Cell Membrane Transport (Passive & Active) Diffusion, Osmosis, Hydrostatic Oncotic Pressure Colloid

Summary

In this video, Nurse Sarah from RegisteredNurseRN.com explains how fluid and solutes move within the body to maintain balance. She covers key concepts like simple diffusion, facilitated diffusion, active transport, osmosis, and the roles of hydrostatic and oncotic pressure. Sarah details how these processes allow substances to move across cell membranes and maintain homeostasis. The video also touches on practical applications in healthcare, such as using IV fluids to correct fluid imbalances in patients. This thorough review provides essential insights into fluid dynamics and cell transport mechanisms.

Takeaways

• 🧬 The human body maintains a balanced homeostatic environment through various transport processes.
• 🫧 Simple diffusion allows molecules to move from high to low concentration without using energy, specifically for small, non-charged molecules like oxygen and carbon dioxide.
• 💡 Facilitated diffusion helps larger or charged molecules move across the cell membrane using carrier proteins, still following a high to low concentration gradient without energy.
• ⚡ Active transport moves molecules against the concentration gradient, from low to high concentration, using energy in the form of ATP.
• 💧 Osmosis involves the passive movement of water through a semi-permeable membrane to balance water concentration inside and outside the cell.
• 🧪 Oncotic pressure (or colloidal osmotic pressure) pulls water into capillaries, driven by proteins like albumin that are too large to exit the capillary wall.
• 🏞️ Hydrostatic pressure pushes water and solutes out of the capillaries into the tissue space through a process known as filtration.
• 💧 In conditions like hypoalbuminemia (low albumin levels), water leaves the blood plasma and can cause swelling as a result of reduced oncotic pressure.
• ❤️ Hydrostatic pressure is created by heart contractions and is strongest in arteries, helping to move blood and nutrients throughout the body.
• 🩺 Osmosis and these fluid transport processes are essential in healthcare, particularly in managing patients with fluid imbalances through targeted IV fluids.

Q & A

What is the primary function of transport processes within the human body?

The primary function of transport processes in the human body is to maintain homeostasis by balancing fluids and solutes, allowing substances to move in and out of cells effectively.

What is the phospholipid bilayer and why is it important?

The phospholipid bilayer is a structure found in cell membranes that acts as a barrier, allowing selective movement of substances in and out of cells. It consists of hydrophilic heads and hydrophobic tails, which help control what can pass through the membrane.

What is the difference between simple diffusion and facilitated diffusion?

Simple diffusion allows small, non-charged molecules to pass directly through the phospholipid bilayer from high to low concentration without energy. Facilitated diffusion, on the other hand, involves larger, charged molecules that require special protein channels to move across the membrane, but it also does not require energy.

How does active transport differ from diffusion processes?

Active transport differs from diffusion because it moves molecules from low to high concentration, going against the concentration gradient. This process requires energy in the form of ATP, unlike diffusion, which is passive and does not need energy.

What role does ATP play in active transport?

ATP provides the necessary energy to move molecules and solutes against their concentration gradient during active transport, allowing them to move from areas of low concentration to high concentration.

What is osmosis, and how does it help maintain homeostasis?

Osmosis is the movement of water through a semi-permeable membrane from areas of high water concentration (or low solute concentration) to areas of low water concentration (or high solute concentration). It helps maintain homeostasis by balancing water levels inside and outside cells.

What can happen to cells if osmosis is not properly regulated?

If osmosis is not regulated, too much water may enter a cell, causing it to swell and potentially burst, or too much water may leave the cell, causing it to shrink and dehydrate.

What is oncotic pressure and how does it relate to osmosis?

Oncotic pressure, also known as colloidal osmotic pressure, is the pulling force on water created by proteins like albumin in the blood. It helps maintain fluid balance by pulling water into the capillaries through the process of osmosis.

How does hydrostatic pressure function in the body?

Hydrostatic pressure is the force exerted by the fluid within blood vessels, created by the heart’s contractions. It pushes water and solutes out of the capillaries into the interstitial fluid, playing a key role in filtration.

How do oncotic and hydrostatic pressures work together to maintain fluid balance?

Oncotic pressure pulls water into the capillaries, while hydrostatic pressure pushes water out. Together, these forces balance fluid movement, ensuring that water and solutes are properly distributed between the blood vessels and surrounding tissues.

