Digestion Flashcards
What happens during digestion?
large biological molecules are hydrolysed into smaller molecules that can be absorbed across cell membranes
How are carbohydrates digested?
carbohydrates require more than one enzyme to hydrolyse them into monosaccharides = amylases and membrane bound disaccharidases
Where is amylase produced and what does it do?
salivary glands - begins digestion in the mouth which helps keep the mouth clean and reduce bacterial infection
pancreas - digests the remaining starch in the duodenum and releases amylase into the small intestine
How does amylase work?
catalysing hydrolysis reactions that break the glycosidic bonds in starch to produce maltose (a disaccharide)
What are membrane bound disaccharidases?
enzymes that are attached to the membranes of epithelial cells lining the ileum
How do membrane bound disaccharidases work?
help break down disaccharides into monosaccharides involving the hydrolysis of glycosidic bonds (completes digestion)
What are examples of disaccharidases?
maltase breaks maltose into glucose and glucose
lactase breaks lactose into glucose and galactose
sucrase breaks sucrose into glucose and fructose
How are lipids digested?
1.) chemical stage = lipase
- lipase enzymes catalyse the breakdown of lipids into monoglycerides and fatty acids by hydrolysing the ester bonds in triglycerides
2.) physical stage = emulsification and micelle formation
- bile salts produced in the liver and emulsify lipids to form tiny droplets (micelles) which increases the surface are for lipase to work on (faster hydrolysis) - micelles helps products to be absorbed
- once lipase worked monoglycerides and fatty acids stick to bile salts (micelles)
Where is lipase produced?
pancreas - released to small intestine where they act
How are proteins digested?
Protein digestion begins in the lumen pf the stomach by protease enzymes
broken down by peptidases - enzymes that catalyse hydrolysis of peptide bonds between amino acids e.g endopeptidase, exopeptidase
What is the difference between endopeptidase and exopeptidase?
Endo = hydrolyse peptide bonds between amino acids in the within /middle of the polymer chain to produce dipeptides
Exo = hydrolyse peptide bonds between the amino acids at the end/terminal of the polymer to produce dipeptides
Where are protease enzymes found?
Fluid secreted by the pancreas travels to the small intestine and helps to neutralize the acidic mixture and increase the pH. This pancreatic juice contains endopeptidases and exopeptidases.
How do membrane bound dipeptidases digest proteins?
These enzymes hydrolyse dipeptides into amino acids which are released into the cytoplasm of the cell (breaks peptide bond between 2 amino acids)
