Cell Structure and Function

Cell Structure and Function

• Cells are the basic units of life, exhibiting diverse shapes and sizes tailored to their specific roles.
• All cells share fundamental components: a plasma membrane, cytoplasm, and genetic material.
• The plasma membrane acts as a selective barrier, controlling the passage of substances into and out of the cell.

Prokaryotic Cells

• Lack a nucleus and membrane-bound organelles.
• Typically smaller and simpler than eukaryotic cells.
• Examples include bacteria and archaea.
• Contain DNA in a region called the nucleoid.
• May possess cell walls, flagella, and pili.

Eukaryotic Cells

• Possess a nucleus and membrane-bound organelles.
• More complex and larger than prokaryotic cells.
• Examples include animal, plant, fungi, and protist cells.
• Nucleus houses the cell's genetic material (DNA).
• Organelles perform specialized functions, contributing to cellular activities.

Key Cell Organelles and Their Functions

• Nucleus: Contains DNA, regulating cellular activities.
• Ribosomes: Synthesize proteins.
• Endoplasmic Reticulum (ER): Rough ER is involved in protein synthesis and modification; smooth ER is involved in lipid synthesis and detoxification.
• Golgi apparatus: Processes, packages, and sorts proteins and lipids.
• Mitochondria: Produce ATP (energy) through cellular respiration.
• Lysosomes: Contain enzymes for intracellular digestion.
• Vacuoles: Store water, nutrients, and waste products.
• Chloroplasts (plant cells): Conduct photosynthesis.
• Cytoskeleton: Provides structural support and facilitates cellular movement.

Cellular Transport

• Passive Transport: Movement of molecules down a concentration gradient, requiring no energy input.

  • Diffusion: Movement of molecules from high to low concentration.
  • Osmosis: Diffusion of water across a selectively permeable membrane.
  • Facilitated Diffusion: Diffusion of molecules across a membrane with the aid of transport proteins.

• Active Transport: Movement of molecules against a concentration gradient, requiring energy input (ATP).

  • Sodium-Potassium Pump: A crucial example of active transport maintaining ion gradients.

Osmosis

• The movement of water across a selectively permeable membrane from a region of high water concentration to a region of low water concentration.
• Crucial for maintaining cell volume and function.
• Tonicity: Refers to the relative solute concentrations of two solutions separated by a selectively permeable membrane.
  • Isotonic Solutions: Solute concentration is equal inside and outside the cell.
  • Hypotonic Solutions: Solute concentration is lower outside the cell. Water moves into the cell, causing swelling or lysis.
  • Hypertonic Solutions: Solute concentration is higher outside the cell. Water moves out of the cell, causing shrinkage or crenation.

Diffusion

• The net movement of molecules from an area of high concentration to an area of low concentration.
• Factors influencing diffusion rate include:
  • Concentration gradient
  • Temperature
  • Molecular size
  • Membrane permeability
• Essential for diverse cellular processes, including nutrient uptake and waste removal.

Test your knowledge on the basic units of life, focusing on the differences between prokaryotic and eukaryotic cells. Explore the roles of various organelles and their functions in cellular activities. This quiz covers essential concepts for understanding cell biology.