Outlines

00:00

🧬 Understanding Transport Mechanisms in Cells

This paragraph introduces the concept of maintaining homeostasis within the human body through various transport processes that balance fluids and solutes. It explains the structure and function of the phospholipid bilayer of cell membranes, highlighting hydrophilic heads and hydrophobic tails. The focus is on different transport mechanisms, including simple diffusion, which allows small, non-charged molecules like oxygen and carbon dioxide to passively move from high to low concentration. Larger, charged molecules use facilitated diffusion, requiring special proteins to move through the membrane.

05:02

💧 Osmosis and Water Movement Across Membranes

This paragraph explains the process of osmosis, focusing on the passive movement of water across a semi-permeable membrane. Water moves from areas of high water concentration to low, or from areas of low solute concentration to high, aiming to equalize concentrations. The example of how water movement is influenced by solute levels inside and outside the cell illustrates potential outcomes like cell swelling or shrinking. It also mentions how medical interventions can use this principle to treat patients with fluid imbalances, such as rehydrating or dehydrating cells based on the patient's condition.

10:03

💪 Oncotic Pressure: The Role of Proteins in Fluid Balance

This section focuses on oncotic pressure, specifically the role of albumin in pulling water across capillary walls into blood vessels. It explains that albumin, a large protein in blood plasma, creates osmotic pressure by attracting water, keeping it inside the vessels. The paragraph highlights the clinical significance of hypoalbuminemia, a condition where low albumin levels reduce oncotic pressure, causing water to move into surrounding tissues and leading to swelling. The interplay of albumin and water in maintaining fluid balance is emphasized.

💦 Hydrostatic Pressure: Pushing Fluids Across Capillaries

This paragraph explains hydrostatic pressure as the force exerted by blood within the capillaries, pushing water and solutes into the interstitial space (filtration). It contrasts this with oncotic pressure, which pulls water back into the vessels. Hydrostatic pressure originates from heart contractions and is highest in arteries, pushing nutrient-rich blood out to tissues, and lowest in veins, where it helps return deoxygenated blood to the heart. The combination of hydrostatic and oncotic pressures maintains fluid movement and balance across capillaries.

Keywords

💡Homeostasis

Homeostasis refers to the body's ability to maintain a stable internal environment. In the video, this concept is central to how fluids and solutes move in the body, as the body uses various transport mechanisms to keep these substances balanced and regulate internal conditions.

💡Phospholipid Bilayer

The phospholipid bilayer is a double layer of lipid molecules that form the cell membrane. In the video, this structure is crucial as it acts as a barrier, allowing selective movement of substances in and out of the cell. Hydrophilic heads face outward, while hydrophobic tails face inward, controlling what passes through.

💡Simple Diffusion

Simple diffusion is the passive movement of molecules from an area of high concentration to an area of low concentration. In the video, it is described as a process that does not require energy, and it allows small, non-charged molecules like oxygen and carbon dioxide to pass through the cell membrane.

💡Facilitated Diffusion

Facilitated diffusion is a passive transport process that uses special proteins to help larger or charged molecules cross the cell membrane. In the video, it contrasts with simple diffusion, as molecules like glucose or ions need assistance from carrier proteins to move through the membrane.

💡Active Transport

Active transport is the movement of molecules from a low concentration to a high concentration using energy in the form of ATP. The video highlights how this process goes against the concentration gradient, requiring energy to move substances like ions out of the cell, which is essential for maintaining cellular function.

💡Osmosis

Osmosis is the movement of water across a semi-permeable membrane from a region of low solute concentration to high solute concentration. In the video, osmosis is explained as a passive process that helps balance water levels inside and outside cells, influenced by solute concentrations like sodium.

💡Hydrostatic Pressure

Hydrostatic pressure is the force exerted by a fluid within a confined space, such as blood in the vessels. In the video, this pressure is important for pushing water and solutes from capillaries into surrounding tissues, playing a vital role in fluid distribution within the body.

💡Oncotic Pressure

Oncotic pressure, also known as colloidal osmotic pressure, is the pulling force generated by proteins (especially albumin) in the blood, which helps retain water in the capillaries. The video explains how this pressure works in opposition to hydrostatic pressure to maintain fluid balance in the body.

