Membranes

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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 1…

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

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