Active Transport, Endocytosis, and Exocytosis

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Transcript Active Transport, Endocytosis, and Exocytosis

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
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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.
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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.mcgrawhill.com/sites/9834092339/student_view0/ch
apter38/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.
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