1. 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.

2. 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

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

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

5. 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)

6. 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

7. 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

8. 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

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

10. 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

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

12. 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

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

14. 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.

15. 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

16. 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

17. 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

18. 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

19. 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?

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

21. 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.

22. 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

23. 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?