Passive transport | membrane transport lecture

Shomu's Biology
12 Dec 201513:55

Summary

TLDRThis educational video delves into the concept of passive transport across the cell membrane, highlighting its fundamental difference from active transport. It explains how molecules move from high to low concentration without energy expenditure, utilizing diffusion. The script details the role of channel and carrier proteins in facilitated diffusion, particularly for hydrophilic molecules and ions. It distinguishes between channel proteins like aquaporins and various types of carrier proteins, including voltage-gated and ligand-gated varieties, emphasizing their importance in cellular processes.

Takeaways

  • 🔬 Passive transport does not require ATP or energy, as molecules move from high to low concentration.
  • 🧬 Membrane transport involves moving molecules across the cell membrane, which is a lipid bilayer.
  • 💧 Diffusion is the primary process of passive transport, where molecules move from high to low concentration.
  • 🌬️ Gaseous substances like oxygen and carbon dioxide easily diffuse through the cell membrane's hydrophobic core.
  • 💦 Water and ions (e.g., sodium, potassium, calcium) also move from high to low concentration but require helper proteins.
  • 🚰 Aquaporin is a channel protein that facilitates water transport across the cell membrane.
  • 🔗 Facilitated diffusion involves proteins that help hydrophilic molecules pass through the membrane.
  • 🔄 There are two main types of proteins in facilitated diffusion: channel proteins and carrier proteins.
  • 🚪 Channel proteins create pores in the membrane for molecules to pass through, while carrier proteins undergo conformational changes.
  • ⚡ Carrier proteins can be voltage-gated or ligand-gated, opening in response to changes in membrane potential or ligand binding.

Q & A

  • What is the main focus of the video tutorial?

    -The video tutorial focuses mainly on the passive mode of transport across the cell membrane.

  • What is meant by membrane transport?

    -Membrane transport refers to the movement of molecules across the cell membrane, which is a lipid bilayer.

  • Why do passive transport processes not require ATP or energy?

    -Passive transport does not require ATP or energy because molecules move from high concentration to low concentration, which is a downhill movement along the concentration gradient.

  • What is diffusion and how is it related to passive transport?

    -Diffusion is the chemical process by which passive transport occurs, where molecules move from an area of high concentration to an area of low concentration without the use of energy.

  • Which molecules can easily diffuse through the hydrophobic core of the cell membrane?

    -Small molecules and gaseous substances, such as oxygen and carbon dioxide, can easily diffuse through the hydrophobic core of the cell membrane.

  • What is the role of aquaporin in facilitated diffusion?

    -Aquaporin is a channel protein that facilitates the movement of water molecules from high to low concentration across the cell membrane by providing a hydrophilic pathway.

  • Why do hydrophilic molecules require a helper protein to pass through the cell membrane?

    -Hydrophilic molecules require a helper protein because they cannot interact with the hydrophobic lipids of the cell membrane on their own; the helper protein provides a hydrophilic pathway for their transport.

  • What are the two types of proteins involved in facilitated diffusion?

    -The two types of proteins involved in facilitated diffusion are carrier proteins and channel proteins.

  • How does the structure of a channel protein differ from that of a carrier protein?

    -A channel protein forms a pore-like structure that allows molecules to pass through, while a carrier protein undergoes a conformational change upon binding to facilitate the transport of specific molecules.

  • What are the two major types of carrier proteins found in facilitated diffusion?

    -The two major types of carrier proteins in facilitated diffusion are voltage-gated and ligand-gated carrier proteins.

  • How do voltage-gated and ligand-gated channels differ in their operation?

    -Voltage-gated channels open in response to changes in membrane potential, while ligand-gated channels open upon the binding of a specific ligand, which can be either intracellular or extracellular.

Outlines

00:00

🚀 Introduction to Passive Transport

This paragraph introduces the concept of passive transport, focusing on the movement of molecules across the cell membrane without the need for energy input. It explains the structure of the cell membrane, composed of a lipid bilayer with hydrophobic tails and hydrophilic heads. The process of passive transport is described as the movement of molecules from areas of high concentration to low concentration, facilitated by diffusion. The paragraph also highlights the types of molecules that can passively transport across the cell membrane, such as small gaseous substances like oxygen and carbon dioxide, which can easily diffuse through the hydrophobic core of the membrane.

05:02

🌟 Facilitated Diffusion and Its Proteins

The second paragraph delves into facilitated diffusion, a type of passive transport that requires the assistance of proteins for hydrophilic molecules and ions to move across the cell membrane. It discusses the role of aquaporins in water transport and introduces two main types of proteins involved in facilitated diffusion: carrier proteins and channel proteins. Channel proteins form pores that allow molecules to pass through, exemplified by aquaporins and ion channels like sodium and potassium channels. Carrier proteins, on the other hand, undergo structural changes upon ligand binding to transport molecules across the membrane. The paragraph also touches on the variety of carrier proteins, including voltage-gated and ligand-gated channels, which open in response to changes in membrane potential or ligand binding, respectively.

