Biology Chapter: 7 Quiz Homework (Chloe, Ethan, and Aiden group)

The Plasma Membrane

• The plasma membrane is a thin, flexible boundary that separates a cell from its environment
• It maintains homeostasis, the internal balance of a cell
• Important for the survival of prokaryotic and eukaryotic cells
• Allows nutrients to enter and waste/products to leave
• Separates the cell from its surroundings

Selective Permeability

• Selectively permeable membranes allow certain substances to pass while restricting others
• This is crucial for maintaining homeostasis within a cell

Plasma Membrane Structure

• Phospholipid bilayer: Two layers of phospholipids
• Polar heads: Face the water environment (hydrophilic)
• Nonpolar tails: Face inwards, away from water (hydrophobic)
• Lipids (phospholipids, cholesterol, glycolipids): Compose the majority of the membrane
• Cholesterol: Embedded to help maintain fluidity
• Proteins: Embedded in the membrane, some span it (integral), others are peripheral
• Carbohydrates: Attached to proteins (glycoproteins) or lipids (glycolipids) on the outer surface
• The arrangement of these components creates a flexible, fluid mosaic structure, allowing movement

Water Soluble Substances

• Water soluble substances do not easily pass through the plasma membrane
• Substances separate the inner environment of the cell from the outside

Transport Proteins

• Transport proteins move needed substances or waste materials through the plasma membrane
• They contribute to the selectivity of the plasma membrane
• Some are channel proteins (allow passage of specific substances)
• Others are carrier proteins (bind to substances to transport them)

Cholesterol

• Nonpolar cholesterol is positioned among phospholipids
• It helps prevent the fatty acid tails from sticking together, maintaining membrane fluidity

Carbohydrates

• Carbohydrates on the membrane are attached to proteins (glycoproteins) or lipids (glycolipids).
• They play a role in cell recognition and communication.

Fluid Mosaic Model

• The components of the plasma membrane (phospholipids, proteins, carbohydrates) are in constant motion.
• They slide past each other, creating a dynamic structure.

Cytoplasm

• The cytoplasm is the environment inside the plasma membrane
• It is where many cellular activities occur

Transport of Molecules Across the Membrane (Passive Transport)

• Diffusion: Substances move from high to low concentration regions across a membrane
• Osmosis: Water moves from high to low water concentration across a membrane
  • Hypotonic Solution: More water outside cell, water moves into the cell to equalize concentration; cell swells
  • Hypertonic Solution: More water inside cell, water moves out to equalize concentration; cell shrinks
  • Isotonic Solution: Equal water concentrations inside and outside the cell; No net movement, cell shape remains the same.

Active Transport

• Active transport: Movement of substances against a concentration gradient (low to high)
• Energy required: Cellular energy (ATP) needed for this movement
• Examples: Na+/K+ ATPase pump moves Na+ out and K+ in, maintaining ion balance

Transport of Large Particles

• Endocytosis: Cell membrane pinches inward to surround and enclose substances within a vesicle
• Exocytosis: Vesicles fuse with cell membrane, releasing their contents outside the cell (vice versa).

Organelles involved in protein synthesis, secretion

• Ribosomes
• Endoplasmic reticulum
• Golgi apparatus