Unit 4 Transport of Materials

Key Questions 1. Why must materials enter and leave cells? 2.What materials need to enter and leave cells? 3.What role does the cell membrane play in the transport of materials into and out of a cell? 4.How do materials get into and out of a cell? 5.How do materials move within a cell?

Transport 1. Why must materials constantly enter and leave cells?

Transport  Cells must maintain a constant internal environment (homeostasis)  So, materials (nutrients and wastes) must constantly move in and out of the cell and throughout the cell.

Transport 2. What materials need to enter and leave cells?

Transport  Examples of substances entering a cell:  Nutrients  Salts  Oxygen  Water  Examples of substances leaving a cell:  Wastes  Carbon dioxide  Synthesized molecules  Water

Transport 3. What role does the cell membrane play in the transport of materials into and out of a cell?

Transport  Cell Membrane:  The cell membrane is selectively permeable  The cell membrane regulates/controls what is transported into (absorption) and out of the cell

Cell Membrane  Certain substances can pass through the membrane more easily than others,  Small molecules pass easily (ex.: water, glucose, amino acids, carbon dioxide, oxygen)  Large molecules cannot pass easily (ex.: starch, proteins)

Cell Membrane  That is why they get broken down during DIGESTION!!!

Cell Membrane  The cell membrane has a large surface area in order for the absorption of nutrients to occur

Transport 4.How do materials get into and out of a cell? DEMO-room spray

Transport  By diffusion/osmosis or active transport!!!

1. Diffusion/Osmosis  Does NOT require ENERGY to move materials into and out of the cell.

Diffusion  Movement of molecules from a high concentration to a low concentration due to a concentration gradient.  Concentration Gradient – difference between high and low

Diffusion  Occurs because the molecules are constantly moving.  Continues until equilibrium is reached – when the molecules are distributed evenly.

Diffusion Animation  hill.com/sites/ /student_view0/chapter 2/animation__how_diffusion_works.html hill.com/sites/ /student_view0/chapter 2/animation__how_diffusion_works.html

Balloons and Diffusion  Why do helium balloons sink over time? DEMO:  Why can you smell the flavor through the balloon?

2. Osmosis  The diffusion of water molecules through a semi-permeable membrane  Occurs from an area with a high concentration of water molecules to an area with a low concentration of water molecules

 DEMO: Beaker and food coloring!

Effects of Osmosis on Cells  Isotonic Solution:  Concentration of water molecules inside the cell and in an isotonic solution solution is the same  No concentration gradient, so cell doesn’t gain or lose water

Isotonic Solution - Animal Cell

Isotonic Solution – Plant Cell Solute concentration inside the cell is equal to outside

Effects of Osmosis on Cells  Hypotonic Solution  Larger concentration of water molecules outside the cell  Solution has less dissolved materials than the cell  Water moves into the cell by osmosis and animal cells swell and could burst

Hypotonic Solution – Animal Cell

Hypotonic Solution – Plant Cell

Effects of Osmosis on Cells  Hypertonic Solution  Larger concentration of water molecules inside the cell  Solution has more dissolved materials than the cell  Water moves out by osmosis and animal cells shrink

Hypertonic Solution – Animal Cell

Hypertonic Solution – Plant Cell

2. Active Transport  Processes that do require use of energy to move materials into and out of cells  Important in movement of molecules into and out of cells

Active Transport  Move materials from a high concentration to a low concentration OR from a low to a high concentration (against concentration gradient)  Moves larger molecules

Inside the Cell  Once materials are inside the cell, they can move throughout by:  Diffusion in the cytoplasm

NY State Required Lab- Diffusion Through a Membrane  Objectives – Week 1:  Testing with chemical indicators  Understanding diffusion (size of molecules)

Results-part 1  Explain the ‘final state.’’  Which molecules diffused and why?  Which molecules did not diffuse and why?

Part 2-Osmosis  Objectives:  Explain what happens when cells are placed in solutions having different concentrations  Explain osmosis

Explain what happened to the cells and why.

What happened to the cell?  There were more water molecules in the cell than in the solution, so water diffused out of the cell and the cell shrank.

Diagram of red onion cell in distilled water:

What happened to the cell?  There were less water molecules in the cell than in the solution, so water diffused into the cell and the cell gained water

Applicable NY State Standards  1.2g, 1.2h, 1.2i