Digestion and Absorption - Exchange Flashcards
Define digestion.
The hydrolysis of large, insoluble
molecules into smaller molecules that
can be absorbed across cell
membranes.
Which enzymes are involved in
carbohydrate digestion? Where are they
found?
● Amylase in mouth
● Maltase, sucrase, lactase in
membrane of small intestine
What are the substrates and products of
the carbohydrate digestive enzymes?
● Amylase → starch into smaller polysaccharides
● Maltase → maltose into 2 x glucose
● Sucrase → sucrose into glucose and fructose
● Lactase → lactose into glucose and galactose
Where are lipids digested?
The small intestine.
What needs to happen before lipids can
be digested?
They must be emulsified by bile salts
produced by the liver. This breaks down
large fat molecules into smaller, soluble
molecules called micelles, increasing
surface area.
How are lipids digested?
Lipases from the pancreas and small intestine hydrolyses the ester bond
between the monoglycerides and fatty acids to make 2 fatty acids and monolgycerides - these are small and lipid soluble so diffuse across the epithelial cells on the microvilli, the components go to the ER where they are fully resynthesises into triglycerides after passing through the golgi they have combined with cholesterol and lipoproteins to form chylomicrons these are adapted for lipid transport - they can exit the cell through exocytosis into a lymphatic capillary
Which enzymes are involved in protein
digestion? What are their roles?
● Endopeptidases= break between specific
amino acids in the middle of a polypeptide.
● Exopeptidases= break between specific amino
acids at the end of a polypeptide.
● Dipeptidases= break dipeptides into amino
acids.
How are certain molecules absorbed into
the ileum despite a negative
concentration gradient?
Through co-transport.
Which molecules require co-transport?
Amino acids and monosaccharides.
Explain how sodium ions are involved in
co-transport.
Sodium ions (Na+) are actively transported
out of the cell into the lumen, creating a
diffusion gradient. Nutrients are then taken
up into the cells along with Na+ ions.
Why do fatty acids and monoglycerides
not require co-transport?
The molecules are nonpolar, meaning
they can easily diffuse across the
membrane of the epithelial cells.
explain an advantage of peptidases being secreted in an inactive form
This is so the peptidases don’t break down other structures made of protein like carrier proteins.
Amylase is not secreted in an inactive form, explain how this is not a disadvantage?
We do not make starch so the amylase would not break down our own cells
Food tests:
Iodine:
Benedicts:
Ethanol:
Biuret:
Iodine is for starch - the reagent is ORANGE-BROWN and it turns blue black
Benedicts is for sugar - the reagent is LIGHT BLUE and it turns green to brick red
Ethanol is for lipids - the reagent is colourless and it turns to make a cloudy emulsion
Biuret is for protein - the reagent is blue and it turn lilac-purple.
give one way in which physical breakdown of food occurs?
chewing with the teeth
