Digestion Flashcards
What do carbohydrates, lipids and proteins break down into?
Carbohydrate: glucose
Lipids: fatty acids & glycerol
Proteins: amino acids
Describe the 4 processes involved in digestion and absorption
1) Ingestion: food taken into mouth
2) Digestion: enzymes break large insoluble molecules into smaller soluble molecules
3) Absorption: products of digestion absorbed into bloodstream
4) Egestion: removal of faeces containing undigested food, bacteria and enzymes
What are the two types of digestion that take place in the mouth?
Mechanical; via chewing
Chemical; amylase released from salivary glands turns starch into maltose
What is the process that takes place in the oesophagus, stomach and intestines to help move the food down?
Peristalsis; waves of muscular contractions
What are the functions of the liver and gall bladder?
Liver: produces bile
Gall bladder: stores and secretes bile
What is the function of bile?
1) Neutralises stomach acid in the duodenum prior to the small intestine so that it doesn’t dissolve intestine tissue.
2) Emulsifies fats into smaller droplets (sometimes micelles), this provides a higher surface area for lipase.
What is digested in the stomach and how?
Proteins are digested into amino acids by the enzyme pepsin as well as mechanical digestion- peristalsis in the stomach (churning)
What cells can be found in the gastric pits of the stomach lining?
1) Mucus cells
2) Chief cells
3) Parietal cells
What is the function of mucus cells?
Line the stomach to prevent pepsin enzyme from digesting the stomach
What is the function of chief cells?
They produce pepsinogen, which can be activated by pepsin or HCl to convert into pepsin.
What does the pancreas do?
Secretes pancreatic juice that contains protease, lipase and amylase.
What occurs in the small intestine?
- Digestion and Absorption
What chemicals are present in the small intestine?
Bile, amylase, lipase and some gastric juice may enter.
What features of the small intestine benefit it’s function?
Villi and microvilli that have good blood supply and can increase surface area for absorption to take place
What are the three types of peptidase and what does each one do?
1) exopeptidase- removes terminal amino acids
2) endopeptidase- breaks polypeptides into smaller chains
3) dipeptidase- hydrolyses dipeptides into amino acids
What occurs in the large intestine?
This is where water is absorbed
How are glucose and amino acids absorbed?
1) Co-transport of Na+ and glucose through the membrane of an epithelial cell
2) Active transport of K+ ions and Na+ ions wiv the use of ATP to maintain a concentration gradient (a potassium pump is used to produce potassium ions)
3) Facilitated diffusion of glucose into capillaries
Describe how the small intestine is adapted to its function
1) Large SA- villi/microvilli
2) thin epithelium- short diffusion pathway
3) network of capillaries- good blood supply
4) Mitochondria provide ATP for active transport
5) Lacteals for absorption of digested fats
Describe and explain roles of diffusion, facilitated diffusion and active transport in the ileum.
-Diffusion
Down concentration gradient. E.g- micelles moving into epithelial cells and chylomicrons moving into lacteals
-Facilitated diffusion
Down concentration gradient, with help of carrier protein. E.g: amino acids moving into epithelial cells
-Active Transport
Against conc. gradient, requiring ATP,
How are lipids absorbed in the digestive system?
1) Bile salts emulsifies fat globules into smaller droplets in the small intestine- this provides a larger surface area
2) Pancreatic lipase digests the far droplets into monoglycerides and fatty acids. These are contained in smaller droplets called micelles
3) Micelles diffuse into the epithelial cells in the small intestine
4) Monoglycerides and fatty acids join together through condensation and form a chylomicron
5) Diffuses into lacteal via exocytosis
What makes up a ‘chylomicron’?
Phospholipids, cholesterol, proteins and triglycerides.
What is exocytosis?
The process by which a small piece of membrane wraps around the lipid droplet and pinches it off
