Lecture 35 - Ruminant Carbohydrate Digestion and Absorption Flashcards
is rumen contraction involuntary
yes, controlled by PNS and ENS
is reverse peristalsis involuntary
no, is controlled by skeletal muscle
how do herbivores live on plants
have microbes in rumen
what source of food do herbivores largely live on
lignocellulose
what is the most abundantly available raw material on earth to produce biofuels
lignocellulose
what is lignocellulose composed of
carbohydrate polymers: cellulose and hemicellulose
polymer: lignin
which component of lignocellulose is most abundant?
cellulose
which component of lignocellulose is hardly used by herbivores and microbes break down very slowly
lignin
what is cellulose composed of
unbranched, linear chains of D-glucose molecules linked together by beta (1-4) glycosidic bonds
structure of hemicellulose
main structure linked together by beta(1-4) glycosidic bonds with many branches
which is more structurally complex: cellulose or hemicellulose
hemicellulose
what allows herbivores to subsist on cellulose? by what mechanism?
microbes that produce cellulases that hydrolyze cellulose
which end product of fermentation do host animals particularly use?**
short chain volatile fatty acids
what bonds to cellulolytic bacteria break
beta 1-4 linkages between sugars that make up cellulose and hemicellulose
T/F: cellulolytic bacteria that can break beta 1-4 linkages in cellulose/hemicellulose are anaerobes
true!
how would you identify obligate aerobes in a test tube
need oxygen so gather at the top of the tube where oxygen concentration is highest
where would you find obligate anaerobes in a test tube
are poisoned by oxygen so would find them at the bottom of the tube where O2 concentration is lowest
where would you find facultative anaerobes in a test tube
can grow with or without oxygen because they can metabolize energy aerobically or anaerobically. Gather mostly at the top because aerobic respiration generates more ATP than fermentation
what do yogurt making bacteria and RBCs have in common
dont have mitochondria
what does glycolysis generate ***
generates 2 pyruvate and 2 ATP
what are the 2 main processes of lactic acid fermentation
Glycolysis and NAD+ regeneration
what is the end result of lactic acid fermentation
2 lactate
what is fermentation? what does it produce?
process of metabolism where an organism converts carbohydrate (sugar/ starch) into an alcohol or acid. it produces energy in the absence of oxygen
how many ATP does aerobic respiration produce
36 ATP
what kind of environment does the rumen provide (02, temp, etc)
anaerobic environment, constant temperature and good mixing
describe the relationship of fermentative microbes in the rumen
interact and support eachother in a food web (waste products of one can be nutrients for other species), can compliment eachother
amylolytic microbes digest
starch
proteolytic microbes digest
protein
starch utilizing bacteria use what
mono and disaccharides
acid utilizing microbes use what
substrates like lactic, succinic and malic acids
are ammonia producers, vitamin synthesizers and methane producing microbes common in the rumen
yes
what do cellulolytic bacteria break and use***
beta1-4 linkages of plant wall structural carbohydrates and utilize liberated hexose and pentoses for energy
end product of cellulolytic bacteria***
are anaerobes so end product of fermentation is VFAs acetic acid, propionic acid and butyric acid
what is the end END product of glycolysis***
glycolysis produces pyruvate and THEN pyruvate further produces volatile fatty acids: acetate, butyrate and propionate
what is the source for host animals to generate energy
volatile fatty acids: acetate, butyrate, propionate
what 3 volatile fatty acids does pyruvate break down into to generate energy for the host animal ***
acetate, butyrate, propionate
what provides majority of herbivore energy
volatile fatty acids
Major VFA product in diet is always**
acetic acid
will sugar molecules from the diet be absorbed by the small intestine of a cow
no, will be used by microbes
what is oxidized throughout most of the body to generate ATP in ruminants
Acetic acid
what is another important use of acetate besides generating ATP in ruminants
major source for synthesis of lipids
***acetic acid is the _____ form of acetate
undissociated form
*** acetate is the _______ form of acetic acid
dissociated
**acetic acid dissociates in water to become ______
acetate
which is dissociated: acetic acid or acetate
acetate
which is undissociated: acetic acid or acetate
acetic acid
what is the major substrate for gluconeogenesis in the liver
proprionic acid
function of proprionic acid
major substrate for gluconeogenesis in liver
why is gluconeogenesis crutial in ruminants
almost no glucose reaches the small intestine for absorption
what is gluconeogenesis
