Digestion Flashcards
What happens during digestion
large biological molecules are hydrolysed to smaller molecules that can be absorbed across cell membranes.
What are the 2 enzymes involved in carbohydrates being broken down and hydrolysed into monosaccharides from them being polysaccharides
Amylase
Membrane bound disaccharidases
Describe the role of amylase in carbohydrates (Starch) and how it hydrolyses polysaccharides into disaccharides
-amylase is produced by the pancreas and salivary glands
-amylase is a digestive enzyme which hydrolyses the polysaccharide starch into the disaccharide maltose by hydrolysing the glycosidic bonds in starch
Describe the role of membrane bound disaccharidases and how they break down and hydrolyse disaccharides into monosaccharides
-disaccharidases ie Maltase sucrase and lactase are membrane bound enzymes
-that hydrolyse the glycosidic bonds of the disaccharides maltose sucrose and lactose into monosaccharides
What are the three monosaccharides produced by membrane bound disaccharidases
Glucose + glucose
Fructose + glucose
galactose + glucose
What enzyme and other molecule digest lipids
-lipase enzyme and the action of of bite salts
What 3 enzymes hydrolyse the polymer proteins
-endopeptidases
-exopeptidases
-membrane bound dipeptidases
Explain the function of endopeptidases
-hydrolyse the peptide bonds between amino acids in the middle of the polypeptide so more ends / surface area for exopeptidases
Explain the function of exopeptidases
Hydrolyse terminal peptide bonds between amino acids at the end of the polypeptide
They remove single amino acids from proteins
Explain the function if membrane bound dipeptidases
Hydrolyse peptide bonds between 2 amino acids
Describe the absorption of lipids by a mammal, including the role of micelles
● Bile salts combine with monoglycerides and fatty acids to form micelles
○ Micelles make monoglycerides and fatty acids (more) soluble in water
○ Micelles carry fatty acids and monoglycerides to cells lining the ileum, where they break down to
release them
○ This maintains a high concentration of fatty acids and monoglycerides near cells lining the ileum
● Monoglycerides / fatty acids are absorbed (into epithelial cell) by diffusion (as they’re lipid soluble)
● Triglycerides reformed in (epithelial) cells and aggregate into globules
In mammals where are the products of digestion absorbed
The cells lining the ileum
How is the ileum adapted to maximise diffusion
-ileum wall is covered in villi which have thin walls to create a short diffusion pathway
-villi is surrounded by a network of capillaries maintaining a a concentration gradient
- epithelial cells have smaller microvilli - larger surface area to volume ratio
Explain the absorption of the monosaccharides(glucose galactose fructose) of digestion by cells lining the ileum of mammals
-glucose/galactose is absorbed by co transport with sodium ions via co-transporter protein
-fructose is absorbed via facilitated diffusion through a transporter protein
Explain the absorption of amino acids (products) and monosaccharides of digestion by cells lining the ileum of mammals
Co transport
● sodium ions actively transported from epithelial cells lining ileum to blood
● Establishing a conc. gradient of sodium ions higher in lumen than epithelial cell)
● sodium ions enters epithelial cell down its concentration gradient with glucose against its concentration gradient
● Via a co-transporter protein
● Glucose moves down a conc. gradient into blood via facilitated diffusion
Describe the digestion of lipids in mammals, including action of bile salts
● Bile salts (produced by liver) emulsify lipids causing them to form smaller lipid droplets called micelles
● This increases surface area of lipids for increased / faster lipase activity
● Lipase (made in pancreas) hydrolyses lipids (eg. triglycerides) → monoglycerides + fatty acids
● Hydrolysis of ester bond
Suggest why membrane-bound enzymes are important in digestion
● Membrane-bound enzymes are located on cell membranes of epithelial cells lining ileum
● (By hydrolysing molecules at the site of absorption they) maintain concentration gradients for absorption
Describe the pathway for absorption of products of digestion in mammals
Lumen (inside) of ileum → cells lining ileum (part of small intestine) → blood
