Section Objectives 1. Explain how the processes of diffusion, passive transport, and active transport occur. 2. The differences between active and passive transport. 3. The importance of these processes to cell.

Important molecules such as oxygen, water, sugar etc Important molecules such as oxygen, water, sugar etc. need to enter the cells in order for them to survive. Waste molecules such as CO2 need to leave the cell. Cell Membrane

These molecules must pass through the cell membrane in order to enter or leave the cell!! . Cell Membrane

Transport: the movement of molecules into and out of the cell membrane. 2 Types of Transport Passive Transport vs Active Transport

Passive Transport the movement of materials from High concentration to Low concentration Cells do not need to put in ATP to move these molecules HIGH Concentration (a lot) LOW Concentration ( a few)

An example of Passive Transport is Diffusion Molecules move from HIGH to LOW concentration Movement from high concentration of that substance to low concentration of that substance. High Low

Predict which way the fat molecules will move Predict which way the fat molecules will move? Moving into the cell or out of the cell? fat fat inside cell fat fat fat outside cell fat fat fat fat fat fat fat fat

The correct answer If you predicted the fat molecules will move into the cell, then you’re correct. Why? Because molecules have a natural tendency to move from high concentration (a lot) to low concentration ( a few). Remember Diffusion!!! fat fat inside cell fat fat Low concentration fat outside cell fat fat fat fat fat fat fat fat High Concentration

Which way will sugar move? inside cell sugar sugar outside cell sugar sugar sugar sugar sugar sugar sugar

Review: Passive Transport An example of Passive Transport is Diffusion Molecules move from HIGH to LOW concentration directly through the cell membrane simple diffusion Cells do not need to put in energy (ATP) to move these molecules HIGH LOW

Another example of Passive Transport is Osmosis Osmosis only deals with the movement of water molecules Water molecules osmosis

Predict which way the water molecules will move Predict which way the water molecules will move? To the left or to the right side? Water molecules osmosis

The correct answer The water molecules will move from the left side to the right side. Can you explain why? osmosis

Review: Osmosis Osmosis is another example of Passive Transport The movement of only water across a cell membrane is called osmosis. Regulating the water flow through the plasma membrane is an important factor in maintaining homeostasis within a cell. Most cells whether in multicellular or unicellular organisms, are subject to osmosis because they are surrounded by water solutions.

Final Summary: Passive Transport When a cell uses no energy to move particles across a membrane passive transport occurs Particles go DOWN their concentration gradient ( high to low concentration). all diffusion & osmosis are passive transport. Concentration gradient Plasma membrane

The Second Type is Active Transport active transport :Movement of materials through a membrane against a concentration gradient and requires energy ATP from the cell. Cellular energy Carrier proteins Cellular energy cell membrane

These molecules will not move inside the cell automatically These molecules will not move inside the cell automatically. The cells need to put in energy ATP to pull the molecules in. Cellular energy Carrier proteins Outside the cell Inside the cell Cellular energy cell membrane

Review: Active transport Cells may need molecules to move against concentration “hill” need to pump “uphill” from LOW to HIGH using energy protein pump requires energy ATP Plants have nitrate & phosphate pumps in their roots. Why? Nitrate for amino acids Phosphate for DNA & membranes Not coincidentally these are the main constituents of fertilizer. ATP

Review Questions Identify a few important molecules that must enter a cell in order for it to survive. Identify one waste product that must leave the cell. In order for molecules to enter or leave the cell, they must pass through the _________. What is transport? How many different types of transport are there? What is passive transport? Explain diffusion in your own words. Explain osmosis in your own words. What is active transport? How is passive transport different than active transport?

Practice Regents Based Questions 1. Which process requires cellular energy? diffusion passive transport active transport osmosis

2. The diagram below represents a cell in water 2. The diagram below represents a cell in water.  Formulas of molecules that can move freely across the cell membrane are shown.  Some molecules are located inside the cell and others are in the water outside the cell. Based on the distribution of these molecules, what would most likely happen after a period of time? The concentration of O2 will increase inside the cell. The concentration of CO2 will remain the same inside the cell. The concentration of O2 will remain the same outside the cell. The concentration of CO2 will decrease outside the cell.

3. In the diagram below, the dark dots indicate small molecules 3. In the diagram below, the dark dots indicate small molecules. These molecules are moving out of the cells, as indicated by the arrows. The number of dots inside and outside of the two cells represents the relative concentrations of the molecules inside and outside of the cells. ATP is being used to move the molecules out of the cell by cell A, only cell B, only both cell A and cell B neither cell A nor cell B

4. Molecule X moves across a cell membrane by diffusion 4. Molecule X moves across a cell membrane by diffusion. Which row in the chart below best indicates the relationship between the relative concentrations of molecule X and the use of ATP for diffusion?