Transport Across Membranes
Active Transport
Active Transport
Learning Objectives
• Describe and explain what
ids meant by active
transport, endocytosis and
exocytosis
Success Criteria
• Define active transport,
endocytosis and exocytosis
(Grade D-E)
• Explain what is meant by
active transport, endocytosis
and exocytosis (Grade c)
• Explain, with examples uses of
endocytosis and exocytosis
(Grade A-B)
Active Transport
Active transport is different from
diffusion and facilitated diffusion
because it uses ENERGY.
Unlike diffusion and facilitated
diffusion, molecules move AGAINST
a concentration gradient.
This happens in the intestines, where
the concentration of nutrients is
very high in the cells already.
This process requires the expenditure of energy in the form of
.ATP (adenosine triphosphate), a molecule produced by
respiration in mitochondria and uses carrier proteins
Active Transport
OUTSIDE
ATP
INSIDE
1. Molecule attaches to carrier protein.
2. ATP molecule provides energy to go against gradient.
3. Carrier changes shape and molecule is released on the
other side (side with higher concentration).
Examples of active transport
Active transport is used in many processes, such as the:

uptake of glucose and amino acids in the small intestine

absorption of mineral ions by plant roots

excretion of hydrogen ions and urea by kidneys

exchange of sodium and
potassium ions in
neurons and muscle
cells.
Cells that undertake active
transport on a large scale
have many mitochondria.
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© Boardworks Ltd 2008
Cells like epithelial cells
in the intestine have to
carry out active
transport.
They’re packed with
mitochondria to
provide the ATP
(energy) needed for
transporting nutrients
against a concentration
gradient.
Active transport
With diagrams – explain active transport
• Task
• With diagrams – explain active transport
• Produce a table to compare active transport
and passive transport (page 24/25 may help)
Summary
• Complete a table to show similarities and differences between the
different methods of movement across a cell membrane
Simple
diffusion
Energy
required?
Substances
moving
Location of
cell
membrane
Factors
affecting
speed
Facilitated
diffusion
Active
transport
Osmosis
What is bulk transport? – Use worksheet
When extremely large substances need to be moved across
a cell membrane, bulk transport is used.
The two types of bulk transport are
endocytosis and exocytosis, and they
involve changes to the membrane shape.

Endocytosis is the bulk transport
of material in to the cell, and can
be split into three processes:
phagocytosis, pinocytosis and
receptor-mediated endocytosis.

Exocytosis is the bulk transport of material out of the
cell – essentially the reverse of endocytosis.
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Mechanisms of endocytosis
Exocytosis
• http://www.youtube.com/watch?v=HndmASfmI8Y
• Exocytosis in paramecium
http://www.youtube.com/watch?v=U9pvm_4-bHg
• Phagocytosis! – amoeba and paramecium
• http://www.youtube.com/watch?v=aWItglvTiLc
Both
http://www.youtube.com/watch?v=bFRoZpIAuyk
Complete exam question June 11 Qu 2
Comparing methods of transport
What’s the keyword?
Multiple-choice quiz
Homework
• Complete exam booklet – next Wednesday!!