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Diffusion is the ___ movement of material from a region of high concentration to ta region of low concentration.
What is lipid permeability determined by?
Partition Coefficient, molecular size, and polarity
What are the specialized protein channels that allow passive movement of water in membranes?
What is turgor?
Plant cells develop turgor in hypotonic solutions; cell walls prevent swelling.
In plant cells, plasmolysis occurs under what kind of solutions?
What are the 3 types of ion channels?
- 1. Voltage-Gated
- 2. Ligand-Gated
- 3. Mechano-Gated
The potassium channel is an example of what type of ion channel?
What is facilitated diffusion?
Large or hydrophillic substances require a facilitative transporter to cross membranes.
Facilitative diffusion is passive, specific, saturable, and regulated
An example of facilitated diffusion is glucose transporter. Explain
Gradient for glucose entery into cell is maintained by phosphorylation of glucose in the cytoplasm.
Insulin stimulates glucose uptake by causing the insertion into the cell membrane of vesicles containing performed glucose transporters.
What does active transport do?
Maintains gradients for potassium, sodium, calcium, and other ion across the cell membrane.
Also, couples the movement of substances against gradients to ATP hydolysis
Sodium Potassium Pump = Na+ / K+ ATPase Fact Slide
- - requires K+ outside, Na+ inside
- - inhibited by ouabain
- - The ratio of Na+ / K+ pumped is 3:2
- - The ATPase is a P-type pump, in which phosphorylation causes changes in conformation and ion affinity that allow transport against gradients
Which pumps use ATP, but are not phosphorylated during pumping.
Some archaebacteria use a protein called ____, which absorbs light energy to transport protons out of the cell.
What is contrasport
Coupling Active Transport to Existing Ion Gradients
What is secondary transport
The use of energy stored in an ionic gradient.
Several inherited disorders have been linked to mutations in genes encoding ion proteins channels. Cystic Fibrosis is an example.
- - genetic disease
- - abnormal fluid secretions from tissues
- - caused by a defective chloride channel
- - deletion in an ABC transporter (the CFTR polypeptide) with two nucleotide dependent regulatory sites
- - defect prevents normal insertion of the CFTR polypeptide into the membrane
What are neurons and what are its functions?
"Neurons are specialized cells for information transmission using changes in membrane potentials"
- -Dendrites receive incoming information
- -cell body contains he nucleus and metabolic center of the cell
- -the axon is a long extension for conducting outgoing impulses
- -most neurons are wrapped by myelin-sheath
Explain the Action Potential (AP)
- when cells are stimulated, voltage-gated Na+ channels open, triggering the AP and causing membrane depolarization
- Na+ channels are inactivated immediately following an AP, producing a short refractory period when the membrane cannot be stimulated
- excitable membranes exhibit all-or-none behavior
The speed of a neural impulse depends on axon ___
diameter and whether axon is myelinated
What is neurotransmission and how does it work?
- - presynaptic neurons communicate with postsynaptic neurons at a specialized junction, called the synapse, across a gap (synaptic cleft)
- - chemicals (nerotransmitters) released from the presynaptic cleft diffuse to receptors on the postsynaptic cell
- - bound transmitter can depolarize (excite) or hyperpolarize (inhibit) the postsynaptic cell
- - transmitter action is terminated by reuptake or enzymatic breakdown