BSC1010 Lecture 7

Chp 7- Plasma Membranenoanimation

Page 1: Structure of the Plasma Membrane

• The plasma membrane consists of a double layer of phospholipids.

• Contains proteins, cholesterol, and other molecules.

Page 2: Membrane Properties

• Membrane fluidity is enhanced by the presence of phospholipids and proteins.

• Most lipids and some proteins can drift laterally within the membrane.

• The membrane is selectively permeable, regulating the traffic of substances into and out of the cell.

Page 3: Role of Cholesterol

• Cholesterol molecules are integral to the fluidity of the membrane.

• They help maintain membrane stability.

Page 4: Selective Permeability

• The plasma membrane acts as a barrier to substances, allowing certain molecules to pass while blocking others.

Page 5: Selective Permeability (Reiteration)

• This selective permeability is integral for maintaining homeostasis within the cell.

Page 6: Types of Membrane Proteins

• There are two main types of membrane proteins:

  • Peripheral proteins: Not embedded in the lipid bilayer.

Page 7: Integral Proteins

• Integral proteins penetrate the hydrophobic core of the lipid bilayer (transmembrane proteins).

• Contact with the lipid core involves hydrophobic regions (nonpolar amino acids) and hydrophilic regions (polar amino acids).

Page 8: Functions of Membrane Proteins

• Various functions include:

  • Transport

  • Intercellular joining

  • Enzymatic activity

  • Cell-cell recognition

  • Signal transduction

  • Attachment to the cytoskeleton and extracellular matrix (ECM).

Page 9: Membrane Carbohydrates

• Membrane carbohydrates are branched oligosaccharides with fewer than 15 sugar units, varying by species and cell type.

Page 10: Membrane Synthesis

• Membranes are synthesized in the endoplasmic reticulum (ER) and Golgi apparatus.

Page 11: Passive Transport Overview

• Passive transport does not expend energy; molecules follow their concentration gradient.

• Simple diffusion involves constant movement of molecules in liquid and gas states.

Page 12: Passive Transport Indicators

• Passive transport involves molecules moving according to their energy and concentration gradients.

Page 13: Simple Diffusion Visual

• Diffusion illustrated with solute molecules, showing net diffusion until equilibrium is reached.

Page 14: Diffusion Examples

• Simple diffusion includes diffusion of one solute and diffusion of two solutes, demonstrating net movements towards equilibrium.

Page 15: Simple Diffusion Mechanism

• Simple diffusion occurs with lipid-soluble molecules like O2 and CO2 across cell membranes.

Page 16: Water Diffusion

• Water molecules can diffuse across a semi-permeable membrane.

Page 17: Concentration of Solutions

• Concentration is the amount of solute mixed with a solvent (e.g., solute=sugar, solvent=water).

• Concentration can be measured in various ways.

Page 18: Tonicity Definitions

• Tonicity: The relative solute concentration of one solution compared to another;

  • Hypertonic: higher solute concentration.

  • Hypotonic: lower solute concentration.

  • Isotonic: equal solute concentrations with equilibrium in water movement.

Page 19: Comparing Solutions

• Example comparing concentrations of solutions in a beaker and a bag; categorization into hypertonic and hypotonic solutions based on solute concentrations.

Page 20: Sugar Solution Comparison

• Comparing concentrations of sugar solutions in a beaker and a bag, noting net movement of water based on solutions' tonicities.

Page 21: Isotonic Solutions

• Examples illustrating isotonic solutions with no net movement of water.

Page 22: Water Molecules in Solutions

• Hypertonic solutions attract more water molecules, while hypotonic solutions have more free water molecules.

Page 23: Movement of Water Molecules

• Free water molecules move from areas of higher concentration to lower concentration for equilibrium.

Page 24: Osmosis Overview

• Osmosis is the diffusion of water across a selectively permeable membrane, a special type of passive transport.

• Continues until the two solutions reach isotonic states.

Page 25: Water Diffusion Representation

• Demonstrates the flow of water across a semi-permeable membrane (similar to Page 16).

Page 26: Red Blood Cell in Isotonic Solution

• An animal cell in isotonic conditions experiences no net water movement.

Page 27: Effects of Tonicity on Red Blood Cells

• Red blood cells in hypertonic solutions lose water, shrivel, and may die; in hypotonic solutions, they gain water, swell, and could burst.

Page 28: Cellular Response to Tonicity

• In hypertonic environments: cells lose water.

• In hypotonic environments: cells gain water.

Page 29: Plant Cell Tonicity Effects

• Comparison of plant cell responses to hypertonic, hypotonic, and isotonic conditions, illustrated with terms:

  • Turgid: normal state in hypotonic.

  • Flaccid: state in isotonic.

  • Plasmolyzed: in hypertonic.

Page 30: Plant Cell Tonicity Visualization

• Similar representation of plant cell's response to changes in water concentration in different tonicities.

Page 31: Lipid-Soluble Molecules

• Reiteration of the diffusion process for lipid-soluble molecules such as O2 and CO2 across membranes.

Page 32: Facilitated Diffusion

• Facilitated diffusion is passive movement of molecules down their concentration gradient via transport proteins, including channel and carrier transport proteins.

Page 33: Water Transport Mechanism

• Water movement via aquaporins within facilitated diffusion frameworks.

Page 34: Active Transport Overview

• Active transport requires energy (ATP) to move ions/molecules against their concentration gradient, utilizing protein pumps.

Page 35: Example of Active Transport

• Sodium-potassium pump is an example of a protein pump requiring energy.

Page 36: Transport Process Overview

• Summary of transport processes:

  • Diffusion, facilitated diffusion (both forms of passive transport), and active transport requiring energy.

Page 37: Exocytosis

• Exocytosis: transport method where substances are secreted out of the cell via vesicles.

• Examples: neurotransmitters, insulin.

Page 38: Endocytosis Types

• Endocytosis is the process by which cells internalize substances, including:

  • Pinocytosis: cellular drinking.

  • Phagocytosis: cellular eating.

  • Receptor-mediated endocytosis.

Page 39: Pinocytosis and Phagocytosis

• Pinocytosis involves vesicle formation around a droplet of extracellular fluid (nonspecific).

• Phagocytosis involves engulfing large particles or organisms into a vacuole for digestion.

Page 40: Receptor-Mediated Endocytosis

• This process is highly specific; substances bind to receptors on the membrane, leading to endocytosis in coated pits.

Page 41: Final Summary of Active Transport

• Active transport encompasses several processes: pumps, exocytosis, endocytosis (including pinocytosis, phagocytosis, receptor-mediated), each requiring energy.