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Active Transport: Protein Pumps and Endocytosis

Section 3.5

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Objectives

• SWBAT describe active transport.• SWBAT distinguish among endocytosis,

exocytosis, and phagocytosis.

• Main Ideas– Proteins can transport materials against a

concentration gradient.– Endocytosis and exocytosis transport materials

across the cell membrane in vesicles.

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Vocabulary Section 3.5

• Endocytosis (endocitosis)• Exocytosis (exocitosis)• Phagocytosis (fagocitosis)• Active transport (transporte activo)• ATP (adenosine triphosphate)

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Starter

• Small lipid molecules are in high concentration outside a cell. They slowly cross the membrane into the cell. What term describes this action? Does it require energy?

• Diffusion and no.

Two Types of Transport• There are two ways of transporting materials

across a cell membrane. They are:– Passive Transport – we have already looked at this.– Active Transport – actively drives molecules

across the cell membrane from a region of lower concentration to a region of higher concentration. Requires energy input.

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Active Transport

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Active Transport

Active transport drives molecules across a membrane from region of lower concentration to a region of higher concentration (remember our bicycle example).

There are transport proteins that allow diffusion but there are others, often called pumps, that move materials against the concentration gradient.

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Active Transport

Active transport requires energy input from a cell and enables a cell to move a substance against its concentration gradient.

Cells use active transport to get needed molecules regardless of the concentration gradient to maintain homeostasis.

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Question

• Are the protein pumps, like the Na/K pump in neurons, active or passive transport?

• Explain how a protein pump works?• What kind of energy does it use?

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ATP (Adenosine Triphosphate)

ATP is chemical energy made in a cell’s mitochondria.

Besides in neurons, like we have already seen, ATP is needed to drive many other processes – including the making of ATP.

ATP is used in the mitochondrial proton pump, moving hydrogen ions (H+) across the inner mitochondrial membrane. This proton pump is essential for the creation of ATP.

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ATP

Like with sodium and potassium in the neuron, the hydrogen ions are “pumped,” using ATP, across the mitochondrial inner membrane (against the H+ gradient).

They then diffuse across the membrane through a protein channel (an enzyme called ATP Synthase).

The enzyme uses the movement of the H+ to create ATP from a precursor called ADP.

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ATP Video

• http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter38/proton_pump.html

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Transport Proteins• All transport proteins/enzymes (which are

proteins) span a membrane.• Most change shape when they bind to a target

molecule or molecules. • As we have seen, some transport proteins bind to

only one type of molecule. • Others bind to 2 different types.

– Those that bind to two types can move both types of molecules either one way or opposite directions (like the sodium/potassium pump we saw in the neuron.

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Question

• How do transport proteins that are pumps differ from those that are channels?

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Endocytosis

• Endocytosis – the process of taking liquids or fairly large molecules into a cell by engulfing them in a membrane. – The cell membrane makes a pocket around the

substance.

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Endocytosis

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Endocytosis

• The pocket breaks off inside the cell and forms a vesicle.– The vesicle then fuses with a lysosome.

Lysosomal enzymes break down the vesicle membrane and the vesicle’s contents are release into the cell.

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Phagocytosis

• Phagocytosis – the word literally means “cell eating.”

• It is a special type of endocytosis which plays a major role in your immune system.

• White blood cells find foreign materials, such as bacteria, engulf them and destroy them. – They are your body’s enforcers.