10 m Human height 1 m Length of some nerve and muscle cells 0.1 m Chicken egg 1 cm Unaided eye Frog egg 1 mm 100 µm Most plant and animal cells 10 µm Nucleus Most bacteria Light microscope microscope Light 1 µm Mitochondrion 100 nm Smallest bacteria Viruses Ribosomes 10 nm Proteins Electron microscope Lipids 1 nm Small molecules 0.1 nm Atoms 1 Fimbriae Nucleoid Ribosomes Plasma membrane Bacterial Cell wall chromosome Capsule 0.5 µm Flagella (a) A typical (b) A thin section rod-shaped through the bacterium bacterium Bacillus coagulans (TEM) 2 (a) TEM of a plasma Outside of cell membrane Inside of 0.1 µm cell Carbohydrate side chain Hydrophilic region Hydrophobic region Hydrophilic Phospholipid Proteins region (b) Structure of the plasma membrane 3 Surface area increases while total volume remains constant 5 1 1 Total surface area [Sum of the surface areas 6 150 750 (height × width) of all boxes sides × number of boxes] Total volume [height × width × length × 1 125 125 number of boxes] Surface-to-volume (S-to-V) ratio 6 1.2 6 [surface area ÷ volume] 4 Nuclear envelope ENDOPLASMIC RETICULUM (ER) Nucleolus NUCLEUS Rough ER Smooth ER Flagellum Chromatin Centrosome Plasma membrane CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Ribosomes Microvilli Golgi Peroxisome apparatus Mitochondrion Lysosome 5 Nuclear envelope Rough endoplasmic reticulum NUCLEUS Nucleolus Chromatin Smooth endoplasmic reticulum Ribosomes Central vacuole Golgi apparatus Microfilaments Intermediate CYTO- filaments SKELETON Microtubules Mitochondrion Peroxisome Chloroplast Plasma membrane Cell wall Plasmodesmata Wall of adjacent cell 6 Nucleus 1 µm Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Rough ER Surface of nuclear envelope Ribosome 1 µm 0.25 µm Close-up of nuclear envelope Pore complexes (TEM) Nuclear lamina (TEM) 7 Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Small 0.5 µm subunit TEM showing ER and ribosomes Diagram of a ribosome 8 Smooth ER Rough ER Nuclear envelope ER lumen Cisternae Ribosomes Transitional ER Transport vesicle 200 nm Smooth ER Rough ER 9 cis face (“receiving” side of 0.1 µm Golgi apparatus) Cisternae trans face (“shipping” side of TEM of Golgi apparatus Golgi apparatus) 10 Nucleus 1 µm Vesicle containing 1 µm two damaged organelles Mitochondrion fragment Peroxisome fragment Lysosome Digestive enzymes Lysosome Lysosome Plasma Peroxisome membrane Digestion Food vacuole Mitochondrion Digestion Vesicle (a) Phagocytosis (b) Autophagy 11 Central vacuole Cytosol Nucleus Central vacuole Cell wall Chloroplast 5 µm 12 Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi 13 Intermembrane space Outer membrane Free ribosomes in the mitochondrial matrix Inner membrane Cristae Matrix 0.1 µm 14 Ribosomes Stroma Inner and outer membranes Granum 1 µm Thylakoid 15 Chloroplast Peroxisome Mitochondrion 1 µm 16 Microtubule Microfilaments 0.25 µm 17 Vesicle ATP Receptor for motor protein Motor protein Microtubule (ATP powered) of cytoskeleton (a) Microtubule Vesicles 0.25 µm (b) 18 10 µm 10 µm 10 µm Column of tubulin dimers Keratin proteins Actin subunit Fibrous subunit (keratins 25 nm coiled together) 7 nm 8–12 nm α β Tubulin dimer 19 Centrosome Microtubule Centrioles 0.25 µm Longitudinal section Microtubules Cross section of one centriole of the other centriole 20 Direction of swimming (a) Motion of flagella 5 µm Direction of organism’s movement Power stroke Recovery stroke (b) Motion of cilia 15 µm 21 Outer microtubule Plasma 0.1 µm doublet membrane Dynein proteins Central microtubule Radial spoke Protein cross- Microtubules linking outer doublets (b) Cross section of Plasma cilium membrane Basal body 0.5 µm (a) Longitudinal 0.1 µm section