Cell basics + membrane phisiology Flashcards
What is the % of proteins in the cell and what types of proteins can be found?
10 to 20 percent of the cell mass
Two types of protein: structural proteins (provide cytoskeletons) and functional proteins (mainly enzymes of the cell).
Mention some examples of repetitive self-induced discharges?
Most smooth muscle and nervous system, like rhythmical heart beat, rythmical intestinal peristalsis and neuronal events.
How does voltage gating work?
It responds to the electrical potential across the cell membrane.
A strong negative charge on the inside of the cell membrane could presumably cause the outside sodium gates to remain tightly closed; conversely, when the inside of the membrane loses its negative charge, these gates would open suddenly and allow sodium to pass inward through the sodium pores.
What is the difference between integral proteins and peripheral proteins?
Integral proteins provide channels (pores) through which water and water-soluble substances (ions), can diffuse between the extracellular and intracellular fluids.
They also act as carrier proteins, sometimes even in the direction opposite to their electrochemical gradients (active transport).
Peripheral proteins are often attached to the integral proteins and function almost entirely as enzymes or as controllers of transport of substances through the cell membrane “pores.”
Describe the action potential stages:
Resting stage -
Depolarization stage -
Repolarization stage -
Resting stage - Is the resting membrane potential before the action potential begins. The membrane is “polarized” during this stage.
Depolarization stage - The membrane suddenly becomes permeable to sodium ions, allowing positively charged ions to diffuse to the interior of the axon. The “polarized” state is neutralized with the potential rising rapidly in the positive direction (depolarization).
Repolarization stage - The membrane becomes highly permeable to Na, the Na channels begin to close and the K channels open to a greater degree than normal. Then, rapid diffusion of K ions re-establishes the normal negative resting membrane potential (repolarization).
In the nerve fibers …
What is the difference between large and small fibers?
Large fibers are myelinated and small fibers are unmyelinated
Mention the 3 types of lipids in the cell membrane.
Which one is the most common?
Phospholipids, sphingolipids, and cholesterol.
Phospholipids are the most abundant of the cell membrane lipids.
What are the phases of mitosis and decribe them.
- Prophase - (A, B, C) - chromosomes of the nucleus become condensed into well-defined chromosomes
- Promethaphase - (D) - growing microtubular spines of the aster fragment the nuclear envelope. The tubules then pull one chromatid of each pair toward one cellular pole and its partner toward the opposite pole.
- Methaphase - (E) - the two asters are pushed farther apart and interdigitate with each other to form the mitotic spindle. Simultaneously, the chromatids are pulled by their attached microtubules to center, lining up to form the equatorial plate of the mitotic spindle.
- Anaphase - (F) - the two chromatids of each chromosome are pulled apart at the centromere and 46 pairs of chromatids are separated forming 2 separate sets of 46 daughter chromosomes.
- Telophase - (G, H) - the two sets of daughter chromosomes are pushed completely apart. The mitotic apparatus dissolutes, and a new nuclear membrane develops around each set of chromosomes.
A plateau occurs in some action potentials due to:
a. Failure of fast sodium channels
b. Slow calcium-sodium and potassium channels
c. Slow sodium and potassium channels
d. Slow closure of inactivation gates
b. Slow calcium-sodium and potassium channels
What is osmotic pressure?
The amount of pressure required to stop osmosis (osmotic pressure of the sodium chloride solution).
Name the organelles and structures of the cell
Oxygen reacts with _________, __________, and ________ to release energy for the cells.
carbohydrate, fat and protein
The membrane potential that prevents net diffusion of an ion in either direction through the membrane is called the _______.
a. Potassium diffusion potential
b. Sodium diffusion potential
c. Nernst potential
d. Goldman potential
c. Nernst potential
Mention examples of positive feedback.
Blood clotting. When a blood vessel is ruptured and a clot begins to form, clotting factors are activated within the clot. Some act on other unactivated enzymes causing more blood clotting. The process continues until the hole in the vessel is plugged and bleeding no longer occurs. Other examples include birthing and stimulation of a nerve fiber.
At the secretory side of the gastric gland cells the hydrogen ion concentration is increased as much as a ________ -fold.
a. Hundred
b. Thousand
c. Hundred-thousand
d. Million
d. Million
Where are baroreceptors located and how do they work to regulate blood pressure?
