Cell Transport and Solutions

Summary

This educational video explores the effects of extracellular solution concentration gradients on cellular transport. It explains how cells respond to hypertonic, isotonic, and hypotonic solutions. Hypertonic solutions cause cells to lose water and shrink due to higher solute concentration outside the cell, leading to crenation in red blood cells and plasmolysis in plant cells. Isotonic solutions have equal solute and solvent concentrations as inside the cell, resulting in no net water movement and cell size remaining constant. Hypotonic solutions, with higher water concentration outside the cell, cause cells to swell due to water influx, potentially leading to cytosis or hemolysis. The video uses clear examples and analogies to help viewers understand these concepts.

Takeaways

• 🌟 Cells can be surrounded by solutions with varying particle concentrations, which can be hypertonic, isotonic, or hypotonic relative to the cell's interior.
• 💧 In a hypertonic solution, the external environment has a higher solute concentration and lower water concentration than inside the cell, leading to water loss from the cell through osmosis.
• 🌱 Plant cells respond to hypertonic conditions by losing turgor pressure and undergoing plasmolysis, which causes wilting.
• 🔄 Isotonic solutions have the same concentration gradient as inside the cell, resulting in no net movement of water molecules across the cell membrane, thus maintaining cell size.
• 🌊 Hypotonic solutions have a higher water concentration outside the cell than inside, causing water to enter the cell by osmosis and potentially leading to cell swelling or cytosis.
• 🩸 In red blood cells, the swelling due to hypotonic conditions is known as hemolysis, whereas in plant cells, the rigid cell wall prevents bursting, avoiding cytolysis.
• 🔑 The process of water diffusion across the cell membrane due to concentration differences is called osmosis, which is key to understanding cell response to different solutions.
• 📉 Hypertonic solutions can cause cells to shrivel and potentially implode due to excessive water loss, a phenomenon known as crenation in red blood cells.
• 📈 Hypotonic solutions can lead to cell swelling as water molecules move into the cell to equalize the concentration gradient, with the potential risk of cell bursting.
• 🌿 The rigid cell wall in plant cells provides structural support and prevents the cells from bursting due to water influx in hypotonic conditions, unlike in animal cells.

Q & A

What factors affect the transport of substances through the cell membrane?

The concentration gradient of extracellular solutions affects the transport of substances through the cell membrane.

What are the three types of solutions that can surround a cell, and how do they differ?

The three types of solutions are hypertonic, isotonic, and hypotonic. They differ based on the concentration of solutes and water: hypertonic solutions have higher solute concentration and lower water concentration outside the cell, isotonic solutions have equal solute and water concentrations inside and outside the cell, and hypotonic solutions have lower solute concentration and higher water concentration outside the cell.

What happens to a cell when it is in a hypertonic solution?

In a hypertonic solution, water molecules diffuse out of the cell through osmosis, causing the cell to shrivel. In extreme cases, the cell could shrivel to the point of imploding.

What is the term for the shriveling of red blood cells in hypertonic solutions?

The term for the shriveling of red blood cells in hypertonic solutions is crenation.

How does a hypertonic solution affect plant cells?

In plant cells, a hypertonic solution causes water to leave the cell by osmosis, leading to a decrease in turgor pressure and a process called plasmolysis, which causes the plant to wilt.

What is an isotonic solution, and how does it affect the cell?

An isotonic solution has the same concentration of water and solute as inside the cell, resulting in equal rates of water molecules entering and exiting the cell. This means the cell does not shrink or swell and stays the same size.

What happens to a cell when it is in a hypotonic solution?

In a hypotonic solution, water molecules move passively into the cell by osmosis until equilibrium is reached, causing the cell to swell. If the water concentration outside the cell is high enough, the cell can swell to the point of bursting, a process called cytosis or hemolysis in red blood cells.

Why don't plant cells burst in hypotonic solutions like animal cells can?

Plant cells don't burst in hypotonic solutions because their rigid cell walls prevent the cells from bursting due to the increased internal pressure from water intake.

What is the trick to remember the effect of hypotonic solutions on cells?

The trick to remember the effect of hypotonic solutions is to think of a 'big swollen hippopotamus' or 'hippo' for short, which helps recall that hypotonic solutions cause cells to swell.

How does the concentration of solutes and water in a solution relate to the process of osmosis?

The concentration of solutes and water in a solution determines the direction of water movement through osmosis. Water moves from areas of lower solute concentration (higher water concentration) to areas of higher solute concentration (lower water concentration) until equilibrium is reached.

Outlines

00:00

🌊 Osmosis and Cell Response to Hypertonic Solutions

This paragraph explores how the concentration gradient of extracellular solutions impacts substance transport across cell membranes. It explains that cells can encounter hypertonic, isotonic, or hypotonic solutions relative to their internal environment. Using a beaker of saltwater and a large cell model, the video demonstrates how cells respond to hypertonic solutions, where the external solution has a higher solute concentration and lower water concentration than inside the cell. This causes water to diffuse out of the cell via osmosis, leading to cell shrinkage or crenation in red blood cells and plasmolysis in plant cells, which involves the loss of turgor pressure and wilting.

