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Transcript
Most cells are microscopic 10 m • Cells vary in size and shape A Tour of the Cell Human height 1m Length of some nerve and muscle cells 100 mm (10 cm) Chicken egg 10 mm (1 cm) Unaided eye Chapter 4 Frog egg 1 mm Light microscope 100 µm Most plant and animal cells 10 µm Nucleus Most bacteria 1 µm Mitochondrion Mycoplasmas (smallest bacteria) Electron microscope 100 nm Viruses Ribosome 10 nm Proteins Lipids 1 nm Birgit Woelker, PhD Small molecules Video Figure 4.2A – A small cell has a greater ratio of sur face area to volume than a large cell of the same shape – A sufficient surface area is important to get nutrients into the cell and wastes out Prokaryotic cells are structurally simpler than eukaryotes Prokaryotic cells are much smaller than eukaryotes Prokaryotic cell Nucleoid region 10 µm 30 µm 30 µm Surface area of one large cube = 5,400 µm2 Atoms Colorized TEM 15,000 ! • The microscopic size of most cells is important 0.1 nm Nucleus 10 µm Total surface area of 27 small cubes = 16,200 µm2 Figure 4.3A Eukar yotic cell Organelles • A typical animal cell • Prokaryotic cells are small, relatively simple cells – That do not have a membrane-bound nucleus – Contains a variety of membranous organelles and membraneous compartments Rough endoplasmic reticulum Prokar yotic flagella Ribosomes Smooth endoplasmic reticulum Nucleus Flagellum Not in most plant cells Capsule Lysosome Cell wall Plasma membrane Microtubule Cytoskeleton Pili Figure 4.4A • A typical plant cell has some structures that an animal cell lacks – Such as chloroplasts and a rigid cell wall Nucleus Rough endoplasmic reticulum Not in animal cells Central vacuole Chloroplast Intermediate filament Mitochondrion ORGANELLES OF THE ENDOMEMBRANE SYSTEM • The nucleus is the cellular control center – Containing the cell’s DNA, which directs cellular activities Nucleolus Smooth endoplasmic reticulum Plasma membrane Microfilament Chromatin Ribosomes Golgi apparatus Golgi apparatus Peroxisome Nucleoid region (DNA) Figure 4.3B Ribosomes Centriole Nucleus Two membranes of nuclear envelope Pore Microtubule Intermediate filament Microfilament Cytoskeleton Cell wall Rough endoplasmic reticulum Mitochondrion Peroxisome Plasma membrane Figure 4.4B Ribosomes Smooth endoplasmic reticulum has a variety of functions • Ribosomes on the sur face of the rough ER • Smooth endoplasmic reticulum, or smooth ER – Produce proteins that are secreted, inser ted into membranes, or transpor ted in vesicles to other organelles – Synthesizes lipids – Processes toxins and drugs in liver cells – Stores and releases calcium ions in muscle cells Smooth ER Transport vesicle buds off Rough ER 4 Ribosome Nuclear envelope Secretory (glyco-) protein inside transport vesicle 3 Sugar chain 1 Ribosomes Rough ER Smooth ER 2 Glycoprotein Polypeptide TEM 45,000! Rough ER Figure 4.7 Figure 4.8 The Golgi apparatus finishes, sor ts, and ships cell products Lysosomes are digestive compar tments within a cell • Lysosomes are sacs of enzymes • Stacks of membranous sacs receive and modify ER products – That function in digestion within a cell Rough ER – Then ship them to other organelles or the cell sur face Golgi apparatus New vesicle forming “Shipping” side of Golgi apparatus Golgi apparatus Plasma membrane Golgi apparatus Transport vesicle from ER Figure 4.9 Transport vesicle (containing inactive hydrolytic enzymes) Transport vesicle from the Golgi Lysosome engulfing damaged organelle 2 Engulfment of particle TEM 130,000! “Receiving” side of Golgi apparatus 1 “Food” 3 Lysosomes 5 Food vacuole Figure 4.10A 4 Digestion • Lysosomes in white blood cells • Lysosomes also recycle damaged organelles – Destroy bacteria that have been ingested Lysosome containing two damaged organelles Lysosome Peroxisome fragment TEM 8,500! Nucleus Figure 4.10B TEM 42,500! Mitochondrion fragment Figure 4.10C Vacuoles function in the general maintenance of the cell • Some protists have contractile vacuoles – That pump out excess water • Plant cells contain a large central vacuole, Nucleus – Which has lysosomal and storage functions Nucleus Chloroplast Contractile vacuoles Figure 4.12B LM 650! Figure 4.12A Colorized TEM 8,700! Central vacuole ENERGY-CONVERTING ORGANELLES A review of the endomembrane system • The various organelles of the endomembrane system – Are interconnected structurally and functionally Rough ER Transport vesicle from ER to Golgi Chloroplasts conver t solar energy to chemical energy • Chloroplasts, found in plants and some protists – Conver t solar energy to chemical energy in sugars Transport vesicle from Golgi to plasma membrane Plasma membrane Chloroplast Stroma Nucleus TEM 9,750! Inner and outer membranes Granum Vacuole Lysosome Intermembrane space Figure 4.13 Smooth ER Nuclear envelope Golgi apparatus Mitochondria har vest chemical energy from food Figure 4.14 THE CYTOSKELETON IS MADE OF PROTEIN FIBERS • Mitochondria carry out cellular respiration – Which uses the chemical energy in food to make ATP for cellular work Tubulin subunit Actin subunit Mitochondrion Fibrous subunits 25 nm 10 nm 7 nm Outer membrane Microfilament Intermembrane space Microtubule Cristae Matrix TEM 44,880! • Microfilaments of actin enable cells to change shape and move Inner membrane Figure 4.15 Intermediate filament • Intermediate filaments reinforce the cell and anchor certain organelles • Microtubules provide anchors for organelles and tracks for organelle movement CILIA AND FLAGELLA ARE MADE OF MICROTUBULES CILIA AND FLAGELLA ARE MADE OF MICROTUBULES • Clusters of microtubules slide against each other and bend the cilia or flagella • Eukaryotic cilia and flagella are important for cellular movement of certain cells Flagellum Electron micrographs of cross sections: Outer microtubule doublet TEM 206,500! Central microtubules Radial spoke Colorized SEM 4,100! Dynein arms Figure 4.17A Flagellum Figure 4.17B Figure 4.17C CELL SURFACES AND JUNCTIONS Basal body (structurally identical to centriole) TEM 206,500! LM 600! Plasma membrane Basal body Animal cells are embedded in an extracellular matrix which binds cells together in tissues • Protect, support and join cells • Plant cells are suppor ted by rigid cell walls made largely of cellulose and connected by plasmodesmata (channels) Glycoprotein complex with long polysaccharide EXTRACELLULAR FLUID Collagen fiber Connecting glycoprotein Walls of two adjacent plant cells Integrin Vacuole Plasmodesmata Plasma membrane Layers of one plant cell wall Cytoplasm Plasma membrane Microfilaments of cytoskeleton CYTOPLASM CELL SURFACES AND JUNCTIONS • In animal cells, tight junctions can bind cells together into leakproof sheets • Anchoring junctions link animal cells into strong tissues • Gap junctions allow substances to flow from cell to cell Tight junctions Anchoring junction Gap junctions Extracellular matrix Space between cells FUNCTIONAL CATEGORIES OF ORGANELLES • Eukar yotic organelles and their functions Eukaryotic organelles comprise four functional categories • Eukar yotic organelles fall into four functional groups – Manufacturing – Breakdown – Energy processing – Suppor t, movement, and communication between cells Table 4.19
