Lesson 6 Membrane Transport
Completion requirements
Active Transport Through the Cell Membrane
Active transport is broken down into the following types:
A6.18 Active transport requires energy
Active transport requires energy because it moves against the concentration gradient. This type of transport is used for maintaining homeostasis rather than equilibrium. It is trying to keep the concentrations of certain particles the same rather
than even out the concentrations.
This type of transport uses channel and carrier proteins, just like facilitated diffusion, but these proteins are more than just passageways in this case. They act more like a pump, pushing the particles across the membrane. This is very difficult; it would be similar to trying to ski uphill, so it requires energy from the cell.
This type of transport uses channel and carrier proteins, just like facilitated diffusion, but these proteins are more than just passageways in this case. They act more like a pump, pushing the particles across the membrane. This is very difficult; it would be similar to trying to ski uphill, so it requires energy from the cell.
Endocytosis and exocytosis are another type of active transport. “Endo” means in, so endocytosis is when particles are brought into the cell. “Exo” means out, so exocytosis is when particles are taken out of the cell. In both of these processes,
vesicles are used to bring the particles in or take them out. These vesicles are needed because the particles that need to be transported are too big to pass through the membrane, even with the help of channel proteins.
In endocytosis, the cell surrounds the particle it wants to bring in. The cell membrane then fuses into a vesicle sac around the particle and “pinches off” from the main cell membrane. This creates a vesicle inside the cell with the particle
inside. The vesicle will then transport the particle to the organelle that needs it.
A6.20 Exocytosis
Exocytosis is the opposite of endocytosis. In exocytosis, a vesicle travels to the cell membrane and fuses with it. The vesicle then becomes part of the main cell membrane, opening the vesicle to the outside of the cell and forcing the
particles inside out.
Both endocytosis and exocytosis require energy to rearrange the cell membrane. The pinching off and fusing with the cell membrane is similar to breaking a stick or a branch. It is difficult to do, and energy is needed for it.
Both endocytosis and exocytosis require energy to rearrange the cell membrane. The pinching off and fusing with the cell membrane is similar to breaking a stick or a branch. It is difficult to do, and energy is needed for it.
A6.19 Endocytosis
Make sure you understand how each of these five kinds of transport work. The five kinds of transport are
- diffusion
- osmosis
- facilitated diffusion
- active transport
- endocytosis and exocytosis
Read This
Please read pages 278 to 281 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on the types of active transport and how they work. Remember, if you have any questions or you do not understand
something, ask your teacher!
Practice Questions
Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.- Explain how the particle model of matter relates to active transport, endocytosis, and exocytosis.
The particle model of matter states these four things:
Active Transport: Points i, ii, and iii are used here. Active transport uses the fact that particles are always moving and that they are attracted to one another to move the particle to the channel or carrier protein. The particles have to be the right size and shape to attach to the channel or carrier protein to be pumped through to the other side of the cell.
Endocytosis and Exocytosis: Points i and ii are used here. These processes use the motion of the particles to move the membrane out and around the particles or away from the particles. They also use the motion of the particles to move the particle close enough to the membrane. The processes use the size and shape of the particles to trigger the membrane to surround the particles or to open to let the particles out.
i. All matter is made of particles, but the particles in different substances may be different in size and composition.
ii. The particles of matter are constantly moving or vibrating.
iii. The particles of matter are attracted to one another or are bonded together.
iv. Particles have spaces between them. These spaces may be occupied by particles by another substance.
ii. The particles of matter are constantly moving or vibrating.
iii. The particles of matter are attracted to one another or are bonded together.
iv. Particles have spaces between them. These spaces may be occupied by particles by another substance.
Active Transport: Points i, ii, and iii are used here. Active transport uses the fact that particles are always moving and that they are attracted to one another to move the particle to the channel or carrier protein. The particles have to be the right size and shape to attach to the channel or carrier protein to be pumped through to the other side of the cell.
Endocytosis and Exocytosis: Points i and ii are used here. These processes use the motion of the particles to move the membrane out and around the particles or away from the particles. They also use the motion of the particles to move the particle close enough to the membrane. The processes use the size and shape of the particles to trigger the membrane to surround the particles or to open to let the particles out.
- What is the difference between active transport and facilitated diffusion?
Active transport uses energy because it moves the particles against the concentration gradient. Facilitated diffusion does not use energy, because it moves particles along the concentration gradient.