05:01

💧 Isotonic Solutions and Their Effect on Cell Volume

The second paragraph delves into isotonic solutions, where the external solution's solute and water concentrations match those inside the cell. This results in no net movement of water across the cell membrane, as the rates of water entering and exiting the cell are equal. The video uses an example of a cell in an isotonic solution to illustrate that the cell's size remains constant due to the balanced osmotic exchange. The paragraph also contrasts isotonic conditions with hypotonic ones, where the external solution has a higher water concentration, leading to cell swelling through osmosis. It warns that extreme hypotonic conditions can cause cells to burst due to cytosis or hemolysis, except in plant cells, which are protected by their rigid cell walls.

Keywords

💡Cell Membrane

The cell membrane, also known as the plasma membrane, is a selectively permeable barrier that separates the cell's interior from its external environment. It plays a crucial role in the video's theme as it is the site where transport of substances occurs. The cell membrane allows certain molecules to pass through while blocking others, which is essential for maintaining the cell's internal environment and responding to the concentration gradients of solutions outside the cell.

💡Concentration Gradient

A concentration gradient refers to the difference in the concentration of a substance across two regions. In the context of the video, it is the difference in particle concentration between the inside of a cell and the extracellular solution. This gradient is critical for understanding how substances move across the cell membrane, as it drives the process of diffusion and osmosis.

💡Hypertonic Solution

A hypertonic solution is one where the solute concentration is higher than that inside the cell. The video uses the example of a beaker of saltwater with a cell submerged in it to illustrate how water moves out of the cell in a hypertonic environment, causing the cell to shrivel. This concept is key to understanding how cells respond to different external solution concentrations.

💡Isotonic Solution

An isotonic solution has the same solute concentration as the cell's internal environment. The video explains that in an isotonic solution, the rate of water molecules entering the cell equals the rate of those exiting, resulting in no net change in cell size. This concept is important for understanding cellular homeostasis, where the cell maintains a stable internal environment.

💡Hypotonic Solution

A hypotonic solution is characterized by a lower solute concentration than inside the cell, leading to a higher water concentration outside the cell. The video describes how this causes water to move into the cell by osmosis, leading to cell swelling. This term is central to understanding how cells can be affected by their surrounding environment, especially in terms of water balance.

💡Osmosis

Osmosis is the passive movement of water across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration. The video explains osmosis as the process by which water moves in and out of cells in response to different solution concentrations, leading to either cell swelling or shriveling, depending on whether the solution is hypotonic or hypertonic.

💡Crenation

Crenation refers to the shriveling of red blood cells in hypertonic solutions due to the loss of water through osmosis. The video uses this term to illustrate the extreme response of cells to hypertonic conditions, where the cell can shrivel to the point of imploding.

💡Plasmolysis

Plasmolysis is the process where the cell membrane of a plant cell pulls away from the cell wall due to water loss in a hypertonic solution. The video describes plasmolysis as a consequence of hypertonic conditions in plant cells, where the loss of water leads to a decrease in turgor pressure and the cell membrane shrinking away from the cell wall.

💡Turgor Pressure

Turgor pressure is the pressure exerted by the water in a plant cell's central vacuole against the cell wall. The video mentions turgor pressure in the context of plant cells, explaining how it helps maintain the cell's shape and structure. A loss of water in hypertonic conditions can lead to a decrease in turgor pressure, contributing to plasmolysis.

💡Cytosis

Cytosis is the process where cells swell due to the intake of water in a hypotonic solution. The video explains that if the external solution's water concentration is high enough, the cell can swell to the point of bursting, a condition known as cytolysis in animal cells or hemolysis in red blood cells.

💡Hemolysis

Hemolysis is the bursting of red blood cells due to water intake in a hypotonic environment. The video uses hemolysis as an example of cytosis in red blood cells, illustrating the extreme outcome of a hypotonic solution on cellular integrity.

Highlights

The concentration gradient of extracellular solutions affects the transport of substances through the cell membrane.

Cells may respond differently to hypertonic, isotonic, or hypotonic solutions.

Hypertonic solutions have a higher solute concentration and lower water concentration outside the cell compared to inside.

In hypertonic conditions, water diffuses out of the cell causing it to shrivel, a process known as crenation in red blood cells.

Plant cells in hypertonic solutions experience plasmolysis, where the cell membrane shrinks away from the cell wall.

Isotonic solutions have the same concentration gradient as inside the cell, resulting in no net movement of water.

In isotonic conditions, the cell maintains its size due to equal rates of water entering and exiting.

Hypotonic solutions have a higher water concentration outside the cell, leading to water diffusion into the cell and cell swelling.

Cytosis, or cell swelling, can occur in hypotonic solutions, potentially causing cells to burst, a process called hemolysis in red blood cells.

Plant cells do not burst in hypotonic solutions due to the protective rigid cell wall.

A mnemonic for remembering hypotonic solutions is to think of a 'big swollen hippopotamus'.

