Mr P bio digestion and absorption Flashcards
What does the mouth do?
Contains teeth which break food into small pieces, increasing its sa:v food is shaped into a bolis and covered in saliva ready for swallowing
What is the oesophagus and what does it do?
Hollow tube with muscular walls. Peristalisis (contractions of the muscle) to help move food down into stomach
What does the stomach do? (protein digestion)
Protein digestion begins here. Glandular tissue produces enzymes and stomach acid. Muscular tissue churns food, mixing it with enzymes and acid. The acid helps to unravel proteins to enable enzyme activity, +lowers pH so optimal for enzymes
What is the name of the space into the small intestine through which food passes through?
The ileum
What are the 3 sections of the small intestine?
Duodenum, jejunum and the ileum
Why does the wall of the small intestine contain muscle?
Contracts (peristalsis) to move food along
What happens in the duodenum?
Carbohydrate, protein and lipid digestion, enzymes produced in the pancreas and small intestine
What is the structure of the ileum?
Long and lined with finger like villi to increase surface area
What happens in the large intestine?
Remaining water is absorbed here. Any digested food material is stored in the rectum and removed through the anus
What does digestive enzymes being extra cellular enzymes mean?
Work outside of cells
What are the 3 main types of digestive enzyme?
Carbohydrates, proteases and lipases
What is the process of carbohydrate digestion?
1) Good enter mouth and broken up by teeth and mixed with saliva
2) salivary amylase starts to hydrolyse the starch to maltose and on the stomach this salivary amylase is denatured
3) in small intestine, pancreatic amylase continues to hydrolyse the starch to maltose
4) maltose then hydrolysed to glucose by maltease in the membranes of the epithelial cells. The glucose can then be absorbed into bloodstream as are small and can be carried through if h membranes of cells lining small intestine
How is the small intestine adapted for surface area?
Lining of small intestine is folded and there are microvilli present.
Where is amylase produced and what does it do?
Produced in salivary glands and pancreas, starch to maltose
where is maltase produced and what does it do?
in epithelium cell membrane of small intestine, maltose to glucose
describe the process of protein digestion
1)digested by a group of enzymes called proteases. 2)protein digestion begins in the stomach where an enzyme called endopeptidase hydrolyses the peptide bonds in the middle of the protein making the protein into smaller chunks which increases the SA for exopeptidase
3) the partly digested food passes from stomach to small intestine where pancreatic juice neutralises the stomach acid. also contains endopeptidases and exopeptidases
4)exopeptidases hydrolyse near the ends of the polypeptide chains producing dipeptides/ amino acids
5)finally dipeptidase enzymes in cell surface membrane of epithelial cells hydrolyse dipeptides into amino acids which are small enough to pass through the cell membrane via protein carriers
what is the process of lipid emulsification?
1) in stomach- solid lipids turned into a fatty liquid consisting of fat droplets
2)when fatty liquid arrives in the small intestine, bile (containing bile salts) which has been made in the liver and stored in the gallbladder is secreted
3) bile salts bind to the fatty liquid and breaks the fatty droplets into small ones via emulsification. emulsification helps increase SA for digestive enzymes
describe the digestion of lipids
1)takes place solely in lumen of small intestine
2) lipase enzymes break down lipids to glycerol and fatty acids
3)lipase enzymes are produced in the pancreas + secreted into the small intestine by the pancreas
describe the absorption of lipids
digestion results in large insoluble molecules being broken down into smaller soluble molecules. by the time products of for reach small intestine, consistency like soup. this is where absorption of products of digestion occurs
what is the process of glucose absorption called?
co-transport
where is glucose absorbed into via co-transport?
epithelial lining of the ilium (small intestine)
describe the process of co-transport
1) glucose and NA molecules are co-tranported across the membranes via facilitated diffusion. involves specific carrier protein that will only carry glucose and NA molecules at the same time
2) once inside the cell, the 2 molecules separated. NA ions transported across other side of the cell into blood via active transport. creates conc grad
3)glucose molecule follows similar path into blood via facilitated diffusion
describe the process of the co-transport of amino acids
1) Na+ moved from epithelial cell into blood via ative transport
2) maintains conc grad of Na+ between cell and lumen
3) amino acid moves from cell into blood via facilitated diffusion
4) amino acid and Na+ move by cotransport down conc grads from lumen into cell
what happens if ATP production is inhibited?
active transport can’t occur so If NA ions are not actively transported into blood from cell then conc of NA ions will rise in cell. if this occurs then facilitated diffusion from the lumen will stop. as glucose/ amino acids can enter cell without NA so would stop their absorption
what happens if the tertiary structure of the carrier protein changes?
facilitated diffusion of glucose/amino acids can’t occur. if molecules are not diffused into blood from cell, then conc of glucose/amino acid acids will rise in cell. if this occurs then facilitated diffusion from lumen will stop. as NA can’t enter the cell without glucose/ amino acids, also stop NA absorption
what are lipids hydrolysed into?
glycerol, fatty acids and monoglycerides
describe how lipids get into the epithelial cell
1)hydrolysed into glycerol, fatty acids and monoglycerides
2) m + f associate with bile salts + phospholipids +form micelles
3)micelles fit between microvilli. constantly break down and reform, building up a small pool of freely dissolved m +f that can be absorbed
4)m + f can diffuse through phospholipid bilayer of epithelial cell membrane coz they non-polar. micelle can’t be absorbed
what are micelles?
small droplets that transport the poorly soluble monoglycerides and fatty acids to the surface of the epithelial cells membrane to be absorbed
describe how lipids travel from the epithelial cell to the blood
1) fatty acids and monoglycerides enter SER + are resynthesises into triglycerides
2)proteins are made in the RER
3)triglycerides are combined in the Golgi with: proteins, cholesterol + phospholipids to form chylomicron
4) they reach the membrane in a vesicle
5) leave via exocytosis
6) enters blood stream and travels to lymphatic system
how do short fatty acid chains travel from the epithelial cell to the blood?
diffuse directly into blood from small intestine lumen through epithelial cells as they can diffuse through phospholipid bilayer
