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57 terms

Membranes

1. Membrane: two meanings 2. Cell membrane: Overview 3. Membrane structure 4. Structural Membrane Proteins: Membrane-Spanning 5. Membrane Proteins that bind molecules 6. Transporter Proteins: Move Products Through Membrane 7. Membrane Proteins that Bind Molecules 8. Transport Proteins: Move Products Through Membrane 9. Membrane Carbohydrates: Form External Glycocaylx 10. Body Fluid Compartments 11. Overview of Movement Across Membranes 12. Diffusion: Passive & down a concentration gradient 13. C…
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Membranous tissues
layer of flattened cells supported by connective tissue
Cell Membrane (plasmalemma)
enclose cells and are formed by PL bilayer
Cell membranes provide?
1. Cell structure & support
2. Barrier isolates cell
3. Regulates exchange
4. Cell communication
Cell Membranes can consist of what types of molecules? (6 total)
Peripheral proteins
Glycoproteins
Glycolipids
Integral proteins
Cholesterol molecules
Phospholipids
Peripheral proteins are
- loosely attached to integral proteins
- anchors the cytoskeleton to the cell membrane
Integral proteins are
membrane spanning and tightly bound to the membrane
Membrana-Spanning proteins are
- many are ATPases
- non-polar or lipid soluble
- link/attach other molecules to Extracellular matrix
- Phosphorylation
Phosphorylation
break/release phospholipid group, change conformation
Membrane Proteins that Bind Molecules have what types activity? What is the function of receptors? What do they bind and what is the result of if?
Membrane associated enzymes --> Internal/External reactions
Receptor bind specific ligand and Ligand-receptor complex trigger intracellular response.
Name two types of Transport proteins?
Channel proteins and Carrier proteins
Channel proteins are
Open or Gated
Open - have gates but spent most time in the open state
Gated - usually closed, respond to chemical/ligand, mechanical, and voltage
Carrier proteins are
VERY SELECTIVE and never in open
bind to substrate
Slower transporters than channel proteins
Do NOT depend on ATP energy
Name two types of Body fluid? What are they made up of?
1. Intracellular (ICF)
2. Extracellular (ECF) made up of plasma and Interstitial
Movement Across Membranes requirements? (Two types) explain each?
1. Energy requirements are required by all, difference is in the type of energy
2. Physical requirements:
Simple diffusion - N/A
Facultative diffusion - channels
Secondary active transport - moving molecules based on the conc. gradient via primary active transport
Primary active transport - ATP
Diffusion (3 things to mention)
1. Passive & down a concentration gradient
2. Stops at equilibrium
3. Rate factors: membrane, temperature, distance, & size
Fick's law of Diffusion:
= (Surface Area Conc. gradient)/(membrane resistance thickness of membrane)
Membrane resistance =
lipid solubility/molecular size
Carrier Mediated Transport can be
Passive or Active
Name three types of CMTransport?
Uniport & Contransport (Antiport or symport)
Uniport carriers
transport only one kind of substrate
Symport carriers
move two or more substrates in the same direction across the membrane
Antiport carriers
move substrates in opposite directions
Facilitated Diffusion requires "_" and is "___"
uses transport proteins
passive diffusion to equilibrium
Name example of Facilitated Diffusion and elaborate? Give example of regulation with/with out insulin
Glut transport:
- found in most cells
- transports in/out of cell [down conc. gradient]
- several isoforms, some regulated by insulin/others not
Ex. Glut4-skeletal muscle- insulin regulated
Ex. Glut3-neurons-not insulin regulated
Primary Active Transport does what and why?
Pumps products
uses ATP to move molecules up conc. gradient
major function to create conc. gradient via unequal transfer of molecules across membrane
Secondary Active Transport uses
Kinetic Energy of [ion]
- Cotransports [ion] restored
- using ATP
- Na+ --> glucose secondary active transport (SGLT)
- Can only transport glucose into cells
--> Intestinal and kindney epithelial cells
Modulation of Protein Transport is
similar to enzyme activity
1) Specificity
2) competition
3) Saturation
Vesicles in Membrane Transport
- move particles
- large molecules
- Phagosome
- Phagocytes are cells that degrade bacteria
Vacuole Transport
Endocytosis and Exocytosis
Pinocytosis is non-selective
Receptor mediated: specific substrate
Transepithelial and Transcytosis
Cross two membranes, APICAL and BASOLATERAL (bottom)
Absorption
Secreation
Transepithelial
What transporters are used in moving glucose from gut lumen to extracellular fluid? Explain what they do and why?
SGLT = Na+ glucose symporter brings glucose into cell against its gradient using energy stored in the Na+ conc. gradient
GLUT transporter transfers glucose to ECF by facilitated diffusion.
Na+/K+ ATPase pumps Na+ out of the cell, keeping ICF Na+ conc. low.
Transcytosis
What type of transporters used in transfer of plasma proteins from blood plasma to Interstitial fluid? Explain?
1. Plasma proteins are concentrated in caveolae, which then undergo endocytosis and form vesicles.
2. Vesicles cross the cell with help from the cytoskeleton.
3. Vesicles contents are released into interstitial fluid by exocytosis.
About what % of body weight is water?
60
What % of water is intracellular?
67%
What % of water is extracellular? Of that, what % is plasma and what % is interstitial?
33%, 8%, and 25%.
% of water distribution varies? Give an example where would this be important?
slightly with sex and age; pharmacokinetics
Osmosis and Osmotic Equilibrium
- water freely crosses membranes
- Osmotic pressure (mmHg)
- Osmolarity
What is osmolarity? how does it differ from molarity?
Molarity = number of molecules/liter
Osmolarity = number of particles/liter
- different b/c molecules may dissociate)
What is osmolality?
solution measured in kg (1kg water = 1L water)
When comparing two solutions which terms are used to define them?
Isosmotic, Hyperosmotic, and Hyposmotic
Isosmotic
equilibrium
Hyperosmotic
greater than
Hyposmotic
less than
Tonicity
how does the solution affect cell volume
Always compare solution to a cell
Penetrating solute?
easily diffuse in/out of cell via simple diffusion
Non-penetrating solute
do not easily diffuse
Isotonic
solution in which no change in cell
Hypertonic
solution in which cell shrinks
Hypotonic
solution in which cell swells
Electrical Disequilibrium
separation of charged ions and electrical gradient
Separation of charged ions
membrane insulates
Potential: the electrical gradient is a form of Potential Energy
Conduction of signal
Electrochemical gradient
Extension of van't Hoff's equation
(delta)G = RT ln ([S]i/[S]o)
Nernst Equation
(delta)G = RT ln ([S]i/[S]o + zFE)
F = Faraday's constant (9.65 * 10^4 joules/volt-mole)
E = Membrane Potential
I = Ion
Equilibrium potential
the resting membrane potential difference at which the electrical gradient exactly opposes the K+ conc. gradient
Vm
Membrane Potential Difference
Depolarization
decrease in Vm over time
Repolarization
Vm restored over time
Hyperpolarization
increase in Vm over time