digestion and absorption

• Starch reacts with iodine to form a black color
• Protein reacts with biuret to form a purple color
• Lipid reacts with ethanol to form a white emulsion
• Glucose reacts with benedict to form an orange/red color
• Hydrolysis reactions are involved in digestion
• Amylase catalyses the hydrolysis of starch into maltose
• Amylase is found in the salivary glands and pancreas
• Enzymes that break down disaccharides are called disaccharidase
• Maltase hydrolyses maltose into glucose and glucose
• Maltase is bound to the epithelial cell membrane lining the lumen
• Lactase hydrolyses lactose into glucose and galactose
• Sucrase hydrolyses sucrose into fructose and glucose
• In digestion, large biological molecules are hydrolysed into smaller molecules that can fit through cell membranes
• Peptidases catalyse the hydrolysis of proteins into amino acids by breaking the peptide bonds between amino acids
• Endopeptidases hydrolyse peptide bonds within the protein chain, for example, trypsin and pepsin
• Endopeptidases are secreted from the pancreas
• Exopeptidases hydrolyse the peptide bonds at the end of the protein, breaking off amino acids
• Bile salts emulsify lipids, then lipase breaks down lipids by breaking the ester bond
• Monoglycerides and fatty acids stick to bile salts to form micelles
• Glucose is absorbed by active transport via co-transporter protein, galactose is absorbed in the same way
• Fructose is absorbed by facilitated diffusion
• Monoglycerides are lipid-soluble and diffuse directly through membranes
• Amino acids are transported by sodium-dependent transporter proteins
• Fatty acids and monoglycerides are emulsified by bile salts to form micelles
• Fatty acids enter the epithelial cells and link to form triglycerides
• Triglycerides combine with proteins in the Golgi body to form chylomicrons
• Chylomicrons enter the lacteal and are transported away from the intestine