Question
14. Describe the plasma membrane according to the fluid mosaic model. Include glycolipids, glycoproteins, phospholipids, cholesterol, integral proteins, and peripheral proteins.
Membrane Transport
15. Define the following terms: intracellular fluid, extracellular fluid, and interstitial fluid.
16. Define diffusion and describe how molecules diffuse across a plasma membrane. Include the following terms in your description: passive process, simple diffusion, facilitated diffusion, carriers, and channels.
17. Define and describe osmosis. Include the following terms in your description: solvent, solute, solution, hypertonic, hypotonic, and isotonic.
18. Explain what happens to a cell placed in a hypertonic, hypotonic, or isotonic solution.
19. List and explain the five factors that affect the rate of transport of substances across cell membranes. These factors are size of the material, temperature, the presence or absence of channels or other facilitating devices, particle charges, and the concentration gradient for the material being transported.
Active Transport Will be Covered in the Week 3 Lecture
20. Define and describe active processes by which materials move across cell membranes. Active processes include active transport and vesicular transport. Include the following terms in your description: ATP, pumps, exocytosis, endocytosis, phagocytosis, and receptor-mediated endocytosis.
Membrane Transport
15. Define the following terms: intracellular fluid, extracellular fluid, and interstitial fluid.
16. Define diffusion and describe how molecules diffuse across a plasma membrane. Include the following terms in your description: passive process, simple diffusion, facilitated diffusion, carriers, and channels.
17. Define and describe osmosis. Include the following terms in your description: solvent, solute, solution, hypertonic, hypotonic, and isotonic.
18. Explain what happens to a cell placed in a hypertonic, hypotonic, or isotonic solution.
19. List and explain the five factors that affect the rate of transport of substances across cell membranes. These factors are size of the material, temperature, the presence or absence of channels or other facilitating devices, particle charges, and the concentration gradient for the material being transported.
Active Transport Will be Covered in the Week 3 Lecture
20. Define and describe active processes by which materials move across cell membranes. Active processes include active transport and vesicular transport. Include the following terms in your description: ATP, pumps, exocytosis, endocytosis, phagocytosis, and receptor-mediated endocytosis.
Answers
GPT-4o mini
### 14. Fluid Mosaic Model of the Plasma Membrane
The **fluid mosaic model** describes the structure of the plasma membrane as a dynamic and flexible barrier composed of various components. This model highlights how the membrane is not static but rather fluid, allowing for the movement of its components.
- **Phospholipids** form the fundamental structure of the membrane, with hydrophilic (water-attracting) heads facing outward towards the aqueous environment, and hydrophobic (water-repelling) tails facing inward, creating a bilayer.
- **Cholesterol** molecules are interspersed within the phospholipid bilayer, providing stability and fluidity. They help maintain membrane integrity at various temperatures, preventing the bilayer from becoming too rigid or too fluid.
- **Integral proteins**, which span the membrane, serve various functions, including transporting molecules across the membrane and acting as receptors for signaling molecules.
- **Peripheral proteins** are located on the inner or outer surfaces of the membrane, often attached to integral proteins or phospholipids. They play roles in signaling and maintaining the cell's shape.
- **Glycolipids** and **glycoproteins** are carbohydrate-containing lipids and proteins, respectively, that protrude from the extracellular surface of the membrane. They are involved in cell recognition, communication, and adhesion.
### 15. Definitions of Body Fluids
- **Intracellular fluid (ICF)**: The fluid found inside cells, accounting for about two-thirds of the body’s total water content. It contains a high concentration of potassium ions and proteins.
- **Extracellular fluid (ECF)**: The fluid outside of cells, which includes all body fluids except for the intracellular fluid. ECF encompasses various components, such as blood plasma and interstitial fluid.
- **Interstitial fluid**: The portion of extracellular fluid that fills the spaces between cells in tissues. It acts as a medium for the exchange of nutrients and waste between blood and cells.