10:04

🔋 Types of Carrier Proteins and Their Functions

The final paragraph provides a deeper exploration into the types of carrier proteins and their mechanisms. It explains how carrier proteins, which are often associated with active transport, can also play a role in passive transport. The paragraph distinguishes between simple carrier proteins and more complex ones, such as those involved in sodium transport, which change structure upon binding to allow ions to enter the cell. It also describes the two major types of carrier proteins: voltage-gated, which open in response to changes in membrane potential, and ligand-gated, which open upon binding with a specific ligand. The summary concludes by emphasizing the importance of these proteins in various biological processes and encourages viewers to like, subscribe, and share the video for more educational content.

Mindmap

Keywords

💡Passive Transport

Passive transport refers to the movement of molecules across the cell membrane without the need for energy input, such as ATP. In the video, it is explained that this type of transport occurs due to the natural tendency of molecules to move from areas of high concentration to areas of low concentration, which is a key concept in understanding how substances move within and between cells.

💡Membrane Transport

Membrane transport is the process of moving molecules across the cell membrane. The video script discusses this in the context of both passive and active transport, emphasizing that it is a fundamental aspect of cellular function. Membrane transport is crucial for maintaining the balance of substances inside and outside the cell.

💡Lipid Bilayer

The lipid bilayer is the basic structure of the cell membrane, consisting of two layers of phospholipids with hydrophilic heads and hydrophobic tails. The script describes how this structure is crucial for passive transport, as it allows small, nonpolar molecules like gases to easily diffuse across the membrane.

💡Diffusion

Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration. The video explains that this is a primary mechanism of passive transport, with examples given such as the movement of oxygen and carbon dioxide through the cell membrane.

💡Facilitated Diffusion

Facilitated diffusion is a type of passive transport that involves the assistance of proteins to move molecules, particularly hydrophilic molecules, across the cell membrane. The script mentions aquaporins as an example of proteins that facilitate the movement of water molecules, illustrating how this process is essential for the transport of larger or more polar molecules.

💡Aquaporins

Aquaporins are specific types of proteins embedded in the cell membrane that facilitate the transport of water molecules. The script highlights the role of aquaporins in allowing water to move from areas of high concentration to areas of low concentration, which is vital for cellular hydration and osmotic balance.

💡Channel Proteins

Channel proteins are a type of membrane protein that forms pores through which molecules can pass. The video script describes how these proteins, such as sodium and potassium channels, are crucial for the facilitated diffusion of ions, which is essential for maintaining electrical gradients across the cell membrane.

💡Carrier Proteins

Carrier proteins are another type of membrane protein that assist in the transport of molecules across the cell membrane. Unlike channel proteins, carrier proteins typically undergo a conformational change to transport their cargo. The script explains that these proteins can be involved in both passive and active transport, depending on the specific mechanism and energy requirements.

💡Ion Channels

Ion channels are a specific type of channel protein that allows the passage of ions across the cell membrane. The video script discusses how these channels are crucial for processes like nerve signal transmission and muscle contraction, as they regulate the flow of ions like sodium, potassium, and calcium.

💡Voltage-Gated Channels

Voltage-gated channels are a type of ion channel that opens or closes in response to changes in the membrane potential. The script explains that these channels play a critical role in the generation and propagation of electrical signals in excitable cells, such as neurons.

💡Ligand-Gated Channels

Ligand-gated channels are ion channels that open or close in response to the binding of specific molecules, or ligands. The video script mentions that these channels can be activated by either intracellular or extracellular ligands, highlighting their role in signal transduction and cellular communication.

Highlights

Introduction to the topic of passive transport and its role in membrane transport.

Explanation of the cell membrane structure, emphasizing the lipid bilayer with hydrophilic heads and hydrophobic tails.

Passive transport does not require ATP or energy because molecules move from high to low concentration.

Basic diffusion is the chemical process by which passive transport occurs, allowing molecules to move down the concentration gradient.

Gaseous substances like oxygen and carbon dioxide can easily diffuse through the hydrophobic core of the cell membrane.

Hydrophilic molecules and ions require a helper molecule or protein, such as aquaporins, for facilitated diffusion.

Different types of proteins involved in facilitated diffusion include carrier proteins and channel proteins.

Channel proteins create pores for molecules to pass through, exemplified by aquaporins and ion channels.

