Biology Cell Theory and Cell Types

Cell Theory

• Composed of three main principles:
  1. All living organisms are made of one or more cells.
  2. The cell is the basic unit of life.
  3. All cells arise from pre-existing cells.

Prokaryotic and Eukaryotic Cells

• Prokaryotic Cells:

  • Lack a nucleus and membrane-bound organelles.
  • Generally smaller and simpler (e.g., bacteria).
  • DNA is in a single circular chromosome.
  • Reproduce asexually through binary fission.

• Eukaryotic Cells:

  • Have a nucleus and membrane-bound organelles.
  • Generally larger and more complex (e.g., plant and animal cells).
  • DNA is linear and organized into multiple chromosomes.
  • Can reproduce asexually (mitosis) or sexually (meiosis).

Organelles

• Nucleus: Contains genetic material; controls cell activities.
• Mitochondria: Powerhouse of the cell; site of ATP (energy) production.
• Ribosomes: Protein synthesis; can be free-floating or attached to the endoplasmic reticulum.
• Endoplasmic Reticulum (ER):
  • Rough ER: Studded with ribosomes; involved in protein synthesis.
  • Smooth ER: Lipid synthesis and detoxification processes.
• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion.
• Lysosomes: Contains digestive enzymes; breaks down waste.
• Chloroplasts: Site of photosynthesis; found in plant cells.
• Cell Membrane: Semi-permeable barrier; regulates entry and exit of substances.

Cell Transport

• Passive Transport: Movement of molecules without energy input.

  • Types:
    • Diffusion: Movement from high to low concentration.
    • Facilitated Diffusion: Uses transport proteins for larger or polar molecules.
    • Osmosis: Special case involving water movement.

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

  • Example: Sodium-potassium pump.

Osmosis

• The diffusion of water across a semi-permeable membrane.
• Movement occurs from an area of low solute concentration to an area of high solute concentration.
• Important for maintaining cell turgor pressure in plant cells.
• Types of Solutions:
  • Isotonic: Equal solute concentration; no net water movement.
  • Hypotonic: Lower solute concentration outside; water enters cell (may burst).
  • Hypertonic: Higher solute concentration outside; water exits cell (may shrivel).

Cell Theory

• All living things are made of cells
• Cells are the fundamental unit of life
• New cells arise from pre-existing cells through cell division

Prokaryotic and Eukaryotic Cells

• Prokaryotic cells lack a nucleus and membrane bound organelles
• Prokaryotic cells include bacteria
• Prokaryotic cells are typically smaller and simpler than eukaryotes
• Prokaryotic DNA is in a single circular chromosome
• Prokaryotic cells reproduce asexually through binary fission
• Eukaryotic cells have a nucleus and membrane bound organelles
• Eukaryotic cells include plants and animals
• Eukaryotic cells are typically larger and more complex than prokaryotes
• Eukaryotic DNA is linear and organized into multiple chromosomes
• Eukaryotic cells can reproduce asexually through mitosis or sexually through meiosis

Organelles

• The nucleus contains genetic material (DNA) and controls cell activities
• Mitochondria are the powerhouses of the cell and produce ATP (energy)
• Ribosomes are the sites of protein synthesis
• The endoplasmic reticulum (ER) is a network of membranes involved in protein synthesis and lipid synthesis
  • Rough ER is studded with ribosomes and involved in protein synthesis
  • Smooth ER is involved in lipid synthesis and detoxification
• The Golgi apparatus modifies, sorts, and packages proteins and lipids for secretion
• Lysosomes contain digestive enzymes that break down waste
• Chloroplasts are the sites of photosynthesis and are found in plant cells
• The cell membrane regulates the entry and exit of substances

Cell Transport

• Passive transport does not require energy input
  • Diffusion is the movement of molecules from a high to a low concentration
  • Facilitated diffusion uses transport proteins to move larger or polar molecules across the membrane
  • Osmosis is the special case of water diffusion across a semi-permeable membrane
• Active transport requires energy (ATP)
  • It moves molecules against their concentration gradient
  • The sodium-potassium pump is an example of active transport

Osmosis

• Osmosis is the diffusion of water across a semi-permeable membrane
  • Water moves from an area of low solute concentration to an area of high solute concentration
  • Osmosis is important for maintaining cell turgor pressure in plant cells
• Isotonic solutions have equal solute concentrations, resulting in no net water movement
• Hypotonic solutions have a lower solute concentration outside the cell, causing water to enter the cell
  • This can lead to cell bursting
• Hypertonic solutions have a higher solute concentration outside the cell, causing water to exit the cell
  • This can lead to cell shriveling

Explore the fundamental concepts of cell theory, including the principles that define living organisms and the basic unit of life. This quiz covers the key differences between prokaryotic and eukaryotic cells, along with essential organelles and their functions. Test your knowledge about the building blocks of life!