Presentation is loading. Please wait.

Presentation is loading. Please wait.

Cell Membrane & Cellular Transport. HOMEOSTASIS AND TRANSPORT Cell membranes help organisms maintain homeostasis by controlling what substances may enter.

Similar presentations

Presentation on theme: "Cell Membrane & Cellular Transport. HOMEOSTASIS AND TRANSPORT Cell membranes help organisms maintain homeostasis by controlling what substances may enter."— Presentation transcript:

1 Cell Membrane & Cellular Transport

2 HOMEOSTASIS AND TRANSPORT Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells Some substances can cross the cell membrane without any input of energy by the cell The movement of such substances across the membrane is known as passive transport To stay alive, a cell must exchange materials such as food, water, & wastes with its environment These materials must cross the cell or plasma membrane

3 Plasma Membrane living cell non-living Boundary that separates the living cell from it’s non-living surroundings. Phospholipid bilayer (2 parts) hydrophilic heads hydrophobic tails Phospholipid

4 Phospholipid Bilayer

5 Plasma Membrane - cont. Controls traffic into and out of the cell with phospholipids and transport proteins. Selectively permeable ( allows some molecules to move across cell membrane ) Transport protein

6 Small molecules like water, oxygen, & carbon dioxide can move in and out freely Large molecules like proteins & carbohydrates cannot move easily across the plasma membrane The Cell Membrane is semi permeable or selectively permeable only allowing certain molecules to pass through

7 Diffusion The net movement of a substance (molecules) down a concentration gradient from an area of high concentration to an area of low concentration. EQUILIBRIUM When the molecules are even throughout a space- it is called EQUILIBRIUM Passive transport: NO energy is required. Facilitated diffusion: Type of passive transport which uses transport proteins.

8 Diffusion Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration Small molecules can pass through the cell membrane by a process called diffusion Diffusion across a membrane is a type of passive transport because it does not require energy Diffusion continues until the concentration of the molecules is the same on both sides of a membrane

9 Diffusion is driven by the kinetic energy of the molecules Kinetic energy keeps molecules in constant motion causing the molecules to move randomly away from each other in a liquid or a gas The rate of diffusion depends on temperature, size of the molecules, & type of molecules diffusing Molecules diffuse faster at higher temperatures than at lower temperatures Smaller molecules diffuse faster than larger molecules

10 Osmosis The diffusion of water across a semi~permeable membrane is called osmosis The water moves from a high concentration to low concentration. 3 kinds of Osmosis in cells: Hypotonic, Hypertonic, & Isotonic

11 OSMOSIS This diagram shows water molecules moving across a selectively permeable membrane. Water molecules are the small blue shapes, and the solute is the green. What's happening? The solute (green blobs) is more concentrated on the right side, which pulls the water molecules toward that side. The green blobs would move to the left to spread out evenly, but the membrane won't let those pass

12 Solutions Solutions have two parts --- the solute which is being dissolved in the solvent Water serves as the main solvent in living things

13 Hypertonic Solution Solute concentration outside the cell is higher (less water) Water diffuses out of the cell until equilibrium is reached Cells will shrink & die if too much water is lost Plant cells become flaccid (wilt); called plasmolysis

14 Hypotonic Solution Solute concentration is more inside the cell. Water moves into the cell until equilibrium is reached Animal cells swell & burst (lysis) if they take in too much water Cytolysis Cytolysis is the bursting of cells Plant cells become turgid due to water pressing outward against cell wall. Turgor pressure in plant cells helps them keep their shape

15 Isotonic Solutions Concentration of solutes same inside & outside the cell Water moves into & out of cell at an equal rate so there is no net movement of water

16 Animal Cells Animal cells HEMOLYSIS (EXPLODE). Animal cells placed into a hypotonic solution will HEMOLYSIS (EXPLODE). Animal cellshypertonic solution CRENATE (SHRIVEL). Animal cells placed into a hypertonic solution will CRENATE (SHRIVEL). Hemolysis Crenation RedBloodCells

17 Plant Cells (vacuole full) TURGID. Firmness or tension (vacuole full) that is found in plant cells (cell wall) that are in a hypotonic environment is called TURGID. TURGOR PRESSURE. This process is called TURGOR PRESSURE. Water Cell Wall Water Central Vacuole

18 Plant Cells plasma membrane cell wall(vacuole empty)hypertonic environment (loss of water) PLASMOLYSIS When the plasma membrane pulls away from the cell wall (vacuole empty) in a hypertonic environment (loss of water) is called PLASMOLYSIS. PLASMOLYSIS Water Cell Wall Water plasma membrane

19 Effect of Solutions on Cells

20 Facilitated Diffusion Faster than simple diffusion Considered passive transport because extra energy not used Occurs down a concentration gradient Involves carrier proteins embedded in a cell’s membrane to help move across certain solutes such as glucose Carrier molecules change shape when solute attaches to them Change in carrier protein shape helps move solute across the membrane


22 Active Transport The movement of molecules (small or large) across the plasma membrane in which energy (ATP) is required. Moves materials against their concentration gradient from an area of lower to higher concentration

23 Sodium-Potassium Pump energy (active transport) splitting ATP Sodium (Na + ) out Potassium (K + ) into cells. The mechanism that uses energy (active transport) released from splitting ATP to transport Sodium (Na + ) out of and Potassium (K + ) into cells. extracellular fluid intracellular fluid Na + K+K+ K+K+

24 Bulk Transport Moves large, complex molecules such as proteins across the cell membrane Large molecules, food, or fluid droplets are packaged in membrane-bound sacs called vesicles Endocytosis moves large particles into a cell

25 There are two forms of endocytosis: a) Pinocytosis - a form of endocytosis that transports liquids into the cell. b) Phagocytosis - a form of endocytosis that transports solids into the cell Exocytosis is used to remove large products from the cell such as wastes, mucus, & cell products  Exocytosis is the movement of a substance out of a cell via vesicles. Exocytosis is the reverse of endocytosis

26 Animation of endocytosis & exocytosis

Download ppt "Cell Membrane & Cellular Transport. HOMEOSTASIS AND TRANSPORT Cell membranes help organisms maintain homeostasis by controlling what substances may enter."

Similar presentations

Ads by Google