Digestion Flashcards
What is the definition of digestion?
Large insoluble biomolecules in food are hydrolysed into smaller, soluble molecules which can be absorbed by the body.
What is physical digestion?
The use of teeth and churning of the stomach to crush food and increase its surface area.
What is chemical digestion?
The use of enzymes to hydrolyse large biomolecules into smaller, soluble ones.
Describe how biomolecules are transported from the digestive system to be used in the body.
They diffuse into the blood from the small intestine and the blood carries them to where they need to be used.
Name 2 enzymes involved in digestion of carbohydrates.
Amylase
Membrane bound dissaccharidase
Where is amylase produced?
Salivary glands
Small intestine
Stomach
What does amylase hydrolyse starch into?
Maltose
Where are membrane bound disaccharidases found?
Cell surface membrane on the small intestine
What do membrane bound disaccharidases hydrolyse maltose into?
2 alpha glucose
How is the SA of the small intestine increased for maximum attachment of membrane bound enzymes?
Microvilli
Name 3 enzymes involved in the digestion of proteins.
Endopeptidase
Exopeptidase
Dipeptidase
Where is endopeptidase secreted?
Stomach
Pancreas
Where in the polypeptide do endopeptidases work?
They split the middle of the molecule.
Where are exopeptidases secreted from?
Pancreas
Where on the polypeptide do exopeptidases hydrolyse?
2 peptide bonds away from the end of the polypeptide chain to produce dipeptides.
Where are dipeptidases found?
The cell surface membrane of the gut.
What do dipeptidases do?
Hydrolyses dipeptides into amino acids
Name 2 stages that form part of the breakdown of lipids.
Emulsification
Digestion
What is emulsification?
The surface area of lipids are increased by turning them into fatty droplets.
Why does emulsification happen?
To increase the surface area of fats for enzymes to work on.
Describe the role of bile and bile salts in the emulsification of lipids.
Bile is secreted when lipids arrive at the small intestine. It is alkaline, so neutralises the low pH of the stomach acid.
Bile contains bile salts which bind to fatty acids and break them into smaller droplets to increase the SA.
Where is lipase produced?
Pancreas
Where does hydrolysis of lipids take place?
Lumen of small intestine
Why do epithelial cells lining the small intestine contain lots of mitochondria?
To produce ATP which release energy for active transport.
Name the mechanism used for absorption of glucose and amino acids.
Co transport
During absorption, what transport process do glucose and amino acids alongside sodium enter the epithelial cells by?
Facilitated diffusion
During absorption, by what transport process do glucose/amino acids leave the cell by?
Faciliated diffusion
During absorption, by what transport process does Na+ leave the epithelial cell by?
Active transport.
During absorption of glucose and amino acids, how is a concentration gradient maintained?
Constant blood flow
- Lipid Absorption
How are micelles formed?
Why are micelles needed?
Monoglycerides and fatty acids associate with phospholipids and bile salts.
They are needed to transport monoglycerides to the surface of the epithelial cell.
- Lipid Absorption
How do monoglycerides get inside epithelial cells?
What forms when micelles break down?
Micelles break down forming a pool of fatty acids so monoglycerides diffuse into the cell by simple diffusion
- Lipid Absorption
By what transport process are short fatty acid chains able to enter the blood in?
Simple diffusion
- Lipid Absorption
As long chain fatty acids cannot enter the blood by simple diffusion, where in the cell do they go to?
What is formed?
They go to the smooth endoplasmic reticulum.
They recombine with fatty acids to form triglycerides.
- Lipid Absorption
What are triglycerides packaged into?
Chylomicrons
What is a chylomicron?
A lipoprotein that can store non polar triglycerides, protecting them from the aqueous external environment.
- Lipid Absorption
Where are chylomicrons transported to?
Lacteals
- Lipid Absorption
Which system do chylomicrons pass through before returning triglycerides to the blood?
Chylomicrons pass through the lymphatic system before eventually returning to the blood.
