Digestion Flashcards
Nutrition
Way in which organisms obtain complex organic molecules
Raw materials from food help build and maintain structures
autotrophic nutrition
Organisms make their own food from single inorganic raw materials, CO2 and water into organic materials
Photoautotrophic organisms
Use light as energy source and perform photosynthesis
Green plants, some protocistor and some bacteria - type of nutrition is holophytic
Chemoautotrophic organisms
Uses energy from chemical reactions - or prokaryotes and perform chemosynthesis
Less efficient than photosynthesis and organisms that do this are no longer dominant life forms
Heterotrophic nutrition
Organisms cannot make their own food and consume complex organic molecules produced by autotrophs- consumers
Either eat autotrophs or organisms that have eaten autotrophs
Eg. Animals, dependent on producers for food
Animals, funky, some protoctista and some bacteria
saprotrophic nutrition
Used by all fungi and some bacteria
Saprotrophs feed on dead or decaying matter
No specialised digestive system secrete enzymes onto food material outside body for extracellular digestion
Absorb soluble products of digestion across the cell membrane by diffusion and active transport
Decomposers
Microscopic sapotrophs and are important in decaying leaf litter and recycling nutrients
Eg. Rhizopus
Rhizopus
process
1) Enzymes secreted from the tip of hypha digests the substrate ( organic matter which fungus grows and feeds)
2) Product absorbed and transports through mycelillum and enzymes perform extracellular digestion
3) nutrients absorbed back into fungal hyphae
Parasitic nutrient
obtaining nutrition from another living organism, the host
parasites
Endo, ecto
Endoparasites live in body of host, while Ectoparasites live on its surface
Parasites host always suffers some harm, often death
Parasites adapted in many ways - highly specialised for way of life Eg. Tapeworm , Head lice, potato blight, plasmodium
Holozoic nutrition
Nutrition used by most animals
Ingest food digest and egest indigestive remains
Food processed inside body in a specialised digestive system. In material absorbed into body tissues and used by cells
nutrition in unicellular organisms
eg amobea
Eg Amobea uses holozoic nutrition
Single sound organisms with large surface area:volume
Obtain all nutrients they need by diffusion, facilitated diffusion, active transport across cell membrane
Take in larger molecules and microbes by endocytosis into food vacuoles, fuse with lysosomes and contents digested by lysosomal enzymes
Products of digestion absorbed into cytoplasm and indigestible remains are egested by Exocytosis
Nutrition in multicellular organisms
hydra
single body opening- eg. Hydra
2 layers cells: On ectoderm and endoderm, separated by jelly layer (contain network nerve fibres)
Tentacle surrounding, only open body opening
Tentacles extend and when small organisms brush against tentacles , stinging cells discharged and paralyse prey
Move prey through mouth into hollow body cavity
Endodermal cells
Some secrete protease and lipase; Prey digested extracellularly and products absorb into cells
Other are phagocytic and engulf food particles (digest in food vacuoles)
Indigestible remains are egested through the mouth
tube gut
Tube with two openings, distinct anterior and posterior and digestive system. That mouth and indigestible waist like egested at the anus
human digestive system
food must be digesed
Food must be digested because:
Molecules are insoluble and too big to cross membrane and be absorbed into blood
Polymers must be converted to monomers so they can be rebuilt into molecules needed by body cells
peristalisis
how food is moved across digestive system
- longitudinal muscles contract to push food forwards then relax
- Circular muscles contract behind the bolus then relax; waiver contraction pushes the bolus down
functions of the digestive sstem
Ingestion- Taken food into body through buccal cavity
Digestion- Breakdown of large and solid ball into soluble molecules small enough to be absorbed into blood
Absorption- Passage of molecules through gut wall into blood
Egestion- Elimination of waste not made by body
chemical digestion
Digestive enzymes, bio, stomach acid contributes to breakdown food
mechanical digestion
Cutting and crushing by teeth and muscle contraction of gut wall - increases surface area so enzymes can act
function of mouth
Ingestion, digestion of starch and glycogen
function of oesophagus
Carriage of food to the stomach
function of stomach
Digestion of proteins
function of duedenum
Digestion of carbohydrates, fats and proteins
function of ileum
Digestion of carbohydrates, fat, protein; absorption of digested food and water
function of colon
Absorption of water
function of rectum
Storage of faeces
function of anus
Egestion
Structure of gut wall
4 layers of tissue surrounding cavity (lumen)
serosa
Muscle
submucosa
Mucosa
serosa
Outermost layer, tough connective, protecting gut wall.