In isotonic solutions, the water concentration inside and outside the cell remains the same, preventing cell size changes.

Hypotonic solutions cause water molecules to diffuse into the cell by osmosis, leading to swelling.

Hypertonic solutions result in water molecules diffusing out of the cell by osmosis, causing the cell to shrivel and potentially implode.

Plasmolysis in plants is the cell collapse observed in hypertonic solutions.

The video provides a comprehensive overview of how cell size and shape are influenced by the type of extracellular solution.

Transcripts

in this video we'll discuss cell

transport and solutions

the concentration gradient of

extracellular solutions affects the

transport of substances through the cell

membrane

what can happen in this process

well cells may be surrounded by

solutions with different particle

concentrations both in a lab as well as

inside a living organism

so we need to know how cells will

respond

compared to the solution inside a cell a

solution outside the cell may be

hypertonic

isotonic

or hypotonic

we'll describe hypertonic solutions

using this beaker of water with

dissolved salt and a rather large cell

submerged in it

to demonstrate water movement in and out

of cells we'll use simple numbers to

illustrate concepts

remember the cell cytoplasm is mostly

water as well

in this example let's say the cytoplasm

inside the cell is a solution containing

10 percent salt which means the other 90

percent is water

keep in mind percentages of substances

within the cell must equal one hundred

percent

the percentages of solute and solvent in

the beaker must also add up to one

hundred percent

however the solution in the beaker is a

different concentration from the

solution inside the cell

it's 20 salt and 80 percent water

so you can see that there's a greater

concentration of water inside the cell

than outside ninety percent compared to

eighty percent

we call a solution hypertonic when its

concentration of water is lower than

inside the cell and its concentration of

solute is higher than inside the cell

as a result water molecules diffuse out

of the cell through osmosis causing the

cell to shrivel a bit

remember osmosis means diffusion of

water

if the solution's water concentration

was significantly lower the cell could

shrivel to the point of imploding

for red blood cells in hypertonic

solutions the shriveling from osmotic

water loss is called crenation

let's look at an example of plant cells

in a hypertonic solution

normally turgor pressure which is the

water pressure in a plant cell's central

vacuole helps support the cell wall and

overall plant shape

when water leaves plant cells by osmosis

the cell membrane and its contents

shrink away from the rigid cell wall and

turgor pressure decreases

this is called plasmolysis

plasmolysis causes a plant to wilt

let's look at another container this

time with a cell floating in an isotonic

solution

sometimes

the solution outside the cell has about

the same concentration gradient as the

concentration gradient inside the cell

once again in this example the solution

inside the cell is ninety percent water

with ten percent salt

but this time the surrounding solution

is also ninety percent water with ten

percent salt dissolved

we call a solution isotonic when its

concentrations of water and solute are

the same as inside the cell

but this doesn't mean that there is no

movement

in an isotonic solution the rate of

water molecules entering the cell is

equal to the rate of water molecules

exiting the cell

the amount of water molecules going in

equals the amount of water molecules

going out

that's why you see the arrows pointing

in two different directions

in an isotonic solution the cell doesn't

shrink or swell it stays exactly the

same size

a third possibility is a solution

outside the cell with a higher

concentration of water than the solution

inside the cell

in this example the solution inside the

cell has 20 salt so that means the

remainder is 80 percent water

but the cell has been placed in a beaker

that only has a 10 salt solution

doing the math we can see that the

solution surrounding the cell is 90

water which means there's a greater

concentration of water outside the cell

than inside

we call a solution hypotonic when its

concentration of water is higher than

inside the cell and its concentration of

solute is lower than inside the cell

so by osmosis the water molecules will

move passively into the cell until a

state of equilibrium is reached

hypotonic solutions cause a cell to

swell up with water

if the water concentration outside the

cell is high enough the cell can swell

to the point of bursting

this is called cytosis

cytosis in red blood cells is called

hemolysis

cytolysis doesn't happen in plant cells

because the rigid cell wall prevents the

cells from bursting

here's a little trick to remember that

hypotonic solutions cause a cell to

swell rather than shrivel when you think

of hypo think of a big swollen

hippopotamus or hippo for short

so to recap we can have solutions that

are hypertonic isotonic or hypotonic

with respect to the cell

in an isotonic solution the water

concentration inside and outside the

cell stays about the same the water

concentration stays the same because the

concentration of solute is the same

as a result there's equal movement of

water in and out of the cell so the size

of the cell stays the same

here's a hypotonic solution

remember this means that there is a

lower concentration of solute outside

the cell compared to inside the cell

this causes water molecules to diffuse

into the cell remember when diffusion

happens with water we call that osmosis

this causes the cell to swell

if the concentration difference is high

enough cytolysis may occur

finally in a hypertonic solution the

solute concentration outside the cell is

higher compared to inside the cell

so through osmosis water molecules

diffuse out of the cell

this causes the cell to shrivel up and

it can even implode or collapse if

enough water leaves

in plants this cell collapse is called

plasmolysis

[Music]

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