MCQs

In hypertonic environments, the external water potential is lower than the cell, causing water to exit by osmosis.

Channel proteins provide a physical pathway, whereas carrier proteins undergo conformational changes to transport substances.

Osmosis is defined as the net movement of water across a membrane driven by a water potential gradient.

Receptors are usually transmembrane integral proteins that span the membrane to receive signals.

They hypothesized that the lipid bilayer was coated on both sides by globular proteins.

According to Fick's law, the rate of diffusion is directly proportional to the steepness of the concentration gradient.

Freeze-fracture techniques show proteins distributed within the bilayer, confirming the mosaic nature.

Glycolipids act as markers for cell identification and adhesion in the extracellular matrix.

Shorter chains decrease van der Waals interactions, and double bonds create fluidity; this combination results in the highest fluidity.

Peripheral proteins are loosely attached to the surface, usually via non-covalent interactions like ionic or hydrogen bonds.

Facilitated diffusion uses transmembrane proteins to move molecules that cannot pass through the lipid bilayer directly.

The hydrophilic phosphate head and hydrophobic fatty acid tails make the molecule amphipathic.

Robertson used electron microscopy to observe the "railroad track" appearance of membranes, implying three distinct layers.

Glycoproteins are proteins covalently bonded to carbohydrate chains, playing key roles in cell-cell recognition.

Active transport moves solutes against their concentration gradient, which is an endergonic process requiring ATP.

The Fluid Mosaic Model dictates that proteins can move laterally within the plane of the lipid bilayer.

Cholesterol acts as a temperature buffer, preventing excessive fluidity at high temperatures and excessive rigidity at low temperatures.

The double bonds in unsaturated fatty acids create "kinks" that prevent tight packing, maintaining fluidity at low temperatures.

The hydrophobic core of the phospholipid bilayer prevents the free passage of polar/charged molecules.