Gut moves while processing food
at Serosa reduces friction (peritoneum) with other abdominal organs
muscle
Two layers in different directions
Inner - circular muscle
Outer- longitude or muscle
They make coordinated waves of contraction (peristalsis)
Behind boiler food, circular muscles contract and longitudal on muscles relaxed, pushing food along
submucosa
thin layer
thin layer of connective tissues, containing blood and lymph and vessels - remove absorbed products of digestion and nerves that coordinate peristalsis
mucosa
Into most layer and lines the gut wall
Epithelium secrets mucus lubricating and protecting mucosa.
In some regions of the gut it secrets digestive juices and in others, absorbs digested food
buccal cavity- mouth
saliva
Food mixed with saliva by the tongue and chewed by teeth
Food surface area increases, giving enzymes more access
saliva in mouth
contents
contains:
- Amylase, Beginning digestion of converting glycogen into maltose
- HCO3- and CO32- ions, P H of saliva varies between 6.2- 7.4 but optimum pH of salivary amylase is 6.7-7.0
- mucus, lubricating foods passage
- mucin, glues food together
oesophagus
Carries food to the stomach. Shows tissue layers in simplest form
Bolus- food swallowed
Stomach
Food enters and kept there by contraction of two sphincters/ rings of muscle
2dm3, food stays for several hours
Stomach wall muscles contract rhymically and mix food with gastric juice- secreted by glands in stomach walls
gastric juice
secreated from glands in depressions in mucosa- gastric pit
Gastric pit
- entrance to gastric pit at top
- mature goblet cells
- submucosa
- Epithelial layer
- Oxyntic cell
- immature mucus cells
- gastric pit
- Zymogen/ chief cell
Mature mucus secreting goblet cells
Mucus secreted by goblet cell at the top of the pit forms a lining, protecting stomach wall from enzymes and lubricates food
Oxyntic cell
secreates HCL
Hydrochloric acid lowers PH of stomach contents to PH2 for enzymes. kills bacteria in the food
Zymogen/ chief cell
secreates enzymes
Peptidases, secreted by Zymogen at base of gastric pit
pepisinogen (inactive enzyme) is secreated and activated by H+ ions to pepsin, an endopeptidase, hydrolyses protein to polypeptides
small intestine
2 regions: Deodenum, Ileum
Relaxation of the pyloric sphincter at base of stomach allows partially digested food into the deodenum, little at a time
now everything is great deodenum receive secretions from liver and pancreas. pH of 8-9
Bile
Made in liver, stored in Gallbladder, passes through bile duct into deodenum
- no enzymes
- contains bike salts, amphipahic
Emulsifies liquids by lowering surface tension and brake large globules into smaller ones- increase surface area and meat digestion by lipase more
More alkaline and neutralises acid and food coming from stomach provides suitable pH for enzymes in small intestine
pancreatic juice
islet
For created by Islet cells- exocrine glands in pancreas, enter deodenum through pancreatic duct
crypts of Lieberkühn
Food coming from stomach is lubricated by mucus, neutralised by alkaline secretions from cells at base of crypts of lieberkühn/ Brunner’s gland
Ileum
Epithelial cells lining the ileum have finger like projections called Villi which synthesised digestive enzymes:
- Endopeptidase and exopeptidase
- carbohydrates
Endopeptidases and exopeptidases
- Peptidases are secreted by villas epithelial cells and digestion continues in the gut lumen
- Dipeptidases in cell surface membranes digest dipeptides to amino acids
carbohydrates
Carbohydrates are created and digestion continues in the gut lumen
Carbohydrates in cell surface membrane digest disaccharides into monosaccharides
Some disaccharides absorbed so their digestion is intracellular
Amylase hyrdolyses starch and glycogen to maltose
Digestion of protein
protease, peptidase
Digested into polypeptides and dipeptides into amino acids
Endopeptidases
Hydrolyzes peptide bonds within the protein molecule
Exopeptidases
hydrolyses the terminal peptide binds at end of shorter polypeptides
Absorption
occurs mainly in small intestine by diffusion, facilitated diffusion and active transport
Active transport needs ATP
Ileum- absorption
Lining folded
On the surface of folds - villi
have projections- microvilli
Increase SA for absorption
Self are produced at base of glands and move out to replace old cells sloughed off by the food
Section of ileum wall
Crypts of lieberkühn- gap between
Epithilium- one cell thick
Villi
Capillary- ends
Lacteal- middle
Venule- carries blood to hepatic partalvein, middle bottom
Artieole- first bottom
Lymph vessel- last bottom
Circular muscle
Longitudinal muscle
villus
Inside Villus is a dense network of blood vessels
They absorb digested food molecules
Also lacteal- blind ended tube of lymphatic system, involved in absorption of lipids
fates of nutrients- glucose
Glucose is taken to body cells and respired for energy or stored as glycogen, in liver and muscle cells. The excess is stored as fat
fates of nutrients- amino acids
Amino acids taken to body cells for protein synthesis