### 16. Diffusion Across Plasma Membrane
**Diffusion** is the movement of molecules or ions from an area of higher concentration to an area of lower concentration without the need for energy, categorizing it as a **passive process**. Molecules can diffuse across the plasma membrane through two primary mechanisms:
- **Simple diffusion**: Small, nonpolar molecules (like oxygen and carbon dioxide) directly pass through the phospholipid bilayer.
- **Facilitated diffusion**: Larger or polar molecules (like glucose) require assistance from **carriers** (transport proteins that change shape to move substances across) or **channels** (transmembrane proteins that form pores through which specific substances can move).
### 17. Osmosis
**Osmosis** is the diffusion of water (the solvent) across a selectively permeable membrane from an area of lower solute concentration (higher water concentration) to an area of higher solute concentration (lower water concentration). In this context:
- **Solvent**: A substance (usually water) that dissolves a solute.
- **Solute**: The substance being dissolved.
- **Solution**: The mixture of solute and solvent.
Osmosis can lead to three types of solutions:
- **Hypertonic**: A solution with a higher concentration of solute compared to the cell's interior, causing water to flow out of the cell, leading to cell shrinkage.
- **Hypotonic**: A solution with a lower concentration of solute compared to the cell's interior, resulting in water flowing into the cell, which may cause the cell to swell and potentially burst.
- **Isotonic**: A solution with an equal concentration of solute to that of the cell, leading to no net movement of water and maintaining cell size.
### 18. Cell Response to Different Solutions
- **Hypertonic solution**: When a cell is placed in a hypertonic solution, water exits the cell, causing it to shrink (crenate).
- **Hypotonic solution**: In a hypotonic solution, water enters the cell, which may cause it to swell and possibly lyse (burst).
- **Isotonic solution**: In an isotonic solution, water moves in and out at equal rates, so the cell remains stable in size.
### 19. Factors Affecting Transport Rates Across Membranes
1. **Size of the material**: Smaller molecules can diffuse more easily through the membrane compared to larger ones.
2. **Temperature**: Higher temperatures increase the kinetic energy of molecules, leading to faster diffusion rates.
3. **Presence or absence of channels or facilitating devices**: Specific transport proteins help facilitate the movement of certain substances, impacting the rate of transport.
4. **Particle charges**: Charged particles may require specific channels or carriers to cross the membrane, thus affecting their transport rate.
5. **Concentration gradient**: The greater the difference in concentration between two areas, the faster the rate of diffusion.
### 20. Active Processes of Material Transport
**Active processes** are mechanisms which require energy (usually in the form of **ATP**) to move materials across cell membranes against their concentration gradient. This includes:
- **Active transport**: Involves specific proteins called **pumps** that move ions or molecules from low to high concentration, such as the sodium-potassium pump which maintains cellular ion balance.
- **Vesicular transport**: This process involves the movement of materials in and out of the cell via membrane-bound vesicles, encompassing:
- **Exocytosis**: The process by which materials are expelled from the cell through vesicles that fuse with the plasma membrane.
- **Endocytosis**: The mechanism by which cells internalize substances, which includes:
- **Phagocytosis**: "Cell eating," where cells engulf large particles or other cells.
- **Receptor-mediated endocytosis**: A specific form of endocytosis where cells absorb molecules (ligands) based on receptor binding, allowing for the selective uptake of substances like hormones or nutrients.
The **fluid mosaic model** describes the structure of the plasma membrane as a dynamic and flexible barrier composed of various components. This model highlights how the membrane is not static but rather fluid, allowing for the movement of its components.
- **Phospholipids** form the fundamental structure of the membrane, with hydrophilic (water-attracting) heads facing outward towards the aqueous environment, and hydrophobic (water-repelling) tails facing inward, creating a bilayer.
- **Cholesterol** molecules are interspersed within the phospholipid bilayer, providing stability and fluidity. They help maintain membrane integrity at various temperatures, preventing the bilayer from becoming too rigid or too fluid.
- **Integral proteins**, which span the membrane, serve various functions, including transporting molecules across the membrane and acting as receptors for signaling molecules.
- **Peripheral proteins** are located on the inner or outer surfaces of the membrane, often attached to integral proteins or phospholipids. They play roles in signaling and maintaining the cell's shape.
