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Cell Transport Mechanisms. Moving molecules across the Cell Membrane Two methods: Passive Transport Active Transport Does not expend energy Does expend.

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Presentation on theme: "Cell Transport Mechanisms. Moving molecules across the Cell Membrane Two methods: Passive Transport Active Transport Does not expend energy Does expend."— Presentation transcript:

1 Cell Transport Mechanisms

2 Moving molecules across the Cell Membrane Two methods: Passive Transport Active Transport Does not expend energy Does expend energy

3 Passive Transport Allows molecules to move on their own according to natural laws of physics Everything tends towards disorder/chaos Three types of passive transport mechanisms: Diffusion Osmosis Facilitated diffusion

4 Passive Transport – Diffusion This forces molecules to move from areas of high concentration to areas of low concentration Down a concentration gradient “Down the hill” High Concentration Low Concentration Movement of molecules is random When they bump into each other, they push each other away When they are highly concentrated, they bump into each other more often

5 Passive Transport – Diffusion When molecules have reached equal concentrations in both locations, diffusion ends. Molecules continue moving, but they move in both directions equally. NO NET CHANGE. = Equilibrium

6 Diffusion across a Membrane Examples: small molecules (CO 2,O 2 ) small lipids alcohol

7 Quick Quiz!! In the situation below, what direction will the net movement of solutes be? A.To the left B.Into the cell C.Out of the cell D.In circles Inside cell Outside cell

8 Passive Transport – Osmosis Moves water molecules across cell membrane (into or out of cells) Molecules still move down the concentration gradient Purple dots are solutes, not water molecules

9 Quick Quiz!! What direction do you think the water molecules will go? A.Nowhere B.From the Right to the Left C.From the Left to the Right

10 Passive Transport – Osmosis

11 Osmotic Pressure – Pressure created by the presence of water in the cell …cell shrinks or expands Example: Blood cell in low/high salt solutions

12 Passive Transport – Osmosis Animal Cell Plant Cell Hypertonic Solution: Conc. of solutes outside cell is higher 5% salt 2% salt Water leaves cell

13 Passive Transport – Osmosis Isotonic Solution: Conc. of solutes outside cell is equal to inside cell Animal Cell Plant Cell 5% salt Water leaves and enters cell at the same rate NO NET MOVEMENT

14 Passive Transport – Osmosis Hypotonic Solution: Conc. of solutes outside cell is lower Animal Cell Plant Cell 2% salt 5% salt Water enters cell

15 Quick Quiz!! This cell is most likely to… 0.05% glucose 0.1% glucose A.Explode B.Shrink C. Lose Water D. Change Color

16 Passive Transport – Facilitated Diffusion Molecules still move down the concentration gradient, but cannot pass phospholipids on their own. Rely on proteins imbedded in membrane to “help” them across Proteins are specific to the type of molecule that uses them Protein Channels Transport Proteins Examples: water salt ions glucose

17 Quick Quiz!! What kind of cell transport is illustrated below? A.Diffusion B.Osmosis C.Facilitated Diffusion

18 Active Transport Moves molecules against the concentration gradient from areas of low concentration to areas of high concentration. Restores order Takes energy to “go uphill” Protein pumps move molecules into or out of cell against gradient. ATP Outside CellInside Cell

19 Active Transport Exocytosis Moving molecules out of cells Endocytosis Moving molecules into cells Phagocytosis: “cellular eating” Pinocytosis: “cellular drinking” Both processes involve moving large quantities of materials with the use of vesicles (wrap materials in membranes).

20 Endocytosis Molecules move into a “pocket” of the cell membrane

21 Endocytosis “Pocket” pinches off the membrane into cytoplasm

22 Endocytosis Vesicle has now formed and can move around inside cell

23 Exocytosis Vesicle pinches off Golgi Apparatus

24 Exocytosis Free vesicle migrates towards cell membrane

25 Exocytosis Vesicle contacts cell membrane and begins to fuse with it

26 Exocytosis As vesicle becomes part of plasma membrane, contents spill out of cell

27 Endocytosis and Exocytosis These two processes occur at roughly the same rate = No overall change in cell’s size


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