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Flashcards in Adaptations For Nutrition Deck (84):

Nutrition definition:-

The process by which organisms obtain nutrients to provide energy to maintain life functions and matter to create and maintain structure.


Subdivisions of nutrition type:-

Autotrophs (Phototrophs and Chemoautotrophs).
Heterotrophs (Holozoic feeders, Saprotrophs and Parasites).



An organism that synthesises its own complex organic molecules from simpler molecules using either light or chemical energy.



Convert CO2 and H2O into glucose using light energy from the sun during photosynthesis. Inc green plants, fungi and some bacteria.



Use energy from chemical reactions to build up organic molecules. These organisms are all prokaryotes and perform chemosynthesis which is less efficient than photosynthesis.



Organisms that obtain complex organic molecules produced by other organisms.
Eat either autotrophs or organisms which have eaten autotrophs.
Inc all animals, fungi, protoctista and some bacteria.


Holozoic feeders:-

Take food into body and digest it internally. Specialised digestive system. Includes most animals.


Holozoic feeder types:-

Herbivores- feed on plants.
Carnivores- feed on other animals.
Omnivores- feed on both animal and plant material.
Detritivores- feed on dead and decaying materials.


Holozoic feeder digestion summary-

Complex organic molecule into simple organic molecule:-
•carbs into glucose
•proteins into amino acids
•lipids into fatty acids and glycerol


Why do molecules monomers need to be broken down?

We can then absorb them (take into the blood stream by diffusion).



An organisms that derives energy and raw materials for growth from the extracellular digestion of dead or decaying material.
No specialised digestive system and secrete enzymes to digest food externally. Inc all fungi and some bacteria.



Microscopic saprotrophs. Important in decomp of leaf litter and recycling of valuable nutrients like nitrogen. E.g. the mould rhizopus found on rotting fruit.


Saprotrophic digestion:-

Enzymes secreted onto organic matter outside body. Enzymes hydrolyse the bonds in the organic matter e.g protein/carbs to make smaller soluble molecules e.g amino acids/glucose.
These smaller molecules are absorbed across the cell membrane by diffusion and active transport.



Live in or on another organism (host) and obtain noirishment at the expense of that host. No digestive systems. Adapted in many ways: endoparasites live in host's body and ectoparasites live on its surface.


Pork tapeworm(gut endoparasite):-(5)

•ribbon-like and up to 10m long. Made up of linear segments (proglottids).
•muscular head (scolex) w/hooks and suckers to attach to duodenum wall.
•2 hosts, human and pig.
•pig infected by eating in areas contaminated by human faeces.
•humans infected by eating undercooked infected pork.



Adult tapeworms may cause little discomfort but long term infection may cause weight loss and abdominal discomfort.
If the person is infected directly by eating the eggs, dormant embryos can form cysts in various organs which damages the surrounding tissue.


Pork tapeworm treatment:-

Adults can be treated w/ drugs (Praziquantel). This induces severe spasm and paralysis of the worm's muscles, preventing the hooks and suckers from holding onto to the wall of the intestine.


Precautions to prevent tapeworm infection (3):-

Making sure meat is well cooked.
Avoid spreading untreated sewage on land.
Inspection of meat and meat producing facilities (Public Health measures).


Problems for the tapeworms(7):

•only room for 1 tapeworm.
•dies if the host dies.
•need to transfer to new host.
•penetrating host.
•mode of nutrition/gas exchange
•could be dislodged by peristaltic contractions of gut wall.
•pH extremes and immune system


Tapeworm solution to host pH and immune system:-

Thick cuticle and produces inhibitory substances on its surface.


Tapeworm solution to gut wall contractions:-

Suckers and a double row of curved hooks for attachment to gut wall.


Tapeworm solution to only room to accomodate 1 tapeworm:-

Each segment contains male and female reproductive organs and 40000 eggs produced by each segment.


Tapeworm solution to host death:-

Has 2 hosts (human and pig).


Tapeworm solution to transferring to other host:-

Eggs have resistant shells so can survive outside the body until eaten by a secondary host.


