Question

1. Define Channels, Carriers, and Pumps

2. Define Leak vs Gated Channel

3. Define conformational change

4. Define Ligand/Chemically-gated, Voltage-gated, and Mechanically-gated

5. Recognize the types of transport from the names of transport proteins used

6 Compare and contrast between all types of membrane transport

Answer 1

CHANNEL : A single protein or protein complex that transverse the lipid bilayer of cell membrane and form a channel to facilitate the movement of ions through membrane according to their electromagnetic gradient is called a channel.A channel may be open or gated.

CARRIERS : A carrier is a protein that carry substances from one side of a biological membrane to the other.A carrier typically has a binding site which will only bind to substances they are supposed to carry.

PUMPS : An ion transporter / ion pump is a trans membrane protein that moves ions across the plasma membrane against their concentration gradient through active transport.It means they are pumping ions from areas of higher to lower concentrations.

LEAK CHANNELS : Ion channels that are always open and responsible for the resting membrane potential.The leak channels allow Na+ and K+ to move across the cell membrane from high concentration to low concentration.

GATED CHANNEL : An ion channel in a cell membrane that opens or closes in response to stimulus such as a neurotransmitter or change in pressure,voltage or light.Their function is to gate the flow of ions across cell membrane,controlling the flow of ions and regulating cell volume.

CONFORMATIONAL CHANGE : Alteration in the shape / tertiary structure of a protein as a result of alteration in the environment,pH,temperature,ionic strength or ninding of a ligand( to a receptor) or binding of subsatance (to an enzyme)

It can also be defined as a change in the shape of a macromolecule induced by environmental factors.It can change its shape in response to changes in environment, each change is called a conformation and a transition between them is called a conformational change.

LIGAND : A ligand is an ion or molecule that binds to a central metal atom to form a complex. Ligands are usually electron donors with neutral or negative charge.Water is a common ligand that provides both of the electrons for the bond that forms between itself and central atom.

LIGAND GATED ION : These are also commonly referred to as ionotropic receptors,a group of trans membrane ion channel proteins which open to allow ions such as Na⁺,K⁺,Cl^- or Ca²⁺ to pass through the membrane in response to the binding of a chemical messenger (ligand)

VOLTAGE GATED : Permitting or blocking passage through cell membrane in response to an electric stimulus (potential difference between two sides of the membrane)

MECHANICALLY GATED : The ion channels that open as a result of any physical forces such as stretching forces on the membrane or the channel.

TYPES OF TRANSPORT PROTEINS :The proteins used in various ways to move substances back and forth across the cell membrane are called transport proteins.Carrier proteins and channel proteins are the two types of membrane transport proteins. CHANNEL PROTEINS serves as a tunnel across the membrane into the cell.Channel proteins help molecules across the membrane through passive transport, a process called facilitated diffusion. For Example calcium channel can only used to transport calcium in and out the cell.CARRIER PROTEIN transports specific substance through intracellular compartments into extracellular fluids or across the cell membrane.For example, GLUT1 is a carrier protein found in all animal cell membranes that transport glucose.

TYPES OF MEMBRANE TRANSPORT:

There are basically two main types of membrane transport namely ACTIVE AND PASSIVE.

ACTIVE TRANSPORT : The movement of ions or molecules across the cell membrane into a region of higher concentration from lower concentration, against the concentration gradient.It requires cellular energy to achieve this movement.It is of two types - primary active transport ( uses ATP as energy source) and secondary active transport ( uses an electrochemical gradient. Example of active transport is the transport of sodium and potassium ions in and out the cell.During active transport the protein pump uses enerygy to pump ions in and out the cell membrane.

PASSIVE TRANSPORT : It is the transport or movement of ions across the cell membrane without the use of any energy.It does not require any energy input.its rate depends on the permeability of the cell membrane.There are 4 kinds of passive transport namely, DIFFISION, FACILITATED DIFFUSION , FILTRATION and OSMOSIS.

Hope the answer was clear and helpful......................

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