ELM 4 H2O, membranes + ions Flashcards
What is the significance of water’s polarity?
Water’s polarity allows it to form hydrogen bonds with other water molecules, creating unique properties such as cohesion, adhesion, and surface tension.
How does the density of solid water (ice) compare to liquid water?
The density of solid water is lower than that of liquid water, which is why ice floats. This is due to the arrangement of water molecules in the solid phase, where hydrogen bonds form a more open lattice structure.
What role do ions play in biological systems?
ions carry signals in the body, act as energy stores, and interact biochemically with proteins and other molecules, playing crucial roles in processes such as muscle contraction and ATP synthesis.
How do ions interact with water molecules in aqueous solutions?
Ions in aqueous solutions attract surrounding water molecules, forming hydration shells around them. These hydration shells affect the mobility and effective size of ions in solution.
What is the significance of hydration shells?
Hydration shells determine the effective “size” of ions in solution and affect their interactions with other molecules, including proteins. Some molecules may remove hydration shells before interacting with ions.
How do lipid bilayers maintain ion gradients?
Lipid bilayers are essentially impermeable to ions but allow lipid-soluble molecules to pass through. This amphipathic nature of lipid bilayers enables the maintenance of concentration gradients across membranes.
What is the structure of a lipid bilayer?
Lipid bilayers consist of hydrophilic polar heads facing outward toward the aqueous environment and hydrophobic tails facing inward, forming a barrier that prevents the passage of ions while allowing lipid-soluble molecules to pass through.
What is the difference between active transport and passive transport?
Active transport requires energy input, typically from ATP, to move substances against their concentration gradient. Passive transport, on the other hand, does not require energy and involves the movement of substances down their concentration gradient.
What are the basic features of pumps involved in primary active transport?
Pumps are membrane proteins that move ions uphill against their concentration gradient, typically using energy from ATP hydrolysis. They nearly always move cations and are essential for maintaining ion gradients across cell membranes.
What is the role of the Na/K ATPase (Na pump)?
The Na/K ATPase generates a sodium (Na) and potassium (K) gradient across the cell membrane, with low sodium concentration inside the cell and high potassium concentration. This pump is crucial for maintaining cell volume and membrane potential and consumes a significant amount of ATP.
How are ion gradients utilized as “batteries” in cells?
Ion gradients represent a source of energy that can be used to transmit information and power cellular processes, such as the transport of other ions via cotransporters. Antiporters move ions in opposite directions, while symporters move ions in the same direction.
What are ligand-gated ion channels?
Ligand-gated ion channels, such as the nicotinic acetylcholine receptor (AChR) and ionotropic glutamate receptors, open in response to the binding of activating ligands, allowing ions to flow through the channel pore.
What are the structural features common to all ligand-gated ion channels?
All ligand-gated ion channels have a pore for ion passage, a binding site for ligand interaction, a coupling mechanism for channel opening, and a desensitization mechanism to terminate channel activity.
How is muscle energy stored in electrical gradients?
Muscle stores energy in electrical gradients generated by pumps such as the Na/K ATPase. Energy release is triggered by ligand-gated ion channels, such as the nicotinic acetylcholine receptor (NAChR), which acts as a “molecular switch” to initiate muscle contraction.
What is the significance of the nicotinic acetylcholine receptor (nAChR) in research on ligand-gated ion channels?
The nAChR has 17 different subunits identified in mammals and has been extensively studied due to its abundance in the electric organs of the Torpedo ray and being the first ligand-gated ion channel (LGIC) to be cloned.
