Transcript Transport Across Membranes

Transport Across Membranes
Active Transport
Active Transport
Learning Objectives
• explain what is meant by
active transport,
Success Criteria
• Make list, table or other
resource from video sources
• Define and explain some
uses of endocytosis and
exocytosis;
• Illustrate by diagrams
methods of bulk transport
• Complete summary sheet
and questions relating to
transport across
membranes
What is active transport?
Diffusion is very important for helping to maintain the internal
environment of a cell. However, molecules and ions often need
to be moved across a membrane against their concentration
gradient.
The cell uses carrier proteins to pump these substances across the
membrane, in a process called active transport.
This process requires the
expenditure of energy in the
form of ATP (adenosine
triphosphate), a molecule
produced by respiration in
mitochondria.
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.
Active transport
Bulk Transport
• http://www.youtube.com/watch?v=HndmASfmI8Y
• Exocytosis in paramecium
http://www.youtube.com/watch?v=U9pvm_4-bHg
• Both in paramecium (with text)
• http://www.youtube.com/watch?v=sn3MTYNe8mM
• Phagocytosis!
• http://www.youtube.com/watch?v=aWItglvTiLc
Both
http://www.youtube.com/watch?v=bFRoZpIAuyk
Try to fill this in from your notes/group discussion
DO NOT use a textbook to start
Type of transport
Description
Diffusion
Net movement of particles from an area of
higher concentration to an area of lower
concentration Passive.
Osmosis
Movement of water molecules...from an
area of higher water potential to an area of
lower wp Passive
Facilitated diffusion
Net movement...high to low concentration
Carrier for large molecules, ions, polar mol
Channel for smaller ions, polar molecules
Passive
Active Transport
Endocytosis
Exocytosis
Movement of molecules against a conc.
gradient carrier proteins.
Active – requires ATP
Movement large molecules/objects into a
cell. Plasma membrane surrounds and
pinches off. Active
Movement out of a cell.  Vesicle fuses with
membrane and releases contents.  Active
What is bulk transport?
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.
Mechanisms of endocytosis
Exocytosis
Comparing methods of transport
What’s the keyword?
Multiple-choice quiz
pinocytosis
phagocytosis
osmosis
exocytosis
endocytosis
phagocytosis
Facilitated diffusion - channel
Facilitated diffusion - carrier
Sodium-potassium pump