Cells transport substances across their membrane. Choose THREE of the following four types of cellular
transport
Osmosis Active transport Facilitated diffusion Endo/exocytosis
For each of the three transport types you choose,
a. Describe the transport process and explain how the organization of cell membranes functions in the movement of specific molecules across the membrane; and
b. explain the significance of each type of transport to a specific cell ( you may use different cell types as examples)
This is one of my AP practice homeworks, and i don't know how to do this one.Please help.
Osmosis:
A) Is the movement of water from higher concentration to lower concentration. Water molecules are small enough to diffuse through the semi-permeable cell membrane, and so it requires no energy from the cell.
B) Osmosis is used in every cell of your body to bring water in and get it out. If placed in a pure water (hypotonic solution) cells would burst because water would continually come in. (Red blood cells must maintain their turgor pressure/shape by having the right amount of water)
Active Transport:
A) Is transport of substances in and out of cells that requires energy from the cell because it goes against the concentration gradient. Proteins on the membrane help in active transport
B) The sodium-potassium pump is the classic example, and is in every cell. The membrane has proteins in it onto which 3 Na ions attach from inside, and 2 K ions from outside. Using the cells energy the protein changes shape and throws the Na out and brings the K in.
Facilitated Diffusion:
A) Not all molecules are small enough or have the right charge (polar) to go through the membrane. Proteins on the cell membrane help in transporting larger substances in and out. But unlike the active transport, no energy is used because the diffusion still occur down the concentration gradient.
B) Helps carry glucose into cells for them to use it as energy.
a.
1. Osmosis: Osmosis is the passive transport of water molecules through a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. This process occurs when there is a difference in solute concentration between the inside and outside of the cell. The organization of cell membranes, specifically the phospholipid bilayer, allows for osmosis to take place. The hydrophilic heads of the phospholipids face outwards, while the hydrophobic tails face inward, creating a barrier that only allows the passage of certain substances, including water.
Significance to a specific cell: Osmosis is vital for the survival of all cells, as it helps maintain the balance of water and solutes inside the cell. For example, in plant cells, osmosis is important for maintaining turgidity, which is the rigidity of plant cells due to the influx of water. Without osmosis, plant cells could become flaccid and lose their shape.
2. Active transport: Active transport is the movement of molecules across the cell membrane against their concentration gradient, which requires the expenditure of energy in the form of ATP. This process allows cells to accumulate molecules or ions on one side of the membrane, creating a concentration gradient. Active transport is facilitated by specific protein pumps embedded in the cell membrane.
Significance to a specific cell: Active transport is crucial in nerve cells, where sodium-potassium pumps actively transport sodium ions out and potassium ions into the cell against their respective concentration gradients. This action generates an electrical potential across the cell membrane, enabling the transmission of nerve impulses.
3. Facilitated diffusion: Facilitated diffusion is the passive transport of molecules across the cell membrane with the assistance of membrane proteins. This process is dependent on concentration gradients and does not require direct energy expenditure. Membrane proteins, such as carrier proteins or channel proteins, facilitate the movement of specific molecules across the membrane.
Significance to a specific cell: Red blood cells rely on facilitated diffusion to transport glucose molecules into the cell for energy production. Glucose moves from an area of higher concentration outside the cell to an area of lower concentration inside the cell, facilitated by glucose transporter proteins.
b.
- Osmosis is significant to plant cells because it allows them to maintain turgidity and perform essential functions like photosynthesis. Without osmosis, plant cells would lose their shape and collapse, leading to wilting and impaired growth.
- Active transport is critical for nerve cells (neurons) because it enables the establishment and maintenance of the resting membrane potential. This potential is necessary for transmitting electrical impulses along the length of the axon, allowing for the processing and communication of information within the nervous system.
- Facilitated diffusion is essential for red blood cells as it allows for the uptake of glucose from the bloodstream. Glucose serves as a vital energy source for the body, and facilitated diffusion enables the red blood cells to maintain a steady supply of glucose needed for their metabolic activities.
Sure, I'd be happy to help you with this question. Let's go through each of the three transport types you've chosen and discuss their processes, the organization of cell membranes, and their significance to specific cells.
1. Osmosis:
a. Osmosis is the passive movement of water molecules across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. This movement occurs to equalize the concentrations on both sides of the membrane. The organization of cell membranes, specifically the presence of aquaporin proteins, plays a crucial role in facilitating the movement of water molecules across the lipid bilayer.
b. Osmosis is significant to red blood cells (erythrocytes), for example. These cells have a mechanism to regulate their internal solute concentration, maintaining a balance with their external environment. The movement of water through osmosis allows red blood cells to maintain their shape and prevent excessive swelling or shrinkage.
2. Active Transport:
a. Active transport is the movement of molecules across the cell membrane against their concentration gradient, requiring energy in the form of ATP. This process involves carrier proteins (membrane pumps) that bind to specific molecules and undergo conformational changes to transport them across the membrane. The organization of cell membranes includes these carrier proteins that actively pump molecules across the membrane.
b. Active transport is crucial to nerve cells (neurons), which use the sodium-potassium pump to maintain the ionic concentration gradients necessary for transmitting electrical impulses. The pump actively moves sodium ions out of the cell and potassium ions into the cell, contributing to the generation and conduction of nerve signals.
3. Facilitated Diffusion:
a. Facilitated diffusion is the passive movement of molecules across a cell membrane with the help of specific transport proteins. These proteins create channels or carriers that allow larger or charged molecules to move across the membrane without the need for energy input. The organization of cell membranes includes these specialized transport proteins to facilitate the diffusion of specific molecules.
b. Facilitated diffusion is significant in pancreatic beta cells, which use glucose transporters to regulate glucose levels in the bloodstream. These cells contain transport proteins that facilitate the diffusion of glucose from the bloodstream into the cell, aiding in glucose uptake and subsequent insulin release.
Remember, the key to approaching questions like this is to understand the basic concepts behind each transport type and then relate them to specific cells and their functions.