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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 are
- loosely attached to integral proteins
- anchors the cytoskeleton to the cell membrane
Membrana-Spanning proteins are
- many are ATPases
- non-polar or lipid soluble
- link/attach other molecules to Extracellular matrix
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.
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)
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
- 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?
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
Vesicles in Membrane Transport
- move particles
- large molecules
- Phagocytes are cells that degrade bacteria
Endocytosis and Exocytosis
Pinocytosis is non-selective
Receptor mediated: specific substrate
Transepithelial and Transcytosis
Cross two membranes, APICAL and BASOLATERAL (bottom)
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.
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.
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)
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)
When comparing two solutions which terms are used to define them?
Isosmotic, Hyperosmotic, and Hyposmotic
Separation of charged ions
Potential: the electrical gradient is a form of Potential Energy
Conduction of signal
Extension of van't Hoff's equation
(delta)G = RT ln ([S]i/[S]o)
(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
the resting membrane potential difference at which the electrical gradient exactly opposes the K+ conc. gradient
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