Transcript Digestion and Absorption, Human Nutrition

Biology Journal 12/1/2014
1. What kind of reaction is shown?
2. Write out the reaction as words:
Sucrose + _______ → ________ + _______
3. When might this reaction be happing in your
life?
+
H2 O
→
+
Biology Journal 12/1/2014
1.
2.
3.
What kind of reaction is shown? Catabolic
hydrolysis
Write out the reaction as words:
see below
When might this reaction be happing in your life?
This happens whenever you eat sucrose (sugar)!
+
sucrose
H2 O
→
+ water →
+
fructose
+
glucose
We will now learn how this is used by the
digestive system!
Biology Journal 12/3/2014
Dialysis tubing made from cellulose has pores in it that allow water and
small molecules and ions to pass through freely, but not large molecules.
• Will the bag gain or lose mass? Why?
• How do these properties mimic the wall of the small intestine?
• What types of membrane transport can be modelled using dialysis
tubing and what parts can’t?
Bag made of
dialysis tubing
(semi-permeable)
• 10 mL of 1% starch
solution
• 1 mL of 1%
amylase solution
Water
Biology Journal 11/25/014
6.1 Homework Quiz!
1. Where are villi found in the digestive tract?
(a) Mouth (b) Stomach (c) Large intestine (d) Small intestine
2. Which organ makes most of the digestive enzymes?
(a) Gall bladder (b) Salivary glands (c) Pancreas (d) Stomach
3. What is peristalsis?
4. What type of transport method could be used to absorb amino
acids from the large intestine? Why?
Biology Journal 12/2/014
D.1 Homework Quiz!
1. Ascorbic acid is …
(a) Vitamin C (b) Vitamin D (c) a mineral (d) an amino acid
2. True or false: It is essential for humans to consume fatty
acids.
3. List any of the following that are considered essential
minerals
Iron, Iodine, Phosphorous, Aluminum, Chlorine, Nickel
4. What is meant by an “essential” nutrient? What would a
“non-essential” nutrient be?
Biology Journal 11/26/014
Do you think you could live without your
pancreas? What would it be like?
Topic 6: Human physiology (20 hours)
6.1 Digestion and absorption: The structure of the wall of the small intestine allows it to
move, digest and absorb food.
Nature of science: Use models as representations of the real world—dialysis tubing to model
absorption in the intestine.
Understandings:
 The contraction of circular and longitudinal muscle of the small
intestine mixes the food with enzymes and moves it along the gut.
 The pancreas secretes enzymes (amylase, lipase and an
endopeptidase) into the lumen of the small intestine.
 Enzymes digest most macromolecules in food into monomers in the
small intestine (starch, glycogen, lipids and nucleic acids are digested
into monomers and that cellulose remains undigested). Some
hydrolytic enzymes have economic importance, for example amylase
in production of sugars from starch and in the brewing of beer.
 Villi increase the surface area of epithelium over which absorption is
carried out.
 Villi absorb monomers formed by digestion as well as mineral ions
and vitamins.
 Tissue layers should include longitudinal and circular muscles,
mucosa and epithelium.
 Different methods of membrane transport are required to absorb
different nutrients.
Applications and skills:
Application: Processes
occurring in the small intestine
that result in the digestion of
starch and transport of the
products of digestion to the
liver.
Application: Use of dialysis
tubing to model absorption of
digested food in the intestine.
Skill: Production of an
annotated diagram of the
digestive system.
Skill: Identification of tissue
layers in transverse sections of
the small intestine viewed with
a microscope or in a
micrograph.
D.1 Human nutrition: A balanced diet is essential to human health.
Nature of science: Falsification of theories with one theory being superseded by another—scurvy was
thought to be specific to humans, because attempts to induce the symptoms in laboratory rats and mice
were entirely unsuccessful.
Understandings:
Essential nutrients cannot be synthesized by
the body, therefore they have to be included
in the diet.
Dietary minerals are essential chemical
elements.
Lack of essential amino acids affects the
production of proteins.
Malnutrition may be caused by a deficiency,
imbalance or excess of nutrients in the diet.
Appetite is controlled by a centre in the
hypothalamus.
Overweight individuals are more likely to
suffer hypertension and type II diabetes.
Starvation can lead to breakdown of body
tissue.
Applications and skills:
Application: Production of ascorbic acid by some
mammals, but not others that need a dietary supply.
Application: Cause and treatment of phenylketonuria
(PKU).
Application: Lack of Vitamin D or calcium can affect bone
mineralization and cause rickets or osteomalacia.
Application: Breakdown of heart muscle due to
anorexia.
Application: Cholesterol in blood as an indicator of the
risk of coronary heart disease.
Skill: Determination of the energy content of food by
combustion.
Skill: Use of databases of nutritional content of foods
and software to calculate intakes of essential nutrients
from a daily diet.
International-mindedness: The Vitamin and Mineral Nutrition Information System (VMNIS), formerly
known as the Micronutrient Deficiency Information System (MDIS), was established in 1991 following a
request by the World Health Assembly to strengthen surveillance of micronutrient deficiencies at the
global level.
D.2 Digestion: Digestion is controlled by nervous and hormonal mechanisms.
Nature of science: Serendipity and scientific discoveries—the role of gastric acid in
digestion was established by William Beaumont while observing the process of
digestion in an open wound caused by gunshot.
