Cell Membranes. Q: What components of the cell membrane are in a mosaic pattern?

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1 Cell Membranes The cell / plasma membrane is. Selective in that it allows things in and some things out of the cell. Recall that phospholipids have hydrophobic and hydrophilic. The term to describe this property is. An early model of the cell membrane is pictured on the left below. This model is called the model. While it is inaccurate, it got other scientists thinking about what makes up the cell membrane. The current and accurate cell membrane model is on the right above. This model is called the model. Fluid because the cell membrane is not. Q: What components of the cell membrane are in a mosaic pattern? The fluid property of the cell membrane allows the phospholipids to move easily in a direction. Sometimes however, the phospholipids can across the membrane. The hydrocarbon tails that have double bonds give the cell membrane more fluidity. While the hydrocarbon tails make the cell membrane more rigid. Q: Image C above shows cholesterol (a steroid/ lipid) in the cell membrane. At room temperature what does adding cholesterol to the cell membrane do to the cell membrane? Q: Same question, but what happens if you add cholesterol to the cell membrane at low temperatures?

2 This property allows that live in very cold climates to still maintain plasma membrane function. I.e. the of animals like a moose have a lot of cholesterol to prevent freezing when exposed to snow. Q: Number the components to the cell membrane below. 1. ECM 2. Integral / Transport Protein 3. Cholesterol 4. Peripheral Protein 5. Cytoplasm / Cytosol 6. Phospholipids 7. Glycoprotein 8. Glycolipid Integral / Transport proteins span the phospholipid bilayer. In actuality, they are (2 structure). They allow molecules to enter or exit the cell. Peripheral proteins are usually found on the of the cell membrane. Their role is to give to the cell. The / tails are what bring about the selectively permeable nature to the cell membrane. Q: What molecules would not be able to get past the non-polar tails? Q: What molecules would easily get past the non-polar tails? The molecules that cannot get past the non-polar tails, will use specific proteins that have a interior.

3 is the tendency for molecules (i.e. a gas or a solute) to spread out in an open space. A gas for example will diffuse from a to a concentration. In other words, the gas molecules go their concentration gradient (a gradient = higher on one side versus the other). Diffusion is spontaneous, therefore no is required. This is called transport. Osmosis is the transport of from a to a concentration across a permeable membrane. Q: In the U-Tube above, what is moving across the selectively permeable membrane (the dashed line)? How is it moving? Q: Draw lines between the correct term and definition. A) Hypertonic Solution Same concentration of solutes on both sides B) Hypotonic Solution High concentration of solutes in the solution C) Isotonic Solution Low concentration of solutes in the solution Water always moves from a solution towards a solution. If 2 solutions are isotonic, water to still move between the 2 solutions at equal. Q: Name the solutions the plant and animal cells are in below. Q: Which solution above do terrestrial animal cells want? Q: Which solution above do terrestrial plant cells want?

4 Animal cells placed in a solution Hypotonic Isotonic Hypertonic Plant cells placed in a solution Hypotonic Isotonic Hypertonic The cell will The cell will Many terrestrial animal s cells are in solutions. Protists however are in tonic environments and must / control their water balance and do so with the aide of vacuoles. Plant cells respond differently than animal cells in a solution due to the presence of a. diffusion is the transport of a substance across the cell membrane from a to a concentration, but it requires a protein. transport differs from diffusion because it requires. Active transport is opposite of diffusion, it goes from a to a concentration. While diffusion occurs spontaneously, active transport is an reaction that goes the concentration gradient. The is a good example of active transport. Q: How many and in which direction are the sodiums and potassiums going?

5 A membrane / electrochemical gradient is the idea that all cells have voltage on each side of the plasma membrane. The insides of cells are in charge, while the outside of cells are. This favors with a positive charge to come into a cell and with a negative charge to exit a cell. main pump in the body is the pump, while main pump is a pump. Proton pumps pump H + ions of cells from a to concentration. Potential energy generated by transmembrane solute gradients can be by the cell and used to transport substances across the membrane. In other words, a substance that is transported across a membrane can do as it back by diffusion ( to concentration, no energy required, through a protein). For example, a plant cell actively pumps out of a cell. H + then leaks back into the cell passively by facilitated diffusion through a transport protein. In doing so it can bring back with it,, or nutrients. This is called. Q: How do large molecules enter or exit a cell? Large molecules such as or polysaccharides enter cells by cytosis and exit cells by cytosis. If a cell takes in food it is called cytosis. If a cell takes in fluids/ drinks it is called cytosis.

6 endocytosis is very in terms of what a cell takes in. on the outside of a cell bind to a specific molecule. In biology, a general term for any molecule that binds is called a. Receptor-mediated endocytosis allows a cell to take in substances than it normally would, even if the substance is in concentrations outside of the cell. For example, (a steroid/ lipid) is acquired this way. Transport proteins can also to changes in the extracellular environment with transport only! For example, if a cell has enough Na +, a transport protein can down the active pumping of the molecule up the concentration gradient. However, or passive transport occurs regardless if a cell has enough of a substance.