OSMOSIS & DIFFUSION SB1.d – Explain the impact of water on life processes (i.e. osmosis and...
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Transcript of OSMOSIS & DIFFUSION SB1.d – Explain the impact of water on life processes (i.e. osmosis and...
![Page 1: OSMOSIS & DIFFUSION SB1.d – Explain the impact of water on life processes (i.e. osmosis and diffusion).](https://reader035.fdocuments.in/reader035/viewer/2022062321/56649dab5503460f94a9ac1e/html5/thumbnails/1.jpg)
OSMOSIS & DIFFUSION
SB1.d – Explain the impact of water on life processes (i.e.
osmosis and diffusion).
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Methods of Cell Transport
• Substances move into and out of cells by several methods.– One method of movement is diffusion.
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Methods of Cell Transport
• Diffusion is the net movement of a substance (liquid or gas) from an area of high concentration to one of lower concentration
• The majority move from higher to lower concentration
• If no energy is put into the system, the molecules will reach a state of equilibrium where they will be distributed equally throughout the system.
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The Cell Membrane
• All cells, in all types of organisms, are surrounded by a cell membrane– a thin layer of lipid and protein that separates the
cell's contents from the world around it.– functions like a gate, controlling what enters and
leaves the cell.– controls the ease with which substances pass into
and out of the cell-some substances easily cross the membrane, while others cannot cross at all.• selectively permeable
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Cells and Diffusion
• Water, carbon dioxide, and oxygen are among the few simple molecules that can cross the cell membrane by diffusion. –Water moves through membranes by a type of
diffusion known as osmosis.–Diffusion is one principle method of
movement of substances within cells, as well as the method for essential small molecules to cross the cell membrane.
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Cells and Diffusion
• Osmosis is the diffusion of water across a semi-permeable (or differentially permeable or selectively permeable) membrane.
• The presence of a solute decreases the water potential of a substance.
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Cells and Diffusion
• Hypertonic solutions are those in which more solute (and hence lower water potential) is present.
• Hypotonic solutions are those with less solute (again read as higher water potential).
• Isotonic solutions have equal (iso-) concentrations of substances. Water potentials are thus equal; although there will still be equal amounts of water movement in and out of the cell, the net flow is zero.
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Cells and Diffusion
Cells placed in distilled water (hypotonic solution) take on water, swell and burst.In a salt solution (hypertonic solution), cells lose water and shrink.
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Active and Passive Transport
• Two additional methods by which substances may move through cell membranes include:– Passive transport requires no energy from the
cell.• Examples include the diffusion of oxygen and
carbon dioxide, osmosis of water, and facilitated diffusion.
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Active and Passive Transport
– Active transport requires the cell to spend energy, usually in the form of ATP.• Examples include transport of large molecules
(non-lipid soluble) and the sodium-potassium pump.
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Active and Passive Transport
Vesicle-mediated transport• Vesicles and vacuoles that fuse with the cell
membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter a cell.
• Exocytosis is the term applied when transport is out of the cell.
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Active and Passive Transport
• Endocytosis is the case when a molecule causes the cell membrane to bulge inward, forming a vesicle.
• Phagocytosis is the type of endocytosis where an entire cell is engulfed.
• Pinocytosis is when the external fluid is engulfed.• Receptor-mediated endocytosis occurs when the
material to be transported binds to certain specific molecules in the membrane. – Examples include the transport of insulin and
cholesterol into animal cells.
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Active and Passive Transport