Digestion And Absorption Flashcards
Define digestion
Hydrolysis of large insoluble molecules into smaller soluble molecules that can be absorbed across cell membrane
Mouth
Physical digestion with teeth
Salivary glands release amylase to break down starch chemically
Oesophagus
Hollow tube with muscular walls that contract to help move food down to stomach
Stomach
Protein digestion
Glandular tissue = enzymes and stomach acid
Muscular tissue churns food to mix
Small intestine
Digests proteins carbs and lipids mainly in duodenum
Produces enzymes : dipeptidase and maltase membrane bound
Soluble food molecules absorbed into blood stream across the ileum
Water absorption
Ileum
Inner walls folded into villi = Large SA
Duodenum
Digestion using enzymes from pancreas
Large intestine
Any water remaining in good is absorbed along with minerals
Undigested food material stored in rectum
Extra cellular
Digestive enzymes that work outside of cells
Digestion of carbs
Takes place in mouth and small intestine
Amylase enzyme used
Hydrolysis of starch into maltose
Maltese is used
Hydrolysis of maltose into 2 glucose molecules
Where Carb digesting enzymes are made
Amylase ; salivary glands pancreas and small intestine
Maltase ; lining of ileum
Digestion of proteins
Begins in lumen of stomach
Protease enzyme
Proteins to amino acids
Endopeptidase
Hydrolysis peptide bonds within proteins to create smaller proteins in stomach
Produced in stomach and pancreas
Pancreatic juice will have endo which hydrolyses peptide bonds within polypeptide chain
Exopeptidase
Hydrolyses peptide bonds at the ends of polypeptide chain to produce dipeptides
Produced by pancreas
Dipeptidase
Hydrolyses dipeptides into amino acids
Found within cell surface membrane of epithelial cells in small intestine
Produced in small intestine
emulsification of lipids
Bile made by liver stored in gallbladder
Bile salts bind to fatty liquid and break them into smaller ones
Digestion of lipids
Only in lumen of small intestine
Lipase hydrolyses ester bonds in tri to form fatty acids and mono
Produced in pancreas
The products of hydrolysis during digestion
Monosaccharides
Amino acids
Monoglycerides
Fatty acids
The ileum and villi
Have thin walls lined with epithelial cells
Have large network of capillaries to maintain diffusion gradient
Increases SA of the ileum so accelerates rate of diffusion
Thin outer layer so shorter diffusion distances
Process involved in absorption and transport of digested lipids from ileum into vessels
Micelles contain bile salts and fatty acids
Fatty acids more soluble in water
Fatty acids absorbed by diffusion into epithelial cells
Triglycerides reformed in epithelial cells ER
Packaged into chylomicrons and enter bloodstream via lacteal
Function of ATP in cotransport
Releases energy to allow ions to move against the conc gradient
Maintains a conc gradient
How does glucose enter by co-transport
Na is actively transported from ileum cells to blood using energy from ATP
This forms and maintains a diffusion gradient for Na to enter cells from the gut by diffusion from high to low
Glucose enters by facilitated diffusion and co transport by sodium
When mentioning why amounts of different molecules decreases or increases
Mention the enzyme (lipase) which breaks down triglycerides so they decrease
Mention hydrolysis
Mention bonds broken (ester bonds)
Role of Micelles in absorption of fats into cells lining ileum
Micelles contain bile salts and fatty acids
Fatty acids more soluble in water so help
Maintains higher concentration of fatty acids to lining of ileum
Fatty acids are absorbed by diffusion
Describe roles of protein enzymes
They hydrolyses peptide bonds
Endopeptidase acts in the middle to produce shorter polypeptide chains and increase ends
Exopeptidase acts on the end of polypeptides and produces dipeptides
Dipeptidase acts between 2 amino acids to produce a single amino acid
Advantage of lipid droplets and Micelle formation
Droplets increase SA so faster hydrolysis
Micelles carry fatty acids and glycerol through membrane to epithelial cells
How Golgi apparatus involved in absorption of lipids
Modifies triglycerides
Combines them with proteins
So that they can be packed for exocytosis
Components of chylomicrons
Cholesterol and phospholipids
Why does emulsion of lipids help digestion
Smaller lipid droplets = more SA
Lipase action faster so higher rate of digestion
How proteins are digested and absorbed
Stomach secretes protease
Endopeptidase acts in the middle to produce more end and shorter chains
Exopeptidase secreted by pancreas and produces Dipeptides
Dipeptidase membrane bound and produce amino acids
Absorption of amino acids in ileum
Facilitated diffusion of amino acids if high conc in the ileum
Co transport by Na ions
Na diffuses down conc gradient
As they’re removed from epithelium cell into blood by active transport
Facilitated diffusion of amino acids into blood
Roles of enzymes in break down if starch
Salivary amylase hydrolyses starch to maltose
Maltase hydrolyses maltose to glucose
hydrolysis of glycoside if bonds in maltose
Glucose absorption
Glucose cotransported by sodium into epithelial cell
Via carrier protein
Sodium removed by active transport into blood
Creates diffusion gradient
glucose can move into blood by facilitated diffusion
Absorption of products of fat
Bile slats associate with monoglycerides to form micelles
Micelles carry monoglycerides to membrane of epithelial cells
Monoglycerides and fatty acids recombine to form triglycerides in ER
Triglycerides combine w proteins to from chylomicrons at Golgi body
Chylomicrons leave epithelial cells by exocytosis to enter lacteal
Chylomicrons
Transport lipids absorbed from the intestine to skeletal muscle tissue
