ANFF topic 1 part 3 Flashcards
What are the steps in obtaining nutrition and energy from food?
- ingestion
- digestion
- absorption
- elimination
What is ingestion?
- process of taking in food through the mouth
Define digestion.
- the mechanical and chemical break down of food into small organic fragments that is a suitable size for absorption across the digestive epithelium
- large, complex molecules of proteins, polysaccharides and lipids must be reduced to simpler particles
What digestion happens in the mouth?
- beginning of digestion
- the salivary enzyme amylase begins the breakdown of food starches into maltose (disaccharide)
What occurs in the oesophagus?
- no significant digestion of carbs take place
- no digestive enzymes present
- produce mucous for lubrication
What do monosaccharides make up the disaccharides?
- maltose –> glucose + glucose
- sucrose –> glucose + fructose
- lactose –> glucose + galactose
What enzymes are present in the small intestinal wall?
- maltase
- sucrase
- lactase
Where is amylase from and what does it break down?
- from pancreatic juice
- breakdown of starch and glycogen into maltose
What happens to glucose after it has been broken down?
- absorbed and can be used in metabolic pathways to harness energy
- transported through the intestinal epithelium into the bloodstream to be transported to the different cells in the body
What takes place in the stomach?
- protein digestion
What breaks down protein in the stomach?
- pepsin
- protein to peptides
What enzymes in the duodenum break down peptides into smaller peptides?
- trypsin
- elastase
- chymotrypsin
What is pepsin produced by?
- stomach chief cells
What enzymes break down proteins into peptides?
- pepsin
- trypsin
- elastase
- chymotrypsin
What enzymes break down peptides into smaller peptides and amino acids?
- carboxypeptidase
- aminopeptidase
- dipeptidase
Where does lipid digestion begin?
- in the stomach
What enzymes break down lipid in the stomach?
- lingual lipase
- gastric lipase
Where does the bulk of lipid digestion occur?
- in the duodenum
What triggers the release of bile?
- when the chyme enters the duodenum, hormonal responses trigger the release of bile
Define emulsification.
- Large lipid globules are broken down into several small lipid globules
What is the function of bile?
- digestion of lipids by emulsification
What happens when there is water around lipids?
- hydrophobic substances
- they will aggregate to form globules to minimize exposure to water
How does bile emulsify large lipid globules?
- bile contains bile salts which are amphipathic
- hydrophilic side of bile salts interact with water on one side and the hydrophobic side interacts with lipids
Why is emulsification important for digestion of lipids?
- if there is no emulsification, the lipid in the chyme would still be in the form of large globules, there is very little surface area of the lipids for the lipase to act on
- emulsification of lipid globules would increase the available surface area of lipids and pancreatic lipases can then act on the lipids more efficiently and digest
How are lipids absorbed in the small intestine?
- bile salts will surround long-chain fatty acids and monoglycerides forming tiny spheres (micelles)
- micelles move into the small intestine absorptive cells where the long-chain fatty acids and monoglycerides diffuse out of the micelles into the absorptive cells leaving the micelles behind in the chyme
- these large spheres are called chylomicrons
- chylomicrons contain triglycerides, cholesterol, and other lipids and they have proteins on their surface
- together, they enable the chylomicron to move in an aqueous environment without exposing lipids to water
- chylomicrons leave the absorptive cells via exocytosis
- chylomicrons enter the lymphatic vessels then enter the blood in the subclavian vein
How are fat-soluble vitamins absorbed?
- same as lipids
How are water-soluble vitamins absorbed?
- directly absorbed into the bloodstream from the intestine
What happens to undigested food?
- enters the colon where water is reabsorbed
What happens in the colon?
- colon has microflora called “intestinal flora” that aid in the digestion process
- semi-solid waste is moved through the colon by peristaltic movements of the muscle
Where is undigested food material stored?
- the rectum
- the rectum expands in response to storage of fecal matter
- triggers neural signals required to set up the urge to eliminate
How is waste eliminated from the body?
- through the anus
- peristaltic movements of the rectum
