Lecture 8 Flashcards
what method was use to move fluid and solutes from interstitial fluid into cells
- Diffusion
- facilitated diffsion
- active
- Co-transport
What move the fluid and solutes from blood to interstitial fluid
Bulk flow and Starling’ Forces
what are the different structures in the Plasma membrae
v Phospholipid bilayer
v Proteins
- Integral {full or partial) &
surface or peripheral
v Cholesterol
v Carbohydrates linked to
proteins & lipidsWhat is the fluid mosaic model
v Noncovalent assemblies
v Lipids & proteins move
around within the membrane
Are the internal and external layer similar
no, they are asymmetric
What are the movements for lipids
- Lateral diffusion
- Rotation
- Swing
- Flexion
- Transverse diffusion (flip flop)
Where are the position of Phospholipids
- Choline (external)
- Ethanolamine (internal)
- Serine (internal)
- Inositol (signalling)
Where are the position of sphingolipids
Sphingomyelin (external)
• Glycosphingolipids
• Associate
What is the role of cholesterol
determines
fluidity and permeability
• Within membrane
What is the membrane lipid made up of
- Phospholipids
- sphingolipids
- cholesterol
How does the membrane lipid tail length affect fluidity
Fluidity decrease with length due to increased van der waal interactions
How does the degree of unsaturation of fatty acids affect the membrane fluidity
It increases fluidity
How does cholesterol affect membrane fluidity
reduce fluidity
How does hydrophobic diffuse
Concentration gradient within membrane is greater, Diffuses quickly
How does hydrophilic diffuse
Hydrophilic (polar) substances in membrane are sparingly soluble
What are the 4 types of molecules that may permeate through the membrane
- Non polar molecules
- Small uncharged polar molecules
- Large polar molecules & ions
- Macromolecules
Does Non polar molecules pass through membrane
Pass freely e.g. fatty acids, steroid hormones, CO2, & O2 (acts as
non polar - linear)
Does small uncharged polar moleccules pass through the membrane
Pass freely but more slowly than non polar molecules e.g. H2O
Does large polar molecules & ions pass through properly
Don’t pass freely eg glucose, Na+ K+
Does macromolecules pass through the membrane
Don’t pass e.g. Proteins , polysaccharides, nucleic acids
What are some molecules cross the cell membrane in their non-charged form but not in their charged form
- base (eg ammonia =NH3)
- acid (eg formic acid = HCOOH)
What determine whether the substance is charged or not
pH
Are the integral membrane protein permanently attached to the membrane?
Yes
What are the types of integral membrane protein
1. Span entire membrane • once or multiple times • many a helices • Examples –voltage gated ion channels , hormone receptors eg insulin 2. Integral monotopic proteins • Examples enzymes -monoamine oxidase • Do not span the entire biological
How does Peripherally associated membrane
proteins attach to integral protein
often non-covalently bound
What are the functions of membrane protein
• Transport v Hydrophilic channel v ATP-pump • Enzyme functions v Active site exposed • Signal transduction v Receptors for external signals • Cell recognition v Molecules recognised by other cells proteins • Control adhesion v between cells and extracellular matrix • Cytoskeletal attachment v Microfilaments
How does simple diffusion function
• Down a concentration or electrical gradient v Through membrane v Through pores – integral cell membrane channel eg aquaporin for water v Through protein channels – selectively permeable, may be gated, eg ion channels
How does facilitated diffusion function
• Down a concentration or electrical gradient
v Carrier mediated - need integral membrane
protein
v Transporter is specific for the molecule
v Rate limited by binding and conformational
change in carrier protein; eg glucose, amino
acids
How does active transport function
• Up a concentration or electrical gradient
v Carrier mediated and energy dependent
What are the type of simple diffusion
• open or closed
• “gated”.
