CELL STRUCTURE & FUNCTION

The rigid plant cell wall serves as a physical barrier that prevents the invagination of the plasma membrane required for endocytosis.

Animal cells form a contractile ring of actin and myosin filaments that pinches the plasma membrane inward, creating a cleavage furrow.

The rigid cell wall prevents pinching; instead, the phragmoplast guides Golgi vesicles to fuse at the equator, forming a new cell plate from the inside out.

Lignin is a complex, non-carbohydrate aromatic polymer deposited in secondary plant cell walls, rendering them woody, waterproof, and rigid.

The middle lamella acts as a cellular glue between neighboring plant cells, composed primarily of sticky sticky pectin compounds.

Animal cells incorporate cholesterol into their membranes to regulate fluidity across temperatures; plants use alternative sterols (phytosterols).

Lacking a rigid cell wall to resist hydrostatic pressure, animal cells absorb water via osmosis until the plasma membrane ruptures.

Water enters the central vacuole, pushing the protoplast against the tough cell wall; this builds turgor pressure, keeping the plant upright.

Higher plant cells completely lack centrioles, utilizing alternative microtubule-organizing centers (MTOCs) to manage spindle formation during division.

Plasmolysis occurs when an external hypertonic solution draws water out of the central vacuole, causing the internal protoplast to collapse.

Plants store excess photosynthetic carbohydrates as insoluble starch (amylose and amylopectin), while animals store energy as glycogen.

Glycogen, a highly branched glucose polymer, serves as the primary multi-branched energy storage polysaccharide in animal tissues.

Plasmodesmata are microscopic channels crossing the plant cell wall, lining up the plasma membrane and endoplasmic reticulum of neighboring cells.

Gap junctions are protein channels made of connexins that bridge the gap between adjacent animal cells, playing a role similar to plasmodesmata.

Lysosomes function as the cell's recycling center under acidic conditions; typical plant cells rely instead on their central vacuole for hydrolytic breakdown.

The development of a massive, turgid central vacuole forces the cytoplasm and the nucleus to the periphery against the plant cell wall.

The rigid, box-like cellulose cell wall forces plant cells to maintain structured, geometric, or rectangular morphologies.

Leukoplasts are non-pigmented plastids found in non-photosynthetic plant tissues (like roots or tubers) that store starches (amyloplasts) or fats.

Animal cells lack a cell wall entirely; their outermost living boundary is the selectively permeable phospholipid bilayer known as the plasma membrane.