Carrier proteins undergo structural changes upon ligand binding to facilitate the transport of molecules.

Voltage-gated and ligand-gated are two major types of carrier proteins, responding to changes in membrane potential or ligand binding.

Intracellular and extracellular ligands can trigger the opening of ligand-gated channels, also known as signal-gated ion channels.

The vital role of different types of channel proteins and ion channels in various biological processes.

Involvement of carrier proteins in both passive and active transport, highlighting their versatility.

The importance of understanding the mechanisms of passive transport for grasping cellular processes.

A call to action for viewers to like, subscribe, and share the video for more educational content.

Transcripts

play00:00

hello again friends in this video

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tutorial I will be talking about passive

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transport we have been talking about a

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membrane transport we have already seen

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all the different summary of the

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membrane transport like active transport

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passive transport what are the

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difference between both of them and what

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are the different features now here in

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this video I'll be focusing mainly on

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the passive mode of transport

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now membrane transport means obviously

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we are talking about moving molecules

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across the cell membrane and you know

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cell membrane is lipid bilayer right so

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two layers of lipid molecules are making

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it so if you look at here in the cell

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membrane structure it will look

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something like this just drawing an

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arbitrary way these are the phospholipid

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head and this is the hydrophobic tails

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hydrophilic head and the hydrophobic

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tails okay like this so let us say this

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is the cell membrane and this is also

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the membrane and overall sales cross

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section view of the cell well this is

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the inside this is the outside of the

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cell similarly let us say this is

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outside and this is inside okay so what

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happens in passive transport there are

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very few properties of pressing

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transport to be remembered of that is

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passive transport do not require any

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sort of ATP or energy for that why

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because in passive transport molecules

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are moving from the high concentration

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towards the low concentration so it's a

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movement of down the concentration

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gradient so we do not require anything

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just you know if there is a slope like

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that you just put something on the top

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between easily fall down like so here it

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is commonly known as the diffusion where

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the molecule is moving from high

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concentration towards the low

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concentration of that molecule so this

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is basic diffusion diffusion is the

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chemical process by which passive

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transport occurs all the time so what

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molecules cell uptake by this

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fusion mode many molecules among them

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very small molecules and majorly gas

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gaseous substances so many gaseous

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substances example is oxygen carbon

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dioxide and so on

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these are the two major gases that the

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cell needs to transport through the cell

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membrane so that's why I write them now

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oxygen carbon dioxide the example so

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these molecules can easily diffuse

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through the cell membrane through this

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bilayer okay because remember this is

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the hydrophobic layer and these are the

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filly Claire filly clear okay for we can

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pili so this is the idea okay

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so oxygen and carbon dioxide can easily

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pass through this hydrophobic core

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region of the membrane easy okay as the

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small molecules and they can easily

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diffuse as their gases name some other

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molecules they take also transfer from

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high concentration to the low

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concentration but they cannot do that

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directly through the cell membrane on

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its own okay because here is a large

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portion of hydrophobicity and there are

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plenty of molecules in our body which

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are hydrophilic in nature that means

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they will not contact with hydrophobic

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conditions they hydrophobic lipids will

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never going to trying to contact with it

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it is not possible right so for those

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hydrophilic molecules and slightly

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bigger molecules like example is water a

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different ions Nexus sodium potassium

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calcium those are the ions they can also

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move from high to low concentration

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using diffusion but they need a helper

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molecule or helper protein to be present

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in the cell membrane to transport them

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okay so they just need us helping hand a

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helping protein to do that and they are

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helping proteins present in the cell

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membrane okay let us say this is one

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example this is a membrane protein which

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can uptake water easily inside the cell

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for example and the name of this

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proteins aquaporin

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aqua marine wife pouring it's like a

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pole formation of the poor in the cell

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membrane aqua because it transports

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water

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so using this aqua purine cell can

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uptake water okay inside the same but in

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this case also water travels from high

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concentration to the low concentration

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but the difference is in this case they

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require helping protein ok diffusion

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with a facility provided by a protein so

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this system this process is known as

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facilitated diffusion diffusion helped

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by other proteins similarly there are

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also ions that can move from one place

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to another place using this type of

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proteins facilitate diffusion now what

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type of proteins that we see in

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facilitated diffusion okay now there are

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proteins most of the proteins that they

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design here having hydrophilic regions

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in both these sides so that it can

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interact with hydrophilic molecules okay

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because that's the only problem with the

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hydrophobic layer of the membrane if

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they also by inbuilt having those

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hydrophilic layers then molecules can

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easily pass but that's not the true

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thing okay now this type of proteins can

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be of two different type mainly they can

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be of two different types okay one is

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known as you know let me write them so

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carrier protein or channel protein these

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are the two types of protein that we can

