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 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.
