7-3 Cell Transport. REVIEW Regulates what enters and leaves the cell Protects and supports the...
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Transcript of 7-3 Cell Transport. REVIEW Regulates what enters and leaves the cell Protects and supports the...
REVIEW
Regulates what enters and leaves the cell
Protects and supports the cell
Composed of Lipids = bilayerProteins = channelsCarbs = identification cards
Different types of movement
• Passive Transport – Diffusion– Osmosis– Facilitated Diffusion
• Active Transport– Membrane Pumps– Endo/Exocytosis
1. PASSIVE TRANSPORT – Diffusion“passive” = no energy required
– Molecules in Motion• Molecules are in constant motion• Move from a region where they are
more numerous (high concentration) to where they are less numerous (low concentration)
• Want to reach a state where molecules are spread out evenly = EQUILIBRIUM
– Diffusion – the process by which molecules of a substance move from areas of higher concentration of that substance to areas of lower concentration
– Factors that contribute to movement of substances:• Unequal concentrations• Permeability
– The cell membrane is selectively permeable – allowing some things to cross while others cannot
1. PASSIVE TRANSPORT – Diffusion“passive” = no energy required
2. PASSIVE TRANSPORT - Osmosis
– Most molecules cannot dissolve in the lipid bilayer of the cell; therefore, they cannot pass through - BUT – WATER CAN…
– Osmosis – diffusion of water across a selectively permeable membrane
– Water will pass through the membrane from a area of high water concentration to an area of low water concentration
– There is a net movement of water from where there is less solute to where there is more solute (in an attempt to dilute it)
– Osmotic pressure – the force exerted by osmosis• Types of tonicity (the
ability of a substance to draw water towards it)
Isotonic Solution
“Iso” = the same
Water will move both ways in equal amounts
Why is important that contact lens solution is isotonic?
Hypotonic Solution
"Hypo" = less Less solute (salt) molecules
outside the cell Water will move in both directions BUT more water will move into the
cell causing it to grow larger (cytolysis)
In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid (turgid), the cell wall keeps the plant from bursting
In animal cells, the cell may be in danger of bursting, organelles called CONTRACTILE VACUOLES (only on paramecium) will pump water out of the cell to prevent this
Hypertonic Solution "Hyper" = more More solute (salt) molecules
outside the cell Water will move in both directions BUT more will move out of the cell
causing it to shrink (plasmolysis) In plant cells, the central vacuole
loses water and the cells shrink, causing wilting (loss of turgor pressure)
In animal cells, the cells shrink In both cases, the cell may die Why is it dangerous to drink sea
water? This is also why "salting fields"
was a common tactic during war, it would kill the crops in the field, thus causing food shortages
1. What type of solution is this “cell” in?
a: hypotonic solution
2. What will happen to this “cell” over time?
a: the cell will expand and possibly burst = CYTOLYSIS
3. PASSIVE TRANSPORT - Facilitated Diffusion
– No energy required– Carrier proteins
transport molecules across the membrane (from high to low concentrations)
– Molecules may be too big or cells may need to get the molecules quickly
4. ACTIVE TRANSPORT
– Requires energy (usually ATP)– Move molecules against the
concentration gradient – the opposite direction of passive transport
4. ACTIVE TRANSPORT - Membrane Pumps
– Transport macromolecules move molecules across the cell membrane
– Requires ENERGY– Examples – calcium, potassium, sodium ions
5. ACTIVE TRANSPORT – Endocytosis vs. Exocytosis
• Endocytosis – taking materials into the cell by infoldings of the cell membrane
– Phagocytosis – when large particles (food, microorganisms) are taken into the cell
– Pinocytosis – when liquids or relatively small particles (solutes) are taken into the cell
– Receptor-mediated endocytosis
• Exocytosis – when large molecules are removed from the cell– Contractile vacuoles – water is pumped
out of the cell so it doesn’t burst