Digestion and Absorption Flashcards
What is hydrolysis?
Breaking bonds by adding water
What is digestion
Physical breakdown
Physical breakdown
-Breakdown of food into absorbable nutrients
Chemical digestion
Hydrolyses large, insoluble molecules
What is the importance of digestion?
Hydrolyses large food molecules into smaller molecules
Oesphagus
carries food from mouth to stomach. adapted for transport. made up of a thick muscular wall
stomach
muscular sac between the oesphagus and the small intestine where digestion of food begins
ileum
Part of small intestine
large intestine
Absorbs water and forms feces
Rectum
stores feces
Salivary glands
Contain amylase to hyrdolyse starch into maltose
Pancreas
Pancreatic juice (hydrolyse proteins, lipids and starch)
Why are different enzymes needed to catalyse the breakdown of carbohydrates, proteins and lipids?
Enzymes are proteins with specific tertiary structures
Where is amylase produced?
Pancreas, salivary glands and small intestine
Where is amylase secreted?
Mouth and small intestine
What is amylase for
Hyrdolyses alternate glycosidic bonds of starch molecule to produce maltose
Where is maltase produced?
(In the cell membrane of epithelial cells)
Maltose
glucose + glucose
Where is maltase secreted?
Small intestine
Role of maltase
Hyrdolyses maltase into monosaccharide (alpha glucose)
Process of carbohydrate digestion
- Saliva breaks down and hydrolyses food to maltose (neutralises pH)
Process of carbohydrate digestion (muscles in intestine)
Muscles in intestine wall push food along ileum
Sucrase
hydrolyses sucrose into glucose and fructose
Lactase
an enzyme that catalyzes the hydrolysis of lactose to glucose and galactose.
What are the roles of the glands in the digestive system?
To produce digestive juices
Name two types of glands in the digestive system
Pancreatic glands
What is the function of the small intestine in the digestive system?
It is where some digestion occurs and the absorption of soluble food also occurs
What is the function of the stomach in the digestive system?
It is where digestion occurs.
What is the role of the liver in the digestive system?
It produces bile
What are enzymes?
Biological catalysts with a specific shape active site
Where is lipase produced?
Pancreas and small intestine
Where is lipase secreted?
The small intestine
Role of lipase
digests lipid molecules; necessary for the preparation of absorption of triglycerides
emulsification
Breakdown of large fat globules into smaller, digestible particles (micelles)
Where is protease produced?
Stomach, pancreas and small intestine
Where is protease secreted?
Stomach and small intestine
Different peptidases
Endopeptidases
Endopeptidase
Hydrolyse peptide bonds between amino acids in central region of protein molecule
Exopeptidase
Hydrolyses peptide bonds on end of peptide molecules (formed from endopeptidases)
Dipeptidase
splits dipeptides into amino acids
What is the role of bile in the digestive system?
Neutralises HCl (from stomach) to provide alkaline conditions in which small intestine enzymes work best
Where is bile produced?
Liver
Where is bile stored?
Gall bladder
What are proteins hydrolysed to?
Amino acids
What is starch hydrolysed to?
alpha glucose
What is fat hydrolysed to?
Fatty acids and glycerol
Why can starch not be absorbed as easily?
It is a large, insoluble molecule
What is starch first digested to?
Maltose
What is maltose digested to?
alpha glucose
Explain how starch is hydrolysed to maltose
Amylase in the small intestine and mouth hydrolyses the glycosidic bonds
Explain how maltose is hydrolysed to alpha glucose
Maltase (membrane bound disaccharidase)
Which monosaccharides is sucrose hydrolysed to?
Glucose
Which monosaccharides is lactose hydrolysed to?
Glucose
How is the small intestine adapted for digestion?
The lining Is folded into villi which give a large surface area
Explain how dipeptides are hydrolysed to amino acids
Dipeptidases in the cell surface membrane of epithelial cells
Explain the steps in the digestion of a protein to a dipeptide
Endopeptidases hydrolyse peptide bonds within the protein
Explain how amino acids are absorbed
Na+ actively transported into the ileum from the epithelial cells
Where does lipid digestion occur?
The lumen of the small intestine
Explain the role of bile in lipid digestion
Bile salts emulsify lipids
Explain lipid digestion
In the small intestine lipase hydrolyses ester bonds
Explain how the products of lipid digestion are absorbed
Micelles move monoglycerides and fatty acids to the epithelium
Explain why chylomicrons leave the cell by exocytosis
They are too large to leave by any other method
Give an advantage of maltose being in the cell membrane and not secreted in pancreatic juice
It’s a more effective way to absorb the products
Why would damage to the microvilli cause the amino acid concentration of the blood to decrease?
Decreases surface area of epithelial cells
Explain co transport of glucose and sodium ions
Na+ actively transported out of epithelial cells into blood
What is the difference in the co-transport of amino acids and the co-transport of glucose?
With glucose - Na+ are actively transported into the blood
How is the ileum adapted for absorption?
- Thin walls lined with epithelial cells on other side which is rich with capillaries, which can carry absorbed molecules away
Absorption of amino acids and monosaccharides
Diffusion and co-transport
Absorption of triglycerides
Micelles break down when in contact with epithelia cells, releasing monoglycerides and fatty acids (non- polar so diffuse)
