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Excitable Cells > Water, Ions & Membranes > Flashcards

Water, Ions & Membranes Flashcards

1
Q

What is the basic meaning of polarity in water?

A

Ends/sides are different

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2
Q

What is an ion?

A

Any atom or molecule that has gained or lost one or more electrons

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3
Q

True or False: Ions are by definition uncharged.

A

False

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4
Q

Why are ions important in biological systems?

A

They carry signals in the body, act as an energy store, and interact biochemically with proteins and other molecules

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5
Q

List two classes of biologically important ions.

A
  • Physiologically useful ions
  • Biochemically useful ions
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6
Q

Which ions are both physiologically and biochemically useful?

A
  • Na+
  • K+
  • Cl-
  • Ca2+
  • Mg2+
  • Trace metals (e.g., Fe3+, Zn2+)
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7
Q

What is the structure of biological membranes?

A

Lipid bilayers with hydrophilic polar heads and hydrophobic tails

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8
Q

What drives the formation of lipid bilayers in membranes?

A

The amphipathic nature of lipids

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9
Q

Fill in the blank: Membranes are essentially impermeable to _______.

A

[ions]

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10
Q

What is the role of pumps in membrane transport?

A

They establish ion gradients using energy, usually from ATP hydrolysis

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11
Q

What is the function of the sodium-potassium ATPase?

A

Generates a Na+ and K+ gradient by moving 3 Na+ out and 2 K+ in

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12
Q

What type of transport do pumps perform?

A

Primary active transport

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13
Q

True or False: Ion gradients can be used to power cellular processes.

A

True

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14
Q

What are cotransporters?

A

Proteins that facilitate secondary active transport of ions

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15
Q

What is an antiporter?

A

A transporter that moves two different ions in opposite directions

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16
Q

What is the maximum rate of ion transport through ion channels?

A

Approximately 1,000,000 ions per second

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17
Q

What characterizes ion channels?

A

Transmembrane proteins that are selectively permeable with gated openings

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18
Q

What are the types of gating mechanisms for ion channels?

A
  • Mechanical
  • Second messenger
  • Phosphorylation
  • Ligand-gated
  • Voltage-gated
  • Temperature-gated
19
Q

Fill in the blank: Ion channels are characterized by their _______ and ion selectivity.

A

[gating]

20
Q

What is the difference between cation and anion selectivity in ion channels?

A

Cation channels allow passage of positive ions (e.g., K+, Na+, Ca2+), while anion channels allow passage of negative ions (e.g., Cl-)

21
Q

What is a hydration shell?

A

The effective size of an ion in solution, influenced by surrounding water molecules

22
Q

What does the term ‘electrogenic’ refer to in the context of sodium-potassium ATPase?

A

It refers to the pump generating a net charge difference by moving 2+ charges in and 3+ charges out

23
Q

What is hyperpolarization in the context of ion concentration?

A

Hyperpolarization occurs when K+ is at 5 mM and Cl- is at 150 mM.

24
Q

What ion concentrations are associated with depolarization?

A

Depolarization occurs when Na+ is in and K+ is out.

25
Q

What is the typical concentration of K+ in a mammalian cell?

A

100 mM K+ outside the cell.

26
Q

What are ligand-gated ion channels?

A

Channels that open in response to binding of an activating ligand (agonist).

27
Q

Which receptors are classified as ligand-gated ion channels?

A
  • Nicotinic AChR
  • GABA A
  • 5HT3 receptor
  • Inhibitory glycine receptor
  • Ionotropic glutamate receptors.
28
Q

What are the four key components of all ligand-gated channels?

A
  • Pore
  • Ligand binding site
  • Coupling mechanism
  • Desensitization mechanisms.
29
Q

What is the structure of the nicotinic acetylcholine receptor?

A

A pentamer of five similar subunits.

30
Q

What triggers energy release in the nicotinic acetylcholine receptor?

A

A molecular switch.

31
Q

What is the structure of voltage-gated ion channels?

A

They have complex structures, such as the tetramer of four equivalent subunits in potassium channels.

32
Q

How many Kv channel genes are present in the human genome?

A

40 Kv channel genes.

33
Q

What are the two main types of voltage-gated channels?

A
  • Calcium channels (CaV)
  • Sodium channels (NaV).
34
Q

What is the potential structure of a native sodium channel?

A

1 α: 1/2 β.

35
Q

Fill in the blank: Ligand-gated channels have a _______ that lets ions through.

A

Pore.

36
Q

True or False: Voltage-gated potassium channels are present in prokaryotes.

A

True.

37
Q

What is the role of the coupling mechanism in ligand-gated ion channels?

A

It couples channel opening to ligand binding.

38
Q

What is desensitization in the context of ligand-gated ion channels?

A

The closure of the channel if the ligand binds for too long.

39
Q

What is the significance of voltage-gated channels in evolution?

A

Kv channels appear early in evolution.

40
Q

What subunits are involved in calcium channels?

A
  • α CaV 1.1-1.4
  • α CaV 2.1-2.3
  • α CaV 3.1-3.3
  • 4β
  • α2δ
  • γ.
41
Q

What is the basic structure of voltage-gated potassium channels?

A

They consist of a tetramer of four equivalent subunits.

42
Q

What happens to the extracellular domain of sodium channel subunits?

A

A disulfide bond is formed and the extracellular domain is cleaved to yield two linked peptides.

43
Q

What is the primary function of the sodium pump in muscle cells?

A

To store energy in electrical gradients.

Excitable Cells (6 decks)

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