Biology Chapter 5 Flashcards

Phospholipids and Membrane Structure

• When phospholipids are placed in water, they form a bilayer with hydrophilic heads in contact with water and hydrophobic tails facing inward.
• Membrane flexibility varies: saturated fats make membranes less flexible, while unsaturated fats increase flexibility. Cholesterol reduces overall membrane flexibility.

Membrane Proteins

• Integral Proteins: Span the phospholipid bilayer, either partially or fully embedded.
• Peripheral Proteins: Located on the inner or outer surface of the bilayer and do not penetrate the membrane.

Functions of Membrane Proteins

• Transporters: Control the passage of specific substances in and out of cells, allowing selective movement.
• Enzymes: Speed up chemical reactions at the membrane surface.
• Attachment: Connect cells to the extracellular matrix (ECM) and cytoskeleton, stabilizing the cell structure.
• Cell-Cell Recognition: Serve as identification tags for cells, facilitating cell communication.
• Intercellular Joining: Enable attachments between neighboring cells.
• Signal Transduction: Relay signals from the environment to the cell's interior, triggering responses.

Transport Mechanisms

• Passive Transport: Moves substances naturally from high to low concentration without using cellular energy. Types include:

  • Simple Diffusion: Direct movement through the membrane; spontaneous and energy-free.
  • Facilitated Diffusion: Requires a protein to assist substances in crossing the membrane.
  • Osmosis: Specific diffusion of water across a semi-permeable membrane from high to low water concentration.

• Active Transport: Requires energy to move substances against their concentration gradient, from low to high concentration.

Types of Proteins in Facilitated Diffusion

• Channel Proteins: Create a pore or tunnel for substances to pass through.
• Ion Channels: Specialized channels for ions, which can open and close to regulate ion passage.
• Carrier Proteins: Bind to specific substances (e.g., sugars and amino acids) to transport them across the membrane.

Solutions and Concentration Types

• Solution: A mixture of a solvent and solute.
• Solute: The substance that dissolves in a solvent.
• Hypertonic: Higher solute concentration leading to lower water concentration.
• Hypotonic: Lower solute concentration resulting in higher water concentration.
• Isotonic: Equal concentration of solutes in comparison to another solution.

Cell Behavior in Different Solutions

• Hypertonic Solutions:

  • Animal cells lose water, resulting in crenation; cells may die.
  • Plant cells undergo plasmolysis where the membrane pulls away from the cell wall.

• Hypotonic Solutions:

  • Animal cells take in water, swell, and may experience hemolysis (bursting).
  • Plant cells swell and maintain turgor pressure, becoming firm due to water pressure in the vacuole.

• Isotonic Solutions: Water moves in and out at a constant rate; animal cells remain normal while plant cells become limp.

Sodium-Potassium Pump and Coupled Transport

• Sodium-Potassium Pump: Actively transports 3 sodium ions out of the cell and 2 potassium ions into the cell, maintaining low sodium and high potassium concentrations inside.
• Coupled Transport: Simultaneously transports two different substances across the membrane, utilizing energy to move one substance out while bringing another in.

Test your knowledge on the cellular structures presented in Chapter 5. These flashcards cover important concepts such as phospholipids and the roles of integral and peripheral proteins in the cell membrane. Perfect for students looking to reinforce their understanding of cell biology.