Lab 3 - How do Cell Respond to Changes in Their Environments?

Summary

This video explains how cells respond to environmental changes to maintain homeostasis, highlighting key processes such as diffusion and osmosis. It describes the importance of the cell membrane's selective permeability and how molecules move across it. The script covers how cells regulate their internal environment, including factors like temperature, osmotic pressure, and available nutrients. Diffusion and osmosis are explored in detail, along with how changes in factors like concentration gradient, surface area, and temperature influence these processes. The content also compares plant and animal cell responses to osmotic pressure.

Takeaways

• 😀 Cells respond to changes in their environment to maintain homeostasis.
• 😀 Homeostasis is the ability of an organism to maintain internal conditions despite external changes.
• 😀 The cell membrane is selectively permeable, controlling what enters and exits the cell.
• 😀 Diffusion is the movement of particles from high to low concentration, requiring no energy.
• 😀 Osmosis is the diffusion of water across a semipermeable membrane to balance solute concentrations.
• 😀 In a hypotonic solution, water moves into the cell, potentially causing it to burst.
• 😀 In a hypertonic solution, water moves out of the cell, causing it to shrink or even die.
• 😀 An isotonic solution maintains equal concentrations inside and outside the cell, keeping it stable.
• 😀 Factors affecting diffusion and osmosis include molecular size, concentration gradient, surface area, and temperature.
• 😀 Increasing temperature or surface area enhances the rate of diffusion, while larger molecules and smaller gradients slow it down.

Q & A

What is homeostasis?

Homeostasis is the ability of an organism to maintain the conditions of its internal environment despite changes in its external environment. This includes maintaining stable temperature, pH, osmotic pressure, nutrients, and waste levels to sustain life.

What does the cell membrane do?

The cell membrane acts as a barrier, separating the inside of the cell from the outside. It is selectively permeable, meaning it regulates what substances can enter or exit the cell, allowing small, uncharged molecules like oxygen and carbon dioxide to pass through easily.

What is the fluid mosaic model of the cell membrane?

The fluid mosaic model describes the cell membrane as a dynamic structure where phospholipids and embedded proteins move around, similar to rubber duckies floating in a tub of water, allowing the proteins and other molecules to move to support the cell's functions.

What is Brownian motion?

Brownian motion is the random motion of particles suspended in a fluid, resulting from collisions with fast-moving atoms or molecules. This motion causes particles to spread out and fill the available space in a solution.

How does diffusion work?

Diffusion is the movement of particles from an area of high concentration to an area of low concentration, driven by Brownian motion. This process requires no energy and continues until the concentration of particles is equal on both sides of a membrane.

What is osmosis?

Osmosis is the diffusion of water across a semipermeable membrane from an area of high water concentration to an area of low water concentration, often to balance the solute concentration on both sides of the membrane.

What are hypotonic, isotonic, and hypertonic solutions?

A hypotonic solution has a lower concentration of solutes and higher water concentration compared to the cell, causing water to enter the cell. An isotonic solution has equal concentrations of solute inside and outside the cell, leading to no net water movement. A hypertonic solution has a higher concentration of solutes, causing water to exit the cell.

How do plant and animal cells react differently to osmotic pressure?

Plant cells have a cell wall that provides additional protection against osmotic changes. In hypotonic solutions, plant cells can take in water without bursting due to the cell wall. Animal cells, on the other hand, can burst or shrink depending on the osmotic pressure (e.g., swelling in hypotonic solutions or shriveling in hypertonic solutions).

What factors affect the rate of osmosis and diffusion?

The rate of osmosis and diffusion is influenced by factors such as molecular size, the size of the concentration gradient, surface area, and temperature. Smaller molecules diffuse faster, larger concentration gradients speed up the process, more surface area allows faster transport, and higher temperatures increase kinetic energy, promoting faster movement of molecules.

Why don't cells get too large, like giant amoebas?

As a cell gets larger, its volume increases more rapidly than its surface area. This leads to a smaller surface area-to-volume ratio, making it less efficient for the cell membrane to meet the demands of the larger volume. This is why cells stay small to maintain efficient nutrient exchange and waste removal.