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Unit 3
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
 Absorption is when nutrients (like glucose
and oxygen) are taken into a cell
 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
 http://highered.mcgrawhill.com/sites/0072495855/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
Osmosis Vocab for Plant
Cells
 Turgor Pressure
 Pressure on cell wall caused by increased
expansion of water in vacuole from osmosis
 The rigid cell wall prevents cell from
bursting
 Plasmolysis
 When in hypertonic solutions, cell
membrane pulls away from cell wall due to
water loss by osmosis
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
FYI – Types of Active
Transport
 1. Membrane/Transport Pump
 Carrier proteins are used to pick up ions
or molecules near the cell membrane,
carry them across the membrane, and
release them on the other side.
Types of Active Transport
 2. Endocytosis/ Exocytosis
 Cell membrane folds in and forms a
small pouch
 Pouch releases the contents inside the
cell
 Exocytosis is the opposite
Inside the Cell
 Once materials are inside the cell, they can move
throughout by:
 Diffusion in the cytoplasm
 Cyclosis – streaming of the cytoplasm – to move
materials throughout the cell
 And the endoplasmic reticulum and golgi body
Cyclosis in Plant Cells
 http://www.dnatube.com/video/361/Cyclosis-inPlant-cells
NY State Required LabDiffusion 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.
Applicable NY State
Standards
 1.2g, 1.2h, 1.2i