Biology Chapter: Cells

Cells: The Building Blocks of Life

• Cells are the smallest units of life, providing structure and performing essential functions.
• Main functions include structural support, growth via mitosis, transportation of materials, energy production, metabolic reactions, and aiding in reproduction.

Characteristics of Cells

• Composed mainly of carbon, hydrogen, nitrogen, and oxygen: 59% Hydrogen, 24% Oxygen, 11% Carbon, 4% Nitrogen, and 2% other elements (Phosphorus, Sulfur, etc.).
• All cells share basic parts: plasma membrane, cytoplasm, and nucleus.

Common Parts of a Cell

• Plasma Membrane:
  • A lipid bilayer that forms a barrier between the cell and its environment.
  • Semi-permeable, allowing selective material entry/exit.
• Cytoplasm:
  • Gel-like substance where cellular chemical reactions occur.
  • Contains organelles such as nucleus, ribosomes, mitochondria, and more.
• Ribosomes:
  • Sites for protein synthesis found in the cytoplasm.
• DNA:
  • Genetic material providing instructions for life functions and traits.

Specific Cell Structures

• Cell Wall:
  • Present only in plant cells, composed of cellulose, hemicellulose, and pectin.
  • Provides rigidity, shape, and protection from mechanical injury.
• Nucleus:
  • Controls cell activity and contains DNA, crucial for protein synthesis.

Cell Organelles and Their Functions

• Nucleolus: Produces ribosomes.
• Endoplasmic Reticulum (ER):
  • Rough ER: Transports ribosomes; involved in protein production.
  • Smooth ER: Synthesizes lipids and detoxifies cell.
• Golgi Bodies: Modifies, sorts, and packages proteins for transport.
• Mitochondria: Known as the powerhouse of the cell; produces ATP, the energy currency.
• Lysosomes: Contain digestive enzymes that help break down waste and protect the cell from foreign bodies.

Protein Shipment Process

• Ribosome synthesis begins in the nucleolus, continues in the rough ER, gets modified in the Golgi body, and is ultimately released from the cell via vesicles.

Homeostasis and Temperature Regulation

• Optimal body temperature is around 37°C; fluctuations can impair enzyme function.
• Enzymes are sensitive to temperature, and extreme deviations can lead to denaturation, affecting life processes.

Nutrient Maintenance

• Insufficient nutrient intake can lead to diseases (e.g., scurvy from lack of vitamin C).
• Essential for maintaining overall health and avoiding symptoms like bleeding gums and lack of appetite.

Gas Exchange and pH Balance

• Carbon dioxide lowers blood pH and needs rapid removal to prevent acid buildup.
• Increased carbonic acid leads to elevated breathing rates to restore pH balance.

Chemical Substances in the Body

• Body activities are controlled by various chemical substances, transported through blood in mammals or vascular tissues in plants for cellular function.

Explore the fundamental unit of life with this quiz on cells. Learn about their characteristics, main functions, and how they contribute to the body's structure and processes. Test your knowledge about the building blocks of life!