Transcript 5.5 Transport
Movement across the Cell Membrane 2006-2007
Diffusion
Diffusion
movement from HIGH
LOW concentration
Down the concentration gradient What did it take to make the concentration gradient?
2006-2007 The concentration gradient stores potential energy
It takes energy to generate the gradient The process is still considered passive
3
Facilitated Diffusion
• Diffusion through protein channels – highly specific – passive process
HIGH
what sort of molecules will use this process?
LOW “The Bouncer”
Active Transport • Cells may need to move molecules
against
gradient concentration – conformational shape change transports solute from one side of membrane to other – protein “pump” – “costs” energy = ATP
LOW Once completed, where has the energy for the active transport gone? ATP HIGH “The Doorman”
Active transport • Many models & mechanisms
ATP ATP antiport symport
Getting through cell membrane • Passive Transport – Simple diffusion • nonpolar, hydrophobic molecules –HIGH LOW concentration gradient – Facilitated transport • polar, hydrophilic molecules • through a protein channel –HIGH LOW concentration gradient • Active transport – against concentration gradient • LOW HIGH – uses a protein pump (requires ATP)
ATP
Transport summary
simple diffusion facilitated diffusion active transport ATP
What about large molecules?
• Moving large molecules into & out of cell – through vesicles & vacuoles – endocytosis • phagocytosis = “cellular eating” • pinocytosis = “cellular drinking” – exocytosis
exocytosis
Endocytosis
phagocytosis pinocytosis receptor-mediated endocytosis fuse with lysosome for digestion non-specific process triggered by molecular signal
What about Osmosis?
• Diffusion of water from HIGH concentration of water to LOW concentration of water – across a semi-permeable membrane
Why does osmosis need a membrane?
Concentration of water • Direction of osmosis is determined by comparing total solute concentrations – Hypertonic - more solute, less water – Hypotonic - less solute, more water – Isotonic - equal solute, equal water
water hypotonic net hypertonic movement of water
Hypotonic , Hypertonic, Isotonic How does sugar concentration lead to water movement? 13
Let’s watch the video Which way would water move if oil was added to the left side of the tube?
Managing water balance • Hypotonic • Animal cell/protist cell problem?
• Solutions?
• Plant cells....
• turgid = full • cell wall protects from bursting
KABOOM! No problem, here freshwater
Managing water balance • Hypertonic • Animal cells: • How can they adjust:
I’m shrinking, I’m shrinking!
• Take up water or pump out solutes.
– plant cells • plasmolysis = wilt Why do people make beef jerky, and add syrup to preserve canned fruit?
I will survive! saltwater
Managing water balance • Isotonic – Animal cell problems: – none – solutes are equally concentrated on both sides of membranes
perfect!
– Plant cell problems – flaccid cells lose structure.
I could be better… balanced
Aquaporins • Water moves rapidly into & out of cells – evidence that there were water channels • protein channels allowing flow of water across cell membrane
Peter Agre John Hopkins Roderick MacKinnon Rockefeller
Which way will water move?
.05 M .03 M
Hey...watch this