Adaptations for nutrition
Autotrophic nutrition- make complex organic molecules from simple inorganic molecules
Photoautrophic, use light energy as a source of energy
Chemoautotrophic, use energy from chemical reactions as a source of energy.
Heterotrophic-organisms consume complex organic molecules and break them down into simple inorganic molecules, they eat autotrophs
Saprotrophic nutrition is when organisms feed on dead or decaying matter, secreting enzymes to decompose the material extracellularly, they absorb the soluble product by endocytosis.
Holozoic- they ingest, digest and egest food by ingestion, mechanical digestion, chemical digestion, absorption and excretion.
Parasitic nutrition means obtaining nutrition from another living organism. Parasites live in the body of a host, the host suffers harm.
Unicellular organisms are holozoic, but can obtain all nutrients by diffusion, facilitated diffusion or active transport.
Hydra extends it's tentacles , stings it's prey and paralyses it, digest it extracellulrly and these products are absorbed into it's cells.
Human digestion
Diagram of digestive system
Food must be digested because it's insoluble and too big to be absorbed into the blood and cross membranes. Polymers must be converted to monomers to be rebuilt into body cells.
Ingestion (taking food into the body through the mouth), mechanical digestion(cutting and crushing by teeth and muscle contraction of the gut wall, to increase the surface area for enzymes to act) Chemical digestion(by secretion of enzymes), Absorption (passage of molecules and ions through the gut wall into the blood), egestion(the elimination of waste not made by the body.
Mouth(ingestion and digestion starch), oesophagus (carriage of food to the stomach) stomach(digestion of protein) duodenum(digestion of carbohydrates fat and protein) ileum (as above and absorption of digested food) colon (absorption of water) rectum (storage of faeces) anus (egestion)
Structure of the gut wall
Outer layer, serosa, is tough connective tissue, to protect the gut wall, serosa reduces friction when the gut moves.
Longitudinal muscle relaxes and circular muscle contracts to create peristalsis
Submucosa is connective tissue containing blood and lymph vessels.
Mucosa is the innermost layer and it lines the gut wall, the epithelium secretes mucus which protects the mucosa.
Pancreatic secretion
Enzymes
Sodium hydrogen carbonate neutralises stomach acid and provides optimum pH for pancreatic enzymes to work
Endopeptidases hydrolyse protein to peptides
Trypsinogen, is an inactive form of trypsin by enterokinase
amylase digests starc to maltose
lipase hydrolyses lipids into fatty acids and monoglycerides
Buccal cavity salivary amylase converts starch to maltose, hydrogen carbonate and carbonate ion to provide optimum pH for amylase. Mucus lubricates food passage.
Stomach, food is kept in the stomach by the contraction of two sphincters. Gastric juice secreted by the glands in the gastric pits..
The mucosa has large folds called rugae
Gastric juice
Peptidases secreted by chief cells, pepsinogen activated by hydrogen ions to pepsin and endopeptidase, they hydrolyse protein to polypeptides.
hydrochloric acid secreted by oxyntic cells, provides optimum temperature and kills most bacteria.
Mucus secreted by goblet cells to protect stomach walls and lubricate food.
Duodenum & ileum
Bile made in liver, stored In gall bladder and goes through the bile duct into the duodenum. Bile salts emulsify lipids neutralises stomach acid
Brunner's glands secrete alkaline.
Endo and exopeptidases are secreted by cells at the top of the villus. Disaccarides are absorbed into the tips of the villi. Carbohydrase in cell membrane convert them to monosaccharides (intracellular)
Absorption
ileum is about 6m long and has villi and microvilli to provide large SA. Occurs by diffusion facilitated diffusion, active transport , epithelial cells have many mitochondria for ATP
Amino acids absorbed by active transport and pass into capillaries by facilitated diffusion, dissolve in plasma.
Glucose passes with sodium ions, co transport dissolve into plasma.
Fatty acids diffuse into the lacteals, part of the lymphatic system, which transports fat soluble molecules to the left subclavian vein.
Large intestine is 1.5m long and is the cecum, appendix, colon and rectum. Undigested food, mucus bacteria and dead cells pass through, it makes vitamin K and folic acid.
Dentition
Omnivores have incisors, canines, premolars and molars
Herbivores, incisors on lower jaw only. Gap called diastema separates teeth from side teeth. Molars interlock, no strong muscles.
Carnivores, sharp incisors, large canines, curved and pointed, sharp premolars, carnassials which slide past each other like scissors, lower jaw moves vertically, jaw is powerful.
Ruminants, grass passes into reticulum and is regurgitated
parasites
Tapeworm primary host-human and secondary host-pig. Pig food becomes infected with human faeces and humans eat undercooked pork.
It as suckers and hooks to penetrate the gut wall and prevent it from being moved along.. A thick cuticle to protect it from digestive enzymes. The ability to make enzyme inhibitors. Large surface area for absorption. Hermaphrodite, can reproduce on their own. each proglottid contains male and female organs.