Nutrition Flashcards
Define autotroph
Organisms that use simple inorganic molecules to create complex organic molecules
Define heterotroph
Organisms that consume complex organic food material
GIve the three types of heterotroph and their definitions
Holozoic feeders follow the process of ingestion, digestion, absorption, assimilation and egestion. Parasites live in or on a host organism and cause it harm. Saprophytes feed by extracellular digestion
Why do we have a tube gut?
Because we have a varied diet each part is specialised to digest/absorb different molecules
From the outside in, what are the layers that make up the gut wall?
Serosa, longitudinal muscle layer, circular muscle layer, submucosa and mucosa
What digestion occurs in the mouth?
Chemical digestion of starch by amylase, mechanical digestion by chewing
How is food moved down the oesophagus?
Peristalsis- circular muscles contract and longitudinal muscles relax to push the food bolus along
What digestion occurs in the stomach?
Chemical digestion of proteins by the enzyme pepsin to shorter chains. Mechanical digestion by churning
Which cells produce pepsinogen in the stomach?
Chief cells (/zymogen cells)
Which cells produce HCl in the stomach?
Oxyntic cells (/parietal cells)
What are the purposes of HCl in the stomach?
To activate pepsinogen to pepsin, to kill bacteria and to give the optimum pH for pepsin enzyme
Why is pepsinogen released in inactive form in the stomach and how is it activated?
Otherwise it would cause autolysis (digest the cells making it). It is activated by HCl
What are endo and exopeptidases?
Endopeptidases hydrolyse peptide bonds in the middle of a polypeptide chain, exopeptidases at the terminal ends
Which enzymes are produced by the pancreas?
Trypsin (endopeptidase), exopeptidases, lipase, amylase
What is the function of bile and where is it produced/stored
Emulsifies lipids to increase surface area for lipase. Made in liver, stored in gall bladder
Why is trypsinogen released in inactive form and how is it activated?
Otherwise it would cause autolysis (digest the cells making it). It is activated by enterokinase, also from the pancreas
Which enzymes are fixed within the cell membrane of the epithelial cells in the duodenum and ileum to digest dimers intracellularly?
Lactase, sucrase, maltase and dipeptidase
How are glucose and amino acids absorbed in the ileum?
Co transport with sodium ions
How are lipids absorbed in the ileum?
Triglycerides have been broken down into fatty acids and glycerol, which can diffuse through the phospholipid bilayer
What happens to glucose after it is absorbed in the ileum?
They enter capillaries by facilitated diffusion then transported via hepatic portal vein to the liver. Used for respiration or stored as glycogen
What happens to amino acids after they are absorbed in the ileum?
They enter capillaries by facilitated diffusion then transported via hepatic portal vein to the liver. Used for protein synthesis or deaminated
What happens to lipids after they are absorbed in the ileum?
Reassembled into triglycerides at SER. These then pass into the lacteal and are carried via the lymphatic system to the blood at the thoracic duct
Why do we need to eat fibre?
Cellulose fibre is required to provide bulk to faeces and stimulate peristalsis.
What is the function of the colon?
Absorbs the remaining water, together with vitamins
