Cell Structure, Junctions, and Membrane Dynamics

Flashcards covering key biological concepts from the lecture including extracellular matrix, cell junctions, plasma membrane composition, transport mechanisms, and cellular adaptation to temperature.

What receptor proteins embedded in the plasma membrane bind directly to extracellular matrix (ECM) proteins such as fibronectin?

Integrins

What three types of fibers compose the cytoskeleton mentioned in the lecture?

Microtubules, microfilaments, and intermediate filaments

Which transport channel is present only in plant cell walls to allow water, small solutes, RNA, and specific proteins to pass between adjacent cells?

Plasmodesmata

What is the primary function of tight junctions in epithelial tissue?

They press neighboring cell membranes closely together to prevent the leakage of extracellular fluid.

How do desmosomes (anchoring junctions) connect neighboring cells?

They fasten cells together into strong sheets, acting similarly to a zipper.

What type of junction provides cytoplasmic channels between adjacent animal cells for communication and nutrient transfer?

Gap junctions

What organelle is present in animal cells but absent in plant cells, according to the transcript?

Centrioles

What structures are present in plant cells that are absent in animal cells?

Cell wall and central vacuole

How do motor proteins transport vesicles to their target organelles along the cytoskeleton?

They carry vesicles along microtubules like a train on a track.

What defines passive transport across a cell membrane?

The movement of substances across the membrane without any input of energy.

What is the functional difference between simple diffusion and facilitated diffusion?

Simple diffusion moves solutes directly through the phospholipid bilayer, whereas facilitated diffusion moves solutes through transport protein channels without requiring energy.

What energy sources can drive active transport across the plasma membrane?

$\text{ATP}$ or $\text{GTP}$

What term describes molecules, such as phospholipids and membrane proteins, that possess both hydrophilic and hydrophobic regions?

Amphipathic

What model depicts the cell membrane as a mosaic of protein molecules drifting in a fluid phospholipid bilayer?

Fluid mosaic model

What is the function of cholesterol in the plasma membrane at body temperature ($37\,^\circ\text{C}$)?

It restrains the movement of phospholipids to stabilize the membrane.

How does cholesterol prevent membrane collapse or damage at low temperatures?

It disrupts the tight packing of phospholipid tails, maintaining membrane fluidity and preventing brittleness.

Why are plasma membranes rich in unsaturated fatty acids more fluid than those rich in saturated fatty acids?

Unsaturated fatty acid tails contain double bonds that create kinks or bends, preventing the lipids from packing tightly together.

How do cold-water fish adapt their cell membranes to stay fluid without cholesterol?

They maintain a high proportion of unsaturated hydrocarbon tails in their membrane phospholipids.

How does winter wheat adapt its cell membrane composition during autumn?

It increases its percentage of unsaturated phospholipids to prevent membrane solidification in winter.

What standard secondary structure is formed by the nonpolar hydrophobic regions of integral transmembrane proteins?

Alpha helix