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Cells and Their Environment

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Presentation on theme: "Cells and Their Environment"— Presentation transcript:

1 Cells and Their Environment
Objectives: 1. Relate concentration gradients, diffusion, and equilibrium. Describe the importance of ion channels in passive transport Identify the role of carrier proteins in facilitated diffusion

2 Passive Transport Passive Transport: is movement across the cell membrane that does not require energy form the cell. Particles move along their concentration gradient. Does not require energy.

3 Concentration Gradient and Equilibrium
Concentration Gradient: A difference in the concentration of a substance across a space. Equilibrium: is a condition in which the concentration of a substance is equal throughout a space.


5 Diffusion Diffusion: The movement of a substance from an area of high concentration to an area of low concentration. If diffusion is allowed to continue, equilibrium will result.

6 Osmosis Osmosis: is the diffusion of water through a selectively permeable membrane along its concentration gradient.

7 The direction of water movement across the cell membrane depends on the relative concentrations of free water molecules in the cytoplasm and in the fluid outside the cell

8 Hypertonic Hypertonic: is when the fluid outside the cell has a higher concentration of dissolved particles. Water moves out of the cell and into the surrounding solution.

9 Hypotonic Hypotonic: The fluid outside the cell has a lower concentration of dissolved solutes than inside the cell. Water moves into the cell.

10 Isotonic Isotonic: When there is no net water movement because there is the same concentration of water on both sides of the membrane.

11 Facilitated Diffusion
Uses carrier proteins embedded in the membrane to transports specific substances, such as amino acids and sugars, down their concentration gradients.

12 Active Transport Active Transport: Transportation of a substance against its concentration gradient, requiring the cell to use ATP!

13 Example of Active Transport The Sodium-Potassium Pump

14 Endocytosis Endocytosis: The cell membrane forms a pouch around a substance, that closes up and pinches off to form a vesicle.

15 Exocytosis Exocytosis: The movement of a substance by a vesicle to the outside of cell


17 Membrane Receptor Proteins
Receptor Protein: is a protein that binds to a specific signal molecule, enabling the cell to respond to the signal molecule

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