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Cells: The Living Units Part A
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The cell is the basic structural and functional unit of life
Continuity of life has a cellular basis
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Structure of a Generalized Cell
Figure 3.2
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Separates intracellular fluids from extracellular fluids
Plasma Membrane Separates intracellular fluids from extracellular fluids Plays a dynamic role in cellular activity Glycocalyx is a glycoprotein area abutting the cell that provides highly specific biological markers by which cells recognize one another
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Double bilayer of lipids with imbedded, dispersed proteins
Fluid Mosaic Model Double bilayer of lipids with imbedded, dispersed proteins Bilayer consists of phospholipids, cholesterol, and glycolipids Glycolipids are lipids with bound carbohydrate Phospholipids have hydrophobic and hydrophilic bipoles
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Fluid Mosaic Model Figure 3.3
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hydrophobic hydrophilic water loving solid
Because of the lipid content, the interior of the membrane is __________.
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Functions of Membrane Proteins
Transport Enzymatic activity Receptors for signal transduction Figure 3.4.1
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Functions of Membrane Proteins
Intercellular adhesion Cell-cell recognition Attachment to cytoskeleton and extracellular matrix Figure 3.4.2
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Plasma Membrane Surfaces
Differ in the kind and amount of lipids they contain Glycolipids are found only in the outer membrane surface Portion of all membrane lipid is cholesterol
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Tight junction – impermeable junction that encircles the cell
Membrane Junctions Tight junction – impermeable junction that encircles the cell Desmosome – anchoring junction scattered along the sides of cells Gap junction – a nexus that allows chemical substances to pass between cells
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Membrane Junctions: Tight Junction
Figure 3.5a
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Membrane Junctions: Desmosome
Figure 3.5b
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Membrane Junctions: Gap Junction
Figure 3.5c
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Desmosomes Microvilli Tight junctions Gap junctions
In areas of the body subject to a higher degree of mechanical stress, which of the following types of membrane junctions would you expect to be most prevalent? Desmosomes Microvilli Tight junctions Gap junctions
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Passive Membrane Transport: Diffusion
Simple diffusion – nonpolar and lipid-soluble substances Diffuse directly through the lipid bilayer Diffuse through channel proteins
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Passive Membrane Transport: Diffusion
Facilitated diffusion Transport of glucose, amino acids, and ions Transported substances bind carrier proteins or pass through protein channels
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Diffusion Through the Plasma Membrane
Figure 3.7
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Passive Membrane Transport: Osmosis
Occurs when the concentration of a solvent is different on opposite sides of a membrane Diffusion of water across a semipermeable membrane Osmolarity – total concentration of solute particles in a solution Tonicity – how a solution affects cell volume
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Effect of Membrane Permeability on Diffusion and Osmosis
Figure 3.8a
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Effect of Membrane Permeability on Diffusion and Osmosis
Figure 3.8b
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Effects of Solutions of Varying Tonicity
Isotonic – solutions with the same solute concentration as that of the cytosol Hypertonic – solutions having greater solute concentration than that of the cytosol Hypotonic – solutions having lesser solute concentration than that of the cytosol
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Passive Membrane Transport: Filtration
The passage of water and solutes through a membrane by hydrostatic pressure Pressure gradient pushes solute-containing fluid from a higher-pressure area to a lower-pressure area
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gain; diffusion gain; osmosis lose; diffusion lose; osmosis
1. A red blood cell placed into a container of distilled water will ________ water via ____________.
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Q 2 Lab 2. Explain one of the following: 3. Provide one example of #2
Passive transport Active transport Diffusion 3. Provide one example of #2 4. Which one has a higher osmolarity (see the board A or B) 5. Predict if osmosis occurs and if so, which direction (assume the semi-permeable membrane is permeable to water but not molasses)?
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