Biochemical Consequences of Protein and Energy Imbalances

Question 1

What are the 3 major constituents absorbed from the gastrointestinal tract in an omnivore?

Answer 1

Glucose
Long chain fatty acids
Amino acids

Question 2

Which hormone drives storage of products absorbed from the gastrointestinal tract?

Answer 2

Insulin

Question 3

Outline storage of glucose in an omnivore

Answer 3

80% stored as muscle glycogen
20% stored as liver glycogen
Excess glucose converted to pyruvate then long chain fatty acids

Question 4

Give 2 parts of the body that are obligate users of glucose

Answer 4

Brain

Red blood cells

Question 5

Outline the process by which red blood cells get energy…

Answer 5

Glycolysis

Obligate anaerobic metabolism

Question 6

How are triglycerides made?

Answer 6

From glycerol and fatty acids

Question 7

Where are triglycerides made?

Answer 7

Adipocytes

Question 8

How are long chain fatty acids utilised as an energy source?

Answer 8

Beta-oxidisation

Question 9

When might long chain fatty acids be used as an energy source?

Answer 9

When glucose is being conserved

Question 10

How are amino acids stored?

Answer 10

Muscle protein
Builds up muscle mass
Source of energy

Question 11

Outline metabolism of excess amino acids…

Answer 11

2 pathways - most can go either way but some are 1 or the other
Glucogenic to pyruvate
Ketogenic to acetyl co-enzyme A

Question 12

Outline how a carnivore’s metabolism differs from that of an omnivore…

Answer 12

Major foodstuff is protein
Metabolism dependent on amino acids
Increased liver metabolism
Glucose made via gluconeogenesis

Question 13

Outline how glucagon effects the switch to fasting metabolism…

Answer 13

Binds to cell surface receptors
Activates G-protein coupled receptor
Activates cAMP which activates protein kinase A
Protein kinase A phosphorylates metabolic hormones to regulate them

Question 14

What molecule is activated by insulin?

Answer 14

Phosphastase

Question 15

Which hormone initiates the fasting metabolism?

Answer 15

Glucagon

Question 16

In omnivores, why does glycogenolysis occur in fasting?

Answer 16

To boost blood glucose

Question 17

Where does glycogenolysis occur?

Answer 17

The liver

Question 18

In omnivores, what is the classical fasting response to spare glucose?

Answer 18

Activation of hormone sensitive lipase
Breakdown of triglycerides
Release of long chain fatty acids into the blood
Tissue with oxygen beta-oxidise long chain fatty acids and use the citric acid cycle for non-toxic energy

Question 19

What is the byproduct of breakdown of triglycerides, and how is it used in omnivores?

Answer 19

Glycerol - goes through gluconeogenesis to boost blood sugar

Question 20

Outline how muscle storage of amino acids can be used for energy

Answer 20

Muscle protein broken down to release amino acids into amino acid pool
Amino acids undergo gluconeogenesis in liver

Question 21

When is muscle storage of amino acids used as an energy source?

Answer 21

Extended fast (last resort as needed for other functions)

Question 22

For how long a fast will omnivore body stores of glycogen last?

Answer 22

~1 day

Question 23

For how long a fast will omnivore body stores of triglyceride last?

Answer 23

Variable - weeks to months

Question 24

Give an example of a condition inducing perceived starvation

Answer 24

Diabetes (lack of insulin causes effective excess of glucagon)

Question 25

Outline the effect of starvation on triglyceride stores

Answer 25

Breakdown into long chain fatty acids is upregulated, increasing their concentration in the blood

Question 26

Give the risk associated with beta-oxidation of long chain fatty acids in the liver

Answer 26

Ketosis

Question 27

Outline how ketosis occurs

Answer 27

- Beta-oxidisation of long chain fatty acids leads to accumulation of acetyl co-enzyme A - Acetyl co-enzyme A use is decreased due to: + High cell energy charge (no need for citric acid cycle - turned off allosterically by cell ATP) + Depletion of citric acid cycle intermediates (used to make glucose) - Build-up of acetyl co-enzyme A by default makes ketone bodies

Question 28

Name the ketone bodies...

Answer 28

Acetoacetate 3-hydroxybutyrate Acetone

Question 29

How is 3-hydroxybutyrate used within the body?

Answer 29

- Oxidised for energy - Broken down into 2 acetyl co-enzyme As - Acetyl co-enzyme A used in other tissues for citruc acid cycle - Important in brain (short chain fatty acids are water soluble and can cross BBB - conserves glucose)

Question 30

Why are ketone bodies useful?

Answer 30

Oxidised in tissues for energy

Question 31

Describe ketoacidosis...

Answer 31

pH falls due to acidic effect of ketone bodies

Question 32

Give 2 examples of conditions in which ketoacidosis may occur...

Answer 32

- Type 1 diabetes - Production diseases Twin lamb disease Bovine ketosis

Question 33

What is the major product absorbed from the ruminant gastrointestinal tract?

Answer 33

Volatile fatty acids (from rumen fermentation)

Question 34

Name the volatile fatty acids

Answer 34

Acetate (2 carbons) Proprionate (3 carbons) Butyrate (4 carbons)

Question 35

What is butyrate?

Answer 35

Volatile fatty acid 4 carbon short chain fatty acid Ketone body

Question 36

Which volatile fatty acids are converted to acetyl co-enzyme A in ruminant metabolism?

Answer 36

Acetate (2 carbons) | Butyrate (4 carbons)

Question 37

How are acetate and butyrate used for energy in ruminant metabolism?

Answer 37

Converted to acetyl co-enzyme A | Used in citric acid cycle

Question 38

What is done with excess short chain fatty acids in ruminant metabolism?

Answer 38

Conversion to long chain fatty acids | Used in tissue or stored

Question 39

What is the major energy storage product in ruminants?

Answer 39

Triglycerides

Question 40

Describe the liver glycogen levels in a ruminant

Answer 40

Low

Question 41

Describe ruminant blood sugar

Answer 41

Low (about half the level of dogs')

Question 42

How do ruminants make glucose?

Answer 42

From proprionate (gluconeogenesis)

Question 43

How is most ruminant glucose used?

Answer 43

Put into blood for essential function

Question 44

Outline prevention of ketoacidosis in high-producing animals

Answer 44

Increase concentrates in diet

Question 45

What is the major form of protein fed to ruminants?

Answer 45

Heat-treated soybean

Question 46

What is the purpose of heat-treating soybeans in ruminant diets?

Answer 46

Harder for rumen microflora to ferment into volatile fatty acids Protein digested in abomasum and absorbed in small intestine as gluconeogenic substrates

Question 47

Describe the difference between ketoacidosis and rumen acidosis...

Answer 47

Ketoacidosis is a fall in the blood pH | Rumen acidosis is a fall in the pH of the rumen contents

Question 48

Why does rumen acidosis occur?

Answer 48

Changing diet too quickly leads to lactic acidosis in the rumen

Question 49

What are the outcomes of ketoacidosis?

Answer 49

Decreased milk production | Hepatic lipidosis

Question 50

What is the effect of increasing concentrates in the diet of a ruminant?

Answer 50

More proprionate absorbed (undergoes gluconeogenesis)

Question 51

When is hepatic lipidosis seen in the ruminant?

Answer 51

Ketoacidosis Starvation Obesity