3.3 Flashcards
what is autotrophic nutrition?
organisms that use simple inorganic molecules to synthesise large complex organic molecules
what are the two types of autotrophic nutrition?
photoautotrophic and chemoautotrophic
what are photoautotrophs?
using light energy in photosynthesis
what are chemoautotrophs?
use energy released in chemical reactions in chemosynthesis
what is heterotrophic nutrition?
organisms that obtain complex organic molecules from other organisms
what are the 4 types of heterotrophic nutrition?
holozoic, saprotrophic, parasitic, mutualistic
what is holozoic nutrition?
internal digestions involving enzymes
what are the stages in holozoic digestion?
ingestion, digestion, absorption, assimilation, egestion
what is saprotrophic digestion?
feed in the dead/decaying by secreting enzymes onto the food and small soluble products of digestion are absorbed back in
what adaptations do fungi have for saprotrophic digestion?
hyptae create a large surface area which are one cell thick
what is parasitic digestion?
parasites obtain nutrients from another organism by living in or on a host organism which is harmed
what is mutualistic digestion?
an association between 2 species and there is a nutritional benefit to both
what is lichen made of?
alga (photosynthesis produces glucose) and fungus (hyptae absorb minerals)
what is rhizobium made of?
nitrogen fixing bacteria (make nitrates for plants) in root nodules of clover (make glucose for bacteria)
what are psendopodia?
temporary extensions of a cells cytoplasm
describe how food is ingested in amoeba
amoeba uses its psendopodia to engulf its prey called phagocytosis. the food is enclosed within a food vacuole in the cytoplasm
what happens for digestion to occur in amoeba?
smaller vacuoles containing digestive enzymes fuse with the food vacuole membrane. they release enzymes into the vacuole and they digest the food
where does absorption occur in amoeba?
the small molecules from digested food are absorbed across the membrane that surrounds the vacuole in the cytoplasm
what type of digestion is amoeba?
intracellular
what is the structure of a hydra?
hollow body cavity, endoderm, jelly layer, ectoderm, mouth, tentacles with stinging cells.
comprises of two layers of cells which are separated by a jelly layer containing a network of nerve fibres. it is cylindrical and has tentacles (usually 6) surrounding its mouth which is its only body opening
describe how hydra ingests food
stringing cells discharge which paralyses prey and the tentacles move prey into mouth and into body cavity
what does extracellular digestion mean?
the enzymes are secreted into the hollow cavity
what type of digestion happens in hydra?
extracellular and then intracellular
what does intracellular digestion mean?
food particles are taken into cells by endocytosis for digestion to occur
what is the difference between a hydras gut and a tube gut?
hydras gut only have one opening and tube guy has two
what is the gut wall structure?
lumen, mucosa, submucosa, muscle layer (circular then longitudinal), serosa
what is the mucosa?
innermost in contact with food
what do goblet cells do?
produce mucus for lubrication and prevent auto digestion
what is the epithelial tissue for in the mucosa?
glandular- secrete enzymes/digestive juices
adapted for absorption
what is the submucosa? and explain its structure
below mucosa. made of connective tissue, contains lots of capillaries for transport of absorbed end products of digestion, contains nerve fibres to coordinate muscle movements
what is the muscle layer responsible for?
peristalsis
what is peristalsis?
wave of muscular contraction that moves food through the digestive system
what are the places of thickened muscles called?
sphincters- they control movement of food (in and out of stomach)
what is the serosa?
outermost layer, tough connective tissue, protects the organs from friction with other organs
what happens in the mouth?
ingestion, chewing (mastication) which is mechanical digestion
what is chewing for?
to increase SA for enzyme action and breaks down food for swallowing
what does the tongue do?
mixes food with saliva
what is saliva
a watery mixture of mucus (binds food together) , salivary amylase and hydrogen carbonate ions (neutralise acids and keep optimum ph for salivary amylase)
how is food moved in the oesophagus?
peristalsis
what is the function of goblet cells in the oesophagus?
secrete mucus to reduce friction and lubricate the passage of food
what layer of the gut is well developed in the oesophagus?
muscle layer
what happens to the food in the stomach?
churned with gastric juice
where does protein digestion start?
stomach
what are the adaptations of the stomach?
mucosa is folded to form rugae (allow stomach to stretch and expand), third layer of muscle called oblique layer (in the circular muscle) which is at angle to help produce strong contractions to churn food
what does gastric juice contain?
mucus, HCl, pepsinogen
what is the function of mucus in the stomach?
lubrication and protection against auto digestion
what is the function of HCl in the stomach?
kills pathogens and provides the optimum pH for pepsin (pH 1or 2)
what is pepsinogen?
inactive precursor of the enzyme pepsin
why is pepsin secreted as pepsinogen?
so the chief cells/ gastric gland cells aren’t digested
how is pepsin activated?
pepsinogen + H+ from HCl
what type of enzyme is pepsin?
endopeptidase
what is an endopeptidase?
hydrolises peptide bonds within the polypeptide chain to produce shorter peptides
what is an exopeptidase?
hydrolises the terminal peptide bond to break off individual amino acids
why does a mixture of endopeptidases and exopeptidases give the fastest rate?
the endopeptidases produce more ends for the exopeptidases to work on
what is the duodenum?
first part of the small intestine, main site of digestion