of cilium Triplet (c) Cross section of basal body 22 Microtubule doublets ATP Dynein protein (a) Effect of unrestrained dynein movement ATP Cross-linking proteins inside outer doublets Anchorage in cell (b) Effect of cross-linking proteins 1 3 2 (c) Wavelike motion 23 Microvillus Plasma membrane Microfilaments (actin filaments) Intermediate filaments 0.25 µm 24 Muscle cell Actin filament Myosin filament Myosin arm (a) Myosin motors in muscle cell contraction Cortex (outer cytoplasm): gel with actin network Inner cytoplasm: sol with actin subunits Extending pseudopodium (b) Amoeboid movement Nonmoving cortical cytoplasm (gel) Chloroplast Streaming cytoplasm (sol) Vacuole Parallel actin filaments Cell wall (c) Cytoplasmic streaming in plant cells 25 Secondary cell wall Primary cell wall Middle lamella 1 µm Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata 26 Collagen Proteoglycan Polysaccharide EXTRACELLULAR FLUID complex molecule Carbo- hydrates Fibronectin Core protein Integrins Proteoglycan molecule Plasma membrane Proteoglycan complex Micro- CYTOPLASM filaments 27 Cell walls Interior of cell Interior of cell 0.5 µm Plasmodesmata Plasma membranes 28 Tight junction Tight junctions prevent fluid from moving across a layer of cells 0.5 µm Tight junction Intermediate filaments Desmosome Desmosome Gap 1 µm junctions Extracellular Space matrix between Gap junction cells Plasma membranes of adjacent cells 0.1 µm 29 Cell Component Structure Function Concept 6.3 Nucleus Surrounded by nuclear Houses chromosomes, made of The eukaryotic cell’s genetic envelope (double membrane) chromatin (DNA, the genetic instructions are housed in perforated by nuclear pores. material, and proteins); contains the nucleus and carried out The nuclear envelope is nucleoli, where ribosomal by the ribosomes continuous with the subunits are made. Pores endoplasmic reticulum (ER). regulate entry and exit of materials. (ER) Ribosome Two subunits made of ribo- Protein synthesis somal RNA and proteins; can be free in cytosol or bound to ER Concept 6.4 Endoplasmic reticulum Extensive network of Smooth ER: synthesis of The endomembrane system membrane-bound tubules and lipids, metabolism of carbohy- (Nuclear regulates protein traffic and sacs; membrane separates drates, Ca2+ storage, detoxifica- performs metabolic functions envelope) lumen from cytosol; tion of drugs and poisons in the cell continuous with the nuclear envelope. Rough ER: Aids in synthesis of secretory and other proteins from bound ribosomes; adds carbohydrates to glycoproteins; produces new membrane Golgi apparatus Stacks of flattened Modification of proteins, carbo- membranous hydrates on proteins, and phos- sacs; has polarity pholipids; synthesis of many (cis and trans polysaccharides; sorting of Golgi faces) products, which are then released in vesicles. Lysosome Membranous sac of hydrolytic Breakdown of ingested substances, enzymes (in animal cells) cell macromolecules, and damaged organelles for recycling Vacuole Large membrane-bounded Digestion, storage, waste vesicle in plants disposal, water balance, cell growth, and protection Concept 6.5 Mitochondrion Bounded by double Cellular respiration Mitochondria and chloro- membrane; plasts change energy from inner membrane has one form to another infoldings (cristae) Chloroplast Typically two membranes Photosynthesis around fluid stroma, which contains membranous thylakoids stacked into grana (in plants) Peroxisome Specialized metabolic Contains enzymes that transfer compartment bounded by a hydrogen to water, producing single membrane hydrogen peroxide (H2O2) as a by-product, which is converted to water by other enzymes in the peroxisome 30 .