Nutrients
• Every organism ( the cells) requires nutrients (macromolecules):
• The basic building blocks of all cell structures are built with
these nutrients
• Almost all nutrients are also a source of energy (can be used by
the mitochondria to produce useable energy in the form of ATP)
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Six basic nutrients are:
1) Carbohydrates
4) Proteins
2) Lipids
5) Minerals
3) Vitamins
6) Water or (fibre)
Nucleic acids = Nucleotides
The Digestive System
• An organism’s digestive system is
responsible for acquiring the nutrients
from food required by all body cells to
survive.
• = maintaining HOMEOSTASIS
Overall Function of the
Digestive System
• The digestive system has four basic
functions:
• A) Ingestion
• B) Digestion
• C) Absorption
• D) Egestion
A) Ingestion
• Ingestion is the uptake of the
appropriate size and kind of food
• Accomplished primarily by the mouth
B) Digestion
• Digestion is the breakdown of food into
it’s nutrient components (carbohydrates,
lipids, proteins, vitamins, and minerals).
• Digestion can be divided into two main
processes:
• Mechanical digestion and
• Chemical Digestion
Mechanical Digestion
• Mechanical digestion is the physical
breakdown of food into smaller pieces.
• Initiated by teeth and saliva
• Continued by hydrochloric acid and the
sloshing action of the stomach
Chemical Digestion
• The chemical breakdown of food into its
basic building blocks by enzymes
(biological catalysts)
• Specific enzymes break down specific
nutrients
• Carbohydrate digesting enzymes
• Protein digesting enzymes and
• Lipid digesting enzymes
C) Absorption
• Food nutrients need to be broken down
completely for absorption:
• Carbohydrates - monosaccharides
• Proteins - amino acids
• Lipids - fatty acids and glycerol
• These building blocks are absorbed into
the body (removed from the tube).
D) Egestion
• Anything that is left over is processed
and removed (expelled) from the
system.
The Human Digestive System
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The human digestive system is
basically a long tube.
It is composed of the: mouth,
esophagus, stomach, small
intestine and large intestine
As well as the liver and
pancreas (accessory organs)
The overall function of any
digestive system is to obtain
nutrients.