Digestion and absorbtion Flashcards
salivary glands function
secrete saliva containing amylase
hydrolyses starch to maltose
stomach function
contains gastric juices
kills microorganisms
contains endopeptidases and exopeptidases
pancreas function
secretes pancreatic juices containing
amylase
endopeptidases
exopeptidases
lipases
small intestine
large surface area for absorption of products
matase enzymes embedded to hyrdolyse maltose to glucose
small intestine
large surface area for absorption of products
matase enzymes embedded to hydrolyse maltose to glucose
digestion of starch
- food enters mouth and is broken by teeth
- salivary amylase hydrolyses glycosidic bonds in the starch producing maltose
- salivary amylase is denatured due to acidic pH
- pancreatic amylase hydrolyses starch to maltose
- maltose is then hydrolysed to glucose by maltase enzymes
- glucose is then absorbed
Describe the role of the enzymes of the digestive system in the complete breakdown of starch. (4)
- Salivary amylase hydrolyses starch into
maltose - By hydrolysing glycosidic bonds
- Maltose is hydrolysed into glucose
- By maltase
Describe how glucose is absorbed from the ilium into the blood [5]
- Na+ are actively transported out of epithelial cell into the blood (by sodium potassium pump)
- This creates a concentration gradient of Na+ between lumen of the ilium and the epithelial cell
3.Cotransporter proteins have 2 binding sites complementary to Na+ and glucose. Only when both molecules bind will the molecules be moved across the membrane - Na+ and glucose enter by facilitated diffusion using complementary cotransporter proteins.
- Na+ diffuse into the cell down its concentration gradient
- Glucose moves into the cell against its concentration gradient
- Glucose moves into the blood by facilitated diffusion
protein digestion processes
- proteins are hydrolysed by enzymes called proteases in the stomach
- endopeptidases hydrolyse the peptide bonds within the polypeptide chain
- produces shorter polypeptide chains and increase surface area for faster absorption
- exopeptidases hydrolyse the peptide bonds at the terminal ends of the protein
- dipeptidases are enzymes in the cell surface membrane
Describe how amino acids are absorbed from the ilium into the blood [5]
- Na+ actively transported out of epithelial cell into the blood by sodium potassium pump
- This creates a concentration gradient of Na+ between lumen of the ilium and the epithelial cell
- Na+ and amino acid enter by facilitated diffusion
- Na+ moves into the cell down its concentration gradient
- Amino acids move into the cell against their concentration gradient
- Amino acids move into the blood by facilitated diffusion
lipid absorption
- Lipid droplets are mixed with bile salts to form smaller droplets
- Smaller droplets increase surface area for faster hydrolysis by lipase
- Triglycerides hydrolysed into glycerol, fatty acids and monoglycerides
- Glycerol and fatty acids form micelles
- Micelles enter the epithelial cell by simple diffusion.
- At the S.E.R: Fatty acids, glycerol recombined to form triglycerides
- At the golgi apparatus: Triglycerides are modified and proteins are added to form lipoproteins (called chylomicrons) and packaged into vesicles (Chylomicrons are water soluble and so can be carried in the blood.)
- Chylomicrons are transported into a lymph vessel by exocytosis.
They then enter the blood.