Cell Transport. Movement of molecules

Transcription

1 Cell Transport Movement of molecules

2 TEKS Students will investigate and explain cellular processes, including homeostasis and transport of molecules

3 Homeostasis The maintaining of a stable body system (within a certain range) Ex: A fish may travel from freshwater to saltwater and back, but it maintains a constant concentration of salt in its cells The homeostasis of our cells is maintained by the plasma (cell) membrane Molecules move until they reach equilibrium (balance)

4 Cell Membrane Selectively (semi) Permeable: The cell membrane lets certain molecules in and out of the cell. This is created by the phospholipid bilayer and transport proteins This is known as the fluid mosaic model

5 Cell Membrane Phospholipids: Heads Glycerol + phosphate Polar (charged) Hydrophilic water-loving Tails Fatty acid chains Non-polar (neutral) Hydrophobic water-fearing Arranged tail to tail with heads facing out Hydrophilic on the surface Hydrophobic at its core Only allow small, non-polar, uncharged particles to move in and out of the cell (selective permeability)

6 Cell Membrane Transport Proteins: Embedded within the phospholipid bilayer May be trans-membrane (span the entire membrane) or peripheral (only span part of the membrane) May have a carbohydrate chain attached to identify chemical signals coming from the cell s environment Serve as channels for larger, polar, charged molecules

7 Cell Membrane Cholesterol: A type of lipid embedded within the phospholipid bilayer Prevents fatty acid tails from sticking to each other or drifting far apart at different temperatures Adds stability to the cell membrane *Only found in animal cells (plants have something different)

8 Cell Membrane Carbohydrate Chains: Attached to the surface of the cell membrane Two kinds Glycoproteins Carbohydrate chains attached to proteins Serve as identification tags; allows cells to recognize each other and distinguish one type of cell from another Glycolipids Carbohydrate chains attached to lipids Used for cell signaling (bind with hormones & neurotransmitters)

9 Selectively Permeable

10 How Do Molecules Move? Concentration Gradient: Molecules that are concentrated in one area spread out until the molecules reach equilibrium. Molecules want to move from an area of high concentration to an area of low concentration

11 Concentration Gradient

12 Types of Transport Passive Transport: The movement of molecules across the cell membrane without using any of the cell s energy. Requires very little work by the cell (like riding a bike downhill or relaxing to float downstream) Molecules move DOWN/WITH their concentration gradient (from an area of high concentration to an area of low concentration)

13 Types of Transport Diffusion: The movement of small molecules from an area of high concentration to an area of low concentration. Examples Gases (O2 and CO2) Lipid-soluble molecules (steroids) Facilitated Diffusion: Movement of small molecules from high to low concentration using proteins Examples: glucose and small amino acids

14 Types of Transport

15 Types of Transport Osmosis: The diffusion of WATER molecules from an area of high water concentration to an area of low water concentration.

16 Factors That Affect Diffusion Temperature as temperature increases, so does the rate of diffusion Size of the molecule smaller particles will diffuse faster than larger ones (all else being equal) Concentration the greater the concentration difference between two areas, the faster the rate of diffusion will be

17 Types of Transport Active Transport The movement of molecules across the cell membrane that uses the cell s energy (ATP). Like riding a bike uphill or paddling hard to swim upstream Molecules move UP/AGAINST their concentration gradient (from an area of low concentration to an area of high concentration) Examples: ions and large amino acids

18 Types of Transport Active Transport Uses transport proteins to carry molecules from outside the cell to inside the cell OR

19 How Do Molecules Get In/Out? Active Transport

20 How Do Molecules Get In/Out? Active Transport The cell membrane surrounds and engulfs a particle (endo/exocytosis) Endocytosis: the cell takes materials INTO the cell (cell is eating/drinking) Exocytosis: cells expel large amounts of material OUT of the cell

21 Types of Osmotic Solutions *Solute = solid *Solvent = liquid

22 Types of Osmotic Solutions Isotonic Solution Same amount of solute and solvent No net movement of water (water is still moving, but is going in and out at the same rate)

23 Types of Osmotic Solutions Hypertonic High solute content; low solvent content Net movement of water OUT OF the cell Cell shrivels

24 Types of Osmotic Solutions Hypotonic Low solute content; high solvent content Net movement of water INTO of the cell Cell swells and bursts

25 Types of Osmotic Solutions

26 Osmotic Solutions and Turgor Pressure Turgor pressure is the pressure exerted on the cell wall of plant cells due to water in the central vacuole In a turgid cell, water enters by osmosis. The vacuole swells and pushes against the cell wall In a flaccid cell, water is lost from the cell, the vacuole shrinks and the cell eventually loses its shape (plasmolysis)

27 REMEMBER!!! Water ALWAYS moves from hypo to hyper!!! Salt sucks!