Cell Biology Quiz: Energy and Metabolism

Cellular Energy Production

• Cells are chemical factories, breaking down organic molecules to produce energy for ATP, the body's main high-energy compound.
• Mitochondria are the primary energy producers in cells.
• Cellular energy production involves oxygen and nutrient intake.
  • Lungs absorb oxygen.
  • Digestive tract absorbs nutrients (water, vitamins, minerals, carbohydrates, lipids, and proteins).
  • The cardiovascular system distributes these to cells.
• Tissue-specific energy needs vary due to cell type diversity.
• Metabolic needs fluctuate based on activity levels (rest/exercise), time of day (awake/sleep), and age (child/adult).
• Energetics is the study of energy flow and its conversions.

Metabolism Overview

• Metabolism encompasses all chemical reactions in the body.
• Cellular metabolism involves the cell's chemical reactions, sustaining homeostasis and essential functions.
• Organic compounds (amino acids, lipids, simple sugars) cross the plasma membrane and contribute to the cytosol's nutrient pool.
• Catabolism is the breakdown of organic molecules, releasing energy to synthesize ATP or other high-energy compounds.
  • Catabolism occurs in steps.
  • Early steps (cytosol) break down large organic molecules into smaller fragments (carbohydrates to short chains, triglycerides to fatty acids and glycerol, proteins to amino acids).
  • Later steps (mitochondria) further break down molecules, generating significant energy capture (approximately 40%).
  • The energy captured converts ADP to ATP. The remaining energy is released as heat.
• Anabolism is the synthesis of new organic molecules that involves the formation of new chemical bonds.
• ATP from mitochondria fuels anabolism and other cell processes.

Nutrient Processing and Energy Production

• Cells obtain organic molecules from the interstitial fluid.

• Catabolism, however, only produces about 40% usable energy in the form of ATP.

• Different cells require varying amounts of ATP based on their specific functions (contraction in muscle cells, secretion in glands).

• Cells synthesize organic materials for several reasons:

  • Maintenance and repair (replenishing cell components).
  • Growth (increased size and protein/organelle synthesis).
  • Secretion (creating and transporting substances).
  • Nutrient storage (preparing for low external supply)

• Nutrients are categorized by preference order for energy.

• Mitochondria are selective in the organic molecules they use.

• Cytosol prepares molecules for mitochondrial processing.

• Mitochondria break down molecules into carbon dioxide, water, and ATP via pathways such as the citric acid cycle and electron transport system.

• ATP is fundamental to all essential cell processes.