Cells The Universal Subunits of Life Cellular Structure • all life is cellular • Cell Theory – Cells are the fundamental units of life. – All organisms are composed of cells. – All cells come from preexisting cells. • each cell possesses the different molecules necessary for sustaining life & specializations (≥10,000) Cellular Structure • all life is cellular – all cells belong to one of two structural categories • prokaryotic cells - relatively simple • eukaryotic cells - more complex Cellular Structure • prokaryotic cells – cytoplasm surrounded by plasma membrane • cytosol + insoluble particles – DNA in nucleoid – no membrane-bound organelles – cell wall (most) – complex, highly regulated metabolism – distinguished by many non-universal characteristics some common prokaryotic characters Figure 4.5 Bacterial Flagellum Figure 4.6 relative sizes of organisms and their constituents Figure 4.2 Cellular Structure • eukaryotic cells – larger, but still small cell size is limited by surface area/volume ratio Figure 4.3 Cellular Structure • eukaryotic cells – larger, but still small – plasma membrane – cytoskeleton – membrane-bound organelles Animal & Plant Cells Figure 4.7 cell fractionation by centrifugation permits biochemical analysis that supplements microscopic observations Figure 4.8 Organelle Functions • information processing organelles – nucleus • an envelope of two membranes –perforated by pores –the outer membrane is linked to the ER • contains –nucleoplasm –chromatin –nucleoli nuclear structures Figure 4.9 Organelle Functions • information processing organelles – nucleus – chloroplasts (cp) & mitochondria (mt) • contain DNA like prokaryotic cells • express some essential proteins Organelle Functions • information processing organelles – nucleus – chloroplasts (cp) & mitochondria (mt) – ribosomes • complex RNA-protein bodies • translate instructions into polypeptides • in cytoplasm, on ER, in cp & mt Organelle Functions • energy processing organelles – mitochondria • major site of oxidative energy production • two membranes surround aqueous matrix that contains energy-processing enzymes • the highly folded inner membrane (cristae) bears energy-processing enzymes Mitochondrion Figure 4.14 chromoplasts leucoplasts Figure 4.17 Organelle Functions • energy processing organelles – mitochondria – plastids • a two-membrane envelope • store/produce energy or display colors • chloroplasts –thylakoid membranes are suspended in the stroma –each contains enzymes of energy production Chloroplast Figure 4.15 endosymbiotic origin of cp & mt Figure 4.18 Organelle Functions • the endomembrane system – a system of interacting membranes located throughout the cell • endoplasmic reticulum (ER) –continuous with the nuclear outer membrane –the membrane encloses the lumen –translates & processes proteins headed for organelles, membranes, outside –RER (rough), SER (smooth) rough & smooth endoplasmic reticulum (RER, SER) Figure 4.11 Organelle Functions • endomembrane system – interacting membrane organelles throughout the cell • endoplasmic reticulum (ER) • Golgi apparatus –flattened sacks (cisternae) + vesicle shuttles –proteins travel from ER to cis face to trans face endomembrane system function Figure 4.12 Organelle Functions • endomembrane system – interacting membrane organelles throughout the cell • endoplasmic reticulum (ER) • Golgi apparatus • lysosome –vesicle with digestive enzymes –fuses with phagosome lysosome function Figure 4.13 Organelle Functions • other organelles – peroxisome • detoxifies peroxides Figure 4.19 Organelle Functions • other organelles – peroxisome • detoxifies peroxides – glyoxysome (plants only) • converts lipids to carbohydrates – vacuole (plants) • maintains turgor pressure • stores reserves, wastes • visual attractant (anthocyanins) Figure 4.20 microfilaments stabilize cell shape Figure 4.22 9+2 arrangement of microtubules in cilium Figure 4.23 mechanism of microtubular movement Figure 4.24 Extracellular Structures • plant, fungi cell wall – prevents cell from bursting Plant Cell Wall Figure 4.25 Extracellular Structures • plant, fungi cell wall • animal extracellular matrix – secreted by adjacent cells – differs from tissue to tissue An extracellular matrix Figure 4.26