Chapter 7 Cell Structure and Function Chapter 7, Section 3 Cell Boundaries and Transport 1
7.3 A. Cell Membrane Is Described Three Ways: 1. Selectively Permeable Membrane: Limits what enters and exits the cell based on size and Polarity (+ and ) 2. Phospholipid Bilayer: Double Layer of Phospholipids arranged in a way as to prevent certain objects from permeating the membrane Polar region is described as Hydrophilic= water loving Non Polar tails are described as Hydrophobic= water fearing 2
3
Because the cytoplasm inside the cell and external environment of the cell is mostly Water, the phospholipids arrange themselves tail to tail, with the tails getting as far away from water as possible (hydrophobic) and the heads getting as close to the water as possible (hydrophilic) 4
Polar is Head is Polar Polar is Head is Polar Head is HeadPolar Polar Head is Head Hydrophillic Hydrophillic Hydrophillic Hydrophillic Hydrophillic Hydrophillic Fatty TailsAcids Tails Fatty Acids Tails Fatty Acids Tails Fatty Acids TailsAcidsFatty Fatty Acids Tails are Hydrophobic are Hydrophobic are Hydrophobic are Hydrophobic are Hydrophobic are Hydrophobic Polar is Head is Polar Polar is Head is Polar Head is HeadPolar Polar Head is Head HydrophillicHydrophillic Hydrophillic Hydrophillic Hydrophillic Hydrophillic 5
3. Fluid Mosaic Model: a. Fluid: The Cell Membrane is not Rigid It is flexible...like a water balloon! b. Mosaic: Many different components acting towards the same goal 6
Components of the Plasma Membrane A. Proteins: 1. Integral/Transmembrane Proteins Transport Channels for materials that are too big to squeeze between phospholipids. 2. Peripheral Structure and Support: Anchor the phospholipids together 7
8
Components of the Plasma Membrane (Cont.) B. Carbohydrates Used to identify the cell Glycoproteins AKA Antibodies Used as indicators of "SELF" This is how your immune system knows which cells belong (Self cells) and which to fight (NON Self Cells) 9
10
Components of the Plasma Membrane (Cont.) C. Extracellular Matrix: A mixture of components that add strength, stability, and protection to the cell membrane Contains Collagen: Scar tissue 11
B. Transmembrane Transport Depends on Concentration: How much of substance is found dissolved in solution Concentration is based on Parts Per Million (PPM) or Parts Per Thousand (PPT) Relative Concentration: Ratio of Concentrations in two seperate areas Concentration Gradient: Areas of High Concentration and areas of Low Concentration Equilibrium: Equal Concentration in two seperate areas EX. The Concentration of Salt in the Ocean is 35 PPT This Means that of 1000 pieces of Ocean Water 35 Of those pieces are Salt Which means Pieces are Water 12
A Little more relevent to our discussion is Blood Alcohol Content or BAC At what BAC are you considered legally drunk in New Jersey? In NJ you are legally drunk at 0.08% This refers to the concentration of Alcohol in your blood 13
Can Be Either Passive or Active 1. Passive Transport: a. Does not require energy b. Particles move DOWN the concentration gradient c. Moves towards EQUILIBRIUM d. Usually works for smaller, non polar products 14
2. Active Transport: a. Does require Energy (ATP) b. Particles move UP or AGAINST the Concentration Gradient c. Moves away from EQUILIBRIUM d. For larger or polar particles Usually requires a "pump" to get materials across the membrane 15
C. Types of Passive Transport 1. Diffusion: Movement of solute (dissolved particles) from an area of high concentration to an area of low concentration (Down the conc. Gradient) across a semi permeable membrane 16
Diffusion will happen until equilibrium is reached! Equal concentrations of both side of the membrane. NO NET MOVEMENT 17
2. Facilitated Diffusion: Facilitate= HELP Sometimes particles are too large to pass between spaces of membranes. So they need help, like an open doorway! This means their diffusion is facilitated! Require open Protein Channels! Especially for charged ions, like Na and Cl 18
19
3. Osmosis: Diffusion of Water across a semi permeable membrane (Mad Important) Water is essential to life and the maintenance of homeostasis!! Water moves opposite solute!!!! 20
21
a. Isotonic Solution: Concentrations of solute and water are equal both inside and outside of the cell The cell is in Equilibrium= No Net Movement Often the function of the Central Vacuole in plants Gives plant cell rigidity! 10 PPT 10PPT Solute Will Move WATER will MOVE ALL PARTICLES TRY TO REACH E 22
b. Hypertonic Solutions: The EXTRACELLULAR Concentration of Solute is greater than the INTRACELLULAR Concentration Solute Will Move WATER will MOVE ALL PARTICLES TRY TO REACH E 23
c. Hypotonic Solution: Concentration of solute is greater in the INTRACELLULAR environment than the EXTRACELLULAR FLUID Therefore: Water moves in and solute moves out! Causes cell to SWELL, BECOME TURGID, and EXPLODE!!!and possibly explode Solute Will Move WATER will MOVE ALL PARTICLES TRY TO REACH E 24
OSMOSIS IN ANIMAL CELLS Identify which type of solution these Red Blood Cells are floating in and why? 25
Osmosis in Plant Cells Identify which type of solution these Plant Cells are floating in and why? 26
What differences do you notice? 27
Types of Active Transport 1. Protein Pumps: Na/K Pump: Needs to counteract natural diffusion of Na and K for a number of reasons. a. Polarize the cell to carry nerve impulses b. Absorption of carbs and water into the cells of the digestive system The body needs to keep levels of K higher inside the cell than outside and levels of Na higher outside the cell than inside the cell This Takes Energy (ATP) 28
2. Bulk transport a. Endocytosis: Taking in materials via a pocket that forms in the cell membrane 1. Phagocytosis= cell eating (Solid Particles) 2. Pinocytosis cell drinking (Liquids) b. Exocytosis: Excretion of larger molecules such as the proteins that determine the function of the cell! ie cell pooping! 29
Endocytosis 30
Exocytosis 31
32