Transport
The cell membrane maintains homeostasis by regulating the movement of molecules from inside and outside of the cell. Movement across the cell membrane is called transport.
The cell membrane is able to keep the cell in balance because it acts similar to a strainer. A strainer allows some materials to pass through and blocks others. A membrane that allows materials to pass through is called permeable. A membrane that blocks materials from passing through is called impermeable. A strainer allows liquid and small materials to pass through the openings. Materials that are bigger than the pores will not pass freely. Membranes that allow some substances to pass across it and not others are selectively permeable. The structure of the cell membrane enables it to act as a selectively permeable barrier.
The cell membrane is able to keep the cell in balance because it acts similar to a strainer. A strainer allows some materials to pass through and blocks others. A membrane that allows materials to pass through is called permeable. A membrane that blocks materials from passing through is called impermeable. A strainer allows liquid and small materials to pass through the openings. Materials that are bigger than the pores will not pass freely. Membranes that allow some substances to pass across it and not others are selectively permeable. The structure of the cell membrane enables it to act as a selectively permeable barrier.
Passive Transport is the movement of molecules across the cell membrane from areas of higher concentration to areas of lower concentration. It does not require energy and therefore uses no ATP. There are three types of passive transport that we will learn: diffusion, facilitated diffusion and osmosis.
Osmosis is the diffusion of water across the cell's membrane. Molecules of water move from an area of higher concentration to an area of lower concentration of water. There are three types of osmotic solutions: hypertonic, isotonic and hypotonic.
A hypertonic solution has more solute than a cell, therefore there is more water inside the cell. Since there is more water inside the cell, water exits or leaves the cell and then the cell shrivels or shrinks.
In an isotonic solution the same concentration of solutes is in both the solution and the cell, therefore the solution and the cell have equal amounts of water and the cell size remains constant or stays the same.
A hypotonic solution has less solute than a cell therefore there is more water in the solution than there is in the cell. This causes the water to move into the cell and the cell expands or swells and could possible burst.
A hypertonic solution has more solute than a cell, therefore there is more water inside the cell. Since there is more water inside the cell, water exits or leaves the cell and then the cell shrivels or shrinks.
In an isotonic solution the same concentration of solutes is in both the solution and the cell, therefore the solution and the cell have equal amounts of water and the cell size remains constant or stays the same.
A hypotonic solution has less solute than a cell therefore there is more water in the solution than there is in the cell. This causes the water to move into the cell and the cell expands or swells and could possible burst.
Active Transport is the movement of molecules across the cell's membrane from an area of lower concentration to an area of higher concentration. This process does require energy and therefore uses ATP. In active transport the molecules move against a concentration gradient.
During active transport, carrier proteins use ATP to pump molecules from an area of low concentration to an area of high concentration.
During active transport, carrier proteins use ATP to pump molecules from an area of low concentration to an area of high concentration.
The prefix endo- means in. Endocytosis is a type of active transport in which the cell membrane starts to fold in, forming a pocket around a substance. The pocket breaks off inside the cell, making a vesicle. The contents of the vesicle are then broken down or released into the cell.
|
The prefix exo- means out. Exocytosis is the opposite of endocytosis. It is the process that moves substances out of the cell. A vesicle surrounds materials that need to be removed. The vesicle then goes to the cell membrane, fuses with it and lets go of the contents. Exocytosis is the cell's way of getting rid of wastes or secreting molecules.
|
Virtual Quizzes
Complete each quiz below. Use your journal as a resource. Show your scores to your teacher upon completion of each item.
Transport Concept Map
Complete the interactive concept map below. Use your journal as a resource. Check your answers and then draw the concept map in your journal.
Bright Bytes Survey
Grad Prep Science
08cellmembranes2009.pdf | |
File Size: | 719 kb |
File Type: |
Osmosis Practice
osmosis_practice_problems.pdf | |
File Size: | 16 kb |
File Type: |