3.3 Digestion and absrobtion Flashcards
what are the two functions of the mouth
mechanical - chew to increase surface area
chemical - salivary glands secrete amylase
what is the function if the oesophagus
muscular - peristalsis (rhythmical contractions pushing food to stomach)
ring of cartilage - flexible and protects
what are the two functions of the stomach
mechanical - muscular to churn food
chemical - hydrochloric acid to kill pathogens and acidic as pepsin needs pH2
what is the function of the liver
produces bile to emulsify fats to increase surface area
what is the function of the gall bladder
stores bile
what is the function of the pancreas
pancreatic juice - enzymes and neutralises acids with bicarbonate to a pH of around 7
what is the function of the small intestine
absorb nutrients produces all enzymes
is one cell thick and has microvilli
what is the function of the large intestine
absorbs excess water and has bacteria that can break down complex carbohydrates
what is the function of the rectum
stores feaces
what is the function of the anus
expeles
what are the three enzymes in digestion
carbohydrates, lipases and proteases
what do carbohydrates work on
carbohydrates into disaccharides and then monosaccharides
what do lipases work on
lipids into fatty acids and glycerol
what do proteases work on
proteins into amino acids
describe the process of amylase
- the salivary gland excretes saliva and it thoroughly mixed with the food while chewing.
- saliva contains the enzyme salivary amylase, this starts hydrolysing any starch in the food to maltose. it also contain mineral salts that help maintain the pH at optimum rate
- the food is swallowed and enters the stomach where the acidic conditions denote the amylase preventing further hydrolysis
- the food is passed into the small intestine where it mixes with the pancreatic juice from the pancreas
- the pancreatic juice contains the enzyme pancreatic amylase, this continues to hydrolyse any remaining starch to maltose. alkaline salts are produced by the pancreas which help maintain the optimum pH
- muscles in the intestine wall push food along the ileum, and its epithelial lining produces the disaccharide maltase, the malted is a membrane bound as it is not released into the lumen of the ileum, membrane bound allows a shorter diffusion distance
what does surcease hydrolyse
the single glycosidic bond in the sucrose molecule, producing glucose and fructose
what does lactase hydrolyse
the single glycosidic bond in lactose, producing glucose and galactose
define endopeptidases
acts to hydrolyse peptide bonds within protein to break down increasing the surface area for exopeptidase
define exopeptidase
acts to hydrolyse peptide bonds at the end of proteins molecules, breaking the protein chain into single amino acids
define dipeptidases
specifically work on two amino acids that make up a dipeptide by hydrolysing the peptide bond between them.
what are triglycerides broken down into
2 fatty acids and a monoglyceride
steps of lipid digestion
- big lipid droplet mixes with bile salts and forms smaller droplets
- lipases into monoglycerides and fatty acids
- these are called micells (a group of monoglycerides and fatty acids) and are absorbed separately as it moves to the epithelial cells
- once in the cell the endoplasmic reticulum reforms the triglycerides
- a vesicle of triglycerides called a chylomicron is released by exocytosis into the lymphatic system then the bloodstream
6 steps of glucose transport
- the transporter is initially facing into the lumen and is able to bind to sodium but not the glucose
- Na+ bonds which induces a conformational change in the protein that opens the glucose binding site
- glucose bonds and the protein reorients in the membrane so that the sites holding glucose and Na+ are moved into the cell
- the Na+ dissociates and goes into the cytoplasm, the glucose binding then destabilises
- The glucose then dissociates into the cytoplasm and the protein then reorients back into its original position.
