Transcript In Small Intestine

ANIMAL NUTRITION
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Figure 41.1 Homeostatic regulation of cellular fuel
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Figure 41.2 A ravenous rodent
Leptin receptors are found in high concentrations in the
hypothalamus, region of the brain that’s known to be involved
in regulating appetite and metabolism.
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Figure 41.4 Essential amino acids from a vegetarian diet
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Table 41.1 Vitamin Requirements of Humans: Water-Soluble Vitamins
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Table 41.1 Vitamin Requirements of Humans: Fat-Soluble Vitamins
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Table 41.2 Mineral Requirements of Humans
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Figure 41.10 Intracellular digestion in Paramecium
Paramecium Still Images
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Figure 41.11 Extracellular digestion in a gastrovascular cavity
Cnidarians
Nematocysts
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Figure 41.12 Alimentary canals
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Figure 41.13 The human digestive system
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Figure 41.14 From mouth to stomach: the swallowing reflex and esophageal
peristalsis (Layer 1)
Components of Saliva
Mucin
Buffers
Antibacterial agents
Salivary amylase
When not swallowing, the glottis is open.
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Figure 41.14 From mouth to stomach: the swallowing reflex and esophageal
peristalsis (Layer 2)
When swallowing: the glottis moves down closing off the
trachea and bolus moves down esophagus.
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Figure 41.14 From mouth to stomach: the swallowing reflex and esophageal
peristalsis (Layer 3)
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Figure 41.15 Secretion of gastric juice
Gastric Juice
a) Pepsin and pepsinogen (zymogen)
b) HCl
Positive feedback:
some activation of
pepsinogen increases
production of pepsin.
Heliocobacter pylori
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STOMACH
Stimulation
Gastrin from stomach into circulatory system
stimulates release of
Pepsin
HCl
Pepsinogen
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Figure 41.16 The duodenum
Duodenal ulcers
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Figure 41.17 Enzymatic digestion in the human digestive system
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CHO Digestion
Sucrase, lactase
Protein Digestion
Trypsin(trypsinogen) and chymotrypsin
(chymotrypsinogen)
look for specific bonds in polypeptides and make
smaller fragments.
Procarboxypeptidase (zymogen) for carboxypeptidase
which will split one amino acid off of a polypeptide at
a time (at the COOH end)
Aminopeptidase as at the amino end of the polypeptide
chain.
All this is triggered by enteropeptidase.
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Figure 41.18 Activation of protein-digesting enzymes in the small intestine
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What Regulates the Secretion of These Digestive Enzymes?
1. Secretin
2. Cholecystokinin( CCK )
3. Enterogastrone
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Small Intestine
Receives low
amino acids and fatty acids
fats
pH chyme
Enterogastrone
Secretin
Cholecystokinin (CCK)
(from intestinal wall)
Pancreas
Procarboxypeptidase
(slows passage of food
into SI)
Gall Bladder
Bile
carboxypeptidase
(Pancreas)
HCO3-
+
Chymotrypsinogen
chymotrypsin
+
Trypsinogen
trypsin
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Figure 41.19 The structure of the small intestine
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Evolutionary Adaptations of Vertebrate Digestive System
1. Dentition and Diet
a) Mammalian vertebrates
b) Nonmammalian vertebrates
2. Length of vertebrate digestive system
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Figure 41.20 Dentition and diet
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Figure 41.21 The digestive tracts of a carnivore (coyote) and a herbivore (koala)
compared
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Figure 41.22 Ruminant digestion
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Symbiotic Relationships in Herbivores
Vertebrates and termites have microorganisms (protists and
bacteria). . .
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What Is Fat?
Fat Or Adipose As A Tissue
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Fat is used for energy storage and insulation
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It is involved in metabolism. It really doesn’t just sit there.
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Fat cells express certain genes and secrete hormones as well as other
signaling molecules.
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What Is Fat?
Fat As a Cell
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Fat cells are called adipocytes
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Adipocytes are specialized for storing fat.
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Inside the adipocyte are the fat droplets
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What Is Fat?
Fat As a Molecule
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It’s a lipid
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Triglycerides are a form of lipid and they consist of one glycerol
molecule and 3 fatty acids (remember?)
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Triglycerides store 3 times more energy than sugars per gram.