formation of glucose from non-carbohydrate carbon sources
what is the function of butyric acid***
oxidized in many tissues for ATP (energy production)
how is fat synthesized
from ruminal acetic acid
what epithelium are the rumen and reticulum lined by
stratified squamous epithelium
where are VFAs rapidly absorbed
across the forestomach (even though it is stratified squamous epithelium) and leaves of the omasum via diffusion –> then are used by ruminant for energy
in their non-dissociated state, are VFAs water AND lipid soluble
yes, have no charge and can cross the lipid bilayer of cell membranes
are VFAS in their dissociated state both lipid and water soluble
NO, are only water soluble and CANNOT cross lipid membranes, remember this is for dissociated state (ex. acetate)
dissociated and non dissociated forms of weak acids and bases are in ______
equilibrium
what is the concentration of nondissociated and dissociated forms dependent on
the pH of solution
describe the importance of pKa in the relationship between acids existing in their dissociated vs non dissociated state
when the pKa is = to pH of solution, 50% of the acid will exist in its dissociated state and 50% in its non dissociated state (aka. at =librium)
given that the pKa for propionic acid is 4.87, and its in a solution with pH 4.8. how much is in the dissociated state vs nondissociated
50% will exist in non-dissociated state (Hporp) while 50% is in the dissociated state (prop-)
given that the pKa of propionic acid is 4.87, at typical rumen pH, what amount of propionic acid is in its non dissociated form vs dissociated form
rumen pH (6-7 according to miss google) is higher than the pKa of propionic acid, so majority is in the dissociated form while only a small percentage is in the non dissociated form.
what happens to the small amount of non dissociated propionic acid (Hprop) in the lumen of the rumen? (aka, how does it travel from lumen of rumen to extracellular fluid)
will freely cross the apical membrane down its concentration gradient from the lumen to the apical/interior of the cell, becuase Hprop is removed from the lumen, the =libirum of propionic acid will shift to replace the lost Hprop, allowing more to cross the membrane
Once of the other side of the membrane, a second propionic equilibrium is set up near the basolateral surf, as Hprop is formed, it will move across the basolateral membrane to the extracellular fluid
the amount of propionic acid existing in the dissociated vs non-dissociated state is dependent on what?
pKa of the acid and the pH of solution
what is the mechanism that alllows all VFAs to cross membranes
diffusion through the epithelium down a concentration gradient
where does venus blood from the fore-stomach and abomasum drain into
portal vein to the liver
VFA purposes
energy production, production of sugars and lipids, etc..
what is rumen-degradable protein***
dietary protein that the rumen can break down***
how is rumen degradable protein lost to the animal and then potentially recovered?
are used by microbes so lost to the animal but can be recovered in the form of microbial protein that enters the small intestine
rumen undigestible protein***
protein that bypasses the rumen bacteria, can be digested in the small intestine and a source of essential amino acids
protein quality
ability of dietary protein to meet the needs for regular metabolism and maintenance or growth of body tissues
protein quality factors
digestibility and quantity of essential amino acids
essential amino acids
cannot be made by the body, must come from food
is rumen bacteria high quality protein
yeso
how is protein within bacteria digested
mammalian proteolytic enzymes
how much microbial protein acounts for total protein digested in cattle
more than 50%
what non-protein nitrogen source can fermentative microbes synthesize protein from
urea (used for inexpensive diets)
what vitamins are fermentative microbes able to synthesize
B vitamins
describe the path of crude protein from feed for the cow to nutrients in the cow (undegradable intake protein vs. degradable intake protein)
Undegradable: starts as crude protein in feed, bypasses fermentation adn goes to the stomach to become amino acids)
degradable: starts as crude protein in feed, is taken by microbes to contribute to growtih and fermentation, then becomes microbial protein and then broken down into aa)
what component of feed is fermented in the rumen to become propionic
starch and sugar
what component of feed is fermented to become acetic and butyric?
fermentable fiber
what component of feed gets fermented in the rumen to become fatty acids
fat
compare protein processing in simple stomach species vs ruminants
in simple stomach: HCL and pepsin in the stomach
ruminants: microbes feed on protein in the forestomach and then are broken down by HCL and pepsin in the true stomach afterwards