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see

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carrier protein and channel protein now

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carrier proteins are again of different

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types but these are the major two

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channel means a protein simply creates

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small pore right just like the aquaporin

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this is a channel protein and there are

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also channel proteins like sodium

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channel potassium channel ion in

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different calcium channel they are known

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as ion channel proteins channel protein

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structure is very simple and easy let us

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say

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this gained a membrane if I draw the

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channel protein it will look something

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like this let's say here and here it

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looks something like this and these are

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the two different units of the protein

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and actually I make this region like

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that but actually if you look at here

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from the top is the three-dimensional

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barrel-shaped protein right just a

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barrel with a pore inside okay because

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it is a cross-section view I draw it

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this way now molecules can easily pass

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through this channel okay this is known

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as channel protein no other function

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helps molecules to be passed down their

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concentration gradient sorry

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second type is a carrier proteins

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carrier proteins are slightly different

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in carrier proteins they have specific

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structures different types of structure

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and they have multiple ligand binding

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side okay let's say let me draw it here

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it's so horrible drawing by the way but

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I am making it quick okay now here the K

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carrier protein it will look something

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different let us say

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like say this this is a carrier protein

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okay as you see it closed here it is

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closed okay and it has two different

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sides for example here and here for

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example this is a side and also it has

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some side like that here okay

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now let us say the idea is we need to

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take a molecule out or in for example

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let's say we are taking something in

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this is outside this is the inside okay

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now let us say the molecule of our

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interest binds here that we need to take

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inside and it also requires energy

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sometimes or sometimes may not now let

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us see if it does not require energy or

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something

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they require another molecule let us say

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that molecule this one once this ligand

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binds along with our interest of protein

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then only it will go through a

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structural change okay and then it will

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open up and then that molecule can pass

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okay so this always happens upon binding

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of either the molecule of interest or

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upon binding of a third molecule a

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ligand to the channel to that specific

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protein the structural conformation is

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changed and then only the protein of our

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interest can be obtained or can be

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released outside this is known as

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carrier protein okay so they carry a

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protein from outside into the inside or

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from inside to the outside okay slightly

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more complicated and actually this

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carrier proteins are mostly found in

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active transport okay but also in

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passive transport there are some carrier

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proteins okay while there are some

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simple carrier proteins well as sodium

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binds then the carrier will change its

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structure and sodium can come inside

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okay then let us say let us say so

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channel structure like this okay sodium

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binds here then it folds back like that

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and sodium come inside similarly we have

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other proteins like calcium channels and

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different ion channel proteins out there

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like this okay now if we go through this

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carrier protein and different names of

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the carrier there are different

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varieties and types of carrier proteins

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out there the examples of carrier

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proteins voltage-gated carrier

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voltage-gated ligand gated and ligand

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could be of intracellular as well as

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extracellular ligand intra intra

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cellular ligand or extracellular ligand

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binding ligand gated okay voltage gated

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ligand gated these are the two major

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types of carrier proteins that we find

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okay so what happens here in the voltage

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gated channel in the voltage gated

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channel the channel will open if the

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membrane potential alters okay

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membrane potential means membrane always

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have a charge outside and inside okay

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let's say like this now once this charge

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shifted or it matches a specific

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potential then only the carrier molecule

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will open and bring the molecule inside

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this is called voltage gated ligand

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gated means I told you a ligand specific

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ligand will come and bind upon the

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binding of the ligand only the channel

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will open otherwise it will not open

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okay so these are the two types in

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normally extracellular ligand is example

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I told you I have shown you the example

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in intracellular case it is also known

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as signal gated so let us say chemical

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signaling is going on cell signaling is

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going on inside the cell intracellular

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space at the some of that molecule can

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go and bind to the intracellular binding

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site of that molecule that can free

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to open that self okay that is the

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example of signal gated ion channel okay

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signal gated carrier channel molecules

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or these are the ion channels also okay

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different types of mainly these are ion

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channel that we know okay because those

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those channels are mainly depending on

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voltage or ligand mainly ions to uptake

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some ions from outside or remove some

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ions to outside from inside that's how

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you use this type of channel molecules

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okay so this in a sense is a passive

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transport with facilitated diffusion and

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different types of channel proteins that

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are present and different types of ion

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channels that we can have okay and all

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of them plays vital role in different

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places in different purposes for us and

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then finally provide us if you liked

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this video please hit the like button

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subscribe to my channel to get more

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videos like that and definitely share

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this video as much as you can thank you

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Related Tags
Passive TransportCell BiologyMembrane TransportDiffusionFacilitated DiffusionAquaporinIon ChannelsCarrier ProteinsChannel ProteinsBiological ProcessesEducational Video