The Cell in Its Environment

1. The Cell in Its Environment Chapter 1 Lesson 4

2. How do Materials Move Into and Out of Cells • Cells have a protective barrier, but they must allow substances in and out. • Cell Membrane • Double layer of lipid molecules with embedded proteins • Selectively permeable • Some substances can pass the membrane but others cannot • Size (small vs. big)

3. Diffusion • Diffusion • Process by which molecules move from an area of high concentration to an area of low concentration • Movement continues until the cells reach equillibrium • Equal concentrations on both sides of the membrane • Passive Transport • Diffusion is a form of passive transport • moves from high to low concentration (down the hill) so… • does not require energy

4. Osmosis • Osmosis • Diffusion of water • Water moves from ____________ concentration to _______________ concentration • Energy (is/is not) used? • When water moves in… • Animal cells swell and possibly burst • Plant cells are at homeostasis • When water moves out… • Plant cells becomes floppy and can die • Animal cells become shriveled and useless

5. Cell Size • Cytoplasm moves materials within the cell. But there must be enough surface area (around the outside) to move materials in and out. • If a cell is very large • Materials cannot move in and out fast enough to keep the cell alive (think food, waste) • If a cell is very small • The cell cannot maintain enough heat in order to survive.

6. Other types of Transport • Facilitated Diffusion • Very large molecules (sugar, proteins) cannot move through the cell membrane. • Protein channels facilitate (help) the large molecules, like sugar and protein, move across the membrane

7. Other types of Transport • Active Transport • Movement from a low concentration to a high concentration (up the hill) • Requires energy • Usually uses a protein pump • Ex include calcium, potassium, sodium • active transport

8. Other types of Transport • Moving Large Particles (--cytosis)- • Energy is required but it does not go through the cell membrane so it is not considered active transport • Endocytosis • Movement of large particles into a cell using a vesicle • Exocytosis • Movement of large particles out of a cell using a vesicle