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Saturated Fats vs. unsaturated fats
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How the Body Processes Fat
The body’s primary energy source is glucose
Any excess glucose is stored in your muscles and liver as glycogen.
Any excess beyond this is converted to fat (triglycerides) for storage.
Between meals when glucose levels drop, either
1) glycogen is broken down to glucose (glycogenolysis) or
2) the body makes glucose from other precursors (gluconeogenesis)
3)
triglycerides can also be catabolized for energy (glycerol is used for
gluconeogenesis and the fatty acids are broken into 2 carbon units for
the Krebs cycle
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How the Body Processes Fat
Cholesterol
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Cholesterol is a form of lipid
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Component of cell membranes
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Used to make steroid molecules and also bile salts
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Transported with fat in what are called “lipoproteins.”
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Low Density Lipoproteins (LDLs) vs. High Density Lipoproteins
(HDLs)
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Transportation of Fat
Lipoprotein Structure
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Phospholipids and cholesterol form a sphere on the outside (where it
would contact water). Therefore the hydrophilic regions are pointing
outward.
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Apolipoproteins, another protein, are also on the surface and these
regulate the function of the lipoproteins.
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Inside this sphere are triglycerides and cholesterol esters.
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Transportation of Fat
Lipoprotein Size and Origin
chylomicron
VLDL
LDL
HDL
Small Intestine
Transports fat and cholesterol
absorbed from digested food
from the gut to the rest of body.
Liver
Supply the body with triglycerides synthesized in the liver.
Converted VLDL
Supply the body with cholesterol
Multiple Sources
Collect excess cholesterol and
transport it to the liver.
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Transportation of Fat
Lipoprotein Conversion
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The lipoproteins can be converted from:
chylomicron
VLDL
LDL
Chylomicron
remnants
Fatty Acid Transport
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Fats are leased from the fat cells in the form of fatty acids.
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These become bound to a protein, albumin, that can transport them
throughout the body.
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Each albumin molecule can carry 7 fatty acids.
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What Goes On Inside Cells?
There are regulatory molecules that control what happens to fat
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PPARγ: fat sensor that belongs to a class of molecules called nuclear
receptors (found in the nucleus).
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PPARγ molecules bind to fatty acids, become activated and cause
cells to store fat.
PPARδ: fat sensor that belongs to a class of molecules called nuclear
receptors (found in the nucleus).
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PPARδ will bind to fatty acids, become activated and cause cells
to metabolize of “burn” fat.
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Endocrine Regulation?
Your hypothalamus in your brain is a center for many activities, one of which
is appetite and hunger.
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Appetite is stimulated by a hormone called ghrelin.
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Appetite is suppressed by leptin, insulin, cholecystokinin and 2 other
peptides (peptide YY and glucagon-like peptide-I)
Normally, the more fat you have in a cell, the more you have a signal that
tells the brain it can reduce food intake. In obese people, the brain does not
sense these higher levels of leptin; they are less responsive to the signal that
tells them to reduce food intake.
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How the Body Processes Fat: Part II
From Mouth To Stomach
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Triglycerides are not digested in mouth but the complex
carbohydrates do get broken down into complex sugars.
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So in the stomach you have triglycerides and complex sugars and off
they go to the small intestine.
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In Small Intestine
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Bile acids made in liver and stored in the gall bladder are delivered to
the duodenum. Bile salts break up the triglycerides into small
droplets.
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Pancreas secretes lipase which removes the fatty acids from the
triglycerides.
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The triglycerides are digested into one fatty acid attached to glycerol,
a monoglyceride, and this can be absorbed into the blood stream.
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At the Liver
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The liver can take stored or absorbed glucose and convert it to:
• glycerol (which can then become a triglyceride)
• glycogen
• fatty acids (which can then become a triglyceride)
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These triglycerides can leave the liver and go to the blood stream and:
• combine with proteins to become VDLP and go to a muscle cell
• or they can go to a fat cell and become fatty acids and be stored
At The Muscle Cell
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the triglycerides can become fatty acids and be used for energy
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What About The Cholesterol
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The cholesterol can be transported as LDLs which can go to a muscle
cell or to a fat cell.
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Some cholesterol can be transported as HDLs and go the liver and be
stored or released back into the blood.
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