Digestion and Absorbtion Flashcards
Why is digestion needed?
- Large molecules in foods are too big to cross cell membranes meaning they can’t be absorbed into blood from gut
- Broken down into smaller molecules during digestion so they can move easily across meme ranges and b absorbed and transported
Polymers are broken down into monomers, what are the monomers of carbohydrates, fats and proteins?
Carbohydrates - disaccharides then monosaccharides
Fats - fatty acids and monoglycerides
Proteins - amino acids
How does amylase break down carbohydrates?
Catalysts the conversion of starch (polysaccharide) into maltose (disaccharide) through the hydrolysis of glycosidic bonds in starch.
Where does amylase come from?
Produced in salivary glands (release it into mouth) and by pancreas (release it into small intestine).
What are membrane bound disaccharides?
Enzymes attached to cell membranes of epithelial cells lining ileum.
What do membrane bound monosaccharides do?
Break disaccharides down into monosaccharides through the hydrolysis of glycosidic bonds.
Describe the disaccharidase and monosaccharide products for maltose.
Maltase
Glucose and glucose
Describe the disaccharidase and monosaccharide products for sucrose.
Sucrase
Glucose and fructose
Describe the disaccharidase and monosaccharide products for lactose.
Lactase
Glucose and galactose
How does lipase and bile salts break down fats?
Lipase catalysts the breakdown of lipids into monoglycerides and fatty acids via the hydrolysis of ester bond. Bile salts emulsify lipids increasing the SA of lipid for lipase to work on. Monoglycerides and fatty acids stick to bile salts creating micelles.
Where does lipase come from and where does it work?
Made in pancreas and work in small intestine.
Where do bile salts come from?
Produced in liver.
What are peptidases?
Enzymes that catalyse the conversion of proteins into amino acids by hydrolysing the peptide bonds between amino acids.
What do endopeptidases?
Hydrolyse peptide bonds within protein.
Trypsin and chymotrypsin synthesised in pancreas and secreted in small intestine.
Pepsin released in stomach by cells in stomach lining - only works in acidic conditions.
What do exopeptidases do?
Hydrolysis peptide bonds at the end of proton molecules.
Dipeptidases work specifically on dipeptides, separating the two amino acids by hydrolysing the peptide bond.
Located on cell surface membrane of epithelial in small intestine.
How are monosaccharides absorbed across cell membranes?
Glucose and galactose absorbed by active transport with sodium ion via cotransport protein.
Fructose by facilitated diffusion.
How are monoglycerides and fatty acids absorbed across cell membranes?
Micelles help move monoglycerides and fatty acids towards epithelium where they break up releasing monoglycerides and fatty acids which diffuse directly across the epithelial cell membrane as they are water soluble.
How are amino acids absorbed across cell membranes?
Sodium ions active,y transported out of epithelium into ileum, they then diffuse back into epithelium cells through sodium dependent transport proteins in cell membranes carrying the amino acids with them.