Tapeworm solution to penetrating host:-

Small eggs/cysts ingested unnoticed.


Tapeworm solution to mode of nutrition and gas exchange:-

Long and thin=short diffusion pathway and large SA:vol so pre-digested food and O absorbed over body surface.


Head lice:-

Wingless insects, legs not well adapted to jumping or walking so transfer is by direct contact. Die if removed by host. Nymphs and adult feed on blood which they suck from host's scalp.


3 stages of louse life cycle:-

Nymph (hatches after 1-2 weeks, empty eggs called nits).
Adult-develops from nymph after about 10 days.


Unicellular organism nutrition:-

•animal like protoctista e.g amoeba use holozoic.
•obtain nutrition by diffusion, facilitates diffusion and active transport across the cell membrane.
•larger molecules taken in by endocytosis into food vacuoles which fuse with lysosomes. Contents digested by enzymes.
•products absorbed into cytoplasm and indigestible are egested by exocytosis.


Hydra (multicellular fresh water) structure:-

Cylindrical, 6 tentacles with stinging cells surrounding mouth (only body opening). Has hollow body cavity and surrounded by 2 cell layers- endoderm and ectoderm which are separated by a jelly layer containing nerve fibre network. Has adhesive foot called basal disc.


Hydra nutrition e.g Daphnia:-

Stinging cells discharfe when tentacles brushed, paralysing prey. Tentacles move prey to mouth and down through hollow body cavity. Endodermal cells secrete protease and lipase, digesting prey. Products absorbed into cells and indigestible remains are egested through mouth.


Hydra experiments:-

Experiments carried out using radioactive carbon show that tentacles contain microscopic protoctista. Protoctista photosynthesise, producing complex organic molecules (sugars) which they pass to the hydra.


Tube gut:-

Many animals have distinctive anterior (front) and posterior end + a digestive system that is a tube w/ 2 openings. Food ingested at mouth and indigestible waste egested at anus.
More complex animals have a more complex gut with diff sections carrying out diff functions.


Why food must be digested in humans:-

The molecules are:-
•insoluble and too big to cross membranes and be absorbed into the blood.
•polymers, so they must be converted into their monomers, so they can be rebuilt into molecules needed by body cells.


4 gut functions:-




Taking food into the body through the mouth.



Breaking down large, insoluble food molecules into smaller, soluble molecules which can be absorbed into the blood. This is done by chemical and mechanical digestion.



The passage of molecules and ions through gut wall into the blood.



The elimination of food that cannot be digested (e.g cellulose cell walls of plants)


Human digestive system (alimentary canal):-

Consists of alimentary canal (gut) which is a muscular tube with glands extending from the mouth to the anus. In adults, up to 10m long and is divided into distinct parts that have been adapted to carry out different functions.


Gut/alimentary canal pathway (MOSSLA):-

Small intestine (duodenum and ileum) with liver, pancreas and gallbladder.
Large intestine (colon).


Gut wall structure:-

4 tissue layers surrounding cavity (lumen).
Outside to in:-
Smooth muscle layer.
Sub-mucosa (connective tissue).
Mucosa (line gut wall).


Mucosa (4):-

•contains glands that produce digestive enzymes.
•secretes acidic/alkaline fluid to provide digestive enzymes' optimum pH.
•goblet cells secrete mucus to lubricate food and protect gut wall from enzyme action.
•absorbs digested food in some areas of gut.


Sub-mucosa (3):-

•contains blood + lymph vessels to take away absorbed molecules.
•contains nerves to control the muscles involved in peristalsis
•in duodenum, contains glands that secrete an alkaline mucus.


Smooth muscle layer (2):-

Consists of 2 layers running in opposite directions- inner circular muscle and outer longitudinal muscle.
•antagonistic muscles that cause peristalsis to move food along the gut.


Serosa (1):-

•tough connective tissue that forms a protective coat around the gut


Mouth mechanical digestion:-

Chewing using teetg makes food easier to swallow and increases its surface area for enzyme action.


