Topic 10: Membrane Transport Flashcards
Explain diffusion and what type of molecules can simply diffuse across the plasma membrane.
Diffusion is part of passive transport. They require no energy to accomplish movement. In the diffusion process substances move from an area of high concentration to low concentration.
The molecules that can more simply diffuse are smaller molecules, such as water, carbon dioxide, and oxygen.
Explain facilitated diffusion. What is the difference between a carrier protein and a channel protein?
Facilitated Transport is also passive transport.
In facilitated diffusion a protein acts as a a shield and helps a molecule or substance move across the membrane.
These proteins are integral proteins embedded in the membrane. They can be either carrier or channel proteins.
Channel proteins can be gated or open. They have a hydrophilic interior that allows polar molecules to pass by.
Carrier proteins are proteins that bind to the substance or molecule and its shape changes and then releases the molecules. It’s a much slower rate.
Explain osmosis and the effect tonicity of the cells environment has on an animal and a plant cell. How do single-celled organisms, such as paramecium, survive in fresh water lakes?
Define hypotonic, isotonic l, and hypertonic
Osmosis is the movement of water from an area of high concentration to low concentration. Water follows where there is high amounts of solutes.
In animal cells environment:
If low amounts of solutes are in the extracellular and high amounts of solutes are in the cell then the water will only move inside the cell causing it to burst.
If high amounts of solutes are in the extracellular and low amount of solutes are in the cell then the water will move out of the cell causing to shrivel.
In a plant cell:
Plant cells contain a cell wall which prevents it from bursting or shriveling but can still die.
It goes through plasmolysis where the cell detaches from the cell wall.
Not watering the plant can lead to water leaving the cell. Overwatering can lead water to enter the cell.
HYPERTONIC: Water leaves the cell causing it too shrivel or detach from cell water.
HYPOTONIC: Water enters the cell causing it to burst or to expand a plant cells vacuole.
ISOTONIC: Water enters and leaves the cell/ Perfectly state.
Paramecium: They survive thanks to contractile vacuoles. These contractile vacuoles absorb excess water and pumps it out. Leaving it at a good state to survive.
Compare and contrast primary and secondary active transport
Both primary and secondary are active transport requiring energy to move molecules or substances against their concentration gradient.
Primary Active Transport: Begins with an enzyme and its high affinity towards sodium (Na+). Na+ binds to the enzyme and the enzyme opens up to the cells exterior releasing them. Then the enzyme has a high affinity for potassium K+. The K+ are then released to cells exterior as well. Moves molecules outside and in the cell known as an anti porter.
The enzyme is known as sodium potassium pump.
Secondary Active Transport: The Na+ in the cells exterior create an electrochemical gradient. The sodium finds a channel it will move against its concentration gradient causing glucose to move as well and enter the cell.
What is an electrochemical gradient?
Describe how an electrochemical gradient is established and how it can be used in active transport.
An electrochemical gradient is the combined concentration gradient and electrical charge that affects if an ion will move into or out of the cell.
An electrochemical gradient is established when a pump or channel moves ions against their concentration gradient driving primary active transport.
It is used by active transport as the electrochemical gradient energy stored by primary active transport is used to move other molecules against their concentration gradient.
Describe Na+/K+ pump and it’s role in the cell. Why is the Na/K+ pump continuously working?
The Na+/K+ pump aka sodium potassium pump role in the cell is to move ions, sodium, and potassium ions across the membrane against their concentration gradient. Helps maintain osmotic equilibrium.
The NA+/K+ is continuously working because it maintains the electrochemical potential for the ions.
Describe exocytosis and the three types of endocytosis. Is this active or passive transport? Why?
Exocytosis is the expelling of waster material to the extracellular fluid. It diffuses out the cell.
Exocytosis is the process of bring substances in the cell by completely invaginating it and creating a vesicle.
Phagocytosis: Known as cell eating because it completely brings in big molecules and even cells into the cell through a vacuole.
Pinocytosis: Known as cell eating as it brings in water and small molecules into the cell through vacuoles.
Receptor mediated transport: Brings in selected molecules into the cell through receptors. The receptors bind and bring in molecules through vesicles.
They are all active transport because they require cell energy.
