Transcript Membrane structure, I

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
Carbohydrate
chains
Proteins
Cell
membrane
Protein
channel
Lipid bilayer
Inside of cell (cytoplasm)
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 traffic
 Passive 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 concentration
 Ex. 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 Diffusion
 Dynamic equilibrium
Once diffusion has evenly distributed the
solute throughout the solvent, movement
of particles continues with no change in
concentration
 Homeostasis
 Preservation 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:
Small
Molecules like WATER,
OXYGEN, AND CARBON
DIOXIDE CAN MOVE in and out
freely.
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
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 World
 Bryophytes, 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
Three Different Types of
Solutions
 Isotonic
Solution
 Hypotonic
Solution
 Hypertonic
Solution
Isotonic Solution
 The 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
Cells in a Hypotonic Solution
Hypertonic Solutions
 The 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
Cells in a Hypertonic Solution
In what type of solution would these cells
be found?
Water Balance Summary
 Osmoregulation~
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 a
Cinepak decompressor
QuickTime™ and a
are needed toCinepak
see thisdecompressor
picture.
are needed to see this picture.
What type of solution is this?
 Hypertonic
What will happen
to the cell?
It will shrink.