Transcript How can we smell our dinner being made in the room next door?

How can we smell our dinner being
made in the room next door?
• diffusion
Diffusion
• Diffusion is the movement of particles from a
region where they are concentrated to a
region where they are less concentrated
• No energy is needed for Diffusion to take
place. It is a Passive process.
• It is important in the movement of substances
between cells and inside cells (occurs only over
short distances, no more than 1mm)
• Hence, larger organisms will require Transport
systems as well i.e. circulatory system in humans
Osmosis
• Osmosis is the movement of water molecules
across a semi-permeable membrane, from an
area of high concentration of water molecules
to an area of low concentration of water
molecules.
Cell Membrane & Osmosis
• The cell membrane controls movement of
substances into and out of the cell
• It is semi-permeable i.e. it allows small
molecules like water, carbon dioxide and
oxygen through by diffusion but stops larger
ones.
• Where energy is required to move molecules
in and out of cells is called Active transport
Osmoreregulation
• Our cells contain sugar and salt at certain
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concentrations.
If these concentrations change, action is taken by
cells to counteract the changes and return to the
normal balanced state.
This balancing action is called Osmoregulation.
Osmosis in Animal Cells
Animal Cells in Pure water
• Red blood cells have 1% salt
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concentration in them.
What would happen if a red
cell is placed in pure water?
Animal cells in Salt water
• What would happen if a red
cell is placed in a very salty
solution?
• The Cytoplasm swells up with • Experiences a loss of water
water and eventually the cell
may burst and die.
which causes the cell to
shrivel up.
Osmosis in Plant Cells
Plant Cells in Pure Water
Plant Cells in Salt Solution
• Onion cells have Salt and
• What happens if an onion cell
• The cytoplasm & vacuole fill
• The cytoplasm & vacuole lose
Sugar in their cytoplasm.
• What happens if an onion cell
is placed in pure water?
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up with water, which stretches
the cell.
The cell wall prevents the cell
from bursting and the cell is
said to be Turgid.
is placed in a very salty
solution?
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water.
The cell membrane comes
away from the cell wall, the
cell is said to be Plasmolysed.
Turgid describes a plant cell in which the cell wall is
rigid, due to the cytoplasm pushing out against it as it
fills with water.
Osmotic pressure is the main cause of support in plant
leaves
(Without water the cell walls are not strong enough to
support the weight of the plant, and so it Wilts)
Osmosis in Food Preparation
• Naturally occurring chemicals like salt, sugar and
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fruit juice will preserve foods by osmosis.
Salt is the oldest and most common method of
preserving fish and meats.
Water moves, by osmosis, from the cells into the
salt solution, causing the tissues to become
dehydrated, which destroys bacteria.
Sugars are used to preserve fruits (jams/tinned
fruit)
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Active Transport
More
In order for Large molecules to move across the cell solute
membrane they must do so at certain ‘gates’ and the molecules
cell has to use energy to do this.
These ‘gates’ are proteins within the cell
membrane, which pump the molecules across,
often against the concentration gradient
(from where there is less to where there
is more of the substance)
Fewer
solute
molecules
SOLUTE CONCENTRATION GRADIENT
• Active Transport is the movement of substances across a
cell membrane against a concentration gradient, using
energy from respiration.