6.1: Digestion & absorption
Why digest?
Define these terms
Ingestion
Digestion
Absorption
Transport
Eat the food
Chemical reactions
breaking down the food
Small molecules passing
into blood/lymphatic
vessels
Circulatory system
delivering absorbed
molecules
What are molecules made of?
Poly, di or monosaccharides 
monosaccharides
Triglycerides  glycerol & fatty acids
Protein  amino acids
DNA, RNA  nucleotides
What is this?
Amino acid!
Mono, Di or Poly?
Maltose
Disaccharide
What is this?
Saturated
fatty acid
Mono, Di or Poly?
Glycogen
Polysaccharide
What is this?
Ribose
What is this?
Unsaturated
fatty acid
Mono, Di or Poly?
Fructose
Monosaccharide
What is this?
Glucose
How are molecules broken
down?
Source
Substrate
Products
Optimum pH
Salivary
enzymes
Salivary glands
Amylose
(starch)
Pepsin
(protease)
Stomach cells
Proteins
(polypeptides)
Pancreatic
lipase
Pancreas cells
lipids
Maltose,
glucose
7
Amino acids
Glycerol &
fatty acids
7
3
Digestive System
aka alimentary canal
Page 280 (154 in the old book) –
draw and annotate a diagram of
the human digestive system.
You will be expected to draw this
from memory!
- Secretes enzymes into the S.I
- Contains two gland tissues types
- Hormone secretions
- Enzyme secretions
- Digestive enzymes synthesized in pancreatic gland cells on
ribosomes (rER) then processed by the Golgi apparatus and
excreted by exocytosis.
- Pancreatic juice contains:
- Amylase
- Lipases
- Proteases
- Duodenum is the first part. Food stuff mixed
with bile (from liver/gall bladder) and trypsin
(protease), lipase, amylase and bicarbonate
(from pancreas)
- Most molecules absorbed through capillary
bed expect fatty acids (absorbed into lacteal)
Tissue layers in transverse section of the small intestines, as seen with an
electron microscope. (also on pg. 281 fig. 2)
It would be a good idea to be able to draw and label this diagram.
Enzymes in the small intestines
Enzyme
Substrate
Product
Amylase
Lipase
Starch
Triglycerides
Phospholipase
Phospholipids
Maltose
Fatty acids &
glycerol or fatty
acids &
monoglycerides
Fatty acids,
glycerol &
phosphate
Protease
Proteins &
polypeptides
Shorter peptides
Immobilized enzymes
Enzyme
Nucleases
Maltase
Lactase
Substrate
DNA, RNA
Maltose
Lactose
Sucrase
Exopeptidases
Sucrose
Peptides
Dipeptidases
Dipeptides
Product
Nucleotides
Glucose
Glucose &
galactose
Glucose & fructose
Remove single
amino acid at a
time until a
dipeptide remains
Amino acids
In summary….
Small intestine is able to absorb a wide
range of substances including:
Glucose, fructose, galactose, the twenty
amino acids, fatty acids, monoglycerides,
glycerol, nucleotides, mineral ions (Ca, K, Na)
and vitamins (vitamin C aka ascorbic acid)
6. 1: Methods of absorption HWK sheet