Module 5 PART B Flashcards
extracellular digestion
digestive enzymes secreted into cavity by gland cells
why does extracellular digestion take a long time?
bc digestive enzymes are diluted in fluid
intracellular digestion
endocytosis - cells lining gastrovascular cavity move partially digested food into cell
Membrane food vacuole fuses w/ lysosome to form digestive vacuole & waste is released by exocytosis
crop (in more complex organisms than hydra or jellyfish which only have 1 gut cavity)
storage chamber where food is stored & digested slowly over time. Enlarged portion of the digestive system (in invertebrates & birds) – e.g. in a worm
gizzard
a muscular part of the gut that has grits or stone in it that helps grind the food mechanically. Gizzards are found in birds, earthworms, some fish, & some reptiles
how do lipids enter the cellular respiration pathway?
by first being broken down into glycerol & fatty acids and then entering through beta oxidation
animals cant synthesize the acetyl group so where does it come from & what is it used to synthesize?
comes form food
Acetyl group used to synthesize steroid hormones + amino acids, heme, & other compounds; fatty acids, citrate, etc.
amount of food needed depends on
- metabolic rate (varies w age, reproductive stage, activity)
- body mass & environmental conditions
- types of food
per unit body mass SMALL animals need more/less than larger ones?
MORE as small animals have larger SA:V ratio
carnivorous teeth
greatly enlarged canine teeth for gripping, killing, & tearing their prey - also have incisors
herbivorous teeth
have incisors - mainly have premolars & molars
omnivorous teeth
multipurpose set of teeth
pyloric sphincter (constriction in tube in stomach)
determines how much chyme is allowed into the next section of the digestive system
enzymatic digestion occurs where?
in duodenum
In the duodenum, large lipid droplets are emulsified into smaller micelles and this increases the SA for the lipases to work in an aqueous environment to break down the lipids into monoglycerides and fatty acids
nutrient absorption occurs where?
in jejunum
gallstones
solidification of bile salts + cholesterol
pancreas secretes. . . ?
bicarbonate ions to neutralize acidity of chyme
hepatopancreatic duct
the common duct that secretes fluids from both the liver and pancreas into the duodenum
what do epithelial cells secrete?
peptidases & enzymes for breaking down oligosaccharides
large intestine (colon)
Just at start of large intestine - caecum: blind ended sac; cellulose digestion (prominent in herbivores)
In large intestine - water absorption & formation of feces
carnivorous digestive tract
short, simple digestive tracts; short intestine & small caecum
herbivorous tracts
long, complex digestive tracts with a large caecum
how do herbivores digest cellulose?
Since most herbivores don’t have the enzyme cellulase, they have symbiotic bacteria & protists (microbes) that live in their digestive tracts & digest cellulose
These symbiotic bacteria have cellulases which hydrolyze the cellulose to produce glucose
This glucose is then used as an energy source by microbes
The microbes produce short chain fatty acids which the host then absorbs & uses as a source of energy
The short chain fatty acids promote good gut health by maintaining the integrity of the intestinal barrier
Foregut fermenters vs hindgut fermenters
–> digestion of cellulose by microbes occurs BEFORE the stomach
–> Digestion of cellulose occurs AFTER stomach (e.g. horse, koala, combat, pig, rabbit)
e.g. of foregut fermenters
kangaroos
e.g. of hindgut fermenters
horse, koala, pig, rabbit
Foregut fermenters & how does it work
The microbes are present in the large forestomach - they produce short chain fatty acids which are then used as an energy source
The microbes wash through to the hind stomach & small intestine & provide the host with a source of protein - the microbes THEMSELVES are a rich source of protein
hindstomach
- acidic & contains pepsin
- Ruminants - special case of foregut fermenters
- Regurgitate their food to reduce size of food particles
Ruminants have LARGE foreguts w/ four chambers:
Rumen
Reticulum
Omasum
True stomach
Hindgut fermenters
Bacteria (only) present in the caecum & proximal colon
Microbes that wash through digestive tract cannot be used as protein source
This is because the microbes are living in the part of the gut that is after where the nutrients / proteins are absorbed in the small intestine
Caecum & proximal colon together are referred to as the HINDGUT
caecotrophy
specialization of eating your own feces (ringtail possums)
- it is a rich source of protein w microbes
- formal fecal pellets (at night)
Movement of water through roots
Water moves through the root via the apoplast and symplast until it reaches the Casparian
strip and is then forced to flow via the symplast to the central vasculature.
