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EQ: What are the basic parts of cell membranes, and what is the job of each
part? Can I diagram diffusion of oxygen, facilitated diffusion of
glucose, and osmosis across a cell membrane?
BOUNDARY OF THE CELL:Cell: smallest unit that can carry out all the activities for life. (the “atom” of biology)Cell Membrane Diagram:
Outside of cell
Inside of cell (cytoplasm)
Cellmembrane
Proteins
Proteinchannel Lipid bilayer
Carbohydratechains
Membrane Descriptives:• Semi-Permeable—certain molecules can pass through the membrane, but not all molecules can
Fluid Mosaic Model—Proteins “float” in a fluid or moveable layer of phospholipids
Components of the Cell Membrane***Reference the image on slide #2***
• Phospholipid bilayer—• phospholipids have a phosphate head (yellow
circle) • lipid tails (the brown tails). • The phosphate heads line up on the outside
because they are hydrophilic (water-loving). • The lipid tails line up on the inside because they
are hydrophobic (water-hating).
• Proteins—act as channels or pumps to help molecules pass through the membrane
• Carbohydrate chains—help cells recognize and communicate with each other
Solution terms: we discussed this during basic chemistry notes…Solution – mixture of solute and solvent
(Ex. Kool-Aid = powder + water)
Solute – substance being dissolved (ex. Kool-Aid powder, Salt, or sugar)
Solvent – substance dissolving solute (ex. Water, which is a universal Solvent)
Membrane trafficPassive transport~ diffusion of a substance across a biological membrane (NO ENERGY needed)Ex. 1 Diffusion~ the overall movement of particles from a region of high concentration
to an area of low concentrationEx. 2 Osmosis~ the diffusion of water across a selectively permeable membrane
Concentration: the relative amount of a given substance contained within a solution or in a particular volume of space; the amount of solute per unit volume of solution.
Results of DiffusionDynamic equilibrium
Once diffusion has evenly distributed the solute throughout the solvent, movement of particles continues with no change in concentration
HomeostasisPreservation of equilibrium
Diffusion depends on concentration gradient:Concentration gradient: the difference in concentration of a substance across space
Diffusion is said to move down a concentration gradient
Diffusion continues until there is NO concentration gradient
Ex: O2 diffuses into oxygen depleted blood
Diffusion Rules:
QuickTime™ and aCinepak decompressor
are needed to see this picture.
Small Molecules like WATER,
OXYGEN, AND CARBON DIOXIDE
CAN MOVE in and out freely.
Large molecules like PROTEINS
AND CARBOHYDRATES CANNOT
Charged IONS CANNOT
Osmosis~ the diffusion of water across a selectively permeable membrane.
Water likes to DILUTE high concentrations of solute
Osmosis in the Real WorldBryophytes, or mosses, are plants that depend on osmosis transfer water from the environment into the plant.
Bryophytes can never grow tall, because they cannot pull the water against gravity just using the concentration gradient.
Bryophytes must also live in wet environments
Review:Osmosis is the diffusion of _______ across a cell membrane.
Osmosis and Diffusion are both types of __________ transport.
Passive transport does or does not require energy?
Small molecules can not move across freely. T or F
Large molecules can move freely. T or F
Isotonic SolutionThe solute outside the cell is equal in concentration to the solute in the cell.
The cell retains its shape.
water moves equally in both directions (into and out of the cell) Normal
looking cells
Hypotonic Solutions
Solution outside the blood cell contains a lower concentration of solute than inside of the cell.
Water will diffuse inside the cell. cell will lyse (burst).
In Animal cells - cytolysis. Plant cells do not burst- turgur pressure— grocers use this idea
Hypertonic SolutionsThe solution outside the cell has a higher concentration of solute than inside of the cell.
Water will diffuse out of the cell, causing the cell to shrink or crenate
Why should you not salt meat before cooking?
CRENATION PLASMOLYSIS
Water Balance SummaryOsmoregulation~ control of water balance
Hypertonic~ higher concentration of solutes
Hypotonic~ lower concentration of solutes
Isotonic~ equal concentrations of solutes
Plasmolysis Turgidity in plant cells.
QuickTime™ and aCinepak decompressor
are needed to see this picture.
QuickTime™ and aCinepak decompressor
are needed to see this picture.