Cellular Transport Notes

The Purpose of the Plasma Membrane is to Maintain Balance called “HOMEOSTASIS” or “To Reach Dynamic Equilibrium”” Is traffic at equilibrium? Why or why not?

Equilibrium occurs when molecules have spread out evenly When the concentration of a solute is equal throughout the solution

ALL cells have a cell membrane made of proteins and lipids Cell Membrane lipid bilayer protein channel protein pump Layer 1 Layer 2 SOME cells have cell membranes and cell walls – ex: plants, fungi and bacteria Cell Membrane Cell Wall

Plant cells have a cell wall made of cellulose – that cellulose is fiber in our diet Bacteria and fungi also have cell walls, but they do not contain cellulose Cell membranes and cell walls are porous allowing water, carbon dioxide, oxygen and nutrients to pass through easily

Components of the Plasma Membrane Phospholipids:ProteinsCholesterol

Cell Membrane Aka: PhosphoLipid Bilayer: 2 layers of phospholipids2 layers of phospholipids provides a barrier for the cell. Allows for selective permeabilityprovides a barrier for the cell. Allows for selective permeability a. Phosphate head (hydrophilic=water loving) b. Fatty acid tails are non-polar non-polar (hydrophobic=water fearing) Phospholipids Phospholipid Lipid Bilayer m/watch?v=Rl5EmUQd kuI&feature=fvwrel

Beaker 1 Lipid Surface Monolayer 1.Draw a to scale 600ml beaker, and fill it 2/3 full of water. 2.By observe the phospholipid on the board that your teacher has drawn 3.Define Hydrophilic and Hydrophobic based on root words. 4.Finally imagine you have 10 phospholipids, draw how these molecules would arrange themselves if they were dropped from above their beaker of water.

Beaker 1

Beaker 2 Lipid Molecule 1.Draw a to scale 600ml beaker, and fill it 2/3 full of water. 2.You now have 10 more phospholipids draw a representation of how they would arrange themselves if they had to meet the criteria that they had to be submerged and surrounded by water. 3.Remember the molecules will work together to solve the problem.

Beaker 2

Beaker 3 The Phospholipid Bilayer of a Cell Membrane 1. For the third thought experiment student are asked to draw their final beaker 2/3 full of water. 2. You now have even more phospholipids, how would they would arrange themselves if they had to meet the criteria that they had to be submerged and surrounded by water, but also be able to contain water.

Beaker 3

Figure 8.9 Some functions of membrane proteins PROTEINS serve many functions for the plasma membrane

Cholesterol Molecules Makes the bilayer stronger but still flexible Holds two layers together Cell to cell communication

Function of the Cell Membrane: Cell membrane separates the components of a cell from its environment—surrounds the cell “Gatekeeper” of the cell—regulates the flow of materials into and out of cell—selectively permeable Cell membrane helps cells maintain homeostasis— stable internal balance pbslearning media.org/r esource/tdc 02.sci.life.c ell.membra neweb/cell- membrane- just- passing- through/

Passive Transport A process that does not require energy to move molecules from a HIGH to LOW concentration DDiffusion OOsmosis  F Facilitated Diffusion

Diffusion is the movement of small particles across a selectively permeable membrane like the cell membrane until equilibrium is reached. These particles move from an area of high concentration to an area of low concentration. outside of cell inside of cell

Where does diffusion take place in the body?

Osmosis is the diffusion of water through a selectively permeable membrane like the cell membrane Water diffuses across a membrane from an area of high concentration to an area of low concentration.

Types of Solution Concentrations 1. Hypertonic 2. Hypotonic 3. Isotonic

Hypertonic Solutions: contain a high concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel.

Isotonic Solutions: contain the same concentration of solute as another solution (e.g. the cell's cytoplasm). When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The fluid that surrounds the body cells is isotonic.

Hypotonic Solutions: contain a low concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly explode.

Figure 8.12 The water balance of living cells HYPO= “More”ISO = “Equal” HYPER = “More”

Facilitated Diffusion is the movement of larger molecules like glucose through the cell membrane – larger molecules must be “helped” Proteins in the cell membrane form channels for large molecules to pass through Proteins that form channels (pores) are called protein channels outside of cell inside of cell Glucose molecules

diffusion of specific particles through transport proteins found in the membrane a. Transport Proteins are specific – they “select” only certain molecules to cross the membrane Ex: channel or carrier proteins a. Transports larger or charged molecules Facilitated diffusion (Carrier Protein) AB Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer)

NO ENERGY NEEDED: Diffusion Osmosis Facilitated Diffusion ENERGY NEEDED: Active Transport ANALOGY:

Active Transport Active transport is the movement of molecules from LOW to HIGH concentration. Energy is required as molecules must be pumped against the concentration gradient. 3 Types: 1. Protein Pumps 2. Endocytosis 3. Exocytosis outside of cell inside of cell Carbon Dioxide molecules

1. Protein Pumps -transport proteins that require energy to do work Protein changes shape to move molecules: this requires energy! Example: Sodium / Potassium Pumps are important in nerve responses.

Food is moved into the cell by Endocytosis Wastes are moved out of the cell by Exocytosis Endocytosis and Exocytosis is the mechanism by which molecules (such as food and wastes) get into and out of the cell

1. Phagocytosis- “cell eating” Extensions of the cytoplasm surround a particle and package it within the vacuole 2 Types of Endocytosis

2. Pinocytosis- “cell drinking” Pockets form along the cell membrane, fill with liquid, and pinch off to form vacuoles within the cell 2 Types of Endocytosis