Mouth chemical digestion:-

Food mixed with saliva from salivary glands when chewed. Saliva's mineral ions help keep mouth's pH 6.5-7.5 (slightly alkaline) = amylase optimum pH. Salivary amylase breaks starch down into maltose. Food rolled into ball (bolus) by tongue and mucus lubricates its passage down oesophagus.


Movement through oesophagus:-

Bolus pushed by wave of muscular contraction (peristalsis). Behind bolus, muscles lining walls of gut work as antagonistic pairs. Circular muscles contract and longitudinal relax, pushing food along in front of wave of contraction. Goblet cells in mucosa secrete mucus for lubrication


Stomach mechanical digestion:-

3 layers of muscle that churn food into liquid chyme


How long can the stomach store food for?

Up to 4 hours.


Stomach chemical digestion:-

Gastric juices secrete:-
•endopeptidase enzymes that hydrolyse proteins to shorter polypeptides.
•HCl that provides the acidic conditions for the emzyme to work (pH 2) and kills bacteria in food.
•mucus which protects stomach linkng from digestive enzymes and acid and lubricates food.


Duodenum (4):-

•first 20cm, main chemical digestion site.
•relaxation of sphincter at stomach base allows small amounts of partially digested food in at a time.
•receives bile from liver and pancreatic juice from pancreas.
•walls also contain Brunner's glands that secrete alkaline juice and mucus.


Bile (5):-

•secreted by liver.
•stored in gallbladder.
•enters duodenum via bile duct.
•contains bile salts which emulsify lipids into smaller droplets, increasing the surface area for pancreatic lipase action.
• bile salts=alkaline so neutralise stomach HCl, providing suitable pH for small intestine enzymes.


Pancreatic juice (6 with 4 enzymes inc):-

•secreted by exocrine glands in pancreas.
•enters duodenum by pancreatix duct.
•amylase hydrolyses remaining starch into maltose.
•lipase hydrolyses lipid droplets into fatty acids + glycerol.
•endopeptidases hydrolyse proteins to shorter polypeptides.
•exopeptidases hydrolyse short polypeptide chains into dipeptides and amino acids


Endopeptidases (4):-

•found in gastric juice (e.g Pepsin-pH opt 2) and pancreatic juice (e.g trypsin opt ph 8).
•secreted invinactive form to prevent digesting of gut wall.
•inactive chymotrypsin- converted to active trypsin by endokinase in duodenum.
•inactive pepsinogen secreted in stomach converted to active pepsin by HCl.


Exopeptidases (3):-

•produced in pancreas and secreted into duodenum.
•carboxypeptidases hydrolyse terminal bond at carboxyl end of polypeptide chain.
•aminopeptidases hydrolyse the terminal peptide bond at the amine end of the polypeptide chain.



Main function = absorption, some digestion takes place:
•maltase hydrolyses maltose into glucose.


Absorption in ileum:-

Takes place by simple diffusion, active transport, facilitated and osmosis. Adapted as has large SA, short diffusion pathway and steep diffusion gradient.


Ileum large SA:-

V. long (6m).
Highly folded.
Mucosa forms finger-like projections called villi.
On villi ends, individual epithelial cells also have finger-like projections called microvilli.


Ileum short diff pathway:-

Epithelium 1 cell thick


Ileum steep diff grad:-

Within each villus there are:-
•blood capillaries-remove glucose and amimo acids, keeping their conc low.
•lacteals (part of lymph system) that remove fatty acids, glycerol (and monoglycerides), keeping their conc low.


Glucose and amino acid transport:-

•glucose and AA are polar molecules that pass into the epithelial cells w/ Na ions by co-transport through specific carrier proteins in epithelial cell plasma membrane.
•both are water soluble so dissolve in blood plasma. Transported by blood w/ other dissolved molecules until they join the hepatic portal vein and are carried to the liver.


Na-glucose cotransport (5):-

•Na-K pump transps Na+ ions out of epithelial cells by active transp.
•this reduces the Na conc and sets up grad between gut lumen and epithelial cell cytoplasm.
•Na+glucose/AA bind to carrier protein and enter by faci diff.
•gluc/AA conc increases inside so they pass into blood by faci diff.
•faci diff= slow so some molecules will pass by active transp to ensure all glucose/AA are absorbed.


