Cell Structure and Function. Cell Membrane and Osmosis

Transcription

1 Cell Structure and Function Cell Membrane and Osmosis

2 Cell Membrane All living things must maintain homeostasis. The cell membrane is the boundary between the cell and the environment that surrounds the cell. It is the cell membrane that plays an important role in homeostasis of the cell. The cell membrane is semi-permeable, meaning that it lets in some materials and keeps others out.

3 The cell membrane is made up of a phospholipid bilayer. Phospholipid: The phosphate group is polar/hydrophillic, and the lipid tails are nonpolar/hydrophobic. This is the fluid mosaic model. (There is a picture on the next slide)

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5 Cellular Transport Passive Transport- the movement of particles from an area of high concentration to lower concentration. Active Transport- the movement of particles from an area of low concentration to higher concentration.

6 Passive Transport: Diffusion The movement of particles from an area of greater concentration to an area of lower concentration; movement of substances into and out of cell. Factors affecting diffusion: Concentration, Temperature, and Pressure.

7 Movement of Particles (Diffusion)

8 Osmosis It is important to understand that diffusion that we have discussed deals with the movement of PARTICLES (ions), while osmosis is the movement of WATER. Osmosis is the diffusion of water through a semi-permeable membrane from a solution of low solute concentration to a solution with high solute concentration.

9 Three types of SOLUTIONS relating to osmosis Isotonic solution-concentration of dissolved substances and water is equal on the inside and outside of the cell membrane. Hypotonic solution-concentration of dissolved substances is lower outside the cell and therefore water will move into the cell causing the cell to swell and possibly burst. Net movement of water into the cell. Hypertonic-concentration of dissolved substances is higher outside the cell and will cause the cell to shrivel. Net movement of water out of the cell.

10 Effect of different solutions on blood cells. Don t drink the salt water if ever stranded in the middle of the ocean!!! Which is an example of drinking salt water?

11 Red Blood Cells have a salt content of 0.9%. When scientists place red blood cells in pure water,osmosis occurs. What net movement of a substance occurs in this instance of osmosis? Water molecules move out of the cell Water molecules move into the cell Salt moves out of the cell Salt moves into the cell

12 Diffusion deals with the movement of, while osmosis deals with the movement of. Water;Particles Particles;Water Water;Water Particles;Particles

13 The solute concentration inside of a cell is equal to the solute concentration outside a cell. The solution is said to be: Hypertonic Hypotonic Isotonic Heterotonic

14 During diffusion, particles will move from an area of concentration to an area of concentration. Low;Low High;Low Low;High High;High

15 During osmosis, water will move from an area of solute concentration, to an area of solute concentration. High;High Low;High Low;Low High;Low

16 In a cell there are 40 molecules of solute and 65 molecules of water. What is the % concentration of solute? 38.1% 40% 42.9% 37%

17 How many molecules of water would it take to make a solution 50% water if it contains 50 molecules of solute?

18 A cell shrivels. It must be placed in a Hypertonic solution Hypotonic solution Isotonic solution Balanced solution

19 A cell contains 55% solute and 45% water. A solution contains 60% solute and 40% water. The solution is: Isotonic Hypotonic Hypertonic Diffusive

20 Passive Transport: Facilitated Diffusion Facilitated Diffusion is a process by which the normal diffusion rate of a substance is increased through interactions with a SUBSTANCE-SPECIFIC membrane protein (facilitative transporter). The binding of the substance to the facilitative transporter on one side of the membrane triggers a conformational change in the protein, exposing it to the inside of the cell. Facilitated Diffusion is particularly important in mediating the entry and exit of polar solutes such as sugars and amino acids that do not penetrate the lipid bilayer.

21 Facilitated Diffusion

22 Four basic mechanisms by which solute molecules move across membranes. Simple diffusion through the bilayer, which always proceeds from high to low concentration. Simple diffusion through an aqueous channel formed within an integral membrane protein. Movement is always down the concentration gradient. Facilitated diffusion in which solute molecules bind specifically to a membrane protein carrier. Active transport by means of a protein transporter with a specific binding site that undergoes a change. ATP is required. Movement of particles against their concentration gradient. What is ATP?

23 Active Transport: Pumps, Endocytosis, and Exocytosis Pumps use energy to pump ions from one side of the membrane to the other and require ATP for the process to occur. Active Transport. Endocytosis is taking in particles against the concentration gradient by engulfing the substance found on the outside of the cell. Exocytosis is getting rid (removal) of particles against the concentration gradient. The substances to be dumped to the extracellular environment begin in the RER.