
For example:
Carbohydrate
digestion starts in
the mouth, stops in
the stomach (why?)
then continues in
the small intestine.
Absorption in the Small Intestine
• Has a huge surface area - Why?
• The enormous surface greatly increases
the rate of nutrient absorption
• The sm. intestine also contains a large
network of blood vessels and small
lymphatic vessels
The large blood flow allows
your body to constantly flush
newly absorbed nutrients out of
the intestine to the rest of the
body.
Figure 31.14 The
small intestine
Absorption in the Large Intestine
• A major function of the colon is to recover
water that has entered the alimentary canal
• Wastes of the digestive tract, the feces,
become more solid as they move through
the colon
• Feces pass through the rectum and exit via
the anus
Lactose Intolerance
• As humans age many lose the ability to
digest the milk sugar lactose
• Lactose is a disaccharide formed from a
glucose and a galactose
Symptoms of Lactose Intolerance
Present after a meal high in lactose:
• Lactose present in stool
• Diarrhea
• Abdominal pain and cramping
Questions about Lactose Intolerance
1. Where is lactose normally digested?
2. Why is lactose uncommon in the stool of
people that are not intolerant – where does
it go?
3. Diarrhea is a condition where excess water
is mixed with undigested food. What part of
the digestive system is normally
responsible for removing excess water?
4. Pain and cramping can result from
bacterial digestion of lactose – where are
bacterial located in your digestive tract?
Carbohydrate digestion
Oral cavity,
pharynx,
esophagus
Polysaccharides
Disaccharides
(starch, glycogen)
(sucrose, lactose)
Salivary amylase
Smaller polysaccharides,
maltose
Stomach
Polysaccharides
Lumen of
small
intestine
Epithelium
of small
intestine
Pancreatic amylases
Maltose and other
disaccharides
Disaccharidases
Monosaccharides
• Lactose usually
digested in small
intestine
• If not it stays in &
– Bacteria eat &
– draws water…
Incisors
Canines
Premolars
(a) Carnivore
(b) Herbivore
(c) Omnivore
Molars
Natural selection has
adapted the
digestive system to
different diets
But notice that the
basic pattern of
teeth is the same –
Homology!
Fungi – the other chemoheterotrophs
• all fungi perform external digestion
• they secrete digestive enzymes into their
surroundings and then absorb back into their
bodies any organic molecules
• many fungi are able to break down the
cellulose in wood
• some fungi are carnivores
– for example, oyster fungus attracts nematode
worms and then feeds upon them
• Fungal hyphae spread
throughout their food
source by growing
• The resulting mat is
called a mycellium
• Because hyphae are so
thin they have very
large surface area
Photoautotrphs
• Generate their own organic molecules from
carbon dioxide & light energy
• Use photosynthesis to capture light energy
and CO2 – this builds complex molecules
• Still need a source of nutrient atoms
Magnesium deficiency in a tomato plant
Nutrient
Carbon
Oxygen
Hydrogen
Source
CO2 in
atmosphere
CO2 in
atmosphere
H2O in soil
Major function
Build organic
compounds
Build organic
compounds
Build organic
compounds
Build Proteins &
Nucleic acids
Nitrogen
Nitrogen
compounds in soil
Phosphorus
Phosphate in soil Build nucleic acids &
phospholipids
Potassium
Potassium in soil Water balance,
stomatal opening
So a nutrition label
for a plant might look
like this.
With information on
amounts of
• CD28020.GIF
commonly
needed
nutrients.
Where is the
information on
calorie content?
Where do plants get nutrients?
• Plant roots absorb water that has nutrients
dissolved in it
• High surface area in the root helps absorb
• Plants can control what makes it into the
stele.
root
hairs
root hair
epidermis
cortex
endodermis
of cortex
pericycle
xylem
phloem
vascular
cylinder
apical
meristem
root
cap
• Plant root cross
section
• Zoom in on the
cylinder
cortex
endodermis
xylem
phloem
• Endodermis is key
region that controls
access to the xylem
• Wax in the cell wall
creates a barrier called
the Casparian strip
• Forces fluid through
endodermal cells
Absorption rates depend on
surface area - so areas
adapted for high absorption
• 30 high surface areas.
have
• CD280931.JPG
• Copyright Biological Photo Service
Some roots
are covered
with fungal
hyphea.
• CD28100.GIF
Mycorrhizal
Fungi can
drastically
increase a plant
roots surface
area and access
to nutrients!