Simple Stomach 1 Flashcards
What does having a simple stomach mean?
-monogastric
-no compartments
What does gluconeogenesis do?
-Make glucose
-synthesis of glucose from non-carbohydrate sources
Where does gluconeogenesis occur?
-the cytosol of cells
What does the irreversible enzyme step pyruvate carboxylase do?
-carboxylates pyruvate to oxaloacetate (added a carbon)
What does the irreversible enzyme step phosphoenolypyruvate carboxykinase (PEPCK) do?
-converts oxaloacetate to phosphoenolypyruvate
What does the irreversible enzyme step Fructose-1,6-biphosphatase do?
-removes 1 phosphate group from fructose-1,6-biphosphate
What does the irreversible enzyme step Glucose-6-phosphate do?
-removes the phosphate group to liberate free glucose
What do ruminants extensively utilize that is produced from fermentation of carbohydrates in the rumen?
-propionate (gluconeogenesis VFA)
What happens when carbohydrates are extensively fermented?
-no or very little glucose is absorbed from the small intestine intact
What is propionate converted to?
-succinyl-CoA
What does succinyl-CoA proceed to?
-the TCA cycle to oxaloacetate to enter gluconeogenesis
Do ruminants depend exculsively on gluconeogenesis?
Yes
What are substrates from gluconeogensis?
-Amino acids
How are amino acids utilized?
-as carbon skeletons for gluconeogenesis
-entry points into TCA cycle to get to oxaloacetate and pyruvate vary by amino acids
What is easy to convert to pyruvate?
Alanine
What control gluconeogensis?
Hormones
What does insulin do to gluconeogenesis?
strongly inhibits it
What does glucagon do to gluconeogenesis?
promotes it
What does cortisol do to gluconeogenesis?
stimulates it
What can simple stomach animals be?
-carnivores
-herbivores
-omnivores
What influences the structures of the digestive tract?
-diet feedstuff composition
What do more digestible diets require?
-less digestive capacity in the gastrointestinal tract
What do more plant material and more fiber require?
-more capacity and complexity in the GI tract to facilitate digestion
What is important for fiber digestion in ruminants?
-retention
-capacity
If an animal eats more plant material what part of their digestive tract is larger?
Large intestine
What does fermentation improve?
-plant fiber digestion
Where does most fermentation take place in a simple stomach animal?
-in the hindgut
-large intestine
As a percentage of total gut volume who has the greatest fermentation capacity?
-ruminants, but some non-ruminants come close
Where do carbohydrates that escape digestion in the small intestine in simple stomach animals go?
-enter the large intestine for fermentation
What enters the large intestine?
-plant fiber
-possibly starch
What does fermentation by bacteria produce?
-VFA
-CO2
-H2
-methane (variable)
