HP exam 1

Cell membrane- Tonicity

the amount of solute dissolved in a solution

Isotonic

solution with equal solute concentration as another solution

hypotonic

less concentrated than inside the cell

water enters causing the cell to swell or even rupture(lysis)

hypertonic

more concentrated than inside the cell

water leaves, causing cells to shrink

What is blood hypertonic to?

other cells and water

What does tonicity always need?

A comparison to something else

Where is the concentration of bodily fluids tightly regulated at?

the kidneys

What fraction of total body water is within cells(intracellular water)

2/3

What is the remaining 1/3 of water of the whole body called?

extracellular water

What fraction of ECW is in blood plasma?

1/3

Outside of blood plasma, where is the remaining fraction of ECW located?

2/3 is in the spaces between cells(interstitial fluid)

In terms of Na and K, compare and contract them in intracellular and extracellular water

Intracellular water has more K than extracellular water

Extracellular water has more Na and Cl than intracellular water

Donnan Equilibrium

Donnan equilibrium is the uneven distribution of charged particles (ions) on either side of a semipermeable membrane.

Do animals have more positive or negative charged proteins

negative

Examples of bases that cannot go through the non-permeability layer of intracellular solutes

-DNA

-Negatively charged amino acids.

What ion is mostly in intracellular fluid and how much is there?

K ; 55mM/L

What ion is mostly in extracellular fluid and how much is there?

Na ; 145 mM/L and Cl; 120mM/L

What the inverse concentrations of the ions

Na; 12mM/L and Cl ; 4mM/L and K ; 4mM/L

What is active transport

transport using ATP

What is facilitated diffusion

Facilitated diffusion is the passive transport of molecules or ions across a biological membrane down their concentration gradient, assisted by specific transmembrane proteins.

What is diffusion

The net physical movement of atoms, molecules, or ions from a region of higher concentration to a region of lower concentration using NO ENERGY

What type of transportation does the sodium/potassium pump use

Active transport.

What is the ratio of Na in : K out

3:2

What are the steps of the Na/K pump

1. Sodium Binding: Three intracellular sodium ions (Na⁺) bind to the pump from inside the cytoplasm.(Sodium is freely moving and happens to attach)

2. ATP Phosphorylation: A molecule of ATP transfers a phosphate group to the pump, providing the necessary energy for the shape change.

3. Conformational Change (Outward): Phosphorylation alters the pump's shape, opening it to the exterior of the cell and releasing the sodium ions into the extracellular fluid.

4. Potassium Binding: The new shape exposes two extracellular binding sites, allowing two potassium ions (K⁺) from outside the cell to attach to the pump.

5. Phosphate Release: The attachment of potassium ions triggers the release of the phosphate group from the pump.

6. Conformational Change (Inward): Without the phosphate group, the pump returns to its original shape, releasing the potassium ions into the cell's cytoplasm and resetting the cycle for the next batch of sodium.

Where is Na/K-ATPase located?

Surface of almost all cells

Why does Cl not try to go through the membrane

Because it’s in Donnan equilibrium

Why does blood cells not use Na/K pump

• it has proteins

• it throws off Na/K pump because of extra negative charge

What is secondary active transport?

Secondary active transport is the movement of a substance across a cell membrane against its concentration gradient, powered by the potential energy of an existing ion gradient rather than direct ATP use.

What are membrane potentials

The potential current flow across the cell membrane IF the barrier of the membrane is removed

What is MP a direct result of?

Unequal distribution of electrical charges across membrane. (Think of Donnan Equalibrium)

Where is MP present at?

ALL cells

How much charge does MPs have

70mV

What are MPs also called

Resting potentials(RMP)

What is dynamic equilibrium

answer this later

Why can’t Na/K be predicated

Because they are ions and respond to the electrical gradients

what is the nernst equation

The Nernst equation calculates the electrical potential (voltage) across a cell membrane at which an individual ion is in equilibrium (i.e., its concentration gradient is perfectly balanced by the electrical gradient).

What is Equilibrium potential

The equilibrium potential (also known as the Nernst potential) is the exact electrical charge difference across a cell membrane that perfectly balances the concentration gradient of a specific ion, resulting in no net movement of that ion.

What does the Nerst Equation predict

Equilibrium potential for each ion

What is the nernst equation

What is the EP for the ions

Na → +65mV

K → -96mV

Cl → -70mV

What is the GHK equation(definition)

The Goldman-Hodgkin-Katz (GHK) equation is a foundational formula in physiology used to calculate the resting membrane potential of a cell. Unlike the Nernst equation, which only accounts for a single ion, the GHK equation determines the overall membrane potential by factoring in the concentration gradients and relative membrane permeabilities of multiple ions simultaneously.

What is the GHK equation

Which ion moves freely during resting potential

K

What does the Dendrites of a neuron do

Collect electrical signals

What does the cell body of a neuron do

integrates incoming signals and generates outgoing signal to axon

What does the Axon of a neuron do

Passes electrical signals to dendrites of another cell or to an effector cell

anterograde vs retrograde transport

Anterograde transport is the movement of molecules and organelles away from the cell body (e.g., toward the axon terminal). In contrast, retrograde transport is the movement of materials toward the cell body (e.g., from the synapse back to the soma).

What are depolarizations