Lecture 5 Flashcards
Describe the polar structure of water, and explain how the formation of hydrogen bonds permits the dissociation of salts (such as NaCl), saccharides, and other polar molecules. Contrast the definitions of hydrophobic and hydrophilic related to water polarity.
water is polar: uneven electron distribution
more - towards O
more + towards H
H bonding allows salts to dissociate and form bonds with the H due to polarity
Describe the composition of a cell membrane. Diagram its cross section, and explain how the distribution of phospholipids and proteins influences the membrane permeability of ions, hydrophilic and hydrophobic compounds.
Polar head: hydrophilic
Non polar tails: hydrophobic
- lipid soluble molecules pass freely.
- non lipid/ charged: need channels or transporters
Using a cell membrane as an example, define reflection coefficient and partition coefficient, and explain how the relative permeability of a cell to water and solutes will generate an osmotic pressure. Contrast the osmotic pressure generated across a cell membrane by a
solution of particles that freely cross the membrane with that of a solution with the same osmolality, but particles that cannot cross the cell membrane.
Reflection Coefficient:
1: impermeable - osmotic pressure
0: permeable - no osmotic pressure
Partition coefficient: lipophilicity
= 1: equal
>1: lipophilic; permeable = no pressure
Contrast the following units used to describe concentration: mM, mEq/l, mg/dl, mg%. List the typical value and normal range for plasma Na+, K+, H+ (pH), HCO3-, Cl-, Ca+2, and glucose, and the typical intracellular pH and concentrations of Na+, K+, Cl-, Ca+2, and HCO3-.
mM: measure of mass but # of moles considered
mEq/l: measure of mass but charge considered
mg/dl: milligrams of material per 100 ml
of plasma
mg%: milligrams material % of volume
Differentiate between the terms osmole, osmolarity, osmolality and tonicity. List the typical value and normal range for plasma osmolality.
Osmole: measure of mass; osmotically active particles
Osmolarity: The number of osmotically active particles per kg water
Osmolality: The number of osmotically active particles per liter water
- Plasma Osmolality: 290 mOsm/L
Tonicity:
Describe the linear relationship between forces and flows (Ohm’s Law, Fick’s Law of diffusion, and the law of hydrodynamic flow).
Fick: linear relationship (ideal semi impermeable membrane)
Write Fick’s Law of diffusion, and explain how changes in the concentration gradient, surface area, time, and distance will influence the diffusional movement of a compound.
High to low conc
J = Px A (C1-C2)/ X
Conc gradient: higher gradient = more flux
SA: greater SA = more flux
Time: will eventually level out
Distance: more distance = less flux (exponential decay)
Based on the principle of ionic attraction, explain how a potential difference across a membrane will influence the distribution of a cation and an anion.
cation: + ion
anion: - ion
Charges ions have a hard time passing through membrane = create flux
cell is negatively charged= cations inside and anion out
Differentiate the following terms based on the source of energy driving the process and the molecular pathway for: diffusion, facilitated diffusion, secondary active transport, and primary active transport.
slide 42
Simple diffusion:
- down gradient
- move until equilibrium
- no net flux
- no concentration gradient
Facilitated Diffusion:
- down gradient
- show substrate specificity
- show saturation kinetics (Tm- transport max) i.e.: Glut2
Primary Active Transport: - protein is ATPase enzyme - driving force is the ATP hydrolysis ie: K-Na-ATPase (3 Na out and 2 K In ) H-ATPase Ca2+ H+ in stomach lumen
Secondary Active Transport:
use Na as exchanger/ antiporter or co-transporter
ie: exchanger: Na/Ca
ie: contransporter: Na/glucose
Describe how transport rates of certain molecules and ions are accelerated by specific membrane transport proteins (“transporter” and “channel” molecules).
Charged Ions + Large Molecules + Polar Ions
- need channels or transporters
- against gradient
Describe how energy from ATP hydrolysis is used to transport ions such as Na+, K+, Ca+2, and H+ against their electrochemical differences (e.g., via the Na+ pump, sarcoplasmic reticulum Ca+2 pump, and gastric H+ pump).
All are primary active transport.
ATP hydrolysis is the driving force for the ATPase enzyme to move these ions against the gradient.
Explain how energy from the Na+ and K+ electrochemical gradients across the plasma membrane can be used to drive the net “uphill” (against a gradient) movement of other solutes (e.g., Na+/glucose co-transport; Na+/Ca+2 exchange or counter-transport).
Na is the secondary active transport molecule. It allows the energy from the Na-K ATPase to drive the molecules either with Na out of the cell (co-transporters) or opposite way of Na (antiporters/ exchangers)
Understand the mechanisms and role of selective transporters for amino acids, neurotransmitters, and nutrients.
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Define the following properties of ion channels: gating, activation, and inactivation.
Gated: selective
Activation: Channel is open and allow ions through until reach saturation
Inactivation: do not allow ions through. The channel is closed.
Contrast the gating of ion selective channels by extracellular ligands, intracellular ligands, stretch, and voltage.
Ion selective channels: permeable to the ion; show saturation kinetics
Ligand gated: specific molecule binding site
Voltage gated: charge
Mechanosensitive gated: stretch