Found at the walls of the bifurcation region of the carotid arteries and in the arch of the aorta in the thorax. They are stimulated by stretch of the arterial wall. When pressure rises too high, nerve impulses are send to the medulla of the brain. They inhibit the vasomotor center, decreasing the impulses through the sympathetic nervous system to the heart and blood vessels, diminishing pumping activity by the heart and dilation of the peripheral blood vessels. A decrease in arterial pressure below normal relaxes the stretch receptors.
Mention 2 examples of negative feedback.
Carbon dioxide. When high it decreases the concentration toward normal, which is negative to the initiating stimulus. Blood pressure is regulated also by negative feedback.
The sodium-potassium pump:
a. Pumps 3 sodium ions out and 2 potassium ions into the cell
b. Pumps 2 sodium ions out and 3 potassium ions into the cell
c. Pumps 3 sodium ions into and 2 potassium ions out of the cell
d. Pumps 2 sodium ions into and 3 potassium ions out of the cell
a. Pumps 3 sodium ions out and 2 potassium ions into the cell
What are the two types of cell membrane proteins?
Integral proteins (protrude all the way through the membrane) and peripheral proteins (attached only to the surface)
Mention 3 features of the α subunit.
- It has three binding sites for sodium ions on the portion of the protein that protrudes to the inside of the cell.
- It has two binding sites for potassium ions on the outside.
- The inside portion of this protein near the sodium binding sites has adenosine triphosphatase (ATPase) activity.
Primary active transport of hydrogen ions occurs:
a. Proximal tubule cells and the parietal cells of the gastric glands
b. Peptic cells of the gastric glands and the cortical collecting ducts of the kidney
c. Parietal cells of the gastric glands and the late distal tubules
d. Parietal cells of the gastric glands and the proximal tubule cells
c. Parietal cells of the gastric glands and the late distal tubules
Explain the difference between the absolute and relative refractory periods.
Absolute refractory period means that no stimulus can generate an action potential. Relative refractory period occurs after the absolute refractory period and a stronger than usual stimulus can elicit an action potential.
Mention the intercellular fluid components (ions)
KMP
K - Potassium
M - Mg - Magnesium
P - Phosphate ions
In myelinated fibers, action potentials occur:
a. All along the myelin sheath
b. Only at the nodes
c. At the nodes and in limited capacity along the myelin sheath
d. Between the nodes
b. Only at the nodes
Mention the extracellular fluid components
NaClBi, sugar, fat, aa, Os and COs
Na - Sodium
Cl - Chloride
Bi - Bicarbonate
And nutrients:
Sugar - glucose, fat - fatty acids, aa - amino acid, Os - oxygen and COs - carbon dioxide
In the action potential… How low does Ca concentration needs to fall before spontaneous discharge occurs? And what does it cause?
Only 50% below normal and it causes muscle tetany
The osmotic pressure exerted by particles in a solution is determined by the_____.
a. Mass of the particles
b. Number of particles per unit volume
c. Types of particles per unit volume
d. Electrical charge of particles
b. Number of particles per unit volume
A deficit of calcium ions causes:
a. Potassium channels to become opened more easily
b. Sodium channels to become opened more easily
c. Sodium-potassium pumps to be less efficient
d. Calcium channels to be more active
b. Sodium channels to become opened more easily
How does chemical (ligand) gating work?
Gates are opened by the binding of a chemical substance (a ligand) with the protein, which causes a conformational or chemical bonding change in the protein molecule that opens or closes the gate.
The repolarization process is speeded by:
a. Opening of the potassium channels
b. Increase in sodium entry into the cell
c. Opening of the activation gate
d. Opening of the inactivation gate
a. Opening of the potassium channels
What is the Nersnts potential?
The diffusion potential level across a membrane that exactly opposes the net diffusion of a particular ion through the membrane.
What causes the plateau in the action potential?
When the excited membrane does not repolarize immediately after depolarization (the potential remains on a plateau near the peak of the spike potential for many milliseconds, and then repolarization begin)
In heart muscle, the voltage-activated sodium channels, and the voltage-activated calcium-sodium channels. The prolonged opening of the slow calcium-sodium channels is largely responsible for the plateau portion of the action potential.