Excess cannot be stored so liver deaminates and converts NH2 groups to urea, Carried in blood and excluded at the kidney
remains of amino acid molecules are converted into carbohydrate for storage or conversion to fat
large intestine
undigested
Undigested food, mucus, bacteria and dead cells pass into the colon
Colon wall has fewer villi in the ileum and these will have major role in water absorption
vitamin k and fulic acid - large intestine
Secreted by mutualistic microorganisms living in the colon, and minerals absorbed from the colon
As material passes along:, water is absorbed and by the time it reaches the rectum, material is semi solid
It passes along the rectum and is egested as faeces in process called defecation
adaptions for diet
When reptiles and amphibians ingest food they swallow it whole
Mammals retain their food in their mouth while it is cut and chewed
Mammals are the only vertebrates to have a palate separating the nasal and mouth cavities, so they can hold food in mouth and chew while breathing
carnivore
Eats only animals and so its diet is mostly protein
Small intestine is short in relation to body length reflecting the ease with which protein is digested
Large intestine is straight with smooth lining
herbivore
It’s only plant material
Smaller testing is long in relation to body length because plant material is not readily digested and a long gut allows enough time for digestion and absorption of nutrients
omnivore
pouch
Gut length is intermediate
A herbivore and omnivore has a pouch large intestine so it can stretch to accommodate larger volume of faeces produced in digesting plants- Much of which is cellulose
Large instestine is also long with Villi where water is absorbed
Dentition
Food must be cut, crushed, ground or sheared
Humans have incisors, canines, premolars and molars
Dentition of Herbivores
Plant cell walls are tough to eat as they contain cellulose and liggin and sometimes silica
The teeth of Hebivores are modified so that the cells can’t be thoroughly ground up before entering the stomach
Herberores - incisors and canine
1
Grazing Herbivore - incisors on lower jaw only
Canine teeth are indistinguishable from the incisors
Animal wraps his tongue around the grass and pulls it tight across the leathery ‘dental pad’ on upper jaw
then lower incisors and canine slice through it
herbivore- diastema
2
Gap called diastema separates front teeth from premolars
Tongue and cheeks operate in this gap, moving freshly cut grass to large grinding surfaces of the molars
herbivore- molar
3
molars interlock- like a W into an M
lower jaw moved side to side- produces circular grinding action in a horizontal plane.
with time- Grinding services of teeth become worn, exposing sharp edged enamel ridges further increasing efficiency of grinding
Teeth have opened unrestricted roots so they continue to grow throughout animals lives replacing material worn down
Herbivore- skull and muscles
Hibbard does not need strong muscles attached to its jaws because it’s food is not likely to escape
Its skull is relatively smooth, reflecting absence of sight for strong muscles to attach
Dentition of carnivores
They have teeth adapted for catching and killing prey, cutting or crushing bones and tearing meat
Carnivores - incisors
1
sharp incisors grip and tear muscle from bone
carnivore- canine
2
Canine teeth are large, curved and pointed for piercing and seizing prey for tearing muscles and killing
carnivore- premolars and molars
3
Premolars and molars have cusps, which are sharp points that cut and crush
carnivore- carnassials
4
Carnivals have pair of specialised cheek teeth called carnassials in each side
They slide past each other like scissor blades, these shear the muscle off the bone
Large and easily identifiable
carnivore- lower jaw
5
Lower Jaw moves vertically
Carnivals open their doors very wide when they deal with prey and side to side movements could dislocate their jaw
ruminant
a cud chewing herbivore possessing a ‘stomach’ divided into 4 chambers
largest-rumen, contains mutualistic microbes
rumen
chamber in the gut of ruminant herbivores, in which mutualistic microbes digest complex polysaccharides
Mutualism
A close Association of organisms from more than one species, providing benefits to both
Mutualistic microbes
Much of Herbivores food is cell war material, mainly cellulose
Animals cannot make cellulase and cannot digest the beta glycosidic bonds in cellulose
Therefore they rely on mutualistic microbes living in their gut to secrete the enzyme instead
What do mutualistic microbes include
Bacteria, fungi and protocista which live in the Rumen
Cellulose digestion
1
Grass is cut by the teeth and mixed with saliva to form the curd, swallow down the oesophagus to the rumen
The Rumen
2
Chamber in which food mixes with microbes. Microbes secrete enzymes which digest cellulose into glucose
Glucose is fermented to organic acids that are absorbed into the blood and are an energy source for cow
Carbon dioxide and methane released as waste products
Cellulose digestion
3
Fermented grass passes to the reticulum and is reformed into cud. It is regurgitated into the mouth for further chewing
