unit 2 week 1 Flashcards

Question

What is influx?

Answer 1

Influx is the movement of substance into the cell.

Answer 2

Efflux is the movement of substance out of the cell.

Answer 3

a spontaneous process in which a substance moves from a region of high concentration to a region of low concentration, eventually eliminating the concentration difference between the two regions

Answer 4

how far away a state is from equilibrium

Answer 5

the concentration is equal on both sides of the membrane

Answer 6

how different the concentration is on the two sides of the membrane

Answer 7

Where delta G is the free-energy change (Section 3.1), R is the gas constant, T is the absolute temperature, and [Ci]/[Co] is the ratio of the concentration of the solute on the inside (i) and outside (o) surfaces of the membrane. *KNOW BETTER HOW IT WORKS

Answer 8

An electrochemical gradient is the combined effect of: Chemical gradient – The concentration difference of an ion across a membrane. Electrical gradient – The charge difference (voltage) between two compartments. Both gradients influence the movement of electrolytes (charged solutes) across membranes.

Answer 9

Ions repel like charges → It is unfavorable for an ion to move into a compartment with the same charge. Ions are attracted to opposite charges → Movement is favored when the ion enters a compartment with opposite charge. The greater the voltage difference, the greater the free-energy change for ion movement.

Answer 10

The free-energy change for an electrolyte moving across a membrane is:

Answer 11

Example: Na+ is 10 times more concentrated outside the cell than inside. The cell membrane voltage is about -70mV. This means Na+ has a strong drive to enter the cell due to both its chemical and electrical gradients. The total free-energy change for Na+ entry = -3.1 kcal/mol, meaning Na+ diffusion is highly favorable.

Answer 12

K+ is more concentrated inside the cell. The chemical gradient favors K+ leaving the cell. However, as K+ leaves, the inside of the cell becomes more negative, creating an electrical gradient that pulls K+ back in. This opposing effect is important in membrane potential and nerve impulses (discussed in Section 4.7).

Answer 13

1. The substance must be present at higher concentration on one side of the membrane than on the other. 2. The membrane must be permeable to the substance.

Answer 14

The partition coefficient is the ratio of a substance's solubility in a nonpolar solvent to its solubility in water.

Answer 15

The size of the compound; smaller compounds tend to penetrate quicker than larger ones.

Answer 16

Membranes are semipermeable because of the difference in penetrability of water vs solutes; water is more penetrable.

Answer 17

Osmosis is the process of moving from lower solute concentration to higher concentration. -water undergoes this process

Answer 18

A hypertonic solution is a compartment with higher solute concentration.

Answer 19

A hypotonic solution is a compartment with lower solute concentration.

Answer 20

It rapidly gains water by osmosis and swells.

Answer 21

It rapidly loses water by osmosis and shrinks.

Answer 22

the difference between the solute concentrations inside the cell and in the extracellular medium

Answer 23

Isotonic refers to when the internal solute concentration equals the external solute concentration, resulting in no net movement of water into or out of the cells.

Answer 24

Plasmolysis is the shrinkage that occurs when a plant cell is placed into a hypertonic medium; its volume shrinks as the plasma membrane pulls away from the surrounding cell wall.

Answer 25

False -is this the correct explanation? [:They are semi-permeable, which means that some molecules can diffuse across the lipid bilayer but others cannot. Small hydrophobic molecules and gases like oxygen and carbon dioxide cross membranes rapidly. Small polar molecules, such as water and ethanol, can also pass through membranes, but they do so more slowly."]

Answer 26

Aquaporins are a family of small integral proteins that allow the passive movement of water from one side of the plasma membrane to the other.

Answer 27

No, some cells are much more permeable to water than can be explained by simple diffusion through the lipid bilayer.

Answer 28

Aquaporins are tetramers, with each subunit containing a hydrophobic-lined central channel that is highly specific for water molecules.

Answer 29

Water molecules pass through in single file at a rate of about 1 billion molecules per second.

