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Types of Transport Across Cell Membranes

Essential Question

Compare/Contrast active/passive transportHow do we make spaghetti noodles soft?

What is the purpose of cell transport?

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Passive Transport

• Requires NO energy• Molecules

move from area of HIGH to LOW concentration

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Passive Transport: Diffusion

–Diffusion is a PASSIVE process–Molecules move

DOWN the concentration gradient

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Diffusion of Liquids

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Diffusion through a Membrane

Cell membrane

Solute moves DOWN concentration gradient (HIGH to LOW)

Essential Question

Explain diffusion

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Passive Transport: Osmosis

• Diffusion (passive transport) of water across a membrane

• Moves from HIGH water potential (low solute) to LOW water potential(high solute)

Diffusion across a membrane

Semipermeable membrane

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Passive Transport: Osmosis across a membrane

High H2O potentialLow solute concentration

Low H2O potentialHigh solute concentration

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Cell in Isotonic Solution

CELL

10% NaCL90% H2O

10% NaCL90% H2O

What is the direction of water movement?

The cell is at _______________.equilibrium

ENVIRONMENT

NO NET MOVEMENT

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Cell in Hypotonic Solution

CELL

10% NaCL90% H2O

20% NaCL80% H2O

What is the direction of water movement?

ENVIRONMENT

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Cell in Hypertonic Solution

CELL

15% NaCL85% H2O

5% NaCL95% H2O

What is the direction of water movement?

ENVIRONMENT

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Cells in Solutions

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Isotonic Solution

NO NET MOVEMENT OF

H2O (equal amounts entering

& leaving)

Hypotonic Solution

CYTOLYSIS

Hypertonic Solution

PLASMOLYSIS

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Cytolysis & Plasmolysis

Cytolysis Plasmolysis

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Osmosis in Red Blood Cells

Isotonic Hypotonic Hypertonic

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hypotonic hypertonic isotonic

hypertonic isotonic hypotonic

Essential Question

How do we make spaghetti noodles soft?

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Three Forms of Transport Across the Membrane

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Passive Transport Review

Diffusion/Osmosis

NO ENERGY required Moves high to low concentration Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out.

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Passive Transport

Facilitated diffusionNO ENERGY required

Uses transport proteins to move high to low concentrationExamples: Glucose or amino acids moving from blood into a cell.

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Passive Transport: Facilitated DiffusionProteins Are Critical to Membrane

Function

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Passive Transport: Facilitated Diffusion

• Types of Transport Proteins: –Channel proteins are embedded in the

cell membrane & have a pore for materials to cross–Carrier proteins can change shape to

move material from one side of the membrane to the other

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Facilitated Diffusion(Channel Proteins)

Molecules will randomly move through the pores in Channel Proteins.

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Facilitated Diffusion (Carrier Proteins)

• Some Carrier proteins do not extend through the membrane.• They bond and drag

molecules through the lipid bilayer and release them on the opposite side.

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Facilitated Diffusion (Carrier Proteins)

• Other carrier proteins change shape to move materials across the cell membrane

Essential Question

Explain Facilitated Diffusion

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Active Transport

Requires energy or ATPMoves materials from LOW to HIGH concentrationAGAINST concentration gradient

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Active transport

Example: Sodium Potassium Pump

Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients.

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Sodium-Potassium Pump

3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential

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Moving the “Big Stuff”

Molecules are moved out of the cell by vesicles that fuse with the plasma membrane.This is how many hormones are secreted and how nerve cells communicate with one another.

Exocytosis- moving

things out.

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Receptor-Mediated Endocytosis

Some integral proteins have receptors on their surface to recognize and take in hormones, cholesterol, etc. to communicate

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Receptor-Mediated Endocytosis

Essential Question

Explain Active Transport

What’s the point?

• To maintain homeostasis=balance

Essential Question

Compare/Contrast active/passive transportHow do we make spaghetti noodles soft?

What is the purpose of cell transport?