Understandings:
•Nervous and hormonal mechanisms control the
secretion of digestive juices.
•The volume and content of gastric secretions are
controlled by nervous and hormonal mechanisms.
•Acid conditions in the stomach favour some
hydrolysis reactions and help to control pathogens
in ingested food.
•The structure of cells of the epithelium of the villi
is adapted (microvilli and mitochondria) to the
absorption of food.
•The rate of transit of materials through the large
intestine is positively correlated with their fiber
content.
•Materials not absorbed are egested.
Applications and skills:
Application: The reduction of
stomach acid secretion by
proton pump inhibitor drugs.
Application: Dehydration due to
cholera toxin.
Application: Helicobacter
pylori infection as a cause of
stomach ulcers.
Skill: Identification of exocrine
gland cells that secrete digestive
juices and villus epithelium cells
that absorb digested foods from
electron micrographs.
6.1, D.1, D.2 Digestion
Hydrolytic Enzymes (ones that do hydrolysis) turn
food polymers into monomers. Many are made by
the pancreas:
1.Amylase: Breaks down
carbohydrates into
sugars
2.Lipase: Breaks down
polyglycerides into
monoglycerides
3.Endopeptidase: Breaks
down polypeptides into
amino acids
X-ray scan of a house cat being digested by a python.
Mouth
Stomach
Esophagus
Liver
Pancreas
Gall Bladder
Large Intestine
Small Intestine
Rectum
Anus
6.1.4
Draw and label a diagram of the digestive system.
mouth
esophagus
liver
stomach
gall bladder
pancreas
small intestine
large intestine
rectum
anus
http://sciencevideos.wordpress.com
Draw the Core
14
Starch digestion in the small intestine
Catalysis
Without a catalyst the reactions
to digest starch would happen at
very slow rates
Illustrates many
processes that we
have learned about
Enzyme
specificity
Membrane
permeability
Starch digestion in the small intestine
Catalysis
Illustrates many
processes that we
have learned about
Membrane
permeability
Enzyme
specificity
Salivary amylase begins the digestion.
Most starch digestion happens in the small
intestine with enzyme secretions from the
pancreas.
1,4 bonds
broken by
pancreatic
amylase
Three enzymes in villi
membranes break the
1,6 bonds and the 1,4
products; dextrinase,
maltase, glucosidase
These small sections
are now broken down
into maltose and
maltotriose
Glucose
Starch digestion in the small intestine
Catalysis
Illustrates many
processes that we
have learned about
Enzyme
specificity
Membrane
permeability
Glucose is absorbed via:
1. co-transport with sodium ions
2. into the interstitial fluid via facilitated
diffusion
3. through large membrane pores into
capillaries.
Cola drinks contain a mixture of substances with different particle sizes. This cola contains
glucose, phosphoric acid, and caramel (a complex carbohydrate added to produce a brown
color).
• Predict which substances will diffuse out of the bag, with reasons for your prediction.
• Predict whether the bag will gain or lose mass during the experiment.
Cola, left to go flat before
being put in a tube
Bags made of dialysis tubing
Water
Peristalsis
 Contractions of circular
and longitudinal muscles.
 Mixes food and moves it
along digestive tract
Peristalsis works in pretty much the same way
throughout the whole digestive tract.
Esophagus
Small Intestine
Stomach
 Has a pH of 2 (because
of HCl)
 Acidic pH kills almost all
bacteria & viruses
 Denatures proteins
So, do you think that the 5
second rule is valid?
Small Intestine
 Absorbs molecules through villi
 Long! (about 7 meters (23 feet) long)
Small Intestine
 Pancreas (and liver and gallbladder) add
hydrolytic enzymes
What are the substrates and products of…
lipase, amylase, endopeptidase
What carbohydrate isn’t digested by humans?
“I love chewing on my
barfed-up cellulose.”
 Cellulose (dietary fiber) isn’t digested
by humans.
 Villi are like a bath towel: the more
surface area, the faster and more
efficient the absorption.
Villi are thin projections
into the gut that maximize
surface area for absorption
of molecules. They have
blood vessels in them to
allow absorption of
molecules into the blood.
 The blood delivers these molecules to
be used or stored (usually stored in the
liver).
Large Intestine
 Absorbs water from food (not nutrients)
 Has large stores of bacteria
How does diarrhea help cure you
from an illness?
 During diarrhea, the large intestine stops
absorbing water and instead attempts to purge
all contents of digestive system.
Identify tissue layers of longitudinal and circular muscles,
mucosa, and epithelium.
Identify tissue layers of longitudinal and circular muscles,
mucosa, and epithelium.
Identify tissue layers of longitudinal and circular muscles,
mucosa, and epithelium.
For next time do…
D.1 Homework!
Essential nutrient: A molecule that the body cannot
synthesize on its own, and is necessary for survival.
It must be obtained from food.
Nonessential nutrient: A molecule that the body can
synthesize on its own. It can, but doesn’t have to,
come from food.
The secretion of hydrolytic enzymes is regulated by
the nervous system via hormones. These organs
contain excretory glands to digest food:
 Mouth
 Stomach
 Pancreas
 Liver
What specific are
some of the
names of the
chemicals that
each one
secretes?
Identify exocrine gland cells from electron micrographs.
A sweat gland is an exocrine gland
that you are familiar with!