💡ATP

ATP (Adenosine Triphosphate) is the primary energy carrier in cells. In the video, ATP is crucial for active transport, providing the necessary energy to move substances against their concentration gradients, which allows the cell to function efficiently despite requiring energy for certain processes.

💡Albumin

Albumin is a large protein found in the blood plasma that contributes to oncotic pressure by pulling water into the blood vessels. The video emphasizes its role in preventing fluid from leaking into tissues, as well as the effects of low albumin levels in conditions like liver disease or burns.

Highlights

The human body maintains a homeostatic environment to balance fluids and solutes using various transport processes.

There are two main types of diffusion: simple diffusion and facilitated diffusion.

Simple diffusion requires no energy and allows molecules to move from a high concentration to a low concentration through the phospholipid bilayer.

Tiny, non-charged molecules like oxygen and carbon dioxide move through the cell membrane using simple diffusion.

Facilitated diffusion, unlike simple diffusion, uses carrier proteins to move larger or charged molecules like glucose and ions across the membrane.

Active transport moves solutes from a low to high concentration, requiring energy in the form of ATP.

Osmosis is the passive movement of water through a semi-permeable membrane, balancing water and solute concentrations.

Water moves from areas of low solute concentration to areas of high solute concentration during osmosis, driven by osmolarity differences.

Osmosis can lead to issues such as cell swelling and rupturing, or cell dehydration, depending on solute concentration.

Osmosis is used in healthcare to rehydrate or dehydrate cells in patients with fluid volume imbalances.

Hydrostatic pressure pushes water out of capillaries into tissue spaces, while oncotic pressure pulls water back into capillaries.

Oncotic pressure is created by proteins like albumin, which attract water through osmosis and keep it inside blood vessels.

Low albumin levels, such as in liver or kidney disease, reduce oncotic pressure, causing swelling as water escapes into surrounding tissues.

Hydrostatic pressure is generated by the heart and is highest in the arteries, where it drives filtration to deliver nutrients to tissues.

The balance between hydrostatic and oncotic pressure ensures proper fluid distribution between blood vessels and tissues.

