BIOL122 liver and metabolic homeostasis

What is the average weight of a human liver?

Approximately 1.4 kg.

What is considered the basic functional unit of the liver?

The liver lobule.

What are Kupffer cells and where are they located?

They are fixed phagocytic cells located within the liver sinusoids that destroy bacteria and old blood cells.

Name six general functions of the liver besides nutrient metabolism.

1. Phagocytosis (via Kupffer cells)

2. Synthesis of bile salts & excretion of haem

3. Processing of drugs and hormones

4. Activation of Vitamin D

5. Storage (e.g., Glycogen, Vitamin A/retinol)

6. Plasma protein synthesis

What are the volume, color, and pH characteristics of bile?

Volume: 800 mL – 1 liter per day

Color: Yellow/green

pH: 7.6–8.6 (Alkaline)

What are the primary functions of bile salts during digestion?

They emulsify fats, which allows pancreatic lipase to break down lipids more easily, and aid in lipid absorption.

Explain how the liver processes old red blood cells into the pigment excreted in faeces.

Haemoglobin's haem is broken down into bilirubin (yellow pigment). Bacteria in the gut then metabolize bilirubin into stercobilin, which gives faeces its brown colour.

Define Glycogenesis (state, hormone, and mechanism).

The conversion of Glucose ➔ Glycogen. It occurs during the absorptive state and is stimulated by insulin.

Define Glycogenolysis (state, hormone, and mechanism).

The breakdown of Glycogen ➔ Glucose. It occurs during the post-absorptive state and is stimulated by glucagon and adrenaline (epinephrine).

Define Gluconeogenesis and list three molecules used to create it.

The generation of new glucose from non-carbohydrate sources during a prolonged post-absorptive state. It utilizes lactic acid, pyruvic acid, certain amino acids, and glycerol. It is stimulated by cortisol and glucagon.

What is Lipogenesis, when does it occur, and what hormone regulates it?

The synthesis of Triglycerides from excess glucose, glycerol, fatty acids, and amino acids. It occurs during the absorptive state and is stimulated by insulin.

What is Lipolysis and what hormones stimulate it?

The breakdown of triglycerides into fatty acids and glycerol during the post-absorptive state. It is stimulated by adrenaline, noradrenaline, and cortisol.

The breakdown of triglycerides into fatty acids and glycerol during the post-absorptive state. It is stimulated by adrenaline, noradrenaline, and cortisol.

During fatty acid catabolism (beta-oxidation), excess Acetyl CoA is converted into ketone bodies (acetoacetic acid, beta-hydroxybutyric acid, and acetone).

What is the pathway of amino acid disposal during protein catabolism in the liver?

Amino acids undergo deamination, producing an organic acid and an ammonium ion (NH4+). The toxic ammonium is converted into urea and excreted in urine.

Give two examples of plasma proteins synthesized by liver hepatocytes (Anabolism).

Albumin and fibrinogen.

What are the major pathway directions during the Absorptive State (just eaten)?

It is an anabolic/storage state:

• Glucose ➔ Glycogen (Glycogenesis)

• Fatty acids + Glycerol ➔ Triglycerides (Lipogenesis)

• Amino acids ➔ Proteins

What are the major pathway directions during the Post-Absorptive State (fasting)?

It is a catabolic/mobilizing state to produce ATP and maintain blood sugar:

• Glycogen ➔ Glucose (Glycogenolysis)

• Triglycerides ➔ Fatty acids + Glycerol (Lipolysis)

• Lactic acid / Amino acids / Glycerol ➔ Glucose (Gluconeogenesis)

• Fatty acids ➔ Ketone bodies