Passive transport | membrane transport lecture
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
🚀 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.
🌟 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.
🔋 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
💡Membrane Transport
💡Lipid Bilayer
💡Diffusion
💡Facilitated Diffusion
💡Aquaporins
💡Channel Proteins
💡Carrier Proteins
💡Ion Channels
💡Voltage-Gated Channels
💡Ligand-Gated Channels
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
hello again friends in this video
tutorial I will be talking about passive
transport we have been talking about a
membrane transport we have already seen
all the different summary of the
membrane transport like active transport
passive transport what are the
difference between both of them and what
are the different features now here in
this video I'll be focusing mainly on
the passive mode of transport
now membrane transport means obviously
we are talking about moving molecules
across the cell membrane and you know
cell membrane is lipid bilayer right so
two layers of lipid molecules are making
it so if you look at here in the cell
membrane structure it will look
something like this just drawing an
arbitrary way these are the phospholipid
head and this is the hydrophobic tails
hydrophilic head and the hydrophobic
tails okay like this so let us say this
is the cell membrane and this is also
the membrane and overall sales cross
section view of the cell well this is
the inside this is the outside of the
cell similarly let us say this is
outside and this is inside okay so what
happens in passive transport there are
very few properties of pressing
transport to be remembered of that is
passive transport do not require any
sort of ATP or energy for that why
because in passive transport molecules
are moving from the high concentration
towards the low concentration so it's a
movement of down the concentration
gradient so we do not require anything
just you know if there is a slope like
that you just put something on the top
between easily fall down like so here it
is commonly known as the diffusion where
the molecule is moving from high
concentration towards the low
concentration of that molecule so this
is basic diffusion diffusion is the
chemical process by which passive
transport occurs all the time so what
molecules cell uptake by this
fusion mode many molecules among them
very small molecules and majorly gas
gaseous substances so many gaseous
substances example is oxygen carbon
dioxide and so on
these are the two major gases that the
cell needs to transport through the cell
membrane so that's why I write them now
oxygen carbon dioxide the example so
these molecules can easily diffuse
through the cell membrane through this
bilayer okay because remember this is
the hydrophobic layer and these are the
filly Claire filly clear okay for we can
pili so this is the idea okay
so oxygen and carbon dioxide can easily
pass through this hydrophobic core
region of the membrane easy okay as the
small molecules and they can easily
diffuse as their gases name some other
molecules they take also transfer from
high concentration to the low
concentration but they cannot do that
directly through the cell membrane on
its own okay because here is a large
portion of hydrophobicity and there are
plenty of molecules in our body which
are hydrophilic in nature that means
they will not contact with hydrophobic
conditions they hydrophobic lipids will
never going to trying to contact with it
it is not possible right so for those
hydrophilic molecules and slightly
bigger molecules like example is water a
different ions Nexus sodium potassium
calcium those are the ions they can also
move from high to low concentration
using diffusion but they need a helper
molecule or helper protein to be present
in the cell membrane to transport them
okay so they just need us helping hand a
helping protein to do that and they are
helping proteins present in the cell
membrane okay let us say this is one
example this is a membrane protein which
can uptake water easily inside the cell
for example and the name of this
proteins aquaporin
aqua marine wife pouring it's like a
pole formation of the poor in the cell
membrane aqua because it transports
water
so using this aqua purine cell can
uptake water okay inside the same but in
this case also water travels from high
concentration to the low concentration
but the difference is in this case they
require helping protein ok diffusion
with a facility provided by a protein so
this system this process is known as
facilitated diffusion diffusion helped
by other proteins similarly there are
also ions that can move from one place
to another place using this type of
proteins facilitate diffusion now what
type of proteins that we see in
facilitated diffusion okay now there are
proteins most of the proteins that they
design here having hydrophilic regions
in both these sides so that it can
interact with hydrophilic molecules okay
because that's the only problem with the
hydrophobic layer of the membrane if
they also by inbuilt having those
hydrophilic layers then molecules can
easily pass but that's not the true
thing okay now this type of proteins can
be of two different type mainly they can
be of two different types okay one is
known as you know let me write them so
carrier protein or channel protein these
are the two types of protein that we can