- **Glycolipids** and **glycoproteins** are carbohydrate-containing lipids and proteins, respectively, that protrude from the extracellular surface of the membrane. They are involved in cell recognition, communication, and adhesion.
### 15. Definitions of Body Fluids
- **Intracellular fluid (ICF)**: The fluid found inside cells, accounting for about two-thirds of the body’s total water content. It contains a high concentration of potassium ions and proteins.
- **Extracellular fluid (ECF)**: The fluid outside of cells, which includes all body fluids except for the intracellular fluid. ECF encompasses various components, such as blood plasma and interstitial fluid.
- **Interstitial fluid**: The portion of extracellular fluid that fills the spaces between cells in tissues. It acts as a medium for the exchange of nutrients and waste between blood and cells.
### 16. Diffusion Across Plasma Membrane
**Diffusion** is the movement of molecules or ions from an area of higher concentration to an area of lower concentration without the need for energy, categorizing it as a **passive process**. Molecules can diffuse across the plasma membrane through two primary mechanisms:
- **Simple diffusion**: Small, nonpolar molecules (like oxygen and carbon dioxide) directly pass through the phospholipid bilayer.
- **Facilitated diffusion**: Larger or polar molecules (like glucose) require assistance from **carriers** (transport proteins that change shape to move substances across) or **channels** (transmembrane proteins that form pores through which specific substances can move).
### 17. Osmosis
**Osmosis** is the diffusion of water (the solvent) across a selectively permeable membrane from an area of lower solute concentration (higher water concentration) to an area of higher solute concentration (lower water concentration). In this context:
- **Solvent**: A substance (usually water) that dissolves a solute.
- **Solute**: The substance being dissolved.
- **Solution**: The mixture of solute and solvent.
Osmosis can lead to three types of solutions:
- **Hypertonic**: A solution with a higher concentration of solute compared to the cell's interior, causing water to flow out of the cell, leading to cell shrinkage.
- **Hypotonic**: A solution with a lower concentration of solute compared to the cell's interior, resulting in water flowing into the cell, which may cause the cell to swell and potentially burst.
- **Isotonic**: A solution with an equal concentration of solute to that of the cell, leading to no net movement of water and maintaining cell size.
### 18. Cell Response to Different Solutions
- **Hypertonic solution**: When a cell is placed in a hypertonic solution, water exits the cell, causing it to shrink (crenate).
- **Hypotonic solution**: In a hypotonic solution, water enters the cell, which may cause it to swell and possibly lyse (burst).
- **Isotonic solution**: In an isotonic solution, water moves in and out at equal rates, so the cell remains stable in size.
### 19. Factors Affecting Transport Rates Across Membranes
1. **Size of the material**: Smaller molecules can diffuse more easily through the membrane compared to larger ones.
2. **Temperature**: Higher temperatures increase the kinetic energy of molecules, leading to faster diffusion rates.
3. **Presence or absence of channels or facilitating devices**: Specific transport proteins help facilitate the movement of certain substances, impacting the rate of transport.
4. **Particle charges**: Charged particles may require specific channels or carriers to cross the membrane, thus affecting their transport rate.
5. **Concentration gradient**: The greater the difference in concentration between two areas, the faster the rate of diffusion.
### 20. Active Processes of Material Transport
**Active processes** are mechanisms which require energy (usually in the form of **ATP**) to move materials across cell membranes against their concentration gradient. This includes:
- **Active transport**: Involves specific proteins called **pumps** that move ions or molecules from low to high concentration, such as the sodium-potassium pump which maintains cellular ion balance.
- **Vesicular transport**: This process involves the movement of materials in and out of the cell via membrane-bound vesicles, encompassing:
- **Exocytosis**: The process by which materials are expelled from the cell through vesicles that fuse with the plasma membrane.
- **Endocytosis**: The mechanism by which cells internalize substances, which includes:
- **Phagocytosis**: "Cell eating," where cells engulf large particles or other cells.
- **Receptor-mediated endocytosis**: A specific form of endocytosis where cells absorb molecules (ligands) based on receptor binding, allowing for the selective uptake of substances like hormones or nutrients.