Digestion And Absorption Flashcards
Large molecules are ——- into smaller molecules
Hydrolysed
What does the hydrolysing of large molecules to small mean?
It means the molecules can easily be absorbed and transported
Most polymers are large ———- that are hydrolysed into ——- (smaller molecules)
- Biological molecules
- Monomers
What are carbohydrates broken down into?
Carbohydrates } Disaccharides } Monosaccharides
What can lipids be broken down into?
Fatty acids and monoglycerides
What are used to hydrolyse Biological molecules in food?
Digestive enzymes
Where and how are digestive enzymes made? And where are they released?
- they are produced by specialist cells in the digestive system of mammals
- they are then released into the gut to mix with food
What are carbohydrates broken down by?
They are broken down by amylase and membrane bound disaccharidases
Describe the role of amylase
- catalyses the conversion of starch into maltose
Where is amylase produced and secreted?
- produced by the salivary gland and released in the mouth
And: - It can be produced by the pancreas and released into the small intestine
Define membrane bound disaccharidases
They are enzymes that attach to the cell membranes of epithelial cells, lining the ileum
What is the role of membrane bound disaccharidases
To help break down disaccharides into monosaccharides
List the disaccharides and the disaccharidases that hydrolyse them
Maltose } maltase
Sucrose } sucrase
Lactose } lactase
what monosaccharides does maltose produce?
Glucose + glucose
what monosaccharide product does sucrose make?
Glucose + fructose
What monosaccharide product does lactose produce?
glucose + galactose
what can monosaccharides be transported across?
The cell membranes of the ileum epithelial cells via specific transporter proteins
what are lipids broken down by?
By the enzyme Lipase and Bile Salts
What is the role of lipase when hydrolysing lipids?
lipase catalyses the hydrolysis of lipids into monoglycerides and fatty acids, through the hydrolysis of ester bonds
Where are lipases made and released?
They are made in the pancreas and secreted in the small intestine
Where are bile salts made?
In the liver
What is the role of bile salts?
To emulsify lipids, causing them to form small droplets
Why is emulsification of lipids important?
As it increases their surface area and means that there’s an increased area for the lipase to work on
What are micelles?
Tiny structures that form as the monoglycerides and fatty acids stick to the bile salt
What are proteins broken down by?
Proteases or peptidases
what bonds need hydrolysing for proteins?
Peptide bonds
Name the two kind of peptidases
Endopeptidase and Exopeptidase
What is the role of endopeptidases?
To hydrolyse peptide bonds WITHIN a protein molecule
Name an example of an endopeptidase and where it’s released
Pepsin
- it’s released into the stomach by cells in the stomach lining
What role do exopeptidases have?
To hydrolyse peptide bonds at the END of protein molecules
Name an example of exopeptidases
Dipeptidases (work on dipeptides, two amino acids)
Where are dipeptidases normally located?
In the cell surface membrane of epithelial cells in the small intestine
The products of digestion are absorbed across the ———- into the bloodstream
Ileum epithelium
How are the monosaccharides absorbed?
Glucose + galactose: absorbed via active transport with sodium ions via a co-transporter
Fructose: is absorbed via facilitated diffusion through a different transporter protein
How are monoglycerides and fatty acids absorbed?
- while the reforming, the micelles “release” monoglycerides and fatty acids
- monoglycerides and fatty acids are lipid-soluble, meaning they can diffuse directly across the epithelial cell membrane
How are amino acids absorbed?
they are absorbed via co-transport
1. Sodium ions are actively transported out of the ileum cells into the blood
2. This creates a sodium concentration gradient
3. Sodium ions can then diffuse from the lumen of the ileum into epithelial cells through sodium dependent transporter proteins
4. The sodium ions carry amino acids with them
