Cell Theory 1 A Tour of the Cell Lecture 2, Part 1 Fall 2008 Cells are the basic unit of structure and function The lowest level of structure that can perform all activities required for life Reproduction Metabolic activity Cell Theory: All organisms are made of cells All cells arise from other cells How do we study cells? 2 How do we study cells? Cell Fractionation 1 Fig. 6.2 Fig. 6.4 Fig. 6.5 Size & Function Prokaryotes & Eukaryotes 3 Limits to size Surface area to volume ratio Prokaryotes Eukaryotes Fig. 6.8
Prokaryote What differences do you see? Prokaryotes vs. Eukaryotes 4 Characteristics of all cells Plasma membrane Cytosol Chromosomes Ribosomes Eukaryote Fig. 6.6 Fig. 6.7 Plasma Membrane Present in all cell types Separates the internal from the external environment Regulate chemical exchanges within the environment Chemical reactions more efficient Dynamic selective barrier 11 Prokaryotes No nucleus Nucleoid region Simple No membrane bound organelles Smaller (1-5 nm) Evolutionarily older Major differences Eukaryotes Nucleus (DNA in a membrane-bound region) Complex Membrane bound organelles Organelle a structure with a specified function w/i a cell Larger (10-100 nm) Evolutionarily younger 5 Views of Prokaryote Cells 6 The Origin of Eukaryotic Cells 1 Evolution of the endomembrane system All the membrane bound organelles within a cell, except for mitochondria and chloroplasts Inward folding of plasma membrane formed nuclear envelope, organelles See Fig. 27.2
Eukaryotes: Animal & Plant Cells Animal cell structures: Plasma membrane Nucleus Cytosol Ribosomes Endoplasmic reticulum Golgi apparatus Mitochondria Cytoskeleton Vacuoles Peroxisome 7 Views of Animal Cells Intestinal (smooth) muscle cells Cheek cells (400X) 8 Not typically found in plants: Centosome Lysosomes Flagella See Fig. 6.9 Animal cell Cardiac muscle cells Brain cells (astrocytes) Eukaryotes: Animal & Plant Cells Plant cell structures: Plasma membrane Nucleus Cytosol Ribosomes Endoplasmic reticulum Golgi apparatus Mitochondria Cytoskeleton Peroxisome 9 Leaf cells Views of Plant Cells Plant cell Root cell w/amyloplasts 10 Not found in animals: Cell Wall w/plasmodesmata Plastids (Chloroplasts, Amyloplasts, Chromoplasts) Central vacuole Fig. 4.6 Animal cell See Fig. 6.9 Plant cell Leaf cells w/chloroplasts Leaf epidermal (surface) cells Cytosol 17 Nucleus 18 Cytoplasm Area between the nucleus and the plasma membrane Cytosol Fluid of the cytoplasm Functions Store genes on chromosomes Regulate gene expression Transport regulatory factors and gene products Produce messages (mrna) that code for Produce the components of ribosomes Replication of genetic material
Nuclear envelope Double membrane Pore complexes Gatekeepers Nuclear lamina Protein filaments Maintains shape of nucleus Nucleus Chromosomes Discrete units of DNA Chromatin - Association of DNA molecules and One chromatin = one chromosome Nucleolus Ball-like mass of fibers & granules Produces ribosomal RNA (rrna) Assembles components of ribosomes Nucleus Fig. 6.10 Fig. 6.10 20 Ribosomes Complex of & rrna Protein synthesis Ribosome parts are made in nucleus by nucleolus Parts travel out of nucleus, into cytoplasm Two types: Bound ribosome Bound to endoplasmic reticulum (ER) Make for membranes or exportation from cell Free ribosomes make that stay in cytosol DNA Control of the Cell DNA Protein production 1. mrna synthesis 2. mrna travels to ribosomes 3. Ribosomes use mrna to synthesize 21 Fig. 6.11 Endomembrane System 22 Endoplasmic Reticulum 23 Functions: Manufacturing and distributing cellular products Detoxification of poisons Contains: Nuclear envelope The endoplasmic reticulum (ER) The Golgi apparatus Lysosomes & Vacuoles Plasma membrane not Endo, but related Membranes unique in structure & function Membranes dynamic manufacturing of many cellular products Large more than ½ of all membrane in cell Continuous with nuclear envelope Cisternae Membranous tubules & sacs Cisternal space Fig. 6.12
Endoplasmic Reticulum 23 Endoplasmic Reticulum 23 Smooth ER No ribosomes Functions: Lipid production E.g., steroids, phospholipds Metabolism of carbohydrates Detoxification of drugs Calcium ion storage Fig. 6.12 Rough ER Ribosomes bound to ER Produces secretory Glyco Transport vesicles Produces membrane Makes phospholipids for membrane Fig. 6.12 The Golgi Apparatus 24 The Golgi Apparatus 24 Receives products from ER Modifies products Stores products Delivers products Other parts of cell Other cells (secretion/exportation) Manufactures some macromolecules Cis face receiving Trans face shipping Products identified and tagged e.g., phosphate groups added to products e.g., recognition on transport vesicles Cisternal maturation model Dynamic process Cisturnae move from cis to trans Products modified as cisturnae move Fig. 6.13 Fig. 6.13 Lysosomes 25 Lysosomes 25 Lysosome Membrane bound sac of hydrolytic enzymes Keeps enzymes from rest of cell Higher ph in lysosome optimal for lysosomal enzymes Production: ER makes hydrolytic enzymes & lysosomal membranes Transported to GA for processing Some bud directly from GA Fig. 6.14 Nutrient digestion Part of phagocytosis Destroy harmful bacteria Recycle damaged organelles Autophagy Embryonic development Fig. 6.14
Vacuoles: Animal Cells 26 Central Vacuole: Plant Cells 27 Membrane bound sacs that form ( bud ) from the ER, Golgi apparatus or plasma membrane. Contain material Food vacuole Water pumps Contractile vacuoles Central Vacuole Large can occupy 90% volume of cell Coalescence of many smaller vacuoles from ER, GA Single membrane Water, salts, other molecules inside Few enzymes Function Storage Growth of cell Protection Helps concentrate enzymes in rest of cell Fig 6.15 Endomembrane System 28 Mitochondria 29 Cellular respiration Converts carbon compounds into ATP ATP (adenosine triphosphate) energy for cellular work Found in most eukaryotic cells Not part of endomembrane systems Contains its own Fig. 6.17 DNA Has a double membrane Membrane made by free ribosomes Cristae infoldings of inner membrane Fig. 6.16 Chloroplasts Photosynthesis Creates carbon compounds using energy from the sun Contain chlorophyll a & other pigments Not part of endomembrane systems Contains its own DNA Has a double membrane Thylakoids flattened interconnected stacks Granum stacks of thylakoids Stroma fluid outside thylakoids Intermembrane space Stroma Thylakoid space Fig. 6.18 30 Other Plastids Plastid Organelle with 2 membranes Has its own DNA & RNA Found in plants, some protists Three main types Chloroplasts Chromoplasts Stores lipid soluble pigments Usually colored Amyloplasts Stores starch 30
Peroxisomes Specialized membrane compartment Single membrane Contains enzymes that transfer hydrogen to oxygen, producing hydrogen peroxide Breaks down fatty acids Detoxify Composed of: Proteins from cytosol Lipids from ER Lipids synthesized in Peroxisome Fig. 6.19