Answer 30

No, aquaporins exclude ions, including protons (H+), from passing through the channel.

Answer 31

At the narrowest point of the channel, positively charged residues attract the oxygen atoms of passing water molecules, causing a reorientation that disrupts the hydrogen bond network.

Answer 32

It prevents protons from hopping along water molecules, ensuring only water passes through the channel.

Answer 33

The exclusion of protons was explained through X-ray crystallography and molecular dynamics simulations, which helped model how the protein functions.

Answer 34

Conductance is the rapid movement of ions.

Answer 35

Ion channels are openings in the membrane that are permeable to specific ions.

Answer 36

Yes, most ion channels are selective; diffusion of ions is always downhill, meaning from higher to lower energies.

Answer 37

A gated ion channel can change conformation between a form open to its solute ion and one closed to the ion.

Answer 38

A voltage-gated ion channel's conformational state depends on the difference in ionic charge on the two sides of the membrane.

Answer 39

A ligand-gated ion channel's conformational state depends on the binding of a specific molecule (the ligand).

Answer 40

A mechano-gated ion channel's conformational state depends on mechanical forces applied to the membrane.

Answer 41

The two distinct domains are the pore domain and the voltage-sensing domain.

Answer 42

The part of a voltage-gated ion channel that forms an ion-conducting channel through the membrane

Answer 43

The portion of a voltage-gated ion channel that allows it to respond to membrane voltage.

Answer 44

[UNSURE IF IT'S THE RIGHT DEFINITION] Facilitated diffusion occurs (in many cases) when substances bind selectively to a membrane-spanning protein (facilitative transporter), facilitating the diffusion process. -important in mediating the entry and exit of polar solutes, such as sugars and amino acids, that do not penetrate the lipid bilayer -[GOOGLE'S DEF.]: a type of passive transport where molecules move across a cell membrane down their concentration gradient, with the help of specific membrane proteins (channel or carrier proteins), without requiring energy input from the cell. -

Answer 45

A facilitative transporter is a transmembrane protein that binds a specific substance and changes conformation to facilitate diffusion down its concentration gradient. *know their features??

Answer 46

Saturation-type kinetics is a condition in which every molecule of an enzyme or transporter is bound with its substrate molecule, so adding more substrate has no additional effect.

Answer 47

Active transport is the energy-requiring process in which a substance binds to a specific transmembrane protein, changing its conformation to allow passage of the substance through the membrane against the electrochemical gradient. -drives ions in 1 direction

Answer 48

Active transport depends on integral membrane proteins that selectively bind a particular solute and move it across the membrane.

Answer 49

Active transport moves solutes against their concentration gradient and requires an input of energy.

Answer 50

Moving a solute against its concentration gradient is an endergonic process, meaning it requires energy input.

Answer 51

The energy comes from exergonic processes such as ATP hydrolysis, absorption of light, electron transport, or flow of other substances down their gradients.

Answer 52

Pumps are proteins that carry out active transport.

Answer 53

The sodium-potassium pump is responsible for ATP hydrolysis and is active in transporting Na+ and K+ ions.

Answer 54

Jens Skou discovered the Na+/K+ -ATPase in 1957. He found that this enzyme, later called the Na+/K+ -ATPase (sodium-potassium pump), was responsible for both ATP hydrolysis and ion transport.

Answer 55

Facilitated diffusion allows movement in either direction, depending on the concentration gradient, whereas active transport moves ions in only one direction using energy.

Answer 56

It maintains a high concentration of Na+ outside the cell and a high concentration of K+ inside the cell.

Answer 57

* Extracellular Na⁺ is balanced by Cl⁻ ions. * Intracellular K⁺ is balanced by negatively charged proteins and nucleic acids.

Answer 58

The ratio is 3 Na+ ions out for every 2 K+ ions in per ATP hydrolyzed.

Answer 59

It creates a charge separation across the membrane by pumping more positive charges (Na+) out than it brings in (K+).

