Digestion and Absorption - B10 Flashcards
What is digestion?
enzymes hydrolyse large insoluble molecules into small soluble monomers(so they can be absorbed and assimilated)
Define absorbed.
to move from the small intestine into the blood.
Define assimilated.
to be used by the body for a function
What are the different organs on the digestive system?
mouth, oesophogus, stomach, large intestine, small intestine, pancreas, liver, gall bladder, appendix, rectum, anus.
What happens in the mouth in the digestive system?
-salivary gland ->amylase which breaks down starch
-mechanical digestion ->teeth->increase SA for enzymes to use
What happens in the oesophogus of the digestive system?
-muscle ->squeezes food down slowly ->peristalsis: the movement of food down the oesophagus in a squeezing manner
-food is now known as bolus.
What happen in the stomach during digestion?
-stomach acid ->HCl ->kills pathogens, protease(works best at pH2)(where protein breaks down)
What is food known as after it leaves the stomach?
chyme
What happens in the small intestine in the digestive system?
food molecules absorbed
What happens in the large intestine during digestion?
water is absorbed
What happens in the pancreas during digestion?
pancreatic juices - enzymes such as amylase, protease, lipase
What is chyme?
a thick, semifluid mass of partially digested food and digestive sections that is formed in the stomach and intestine during digestion
What are the 3 sections of the small intestine?
-duodenum : 25cm long, resistant to acids, it neutralises acids
-jejunum: 2/5 of the small intestine, lots of villi, where absorption occurs
-ileum: final chance for absorption(about 3/5)
What are the adaptations of the villi?
-large SA-> increased rate of diffusion->microvilli
-good blood supply->maintain conc. gradient
-one cell thick ->short diffusion distance
-lots of carrier/channel proteins
-mitochondria ->active transport
How is glucose/starch digested?
1)starch is hydroysed by maltose in the salivary glands
2)amylase is denatured by stomach acid
3)pancreas secretes more amylase(small intestine), leaving remaining starch and maltose
4)maltase is found in epithelial cell membranes(small intestine) will break the maltose into glucose
-uses hydrolysis of glycosidic bonds
What is co-transport?
the movement of two substances at the same time
What are co-transporters?
A type of carrier protein. They bind two molecules at the same time. The conc. of one of the molecules is used to move the other molecule against it’d own conc. gradient(known as secondary active transport - passive but against the conc. gradient)
What other protein is involved in co-transport other than carrier proteins?
symport
What is glucose diffusion?
glucose in the epithelial cell now moves down its conc. gradient into the capillary by facilitated diffusion through basal membrane.
Describe the process of glucose co-transport?
-when glucose conc. is lower in the lumen it moves into the epithelial cell through a carrier protein called a symport.
-to move through this symport it must move with sodium
-sodium moves down its conc. gradient as there is a low conc. of sodium ions in the epithelial cell.
Sodium/Potassium pump:
-low conc. of sodium ions in the epithelial cell is brought about by active transport of sodium out of the capillary
-this occurs through the sodium/potassium pump that uses ATP to swap 3 sodium ions out and 2 potassium ions in
-glucose and sodium ions bind together in the symport(co-transporter)
-they move together as their binding changes the tertiary structure to open the protein carrier
-glucose moves in against its conc. gradient while sodium ions move in down their conc. gradient