A second factor is that the voltage-gated potassium channels are slower to open than usual, often not opening until the end of the plateau, delaying the return of the membrane potential toward its normal negative value. The plateau ends when the calcium-sodium channels close and permeability to potassium ions increases.
Spontaneous discharge or “tetany” occurs when calcium ion concentration falls to:
a. 30% below normal
b. 15% below normal
c. 20% below normal
d. 50% below normal
d. 50% below normal
The resting membrane potential of spontaneous rhythmic cells is:
a. -50 to -60 mV
b. -80 to -85 mV
c. -60 to -70 mV
d. -65 to -75 mV
c. -60 to -70 mV
A negative charge of -4 millivolts inside the cell membrane is caused by the:
a. Sodium diffusion potential
b. Membrane permeability
c. Electrogenic nature of sodium-potassium pump
d. Potassium diffusion potential
c. Electrogenic nature of sodium-potassium pump
Conduction of the nerve impulse in the myelinated nerve fiber is accomplished almost entirely by ion conduction through:
a. Voltage-gated potassium channels
b. Voltage-gated calcium-sodium channels
c. Sodium-potassium pumps
d. Voltage-gated sodium pumps
d. Voltage-gated sodium pumps
Hydrogen counter-transport occurs especially in:
a. Late collecting tubules
b. Proximal tubules
c. Distal tubules
d. Intercalated cells
b. Proximal tubules
Calcium counter-transport occurs with:
a. Calcium moving into the cell and sodium out
b. Sodium moving into the cell and calcium out
c. Calcium moving into the cell and potassium out
d. Potassium moving into the cell and calcium out
b. Sodium moving into the cell and calcium out
Sodium co-transport of glucose and amino acids occurs in the:
a. Epithelial cells of the intestine and renal tubules of the kidney
b. Myelin sheath membrane and intestinal epithelium
c. CNS neural tissue and renal tubules of kidney
d. Renal tubules of kidney and cardiac myocytes
a. Epithelial cells of the intestine and renal tubules of the kidney
The equation used to calculate the diffusion potential when the membrane is permeable to several different ions is ________.
a. Nernst equation
b. Net diffusion equation
c. Multivalent diffusion equation
d. Goldman-Hodgkin-Katz equation
d. Goldman-Hodgkin-Katz equation
What is the difference between primary and secondary active transport?
Mention examples of both.
Primary active transport.- The energy is derived directly from breakdown of adenosine triphosphate (ATP) or some other high-energy phosphate compound.
Ex - Na-K pump, Hidrogen pump and Ca pump
Secondary active transport.- The energy is derived secondarily from energy that has been stored (in ionic concentration differences between the two sides of a cell membrane), created originally by primary active transport.
Ex - Co-transport of glucose and aminoacids with Na, Sodium-calcium counter-transport (with Na moving into the cell and Ca moving out; both are bound to the same transport protein).
One of the most important functions of the sodium-potassium pumps is:
a. Maintain cell membrane integrity
b. Maintain normal cell volume
c. Co-transportation of amino acids
d. Co-transportation of glucose
b. Maintain normal cell volume
What are the stages of the action potential?
Resting stage, depolarization and repolarization stage.
What are the 2 types of transport through the cell membrane and how are they different?
Diffusion and active transport.
Diffusion means random molecular movement of substances molecule by molecule, either through intermolecular spaces in the membrane (simple difussion) or in combination with a carrier protein (facilitated difussion).
Active transport means movement of ions or other substances across the membrane in combination with a carrier protein. The carrier protein causes the substance to move against an energy gradient (from a low-concentration state to a high-concentration state).
What are protein channels?
They are tubular pathways that connect extracellular and intacellular fluid. They are composed of integral cell membrane proteins that form open tubes that always open.
Protein channels are distinguished by two important characteristics: (1) Often selectively permeable to certain substances
(2) Many can be opened or closed by gates regulated by electrical signals (voltage-gated channels) or chemicals that bind to the channel proteins (ligand-gated channels).
Mention 3 important features of the Na+-K+ pump.
- One of the most important functions is to control the volume of each cell.
- The carrier protein is a complex of two separate globular proteins (a larger one - α subunit and a smaller one - β subunit).
- When two K ions bind on the outside and three Na ions bind on the inside, the ATPase function becomes activated.
Saltatory conduction through myelinated nerves is beneficial because of:
Increased velocity and energy conservation