Answer 60

It is a P-type ion pump, meaning ATP hydrolysis phosphorylates the pump.

Answer 61

It binds Na+ or K+ from areas of low concentration (high affinity), ATP hydrolysis triggers a conformational change, and it releases ions into areas of high concentration (low affinity)

Answer 62

The cycle follows a sequence of conformational changes from E1 to E2, binding and releasing Na+ and K+ ions. details: [1. E1 conformation – The binding sites are open to the inside of the cell, allowing the protein to bind three Na⁺ ions and ATP. 2. A gate closes, preventing Na⁺ from flowing back into the cytosol. 3. ATP hydrolysis and ADP release trigger a conformational change from E1 to E2, exposing the binding site to the extracellular space. 4. The protein loses affinity for Na⁺, releasing the three Na⁺ ions outside the cell. 5. The protein then binds two K⁺ ions from the extracellular space. 6. Another gate closes, preventing K⁺ from leaking back out. 7. Dephosphorylation and ATP binding return the protein to its E1 conformation, opening the binding site to the inside of the cell and releasing K⁺ into the cytosol. 8. The cycle repeats.]

Answer 63

The Na+/K+ -ATPase moves ions across membranes at much lower rates than ion channels.

Answer 64

The sodium-potassium pump is found only in animal cells.

Answer 65

It consumes one-third of the energy produced by most animal cells and two-thirds of the energy produced by nerve cells.

Answer 66

Digitalis is a steroid from the foxglove plant that binds to and inhibits the Na+/K+ -ATPase.

Answer 67

Other important P-type ion pumps include Ca2+-ATPase and H+-ATPase in plants.

Answer 68

Prilosec inhibits the H+/K+-ATPase directly, while Zantac and similar drugs block receptors on parietal cells.

Answer 69

V-type pumps use ATP without forming a phosphorylated protein intermediate and actively transport H+ ions.

Answer 70

ABC transporters are a diverse group of ion transport proteins that all share a homologous ATP-binding domain.

Answer 71

Some organisms use light-driven proton pumps to transport ions across membranes.

Answer 72

Bacteriorhodopsin is a light-driven proton pump found in Halobacterium salinarium (an archaebacterium that lives in salty environments like the Great Salt Lake).

Answer 73

The movement of protons creates a steep proton gradient across the plasma membrane. This gradient is then used by an ATP-synthesizing enzyme to phosphorylate ADP, producing ATP for cellular energy.

Answer 74

Secondary active transport is the process of using the energy stored in ion gradients to transport other molecules across a membrane.

Answer 75

Secondary active transport (or cotransport) is the process of using the energy stored in ion gradients (such as Na+, K+, or H+) to transport other molecules across a membrane.

Answer 76

In the intestine, glucose absorption relies on the Na+/glucose cotransporter. Primary active transport by the Na+/K+-ATPase keeps Na+ concentrations low inside epithelial cells. This creates a Na+ gradient, where Na+ wants to diffuse back into the cell. The Na+/glucose cotransporter uses this gradient to bring in two Na+ ions and one glucose molecule, allowing glucose to enter against its concentration gradient. Once inside, glucose moves out of the cell through facilitated diffusion.

Answer 77

It can transport glucose against a 20,000-fold concentration gradient, making it extremely powerful.

Answer 78

Instead of Na+, plant cells use H+ gradients to uptake nutrients like sucrose, amino acids, and nitrate. This process is also symport, where H+ and sucrose move in the same direction into the cell.

Answer 79

Symport: Both molecules move in the same direction (e.g., Na+ and glucose or H+ and sucrose). Antiport: Molecules move in opposite directions (e.g., Na+ moves in, while H+ moves out to regulate pH). Antiport proteins are also called exchangers.

Answer 80

Like the Na+/K+-ATPase, secondary transporters work through a transport cycle, where the protein’s binding sites alternately face the cytoplasm and extracellular space.