• Rate of movement is limited by the
rate of diffusion
Types of gated ion channels
• voltage-gated, e.g. Na+ or K+ (specific channel for each) • Chemical or ligand-gated, e.g. acetylcholine • mechanically-gated, e.g. sound waves in inner ear open ion channels
What are the Ion movement via transport protein affected by
- Concentration gradient
2. Electrical gradient
What is the nernst equation
Ex= Equilibrium Potential for x (or electromotive
force preventing further diffusion)
• Value is the membrane voltage for ion to be in
equilibrium
• = (61mV/charge) x log10 (internal
concentration/external concentration)
What is the nerve cell transmission activated by
• Electrical stimulation (action potential)
• Chemical stimulation (neurotransmitter) eg
acetylcholine
What is Epilepsy and tinnitus
Overly excited nerves
Voltage-gated K channels usually open to regulate
nerve signals
Remain closed in epilepsy and tinnit
What is
• Hyperkalemic Periodic Paralysis in horses
(muscle weaknes
Genetic defect in voltage-gated Na channels of muscle
cells
Channels remain open
Results in muscle weakness and co
Where are the ion channels gated at
Some ion channels are gated by
extracellular ligands; some by
intracellular ligands.
What are some external ligands
- Acetylcholine (ACh)
n - Gamma amino butyric acid
What is Gamma amino butyric acid
BA) Binding at certain synapses in the central nervous system Admits Cl- ions into the cell Inhibits the creation of a nerve
What is Acetylcholine (ACh) ion channel
• Ionotropic receptor Nicotinic Ach receptor Opens Na+ ion channel Depolarization • Metabotropic receptor Muscarinic receptor Opens K+ ion channel Hyperpolari
What is Gamma amino butyric acid
BA) Binding at certain synapses in the central nervous system Admits Cl- ions into the cell Inhibits the creation of a nerve
What are the traits of ion channels
- Traverse the
membrane - Ion selective
- Gated
What are the Different mechanisms for
activating the ion gates
- Voltage-gated
- Ligand-gated
- Intracellular
messengers-gated - Mechanically-gated
• Stretch
• Sound waves
What does pump protein do
against
concentration/electrical
gradients
What does gate channels do
with
concentration/electrical
gradients
What are symporters
• Na+ ions flow down their concentration gradient
• Glucose co-binds with Na – transported up the
glucose concentration gradient.
(In most cells: glucose also goes down its concentration
gradient and uses a simple uniporter)
What are antiporters
• Substances are transported in opposite directions
• Electrochemical gradient for Na+ drives H+ or
Ca++ in in the opposite directio
What is a uniporter
only a single ion is transported at a time
what is a example of symporter
(Na /amino acids+)
What is an example of an antiporter
( Na+/ H+ )
What are the secondary “active” trnsport
symporter and antiporter
Simple
diffusion -
membrane
H2O
O2
CO2*
Simple
diffusion -
pore
H2O
aquaporin
Where does active transport happen along the epithelial sheet?
one side of the cell
Where does simple or facilitated diffusion happen along the epithelial sheets?
On other side of the active transport side
What is the function of pinocytosis
• Large molecules and particles require specialised processes to cross the plasma membrane - endocytosis • Molecules and particles are engulfed into intra-cytoplasmic vesicles • Endocytosis requires energy
Does endocytosis require energy
yes
What are the three types of endocytosis
1 Non-receptor mediated pinocytosis
2 Receptor mediated
endocytosis
3 Phagocytosis
Non-receptor mediated pinocytosis
Continuous nonspecific uptake of extracellular fluid and small dissolved molecules 1. Vesicle buds off from plasma membrane 2. Vesicle transported intact, releasing contents to exterior by exocytosis or fuses with a lysosome 3. Membrane components recycled to the plasma membrane
Receptor mediated
endocytosis
vVia clathrin–coated pits in epithelial and phagocytic cell membranes • Pits contain integral protein receptors for molecules being endocytosed vVia caveolin-coated pits (Caveolae) in cell membranes of vascular endothelial cells and adipocytes • Transport of albumin • Folate receptor
Phagocytosis
• Endocytosis of large particulate matter such as microorganisms or cell debris • Receptor-mediated • Carried out by specialised phagocytic cells • Immune-related 1. Microbe recognised by receptor 2. Phagosome forms 3. Phagosome fuses with lysosome (phagolysosome) 4. Microbes killed by proteolytic enzymes, reactive oxygen species (ROS) and nitric oxide (NO)
