HUMAN NUTRITION
Emulsification of Fats & Oils
● Cells in the liver produce bile which is then stored in the gallbladder
Bile Production Diagram
Bile production and secretion
Bile has two main roles:
● It is alkaline to neutralise the hydrochloric acid which comes from the stomach
● The enzymes in the small intestine have a higher (more alkaline) optimum pH
than those in the stomach
● It breaks down large drops of fat into smaller ones
○ This is known as emulsification
○ The larger surface area allows lipase to chemically break down the lipid
into glycerol and fatty acids faster
Emulsification of Fat Diagram
, Emulsification of a large droplet of fat
Examiner Tips and Tricks
Emulsification is the equivalent of tearing a large piece of paper into smaller pieces of
paper.
This is an example of mechanical digestion, not chemical digestion – breaking
something into smaller pieces does not break bonds or change the chemical structure of
the molecules which make it up, which is the definition of chemical digestion
Absorption
Absorbing Nutrients
● Absorption is the movement of digested food molecules from the digestive
system into the blood (glucose and amino acids) and lymph (fatty acids and
glycerol)
● Nutrients are absorbed in the small intestine
● Absorption can occur by diffusion, osmosis and active transport
● Absorption is the movement of nutrients from the intestines into cells lining the
digestive system and then into the blood
Assimilation
● Assimilation is the movement of digested food molecules from the blood
● The molecules pass into the cells of all tissues and organs
○ Where they are used, becoming part of the cells
Absorbing Water
Emulsification of Fats & Oils
● Cells in the liver produce bile which is then stored in the gallbladder
Bile Production Diagram
Bile production and secretion
Bile has two main roles:
● It is alkaline to neutralise the hydrochloric acid which comes from the stomach
● The enzymes in the small intestine have a higher (more alkaline) optimum pH
than those in the stomach
● It breaks down large drops of fat into smaller ones
○ This is known as emulsification
○ The larger surface area allows lipase to chemically break down the lipid
into glycerol and fatty acids faster
Emulsification of Fat Diagram
, Emulsification of a large droplet of fat
Examiner Tips and Tricks
Emulsification is the equivalent of tearing a large piece of paper into smaller pieces of
paper.
This is an example of mechanical digestion, not chemical digestion – breaking
something into smaller pieces does not break bonds or change the chemical structure of
the molecules which make it up, which is the definition of chemical digestion
Absorption
Absorbing Nutrients
● Absorption is the movement of digested food molecules from the digestive
system into the blood (glucose and amino acids) and lymph (fatty acids and
glycerol)
● Nutrients are absorbed in the small intestine
● Absorption can occur by diffusion, osmosis and active transport
● Absorption is the movement of nutrients from the intestines into cells lining the
digestive system and then into the blood
Assimilation
● Assimilation is the movement of digested food molecules from the blood
● The molecules pass into the cells of all tissues and organs
○ Where they are used, becoming part of the cells
Absorbing Water
