Upload
jeremy-chambers
View
230
Download
1
Embed Size (px)
DESCRIPTION
Plasma Membrane Membrane Lipids Cell membranes consist of a phospholipid bilayer
Citation preview
Copyright © by Holt, Rinehart and Winston. All rights reserved.Copyright © by Holt, Rinehart and Winston. All rights reserved.
Cell Transport
Ch. 7.3 & 7.4
1
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Plasma Membrane
Membrane Lipids• Cell
membranes consist of a phospholipid bilayer
2
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Plasma Membrane
Membrane Proteins• Cell membranes often contain proteins
embedded within the phospholipid bilayer.
3
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Plasma Membrane
Fluid Mosaic Model• the phospholipid bilayer behaves like a
fluid more than it behaves like a solid.
4
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Diffusion
• Diffusion– the movement of a substance from an area of high
concentration to an area of lower concentration – caused by the random motion of particles of the
substance
Chapter 4
5
Copyright © by Holt, Rinehart and Winston. All rights reserved. 6
Copyright © by Holt, Rinehart and Winston. All rights reserved.
passive transport– movement across the cell membrane that does not
require energy
• concentration gradient– A difference in the concentration of a substance, across
a space
7
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Equilibriumequilibrium
the concentration of a substance is equal throughout a
space
8
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Some substances move across the cell membrane
without any use of energy by the cell.
9
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Simple Passive Diffusion
• Many substances enter or leave cells by diffusing across the cell membrane.
10
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Osmosis• osmosis
– the diffusion of water through a selectively permeable membrane
– determined by solute concentration on both sides of the cell
Chapter 4
11
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Osmosis is a type of passive transport
12
Copyright © by Holt, Rinehart and Winston. All rights reserved.Copyright © by Holt, Rinehart and Winston. All rights reserved.
There are three possibilities for the direction of water movement:
13
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Osmosis
Hypertonic solution– solute concentration
outside the cell is HIGHER THAN the cytosol
– there is a NET movement of water out of the cell.
– the cell shrinks.
Chapter 4
14
Copyright © by Holt, Rinehart and Winston. All rights reserved.
OsmosisHypotonic solution
– solute concentration outside the cell is LOWER THAN the cytosol
– there is a NET movement of water into the cell.
– the cell swells.
15
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Isotonic solution
– the solute concentration outside the cell is EQUAL TO the cytosol
– there is no NET movement of water.
16
Osmosis
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Compare
17
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Facilitated Diffusion
• Passive transport across the membrane using an embedded protein
18
Copyright © by Holt, Rinehart and Winston. All rights reserved. 19
Carrier proteins
bind to a specific substance on one side of the cell membrane,
carry the substance across the cell membrane, and release it on
the other side.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
• Ion channel
–a transport protein with a polar pore through which ions can pass.
20
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Movement Against a Concentration Gradient
• active transport– the transport of a substance across the cell
membrane against its concentration gradient. Energy is required.
21
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Comparing Active and Passive Transport
22
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Movement in Vesicles
• endocytosis – The movement of larger substances across the cell
membrane by vesicles.
23
Copyright © by Holt, Rinehart and Winston. All rights reserved. 24
Copyright © by Holt, Rinehart and Winston. All rights reserved.
exocytosis
the movement of a substance by a vesicle to the
outside of a cell
25