ISSA PT Chapter 6: Energy and Metabolism.

What is Metabolism?

All of the chemical processes that occur in the body to support life, including converting food into usable energy.

What is Bioenergetics?

The study of how energy is transformed within living organisms.

What is Adenosine Triphosphate (ATP) and how much energy is lost as heat?

The primary energy-carrying molecule used to fuel cellular processes. Roughly 40% of its energy is used for cellular work, while 60% is released as heat.

How many ATP molecules are required for one complete muscle contraction and relaxation sequence?

Two molecules of ATP (one to energize the myosin head for contraction/power stroke, and a second to cause actin detachment for relaxation).

What is the Phospholipid Bilayer and what gives it fluidity?

A dual layer of lipids (glycerol, fatty acids, and phosphate groups) that makes up the plasma membrane. Embedded cholesterol allows it to maintain fluidity and structure.

Which organelle initiates cell division (mitosis) and holds DNA?

The Nucleus.

What metabolic reactions occur in the Cytoplasm (Cytosol)?

1. Glycolysis

2. Gluconeogenesis

3. Fatty acid synthesis

4. Activation of amino acids

What is the functional difference between free-floating and attached Ribosomes?

• Free-floating ribosomes: Synthesize proteins intended to act inside the cell.

• Attached ribosomes (on Rough ER): Synthesize proteins intended to be exported outside the cell.

What are the key roles of the Smooth Endoplasmic Reticulum (SER)?

Produces/metabolizes lipids, breaks down glycogen into glucose (in liver cells), produces steroid hormones, and releases calcium ions to trigger muscle contraction (as the sarcoplasmic reticulum).

What is the function of the Golgi Apparatus?

Packages and transports membrane-bound proteins using vesicles (often as glycoproteins for cellular communication).

What is the function of Lysosomes?

Acts as the digestive system of the cell; contains ~50 enzymes to break down absorbed materials or worn-out cellular parts.

What is the Mitochondria and what process occurs inside it?

Known as the "powerhouse of the cell," it generates cellular energy via oxidative phosphorylation (aerobic energy production).

What is the typical energy fuel mix at rest?

Approximately 70% fats and 30% carbohydrates.

What is the formula for Respiratory Quotient (RQ)?

$$\text{RQ}=\frac{\text{Volume of }CO_2\text{ exhaled}}{\text{Volume of }O_2\text{ inhaled}}$$

What are the RQ values for Carbohydrates, Fats, and Proteins?

• Carbohydrates: 1.0

• Fats: 0.7 (Requires more $O_2$ to oxidize)

• Proteins: 0.8

• Average Rest Mix: ~0.8

When is Protein used as a primary substrate for energy?

Only during severe starvation or when carbohydrate and fat intake/stores are severely depleted.

What are the primary characteristics of the ATP/CP System?

• Type: Anaerobic

• Duration: 0–10 seconds

• Intensity: Maximal / Explosive (e.g., 100m sprint, heavy lift)

• Enzyme: Creatine Kinase (breaks down CP to donate a phosphate back to ADP)

What are the primary characteristics of Anaerobic Glycolysis?

• Type: Anaerobic

• Duration: ~10 to 120 seconds (2 minutes)

• Fuel Source: Glucose or Glycogen

• By-Product: Lactic Acid (Lactate) + H^+ ions

What are the 3 main ways the body uses Lactate?

1. Directly as fuel for mitochondria, heart, and brain tissue.

2. To create glucose in the liver (gluconeogenesis).

3. As a signaling molecule to shift away from fat burning toward rapid glucose burning.

What are the three stages of the Oxidative Pathway and its ATP yield?

1. Aerobic Glycolysis (Glucose —→ Pyruvate ——> Acetyl-CoA)

2. Krebs Cycle (Yields 2 ATP, CO2, H^+)

3. Electron Transport Chain (Yields 35–38 ATP per glucose molecule)

What is Beta-Oxidation and how many ATP molecules can one fat molecule yield?

The process of breaking down triglycerides into fatty acids and converting them to Acetyl-CoA for the Krebs cycle. One fatty acid molecule (e.g., palmitic acid) can yield up to 129 ATP.