Final Exam GI Physiology: Ruminant Digestion Flashcards Preview

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Flashcards in Final Exam GI Physiology: Ruminant Digestion Deck (56):
1

What is the principal distinguishing characteristic of ruminant digestion?

Fermentation of ingesta by microbes in the ruminoreticulum

2

What is fermentation?

The anaerobic oxidation of substrate followed by reduction of an organic molecule

3

Lactate formed from pyruvate is an example of what?

Fermentation

4

Methane formed from CO2 is an example of what?

Fermentation

5

Fermentation of amino acids yields what products?

Sulfates and Nitrates

6

What products are produced when sulfates and nitrates are reduced?

H2S
NH3
NH4+

7

In regards to fermentation of carbohydrates, put the following in order from which ferments fastest to which ferments slowest:
Simple sugars
Starches
Cellulose

Simple sugars RAPID
Starches MODERATE
Cellulose SLOW

8

What are the products of fermentation of simple sugars, starches, and cellulose (carbohydrates)?

CO2
CH4
Lactic Acid
VFAs
Acetic Acid
Proprionic Acid
Butyric Acid

9

T or F: Microbes can perform oxidation in the absence of oxygen.

TRUE

10

What enzyme is utilized by microbes in the rumen to oxidize pyruvate to acetyl CoA?

Pyruvate-ferrodoxin oxidoreductase

11

What enzyme in the rumen acts on the acetyl CoA produced?

Phosphotransacetylase

Adds Pi to Acetyl CoA --> Acetyl-Pi and Coenzyme A

12

What enzyme in the rumen is used by microbes along with ADP to act on Acetyl-Pi produced earlier?

Acetate kinase

Acetyl-Pi + ADP ---acetate kinase---> acetic acid + ATP

13

What are the waste products of carbohydrate fermentation?

Volatile Fatty Acids!

14

How do anaerobic microbes generate ATP?

By glycolysis and microbe-enzyme reactions in the rumen

15

In the rumen/reticulum, what are O2 and CO2 ultimately reduced into?

H2O and CH4

16

The ratio of VFA : Lactic acid is a function of ______ .

Diet

17

A low VFA : Lactic Acid (and therefore low rumen pH) ratio is indicative of what kind of diet?

High % of easily digestible carbs

18

What ruminal pH is considered normal?

pH of 6

19

What is a dietary cause of Ruminal Lactic Acidosis?

A low VFA : Lactic Acid ratio (caused by too much easily digestible carbs in diet)

20

What conditions can Ruminal Lactic Acidosis lead to?

Ulceration, pain, going off feed, systemic ketoacidosis

21

How is protein digested in the rumen?

Through microbial digestion and hydrolysis via pancreatic and brush border enzymes

22

What do microbes do to proteins in the rumen?

Hydrolysis of protein --> amino acids
Hydrolysis of amino acids ---deamination---> VFA

23

What is generated as a result of amino acid deamination to VFA?

AMMONIA (NH3)

24

What is produced Ammonia utilized for?

To make microbial protein

To be converted into urea by the liver

25

What % of protein escapes microbial digestion?

50%

26

The 50% of protein that escapes microbial digestion is hydrolyzed in the _______ and _________ via pancreatic and brush border enzymes.

Abomasum and Small Intestine

27

Protein hydrolyzed by pancreatic and brush border enzymes yield what products?

Small peptides and amino acids

28

Where are dead microbes digested?

Abomasum and small intestine

29

Where can urea be found after it is produced by the liver?

Urea can diffuse into GI tract lumen
Urea can be secreted by salivary glands

30

What enzyme converts urea into NH3 (ammonia) and CO2?

Microbial urease

31

How is produced CO2 utilized?

CO2 is used in carboxylase reactions

Ex: Pyruvate ---oxaloacetate---> Proprionate

32

What are triacylglycerol and phospholipids hydrolyzed (by microbes) into?

Glycerol and FFA

33

Ruminants characteristically have a _______ level of saturated fat.

HIGH

34

What is produced FFA used for?

Incorporation into chylomicrons

35

What is the fermentation product of glycerol?

VFAs! Specifically proprionic acid

36

All VFAs are _______ acids

All VFAs are carboxylic acids

37

VFAs constitute what percentage of a ruminant animal's daily energy requirement?

70%

38

VFAs constitute 70% of a ruminant animal's daily energy requirement. What is the relative percentage of ACETIC ACID?

60%

39

VFAs constitute 70% of a ruminant animal's daily energy requirement. What is the relative percentage of PROPIONIC ACID?

25%

40

VFAs constitute 70% of a ruminant animal's daily energy requirement. What is the relative percentage of BUTYRIC ACID?

15%

41

VFA's are largely __________ at normal ruminal pH of 6.

NON DISSOCIATED

42

What is the fate of Acetic Acid (a VFA)?

Acetic Acid is converted into Acetyl CoA in muscle and fat.

43

What is the fate of Propionic Acid (a VFA)?

Propionic Acid is REMOVED from plasma by the LIVER

44

What is the fate of Butyric Acid (a VFA)?

Converted to ketone bodies, acetyl CoA, or removed by the liver

45

Is Lactate a volatile fatty acid?

NO. Lactate is NOT a VFA

46

If VFAs constitute 70% of a ruminant's daily energy requirement, what makes up the remaining 30%?

LACTATE

47

What happens to Lactate in circulation?

Lactate is REMOVED from plasma by the LIVER (just like propionic and butyric acids)

48

What happens to Lactate in the liver?

Lactate is converted to PYRUVATE in the liver

49

What happens to Propionate in the liver?

Propionate is converted to SUCCINYL COA in the liver

50

What happens to Butyrate in the liver?

Butyrate is converted to 2 Acetyl CoAs in liver mitochondrion

51

What does an increased concentration of Acetyl CoA in the liver inhibit?

Increased Acetyl CoA in the liver inhibits PDH (pyruvate dehydrogenase) Complex and increases activity of pyruvate carboxylase

52

What is the function of pyruvate carboxylase?

Converts pyruvate into oxaloacetate

53

Which 2 VFA's are converted to TCA intermediates and then Glucose via gluconeogenesis?

Lactate and Propionate

54

Where does the energy come from that supplies the process of turning lactate and propionate into glucose?

The oxidation of Butyrate

55

Almost ALL carbohydrates ingested by ruminants is ________.

FERMENTED

56

Almost NO glucose is ________ by the GI Tract of ruminants.

no glucose absorbed