L28 Metabolism & energy balance

Question 1

Define “metabolism”

Question 2

Describe the difference between “anabolic” and “catabolic” processes

Answer 2

Anabolic = large molecule built from smaller ones;

require energy

Catabolic = processes that break down complex structures to smaller, simpler ones;

release energy

Question 3

Explain the absorptive (fed) and post-absorptive (unfed) states

Answer 3

absorptive (fed) state:

• the period of time following a meal where products of digestion are being absorbed, used and stored.

(primarily ANABOLIC)

• during an immediately following meal consumption
• is the most important fuel

Postabsorptive (unfed) state:

• the period of time when nutrients from a meal are no longer available

(primarily CATABOLIC)

• GI tract is empty and energy is derived body reserves
• maintain glucose levels

Question 4

List the fate of the various nutrients that occur in the absorptive state and post-absorptive state

Answer 4

Major metabolic pathway in the absorptive state

- Glucose generally serves as a major energy source immediately following a meal *exception are ruminants (VFAs)

• Very little of absorbed fat/ aa used as intermediate energy source in fed state

(most cells preferentially use glucose first)

Post- absorptive state:

• primary goal (spare glucose)
• endogenous energy stores ( fat ad glycogen）
• gluconeogenesis maintain blood glucose
• fat is mobilized as alternative energy source (especially for muscle)
• protein is mobilized for glucose formation

Question 5

Explain why catabolism dominates in the post-absorptive state

Question 6

Explain the role of insulin and glucagon in the regulation of digestion

Question 7

Explain the processes regulating feeding and digestion

Question 8

Starvation response

Question 9

Key tissue and organ

(various tissue play different roles between these alternating states)

Answer 9

Liver:

• primary role in maintaining blood glucose level
• store glycogen, release glucose to blood, gluconeogenesis
• *Adipose tissue:**
• main energy storage site
• regulates fatty acids

Muscle:

• the primary site of aa storage and major energy user
• use lipids for energy during long-term fasting

Brain:

• relies on