Exam 2 Flashcards
Membrane protein functions
-Transport (stuff in and out of cell)
-Enzymatic activity (activity between enzymes)
-Signal transduction (signaling molecules and receptors)
-Cell-cell recognition (hey this is me)
(Ex: HIV can only enter in cell if CD4 proteins and co-receptor CCR5 are there (needs coreceptor to recognize))
-Intercellular joining (combine two cells)
-Attachment to cytoskeleton (stability of cell)
Diffusion
movement from [high] to [low]
Osmosis
-Movement of water through membrane from [high] to [low]
-moves through aquaporins
-passive transport
Isotonic
Solution around cell has same solute concentration
Hypotonic
Solution around cell has lower solute concentration, so water moves into cell
Hypertonic
solution around cell has higher solute concentration, so water leaves cell
Equilibrium
net movement of molecules is the SAME on both sides of the membrane
Selective Permeability
small hydrophobic molecules move the fastest through membranes (hydrophilic molecules have a hard time passing across because they are hydrophilic like the exterior of the membrane, so have a hard time passing through)
Types of Transmembrane Proteins
Channel and Carrier proteins
Channel proteins
- passive transport only
-hydrophilic pores
-may be gated to control diffusion
Types of gated channel proteins
-Ligand
-Electrically
-Mechanically
Carrier proteins
-specific binding of a solute
-slower than channel proteins
-passive or active transport
-can be fully saturated
Passive Transport
- no energy required
-[high] to [low]
-driving force is electrochemical gradient
-channel and carriers
Active transport
- requires energy like ATP
-[low] to [high]
-only by carriers
-can create an electrochemical gradient
Symport
molecules move through in same direction
Antiport
molecules move through in different direction
Primary active cotransport
-energy put in to actively move two substances across membrane
-Ex: Na+/ K+ ATPase Pump
-creates gradient
Secondary active cotransport
-fueled by gradient
-Ex: secondary active glucose pump to pump glucose from [low] to [high]
Bulk transport definition and types
Moves large molecules
Types:
-Phagocytosis: cell engulfs food
-Pinocytosis: cell engulfs fluid
-Receptor-Mediated Endocytosis: ligands bin to receptors to bring in specific molecules
Juxtacrine signaling
adjacent cell signaling
Paracrine signaling
nearby cell signaling
Synaptic signaling
electrical signal triggers release of neurotransmitter
Endocrine signaling
distant cells (bloodstream)
cell response
change in cellular activity:
-gene expression
-enzyme activity
-cell division
-cytoskeletal structure
-motor activity
Lipid-soluble signals
-hydrophobic- so can move through membrane
-binds to intracellular signals
-commonly steroids, thyroid hormone, NO
Water soluble signals
-hydrophobic
-needs help of receptors
-activates signal transduction pathway
Ligand-gated ion channel
ACh (signal) molecule binds to gated channel to allow Na+ through
G protein- coupled receptor
signal binds to receptor to dissociate G-protein and then activate effector protein that starts cell responses
Enzyme linked receptor
Insulin links to insulin receptor, which then binds phosphates to insulin receptor inside cell and carries out cellular responses
Phosphorylation
addition of a phosphate group to a molecule or ion
-protein kinase adds
-phosphatase removes
Second Messenger
-carry instructions from first messenger throughout cell
-most important is cAMP
G-protein –> adenylyl cyclase –> cAMP –> protein kinase A –> cellular response
Signal Transduction Pathway
-reception
-transduction
-cellular response
Amplification
small signal= large response
Regulation/ specificity
Cells responds to same signals differently
Ex: epinephrine in heart increases rate, but relaxes smooth muscle
Termination
-cell responses are limited
-balances kinase and phosphatase activities
Reduction
gaining electron
Oxidation
losing electron
reducing agent
gets oxidized
makes other molecule get reduced
oxidizing agent
gets reduced
makes other molecule get oxidized
Electrons move with what ion?
Hydrogen ions!