Cell Membrane And Membrane Transport Flashcards
What are phospholipids?
They are the base make up for cell membranes
They consist of hydrophilic phosphate head and hydrophobic lipid tail.
What is the nature of phospholipids in an aqueous environment
The phospholipids form a bilayer where the hydrophilic heads are on the outer side and the hydrophobic tails are on the inside(away from the water and aqueous environment)
What is the currently accepted model of the membrane structure and why is it named so?
It is the fluid mosaic model.
This name is given since the membrane isn’t a solid ridgid layer but rather a fluid elastic layer
And the word mosaic is added considering the various components it is comprised of.
Describe the fluid mosaic model
There is a double layer of phospholipids (the lipid bilayer)
The lipid bilayer is fluid with many proteins floating in it freely suspended
Proteins, glycolipids, glycoproteins and cholesterol contribute majorly to the properties of a semi permeable membrane
What do glycoproteins do in the bilipid layer
They play an important role in cellular recognition and immune response and help protect the cell
What do proteins do in the bilipid layer
Proteins form channels and are responsible for the movement of substances and solutes.
What do glycolipids do in the bilipid layer
Act as surface receptors and stabilize the memebrane
They also help in the formation of tissues
What does cholesterol do in the plasma membrane
It acts as a packing molecule and regulates the fluid structure of the membrane
What are substances that pass through the semi permeable easily? How do complex substances pass through?
Substances that pass through easily are water oxygen and carbon dioxide.
More complex substances require proteins for their transport as the bilipid layer might prevent them from entering.
How do water molecules pass easily through the plasma membrane even considering the hydrophobic lipid layer?
Water are small molecules and are usually not recognized by the hydrophobic lipids and hence can pass through easily
______________ molecules can.move through the membrane by diffusion
Lipid soluble molecules
What are carrier proteins in the bilipid layer
They form a passageway for substances to move against their concentration gradient
What are transmembrane proteins used for?
To form a passageway for substances that cannot pass through the plasma membrane easily
The two major type of transport across the cell membrane?
Passive transport and active transport
Give examples of passive transport
Diffusion
Facilitated diffusion
Osmosis
Give examples of active transport
pumps and endocytosis
What is the main difference between active and passive transport?
Passive transport doesn’t require energy and the substances move with the concentration gradient. (Osmosis water moves with the water concentration gradient)
Active transport required energy as it moves against the concentration gradient.
What is a concentration gradient
A gradient or change in values occurs when the two environments (inside and outside of the cell) have different concentrations of a solute.
The solute tries to reach equilibrium (by moving down the concentration gradient) where the difference no longer exists and hence substances are always moving.
What is simple diffusion
Molecules move directly through the memebranes without the help or support of proteins and passageways and they move down the concentration gradient
Oxygen and carbon dioxide
State an example where we might see simple diffusion in the lungs.
The blood cells in the lungs take in oxygen and diffuse out carbon dioxide.
Facilitated diffusion
Diffusion that is assisted by proteins to form a passageway.
This is required as the plasma membrane doesn’t allow for direct movement of these substances.
It is also passive transport and moves down the concentration gradient.
Examples of facilitated diffusion/types?
Channel mediated diffusion and carrier mediated diffusion
What is channel mediated diffusion
Channel mediated diffusion is when proteins hydrophilic (water loving) passageways for ions to pass through.
Carrier mediated diffusion
Protein channels do not remain as a passageway but rather change shape to translocate the substance.
Example of carrier mediated diffusion is
Glucose into muscle cells
What is osmosis
It is the diffusion of water
It works against the concentration gradient of solutes
But it works down the concentration gradient of water.
Through a semi permeable membrane without the use of ATP
How do we determine the direction of translocation of water?
If the environment that a cell is in:
Hypotonic (less concentration of water than cells) the water moves out of the cell.
Isotonic: when the cell and out of cell have same water concentration.
Hypertonic: when there is higher water concentration so water moves into the cells.
Example of use of isotonic solutions
It is used as IV water so blood cells do not take effect based on the concentration of water
Water uses _____________ protein channels to move through
Aquaporin
Water moves from hypotonic to hypertonic. true or false
True
What is active transport
Lower concentration of solute to higher concentration
Moves against concentration gradient
It requires ATP
Proteins act as carriers or passages for movement
What are sodium potassium pumps
These pumps exchange sodium ions and potassium ions between the membrane.
This requires energy to do so as the ions are pumped to higher concentration areas.
For every 3 sodium ions pumped out, 2 potassium ions are taken in and hence they create an unbalanced charge level.
The change in unbalanced charges creates a gradient for another active transport processes
What are the proton pumps
Hydrogen ions are moved out of the cell through the protein.
These ions pair up outside the cell to transport other materials or perform other processes
Vesicular transport meaning (cytosis)
The process by which large molecules are moved into the cell.
The molecules go through the plasma membrane and form a membrane around itself taking the structure of a vesicle.
This process requires energy and is active transport.
It is of two types:
Endocytosis and exocytosis.
What are the types of endocytosis
-phagocytosis
-pinocytosis
-Receptor mediated cytosis
What is receptor mediated cytosis
Engulfing/internalization of particles according to the receptors on the membrane
What is endocytosis
Particles are surrounded by the invagination of the cell membrane.
The vesicle buds of the cell membrane and into the cytoplasm
The vesicle is digested by the lysosome.
What is exocytosis
The vesicle carrying export materials moves to the perimeter of the cell
The membrane of the vesicle fuses with the plasma membrane
Contents are expelled into the intercellular space.
What is pinocytosis
Poni cytosis is a type of endocytosis which is involved in the internalization of liquid materials.
What is phagocytosis
It is a type of cytosis that is involved in the internalization of solid particles and substances
What are the steps that occur in phagocytosis
Microbe attaches to the phagocyte
Microbe is engulfed or surrounded by the invagination of the memebranes
Engulfed microbe is called a phagosome
Phagosome fuses with a lysosome to make a phagolysosome
The microbe is digested and the insisted particles form a residue
A residue is carried out of the cell through exocytosis.
