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Digestion
Vocab Words:
• Ingestion: the food that you eat
• Digestion: a series of chemical reactions, whereby you
convert the ingested food to smaller and smaller
molecule forms
• Absorption: small molecular forms are absorbed
through cells of your digestive system and pass into
nearby blood or lymphatic vessels
• Transport: your circulatory system delivers the
small molecular nutrients to your body cells
6.1.1 Explain why digestion of large
food molecules is essential.
1. Large food molecules need to be broken down
into smaller ones, to be absorbed.
Molecule Type
Molecular
Form Digested
Molecular
Form After
Digestion
Protein
Protein
Amino Acids
Lipids
Tryglycerides
Glycerol and
Fatty Acids
Carbohydrates
Polysaccharides,
Disaccharides,
Monosaccharides
Monosaccharides
Nucleic Acids
DNA/RNA
Nucleotides
2. When digesting food molecules, they are broken
down into their smallest components, in other
words we hydrolyse them. They are then
reassembled into larger molecules we can use.
6.1.2 Explain the need for
enzymes in digestion.
1. Enzymes break down large food molecules into
smaller food molecules.
2. Enzymes speed up the process of digestion by
lowering the activation energy needed for the
reaction.
3. Enzymes allow digestion to occur quickly while
remaining at a normal body temperature.
6.1.3 State the source, substrate,
products, and optimum pH
conditions for one amylase, one
protease, and one lipase.
Amylase
Protease
Lipase
Enzyme
Salivary Amylase
Pepsin
Pancreatic Lipase
Source
Salivary Glands
Chief cells in
stomach lining
Pancreas
Substrate
Starch
Proteins
Triglycerides such
as fats and acids
Products
Maltose and
Glucose
Amino Acids
Fatty acids and
Glycerol
Optimum pH
7 (Neutral)
1.5-2 (Acidic)
7 (Neutral)
6.1.4 Draw and label a diagram
of the digestive system.
6.1.5 Outline the functions of the
stomach, small intestine, and large
intestine.
Food is brought from
your mouth to the
stomach through a
muscular tube called
the esophagus. Which
after you swallow
moves the food to
your stomach through
smooth muscle
contractions. Called
Perstalsis.
Stomach:
1. Stomach secretes HCL which kills bacteria, to
prevent food poisoning.
2. HCL provides optimum pH for Pepsin.
3. Stomach secretes Pepsin for protein digestion.
4. A Mucus lining protects the stomach walls for
the Hydrochloric Acid.
5. Pepsin, HCL, and the Mucus lining are
collectively known as Gastric Juices.
Gastric Pit:
Small Intestine:
1. The main function of the small intestine is absorption.
2. Has villi lining the walls, to increase the surface area for
absorption.
3. Receives enzymes from the pancreas, liver, and gall
bladder.
4. These enzymes are:
Accessory Organs
Enzyme
Gall Bladder
Bile
Liver
Bile
Pancreas
Trypsin(protease), lipase,
amylase, bicarbonate
Large Intestine:
1. Moves material that has
not been digested on.
2. Absorbs water, which
helps in moving the food
along.
3. Produces wastes to be rid
of through the anus.
4. Home to mutualistic
bacteria. Our body
provides nutrients, water,
and a warm environment.
The bacteria synthesize
vitamin K.
6.1.6 Distinguish between
absorption and assimilation.
Absorption vs. Assimilation
• Absorption: small
molecular forms are
absorbed through
cells of your digestive
system and pass into
nearby blood or
lymphatic vessels.
• Assimilation:
occurs when food
molecules becomes
the part of the bodies
tissues.
*Absorption is followed
by assimilation
6.1.7 Explain how the structure of
the villus is related to its roles in
absorption and transport of
products of digestion.
Structure of Villus:
1. Many villi increase the surface area for absorption.
2. Epithelium is only one cell layer thick, so food can be
quickly absorbed.
3. Microvilli on the villi further increase the surface area
for more absorption.
4. Protein channels and pumps are present in the
microvilli for rapid absorption.
5. The plasma membranes of the microvilli contain brush
border enzymes, which complete digestion of
proteins/carbs.
6. Mitochondria in the epithelium provide the ATP needed
for active transport.
7. Blood capillaries are very close to the epithelium layer
so diffusion in small.
8. Lacteal takes away fat for absorption.
Capillaries
Epitheal
Cell Layer
Artery
Vein