Transcripts

hey everyone it's nurse Sarah with

registered nurse rn.com and in this

video I'm going to talk about how fluid

and solutes move within our body so

let's get started the human body likes

to maintain a homeostatic environment to

make sure that our fluids and solutes

are equally balanced and to do this it

has different types of transport

processes that allow this to be achieved

so in this review I'm going to be

talking about the two types of diffusion

known as simple diffusion and

facilitated Fusion along with osmosis

and active transport and hydrostatic

pressure and oncotic pressure also known

as colloidal osmotic pressure first

let's talk about the processes that move

substances within the cell specifically

that cell membrane here you're going to

see a phospholipid bilayer that is found

within the cell membrane and this

phospholipid bilayer acts as this medium

to really allow substances to flow in

and out of the cell so here you see the

circular yellow little balls those are

known as the hydrophilic heads and then

coming off those heads are the

hydrophobic tails and they really just

come together to help form this barrier

that separates the extracellular part

the outside of the cell from the

intracellular part the inside of the

cell and then scattered within this

membrane are these channels carrier

proteins now one thing I want you to

remember about this bilayer is that it

is very particular it only allows

certain substances to go in through

certain processes so really based on the

size and if this solute is charged will

depend on how it's going to enter or

exit the cell so first let's talk about

simple diffusion simple diffusion is

just as its name says it's a very simple

process because it requires no energy

from the cell and it's a passive form of

Transport so what happens with this

process is that molecules hence solutes

are going to move from a high

concentration to a low concentration so

here we see outside of our cell a lot of

solute there's a high concentration of

them and according to simple diffusion

they are just going to easily diffuse

hence move through that phospholipid

bilayer to the inside of the cell where

there's not a lot of solutes until

homeostasis has been achieved so this

mass movement will continue until we

have equilibrium where we have a balance

of these solutes now an important thing

to remember about simple diffusion is

that only tiny non-charged molecules are

going to be able to go straight through

this phospholipid bilayer so we're

talking about things like oxygen carbon

dioxide and so forth now a bigger

charged polar molecules want to move in

and out of the cell they need to do it

through a different process known as

facilitated diffusion and facilitated

diffusion is very similar to simple

diffusion but with facilitated diffusion

it's going to use these special help

proteins that are found within that

phospholipid membrane to move these

solutes molecules to and from the cell

so again these molecules hence solutes

are going to go from a high

concentration to a low concentration

it's going to go down that concentration

gradient it's a passive form of

Transport requires no energy but it's

going to allow big molecules that are

charged and polar to move to and from

the cell they just can't go straight

through the phospholipid bilayer so we

can move glucose and ions to and from

the cell now we have a different type of

transport that's sort of going to do the

opposite of what diffusion did because

with diffusion we went from high to low

concentration we were going down the

concentration gradient it was a very

simple process we didn't have to go

against it but sometimes our body wants

to move against this concentration

gradient and wants to go from a low

concentration to a high concentration

and this is where where active transport

comes into play so with active transport

there's going to be the movement of

molecules and solutes from a low

concentration to a high concentration

through these special proteins found

within that phospholipid bilayer but

it's going to use energy in the form of

ATP so here we have our phospholipid

bilayer notice on the inside of the cell

we don't have a lot of solutes but on

the outside of the cell we have a lot of

them so with this transport process we

want to go from low to high so we're

going against that concentration

gradient rather than just down the

concentration gradient so when we go

against it it requires effort a lot of

energy so this is where we utilize ATP

so in order to move this molecule from

the inside the cell to the outside of

the cell it's going to flow through this

special protein Channel but ATP is going

to help energize this process and we're

going to be able to flow to that higher

concentration now let's take a look at

all osmosis so with osmosis we're

talking about the movement of water

water is going to move through a

semi-permeable membrane that is only

permeable to water and nothing else and

it's going to do this through a passive

process it's a passive form of Transport

requires no energy and the whole goal of

Osmosis is to achieve homeostasis in the

terms of water it water wants to shift

around until we've equaled out the

concentration of water inside and

outside the cell and we've equaled out

that solute concentration so whenever

you're trying to understand osmosis you

can look at it one of two ways one way

is that you can remember that water will

move from a high water concentration to

a low water concentration or water is

going to move from a low solute

concentration so the solutes hints the

dissolved substances that are in that

water are low and that water wants to

move to a fluid hence water situation

where the solutes are high it has a high

osmolarity of is a lot of solutes in it

so water is attracted to solutes hence

water is attracted to sodium got a lot

of sodium on board it's going to draw a

lot of water in so those are two ways

you can look at osmosis and when we're

talking about a cell we're talking about

water moving in and out of the cell and

it all really depends on that solute

concentration whether it's High inside

of the cell or outside of the cell so

let's look at this illustration here on

the outside of this our extracellular

part of our cell there is a lot of water

but there's not a lot of solute so it

has a low osmolarity on that

extracellular fluid but on our inside of

the cell notice there's a lot of solute

but not a lot of water so it has a high

osmolarity in there so according to

osmosis effortlessly no energy needed

that water wants to achieve some

homeostasis it's really salty or high

osmolarity inside of that cell so that

water is going to be drawn through a

semi-permeable membrane and it's going

to go and enter in to that cell until

it's tried to equal out osmolarity

