Sites of Digestion
What enzyme begins carbohydrate digestion in the mouth?
Salivary amylase
What enzymes in the small intestine break down disaccharides?
Maltase, sucrase, and lactase
What process produces VFAs in the rumen and colon?
Fermentation
Where in the cell does glycolysis occur?
Cytosol
What process converts glucose to glycogen for storage?
Glycogenesis
Where does the majority of carbohydrate digestion occur in monogastrics?
Small intestine
Which enzyme hydrolyzes starch into maltose and dextrins?
Amylase
Name the three major VFAs produced.
Acetate, propionate, and butyrate
What is the end product of glycolysis under aerobic conditions?
Pyruvate
What two hormones regulate blood glucose concentration?
Insulin and glucagon
What organ secretes amylase into the small intestine?
Pancreas
Name one feed additive that can reduce methane loss in ruminants.
Monensin or Lasalocid
Which VFA is the precursor for glucose synthesis in ruminants?
Propionate
How many total ATP are produced per glucose after glycolysis and the TCA cycle?
38 ATP
When blood glucose increases after a meal, what happens to excess glucose?
It is stored as glycogen or converted to fat
Where are volatile fatty acids (VFAs) primarily absorbed in ruminants?
Rumen
How are glucose and galactose absorbed in the upper small intestine?
Active transport via sodium-glucose transporters
Which VFA is the precursor for milk and body fat synthesis?
Acetate
What are two other names for the TCA cycle?
Citric acid cycle and Krebs cycle
According to the slides, how much glycogen does the average human store in the liver and muscles combined?
About 380 g total (100 g liver, 280 g muscle)
Which parts of the digestive system contain bacteria that ferment undigested carbohydrates?
Mostly rumen, with small amount in large intestine
According to the slides, what happens when young animals consume too much sucrose or lactose?
They develop diarrhea (may result in death)
How much of a ruminant’s gross energy intake is typically lost as methane?
8–12%
Which pathway produces water and energy by transporting reducing equivalents?
Electron transport chain (respiratory chain)
What pathway occurs in the cytosol, produces CO₂ and NADPH, but no ATP?
Pentose phosphate pathway