Cellulose digestion
4
Cud may be swallowed and regurgitated into the mouth several times
Cellulose digestion
4
Cut passes next into the omasum where water and organic acids made from fermented glucose are absorbed into the blood
Cellulose digestion
5
4th chamber -abomasum is the ‘true’ stomach, where protein is digested by Pepsin and at P H two
Cellulose digestion
6
Digested food passes to the small intestine, from where the products of digestion are absorbed into the blood
Functions of large intestine are comparable with those of human
Parasites
An organism that obtains nutrients from another living organism or host, to which it causes harm
They may live on or in an organism
Parasites in plants
Bacteria fungi viruses, nematodes and insects
Parasites in animals
Also parasited by Protoctistans, tapeworms and mites
Parasites in bacteria
By viruses called bacteriophages
pork tape worm
Taenia Solium
It has no competition- cannot be predated upon
Endoparasite
Pork tapeworm description
Ribbon like- shape allows plenty of space for host food to move past it
Ten metres long
And your end - scolex made of muscle carrying suckers and hooks
But he has linear series of sections proglottids
Rostellum
proglottids
mature and terminal
mature proglittids- Contain uterus with embryos
Terminal proglottids- Fall off and are discharged with the faeces
Tapeworms Lifecycle
Requires it to alternate between two hosts
Primary host- human
Secondary host - pig
larval forms develop
The peak becomes infected when food is contaminated with human faeces
Human are infected by eating undercooked pork containing live larval forms
how the tape worm survives hostile conditions in the gut
- Surrounded by digestive juices and mucus
- Must withstand peristalsis
- Experiences pH changes as it moves down the gut to the deunodum
- Exposed to hosts immune system
- If host dies parasite dies
Tapeworm structural modifications
Scolex
Has suckers and a double row of curved hooks to attach it strongly to the duodenum wall
Tapeworm structural modification
Cuticle
a thick body covering protecting it from the host’s enzymes and immune system
Tapeworm structural modifications
Enzyme inhibitors
It makes enzyme inhibitors which prevent the hosts enzymes digest in it
Tapeworm structural modifications
Reduced gut
It has a very reduced gut; a large surface area to volume ratio lets it absorb pre digested food over its whole surface
Tapeworm structural modifications
hermaphrodite
Each proglottid has male and female reproductive organs. Guts usually only has one tapeworm but each mature proglottid may contain forty thousand eggs - pass out of host body with faeces
Lots of eggs increase chances of infecting secondary host
Tapeworm structural modifications
Resistant shells
The eggs have resistant shells and survive until eaten by pig. Hatch and move through intestine wall into pig muscles
remain dormant there until meat is eaten
harmful effects of pork tape worm
Adult tapeworm may cause little discomfort but long term infection may produce taeniasis - giving abdominal pains and weakness
Can be treated with drugs
If eggs are eaten directly - embryos can form cysts in various organs and damage surrounding tissue
Head lice
Pediculus
ectoparasite
Wingless insects. Fly and legs are poorly adapted to jumping and walking so they are transferred from one host to another by direct contact
They die if removed from human
3 stages in Louse life cycle
Adult Louse lays eggs - hatch after 12 weeks into nymphs leaving nits, empty egg cases
Nymph is like an adult but smaller
Becomes adult after 10 days and feeds on blood
Absorption of amino acids
into epithieal cells
Amino acids absorbed into epithelial cells by active transport and, as amino acids, they pass into capillaries by facilitated diffusion
Water soluble and dissolving the plasma
Absorption of glucose
Glucose passes into epithelial cells with sodium ions by co-transport
Move into capillaries
sodium by active transport and glucose by facilitated diffusion and dissolving plasma
Diffusion I’m facilitated diffusion are slow and not all the glucose is absorbed
To prevent it leaving body in faeces, some is absorbed by active transport
Absorption of fatty acids
Fatty acids and monoglycerides diffuse into epithelial cells and into lacteals
Lacteals are blindly ending lymph capillaries in the villi
They are part of lymphatic system transport soluble molecules to the left subclavian vein near the heart
Absorption of minerals
taken into the blood
minerals are taken into blood by diffusion, facilitated diffusion and active transport and dissolve in plasma
Absorption of vitamins
Vitamin B and C are water soluble and are absorbed into blood
Vitamin A D and E are fat soluble and are absorbed into lacteals
autotroph
Organism that synthesises its own complex organic molecules from simpler molecules using either light or chemical energy
Heterotroph
Organism that obtains complex organic molecules by consuming other organisms
Saprotroph/ saprobiont
Organism that derives energy and raw materials for growth from extracellular digestion of dead or decaying material
