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AP Bio- Cells 4: Transport
Transcript of AP Bio- Cells 4: Transport
Movement of material from [High] to [Low]
No energy required
Chemistry must be Considered
A Free Ride
The passive transport of molecules across a semi-permeable membrane
The Diffusion of water (opposite direction to solute)
Movement of material from [Low] to [High]
Energy is required
All other things being equal:
Tonicity is Important
Must Use A Protein! (Why?)
How does the cell control what is transported at the cell membrane?
Why is transport of materials between the cell and its environment necessary for life?
How does the environment influence living systems?
How do cells exist within the confines of the Laws of Thermodynamics?
Diffusion is inescapable (as long as you can fit through the membrane).
Diffusion is an emergent & inescapable property of large concentrations of constantly moving molecules
What can diffuse through the bi-layer?
What does all the other stuff do?
aquaporins and ion channels
Channels and Carrier proteins control the diffusion of charged and polar molecules
How can you "control" diffusion?
What's Happening Here?
What's Happening Here?
The Sodium Potassium Pump:
Can't Have A Nervous System Without Them!
ATP Fills The Energy Reqirement
Phosporylation Triggers a Conformational Change!
Tonicity is a relative measure of solution concentration
The tonicity of a cell's environment has serious consequences for the cell
Tonicity as it effects plant and animal cells.
Explain all situations shown!
Circles indicate homeostatic condition
Which way does sucrose go?
What if it can't?
The contractice vacuole of a paramecium is an adaptation for living in an environment that is hypotonic compared to the cell
Different osmoregulatory adaptations in salt-water and fresh-water fish
Moving Big Stuff
Intake of large molecules.
"Cell being picky"
Release of large cellular products into outflow
Make Sure You Can
Explain how the consequences of the second law of thermodynamics allow diffusion to occur in the universe without an input of energy.
Compare passive and active transport.
Compare facilitated and simple diffusion.
Compare diffusion of a solute with osmosis of water.
Determine the tonicity relationships when given the concentrations of solutes of multiple solutions.
Predict the movement of specific molecules when given information about their relative concentrations and the characteristics of a given semi-permeable membrane.
Explain why animals and plants have evolved adaptations to survive in solutions of different toncities.
Predict the effect of altering tonicity on a plant or animal cell.
Compare exocytosis and endocytosis.
Explain the purposes and processes of the different modes of endocytosis employed by the cell.
Primary Active Transport:
Secondary Active Transport:
Direct hydrolysis of ATP
Ion concentration, not ATP directly, is the driving force
Ex: Na+/K+ pump, an integral protein, pumps out 3 Na+ and brings in 2 K+
Ex: Na/K, Na establishes a gradient outside of the cell, movement of Na back into the cell allows glucose to come in
This is absorb into the bloodstream from the digestive tract
Occurs in endothelial layer of cells to take up dissolved substances from blood
Uses integral proteins as receptors to bind to ligands
Ex: Cholesterol is taken up by liver cells and packaged as LDL and moved to the bloodstream.
Lack of receptors LDL builds up in arteries
Cells then take up the LDL and utilize it
1. Enzyme release from the pancreas
3. Plant cell wall build up
Signal Transduction Pathway
May be physical signals; light, heat
May be chemical signals; hormones, ligands
Mode of Delivery
Autocrine- affect the cells that release the chemical
Ex: Tumor cells will release division signals that bind directly to them
Paracrine- affect nearby cells
Hormones- circulate via the bloodstream
Step 1: Reception
Step 2: Transduction/Integration
Step 3: Response/Expression
3D shape alteration due to binding of signal/ligand somewhere other than active site
Ion gated channels
Two Types of Receptors
Cytoplasmic- non-polar molecules diffuse into cell and bind
Membrane- polar molecules can't cross the membrane
3 types of plasma membrane receptors:
1. Ion channels- Na+/K+/Ca2+/Cl-
2. Protein kinases
3. G protein linked
Ion gated channel
Ex: Na+ channels in skeletal muscle are opened by a neurotransmitter, acetylcholine, to result in muscle contraction
Ex: Insulin binds to protein kinases activating them and phosphorylating a target protein
G-proteins bind to receptors on the cytoplasmic side after outside signal arrives
Ex: Liver cells responding to epinephrine to breakdown stored glycogen into sugars
Discovery of secondary messengers
Ex: cAMP; amplifies the signal in the cytoplasm by non-covalently binding to enzymes and activating them