4-4: Unique Features of Plant Cells. Plant Cells 3 Additional structures are found in plant cells: – Cell Walls – Central Vacuole – Plastids Why? – Different.

4-4: Unique Features of Plant Cells

Plant Cells• 3 Additional structures are

found in plant cells:– Cell Walls– Central Vacuole– Plastids

• Why?– Different lifestyles

compared to animal cells• Go through photosynthesis

– CO2 + H2O = sugars

Cell Wall• Location: rigid covering outside C.M. (composed

of cellulose – stored glucose)• Function: support + protection• Two types:– Primary – develops right outside C.M.– Secondary – develops between primary + C.M. but

only when plant cell reaches full size; tough and woody structure • Ex. Your desk tops has billions

Vacuole• Location: within the cytosol• Size: may occupy up to 90% of the plant cell’s

volume; formed by fusion of smaller vacuoles

• Function: Fluid-filled vacuoles store enzymes + metabolic wastes, toxic materials, pigments

Plastids

• Location: within the cytosol• Appearance: double-membraned organelle which

contains DNA• Functions:

– Storage of fats or starches– Storage of pigments

• Most common type – chloroplast– System of thylakoids in stacks (grana)

• Contain chlorophyll – pigment that captures light nrg

– Site of photosynthesis– Endosymbiosis

• Chloroplasts thought to be descendants of ancient prokaryotic cells that were incorporated into plant cells

Plastids• Chromoplasts– Contain colorful pigments

• Ex. carotenoids

– May/may not be involved in photosynthesis

• Amyloplasts– Store starch

• Precursor to plastids? – Protoplastids

Cell Comparison• Prokaryote vs. Eukaryote– Pro: lacks nucleus + membrane-bound organelles,

genetic info. contained within nucleoid region• Plant vs. Animal– Plant: Cell Walls, Vacuole, Plastids