see
carrier protein and channel protein now
carrier proteins are again of different
types but these are the major two
channel means a protein simply creates
small pore right just like the aquaporin
this is a channel protein and there are
also channel proteins like sodium
channel potassium channel ion in
different calcium channel they are known
as ion channel proteins channel protein
structure is very simple and easy let us
say
this gained a membrane if I draw the
channel protein it will look something
like this let's say here and here it
looks something like this and these are
the two different units of the protein
and actually I make this region like
that but actually if you look at here
from the top is the three-dimensional
barrel-shaped protein right just a
barrel with a pore inside okay because
it is a cross-section view I draw it
this way now molecules can easily pass
through this channel okay this is known
as channel protein no other function
helps molecules to be passed down their
concentration gradient sorry
second type is a carrier proteins
carrier proteins are slightly different
in carrier proteins they have specific
structures different types of structure
and they have multiple ligand binding
side okay let's say let me draw it here
it's so horrible drawing by the way but
I am making it quick okay now here the K
carrier protein it will look something
different let us say
like say this this is a carrier protein
okay as you see it closed here it is
closed okay and it has two different
sides for example here and here for
example this is a side and also it has
some side like that here okay
now let us say the idea is we need to
take a molecule out or in for example
let's say we are taking something in
this is outside this is the inside okay
now let us say the molecule of our
interest binds here that we need to take
inside and it also requires energy
sometimes or sometimes may not now let
us see if it does not require energy or
something
they require another molecule let us say
that molecule this one once this ligand
binds along with our interest of protein
then only it will go through a
structural change okay and then it will
open up and then that molecule can pass
okay so this always happens upon binding
of either the molecule of interest or
upon binding of a third molecule a
ligand to the channel to that specific
protein the structural conformation is
changed and then only the protein of our
interest can be obtained or can be
released outside this is known as
carrier protein okay so they carry a
protein from outside into the inside or
from inside to the outside okay slightly
more complicated and actually this
carrier proteins are mostly found in
active transport okay but also in
passive transport there are some carrier
proteins okay while there are some
simple carrier proteins well as sodium
binds then the carrier will change its
structure and sodium can come inside
okay then let us say let us say so
channel structure like this okay sodium
binds here then it folds back like that
and sodium come inside similarly we have
other proteins like calcium channels and
different ion channel proteins out there
like this okay now if we go through this
carrier protein and different names of
the carrier there are different
varieties and types of carrier proteins
out there the examples of carrier
proteins voltage-gated carrier
voltage-gated ligand gated and ligand
could be of intracellular as well as
extracellular ligand intra intra
cellular ligand or extracellular ligand
binding ligand gated okay voltage gated
ligand gated these are the two major
types of carrier proteins that we find
okay so what happens here in the voltage
gated channel in the voltage gated
channel the channel will open if the
membrane potential alters okay
membrane potential means membrane always
have a charge outside and inside okay
let's say like this now once this charge
shifted or it matches a specific
potential then only the carrier molecule
will open and bring the molecule inside
this is called voltage gated ligand
gated means I told you a ligand specific
ligand will come and bind upon the
binding of the ligand only the channel
will open otherwise it will not open
okay so these are the two types in
normally extracellular ligand is example
I told you I have shown you the example
in intracellular case it is also known
as signal gated so let us say chemical
signaling is going on cell signaling is
going on inside the cell intracellular
space at the some of that molecule can
go and bind to the intracellular binding
site of that molecule that can free
to open that self okay that is the
example of signal gated ion channel okay
signal gated carrier channel molecules
or these are the ion channels also okay
different types of mainly these are ion
channel that we know okay because those
those channels are mainly depending on
voltage or ligand mainly ions to uptake
some ions from outside or remove some
ions to outside from inside that's how
you use this type of channel molecules
okay so this in a sense is a passive
transport with facilitated diffusion and
different types of channel proteins that
are present and different types of ion
channels that we can have okay and all
of them plays vital role in different
places in different purposes for us and
then finally provide us if you liked
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