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Monday, November 16, 2015

Biology - Chapter 11
The Digestive System

Macromolecules
- Carbohydrates
- Lipids
- Proteins
Carbohydrates
Monosaccharides: Long chains of simple sugar, has 3-7 carbons and usually has a
ring formation (hexagon)
...
The amino acids form cross links between them
...
Each nucleotide may contain
any one of them
...
It copies one side of the DNA double helix and
transports the code out of the nucleus
DNA provides the recipe to the ribosomes to make proteins
A-T, G-C = Complimentary base layers
4 Main Differences:
1) Location: DNA only in nucleus, RNA nucleus and cytoplasm
2) Sugar: DNA uses deoxyribose, RNA uses ribose
3) Base difference: Thymine vs
...
rat
poison)
Water Soluble Vitamins
Vitamin C Deficiency: causes scurvy
...
5 m (breaks down disaccharides and proteins, absorbs nutrients)
3) Ileum = 3
...
5m in length
- Water absorption
- Mineral absorption
- Bacteria makes vitamins B & K

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- Remaining bacteria is feces, passes through the rectum and into the anal canal and
exists through the anus
Digestive Tract = Alimentary Canal
Roles of Related Organs: Pancreas, Gallbladder
Liver: Produces bile which emulsifies fat, gallbladder stores bile
Pancreas

- Produces digestive enzymes that work on
- Carboghydrases (amylase)
- Proteases (trypsinogen)
- Lipases

- Also produces bicarbonate (a basic solution) to neutralize the stomach acid when it
enters the duodenum
Enzyme

Origin

What it does

Amylase

Salivary Glands
and Pancreas

Polysaccarides —> Disaccarides

Trypsinogen

Pancreas

Converted to trypsin in small intestine
Polypeptides —> Small Peptides+Amino Acids

Lipases

Pancreas

Triglycerides —> Glycerol + Fatty Acids

Bile (not an enzyme)

Liver (stored in
gallbladder)

Emulsifies fat

Pepsinogen

Stomach

Converted to pepsin by the HCl
Proteins —> Polypeptides

Lactase

Small Intestine

Lactose —> Glucose + Galactose

Maltase

Small Intestine

Maltose —> Glucose

Sucrase

Small Intestine

Sucrose —> Glucose

The Small Intestines
Mechanisms to increase the SA of the intestine
1) Intestinal lining is folded
2) On the folds there are fingerlike projections called villi

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Monday, November 16, 2015
3) On the villi there are smaller projections called microvilli
Villi
Inside
1) capillaries
2) lacteal (small lymph vessel)
At the base of each villus there is an intestinal gland which secretes digestive juices
(lactase, maltase, sucrase)
Peristalsis

- long, wave like contractions of smooth muscles that move food along the alimentary
canal

- Helps mechanically digest food
- Mixes food with enzymes
- Pushes food past villi to aid in absorption of nutrients
Digestion of a Carbohydrate
1) Mouth - chew (mechanical)
- Saliva will moisten it
- Amylase will breakdown polysaccharides —> disaccharides
2) Stomach - mechanical breakdown by peristalsis
3) Small Intestine
- Amylase from pancreas polysaccharides—> disaccharides
- Sucrase, maltase, lactase = disaccharides —> monosaccharides
4) Villi - Monosaccharides are absorbed by capillaries and enter the blood
Digestion of a Protein
1) Mouth - chew (mechanical)
2) Stomach
- Pepsinogen -HCl-> Pepsin

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- Proteins -Pepsin-> Polypeptides
- Hal breaks down the crosslinks in the protein
3) Small Intestine
- Pancreas releases trypsinogen to the duodenum
- In the duodenum, trypsinogen is converted to trypsin
- Polypeptides -trypsin-> smaller peptides + amino acids
4) Villi- amino acids are absorbed by the capillaries to enter the blood
Digestion of Lipids
1) Small intestine
- Bile (from gallbladder)
- Bile emulsifies fat (increases SA for enzymes)
- Lipases from pancreas digest the small molecules of fat to fatty acids + glycerol
2) Villi - absorbed by the villi by the lacteal lymph vessel

Digestive Disorders
Stomach Ulcer

- HCl eats a hole in the stomach lining, the protective mucus layer is sometimes
disrupted by the bacteria H

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