Cell membrane
The cell membrane is primarly made of _____, which are amphiphatic molecules.
phospholipids
Passive transport doesn't need ____, and molecules move ____/___ the concentration gradient.
_energy_
_down/with_ (from higher to lower concentration)
Active transport needs ___, because molecules are being moved ____/___ the concentration gradient.
_energy_
_up/against_ (lower to higher concentration)
A cell moves H+ from low concentration to high concentration.
-Active transport- proton pump
An animal cell is in a hypotonic solution; it will ___ and lyse
_swell_
πΎπππ'π ππππ πππππππ ππππ?
I go through the plasma membrane, I am amphiphatic, and I am very important for transporting molecules.
-Integral~transmembrane protein
πΎπππ'π ππππ ππππ ππ πππππππ πππππππππ?
The molecules that use this passive transport can easily go through the plasma membrane because they are small & hydrophobic/nonpolar. Examples of such molecules include O2 and CO2 .
(simple) diffusion.
πΎπππ'π ππππ ππππ ππ ππππππ πππππππππ?
Large molecules, or large quantities of molecules, enter the cell by pinching in and creating a vacuole/vesicle around the material. There are three types of this active transport: phagocytosis, pinocytosis, and a receptor-mediated type.
Endocytosis
A cell takes in large amounts of a specific solute (along with some dissolved nutrients in the extracellular solution)
-Receptor-Mediated Endocytosis.
πΎπππ'π ππππ ππππππππ?
A root cell is placed in a solution. Over time, the cell loses mass.
-Solution is hypertonic to the cell
Explain why the cell membrane is referred to as a Fluid Mosaic model.
Fluid= the phospholipids can slide and shift past each other because they are held in formation by hydrophobic interactions, not by any chemical bond. The proteins can sometimes shift slightly (depends on if they're anchored to anything), but fluidity of the membrane primarily refers to phospholipids.
Mosaic=The cell membrane is made up of various macromolecules: phospholipids, different proteins, and even carbohydrates which are part of the membrane as glycoproteins & glycolipids
Explain what the net movement of water will be if:
A U-shaped tube has a semipermeable membrane, the left portion of the tube has a high solute concentration, and the right portion of the tube has a low solute concentration.
Which portion has the hypotonic solution, and which has the hypertonic solution?
-The net movement of water will be from the right to the left; During osmosis, water moves from low solute concentration to high solute concentration.
-Right: hypotonic Left: hypertonic
Compare and contrast Pinocytosis and Receptor-Mediated Endocytosis.
-Compare: both are types of endocytosis, and therefore are types of active transport and require energy. Both take in large amounts of solutes by having the plasma membrane pinch in and form a protein-coated vesicle.
-Contrast: Pinocytosis takes in nonspecific dissolved nutrients in the extracellular solution. Receptor-Mediated Endosytosis takes in large amounts of a specfic solute; the solute binds to the receptors, causing a vesicle to form with the solute and receptors inside.
Water diffuses from high concentration to low concentration.
Osmosis
Explain what water potential is and 3 ways it flows.
Water potential is a physical property that predicts the direction water will flow.
Water flows:
- High to low water potential.
- Low to high solute concentration
- High to low pressure.
One has a tunnel, and large amounts of water molecules are diffusing through it.
The other has a molecule bind to it, and then the protein changes shape and moves the molecules across the membrane.
What is each protein type called, and can they be found in passive and/or active transport?
-Tunnel described protein: Channel (transport) protein, specifically an aquaporin. Channel proteins assist in facilitated diffusion π‘ Passive Transport
-Protein that changes shape: Carrier (transport) protein. Carrier proteins assist in both facilitated diffusion (passive transport) and in active transport as pumps or cotransport proteins.
A potato chunk loses mass after being in a sucrose solution for 24 hours.
Identify if the sucrose solution is hypotonic, isotonic, or hypertonic to the potato.
If the potato chunk were instead placed in distilled water, what would happen to the potato's mass? Why?
-hypertonic
-The mass would increase because distilled water has no solutes, and the solute concentration would be lower compared to the potato. The water would move from the hypotonic distilled water into the potato chunk.
Na+/K+ pumps can be found in Animal cells, maintaining a high concentration of K+ and low concentration of Na+ in the cell.
How does this process work, and what does this movement of ions contribute to?
-3 Na+ bind to the pump, ATP phosphorylates the protein, causing it to change shape and move the ions against their gradient. The ions leave, and the protein now has an affinity for 2 K+. When those two ions attach, the phosphate group given by the ATP detaches, and the protein returns to its original position/shape. 2K+ are moved into the cell.
-Because only 2 cations enter the cell per 3 cations leaving the cell, the extracellular side of the membrane has a higher ion concentration and a relative positive charge. This is called the membrane potential, and pumps like this one contribute to it.
Sucrose goes into a plant cell, against its concentration gradient, when it is coupled with H+ going down its concentration gradient.
-Cotransport: A favorable action is coupled with an unfavorable action.
A cell has a water potential of -0.15 bars, and the surrounding solution has a water potential of 0 bars. Which way will water flow?
Water will flow into the cell. (from high to low water potential)
If you were to zoom in on a cell of a fish that lives in a very cold environment, what would the membrane look like?
(Think: How is the primary component of cell membranes affected by drastic temperatures? What is needed for proper molecule transport?)
Option 1:
Since this is an animal, you could find a higher amount of cholesterol in the plasma membrane. This is because cholesterol acts as a spacer, preventing tight packing of phospholipids at colder temperatures. Remember, need a certain level of fluidity for molecules to be able to transport in&out
Option 2:
Discuss an increase in unsaturated fatty acids in the phospholipids, and how those kinky tails prevent packing of phospholipids.
A researcher was trying to figure out if a certain molecule can easily diffuse through the plasma membrane.
Knowing the properties of the plasma membrane, explain what kind of molecules could easily diffuse through it, which ones would need assistance, and what that assistance looks like.
-Small molecules such as CO2, O2 can diffuse across the membrane because of their size and lack of a significant charge. H2O, although polar, can also diffuse, but at a slower rate.
-Large, polar molecules such as sucrose and ions such as K+ require facilitated diffusion, a diffusion that occurs with the assistance of transport proteins. Channel proteins provide a hydrophilic tunnel for a specific molecule to pass through. They can be gated and opened by a stimulus. Carrier proteins have a binding site, a molecule binds to the site and the protein changes shape to move it down its concentration gradient.
A researcher wants to find out how a specific molecule S enters cell Q. After experimenting and collecting data, the researcher found that cell Q had food vacuoles present when molecule S was in the surrounding solution.
Identify what type of transport molecule S used to get into the cell, and why energy is or is not required.
-Phagocytosis, a type of endocytosis. Endocytosis is a type of active transport. Energy is needed because the cell has to actively engulf molecule S with pseudopodia and form a food vacuole.
An ion flows from a high concentration to a low concentration.
Facilitated diffusion
A graph was made that displays the data of potato chunks in sucrose solutions of various molarities. A trend line was made, and it intersected the x-axis at 0.24.
What does this mean?
The potato chunk has a sucrose molarity of 0.24. When placed in a sucrose solution of the same molarity, the solution would be isotonic to the potato chunk, and there would be no net movement.