Amino acid absorption:(2)-

•absorbed for protein synth, excess can't be stored so is deaminated- amino groups are converted to urea + egested + remainder is converted to carbohyd and either respired or stored as fats.
•glucose is used in cells for energy release in resp. Excess is converted to fat for energy storage.


Fatty acid and glycerol absorption (5):-

•non-polar + diffuse through phospholipid bilayer.
•then diffuse into lacteals (part of lymphatic system).
•lymphatic system eventually drains into circulatory system via thoracic duct.
•used to synth phospholipids for plasma membs and some hormones.
•excess stored as fat in adipose tissue.


Vitamin B + C absorption:-

Water soluble so absorbed into blood by facilitated diff.


Vitamin A + D absorption:-

Fat soluble so absorbed into lacteals by diff.


Water absorption:-

Absorbed into ileum epithelial cells by osmosis.


Large intestine (colon) (4):-

Main function = absorption of remaining H2O along w/ vitamins secreted by mutualistic micro-orgs living in colon to produce solidified faeces.
•faeces also contains undigested cellulose, bacteria and sloughed cells.
•cellulose provides bulk and stimulates peristalsis in colon.
• this enables movement of faeces into rectum + onto the anus where it is egested in a process called defecation.


Carnivore gut vs herbivore gut:-

Carnivores = short gut because their diet largely consists of easy to digest protein. Herbivores= long gut because diet is high in cellulose which is very difficult to digest.


Herbivore digestion:-

Mammals don't produce the enzyme cellulase to break down cellulose, so have evolved a symbiotic relationship with bacteria which do produce cellulase, called mutualism.
Can be divided into ruminants (fore-gut digesters) and non-ruminants (hind-gut digesters)



A close association between organisms of 2 different species where both organisms benefit from the relationship.



4 chamber stomach. 3 formed by oesophagus and 1 is the true stomach.
Region of gut occupied by bacteria is kept separate so that:- • food can be kept there long enough for bacteria to digest cellulose.
•bacteria are isolated from cow's own digestive juices so they aren't affected by the pH.


Ruminant cellulose digestion (6):-

•grass mixed with saliva whilst chopped by teeth. Cud formed is swallowed.
•rumen (first chamber) contains mutualistic bacteria which secrete cellulase, hydrolysing cellulose into glucose.g
•cud passes to reticulum but is regurgitated + chewed again, increasing SA.
•passes into 3rd region (omasum) where water is reabsorbed.
•4th region (abomasum) acts like "true" stomach + protein is digested.
•products of digestion absorbed in small intestine.



Caecum is enlarged to provide a region for mutualistic micro-organisms to break down cellulose.
•glucose can't be absorbed as digestion from cellulose to glucose occurs after ileum.
•so they re-early the faeces and absorb the glucose the second time round.


Ruminant vs non:-

•ruminants more efficient as the rumen contains a greater variety of mutualistic bacteria than the caecum.
•ruminants can therefore achieve a more complete breakdown of cellulose and consequently absorb more glucose.


Carnivore vs herbivore incisors:-

Carnivores=sharp, grip and tear flesh from bone.
Grazing herbivore has small flat incisors on bottom jaw only + cuts against a horny pad on upper jaw.


Carnivore vs herbivore canines:-

Herbivores =not present/same as incisors. Carnivore= large, curved and pointed for seizing/killing prey and tearing flesh.


Carnivore vs herbivore jaw movement:-

Carnivore= vertical which allows wide opening for capturing and killing prey.
Herbivore=circular grinding in horizontal plane.


Carnivore carnassials:-

Specialised check teeth which have a scissor-like shearing action for cutting flesh.


Herbivore diastema:-

Gap that separates front incisors from side teeth (premolars). Tongue uses gap to move freshly-cut grass over large grinding surfaces of the molars at the back of the mouth.


Continuously growing herbivore teeth:-

As are continuously being worn down- made possible by their open, unrestricted roots.


Carnivore molars and premolars:-

Have cusps which are sharp points to cut and crush