inside and outside of the cell and

whenever that's achieved osmosis will

cease now some problems that can arise

whenever fluid does move in this

Direction with osmosis because we have a

cell that has such a high osmolarity is

that too much water can go inside that

cell and it can cause it to swell and

rupture and the flip side can happen

let's say that inside of the cell had a

low osmolarity but the outside of the

cell had a high osmolarity had a lot of

solutes but and it didn't have a lot of

water well too much water can leave that

cell and go in the opposite direction to

extracellular fluid and we could

dehydrate that cell and shrink it now

the neat thing about this osmosis

process is that in healthcare we can

actually use this to benefit our patient

because sometimes patients come in with

fluid volume deficit or fluid volume

overload and they need certain fluids to

help correct that imbalance and we can

manipulate this osmosis process with

those fluids based on the solute

concentration of these fluids to help

either rehydrate that cell or dehydrate

that cell depending on what's going on

with that patient so if you'd like to

watch more in-depth review over IV

fluids and this whole osmosis process

you can check out these videos up here

so we just reviewed how certain

transport processes move fluid and

substances to and from that cell through

that cell membrane now let's look at

some processes that move fluid from the

capillaries to the inner stitchum also

known as the tissue Space by talking

about hydrostatic and oncotic pressure

hydrostatic pressure and oncotic

pressure are two pressures that

literally work the opposite of each

other but they work beautifully together

to help maintain fluid going across our

capillary wall into our inner stitching

our tissue space with oncotic pressure

it's going to pull water across that

capillary a wall and hydrostatic

pressure is going to push water across

that capillary wall so first let's talk

about oncotic pressure so oncotic

pressure you may hear also referred to

as colloidal osmotic pressure so if you

also hear that term as well that's what

it's talking about because sometimes I

can get a little confusing and this is

that pulling force on water created by

proteins specifically the protein

albumin which is known as a colloid and

a cool thing about albumin is that a lot

of it hangs out in our blood plasma and

it is way way too big to pass through

that capillary wall so it just hangs out

there in that blood plasma and that

intravascular space in high

concentrations and whenever it does this

by hanging out in high concentration it

creates an osmotic pressure which pulls

water through a process known as osmosis

and we just talked about osmosis and we

know that osmosis occurs because water

loves to be where there's a high

concentration of something hence solutes

and in this case we're talking about

albumin so there's a lot of albumin

hanging out in this capillary wall which

is going to result in water being pulled

in so water is going to stay inside that

capillary which is what we usually want

so again just to drive home that point

let's look at this illustration we have

this example of a capillary and in white

you see all these colloids since album

and the proteins hanging out within this

vessel and it's highly concentrated so

what it's going to do is it's going to

pull water from that surrounding area

that interstitial area with the fluid in

there and it's going to cause water to

stay inside that vessel and the reason

it's doing that is because there's a

high concentration of the albumin inside

that vessel it causes osmotic pressure

to occur which is going to pull water in

there and water is going to stay inside

that vessel hence our capillary now

sometimes problems arise in some

patients where they don't have enough of

this albumin in their blood plasma and

they're experiencing a condition known

as hypoalbum anemia and this can happen

in cases of liver or kidney failure

because your liver makes albumin so you

just don't have enough in your blood or

the patients let's say had severe burn

so we've dropped those levels so what do

you think is going to happen if you

don't have enough albumin in your blood

plasma well your oncotic pressure is

really going to be affected you're not

going to have a lot of it because

there's not enough of it hanging out in

the blood to create that pressure so

instead water is going to leave that

blood plasma go into that interstitial

space and we're going to experience

swelling now let's talk about

hydrostatic pressure so this is the

opposite of oncotic pressure because it

creates a pushing effect on water across

that capillary wall and in other words

really what hydrostatic pressure is is

it's the pressure or force of a fluid

inside a restricted space so in our body

when we're trying to think of that the

restricted space is going to be our

blood vessels hensor capillaries and

that fluid is going to be our blood so

what happens is that this pressure is

created somewhere and it's created by

our heart so our heart contractions

create hydrostatic pressure and

hydrostatic pressure varies throughout

your circulatory system it's really high

in the arteries and we need it to be

high in the arteries because your

arteries take that fresh oxygenated

nutrient-rich blood it needs to push it

out throughout your body so we need

hydrocy pressure to be high but as we

get closer to the venous system it gets

lower because the venous system's job is

to take that used blood back to the

heart so we can make it better again

give it more nutrients so whenever

you're looking at the capillary and

you're trying to figure out where these

pressures are highest on the end of the

arterial part of the capillary is where

the hydrostatic pressure is the highest

versus where it's the lowest which is

the venous in of the capillary and the

whole goal of hydrostatic pressure is

that it needs to create a process known

as filtration because we need to get

this water and solute out of the

capillary into their interstitial fluid

so we can go and do its thing and then

come back to us so what hydrostatic

pressure does is it's that pressure that

pushes that water and solutes out of the

capillary into the interstitial fluid

which is again known as filtration so as

you can see with these two processes

oncotic pressure and hydrostatic

pressure how our body needs them to work

we have one that's going to push out the

water in the nutrients which is

hydrostatic pressure and then we have

the other oncotic pressure which is

going to pull it and keep it inside the

vessels okay so that wraps up this

review and if you'd like to watch more

videos in this fluid and electrolyte

series don't forget to check out the

link in the YouTube description below