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A Tour of the Cell Lecture 2, Part 1 Slide 2 Cell Theory 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 1 Slide 3 How do we study cells? Fig. 6.2 2 Slide 4 How do we study cells? Fig. 6.4 Fig. 6.5 Cell Fractionation 3 Slide 5 Size & Function Limits to size Surface area to volume ratio Fig. 6.8 4 Slide 6 Prokaryotes & Eukaryotes 5 Prokaryotes Eukaryotes Slide 7 Prokaryotes vs. Eukaryotes What differences do you see? 6 Eukaryote Prokaryote Fig. 6.6 Slide 8 Characteristics of all cells Plasma membrane Cytosol Chromosomes Ribosomes Fig. 6.7 7 Slide 9 Plasma Membrane Present in all cell types Function: Separates the internal from the external environment Regulate chemical exchanges within the environment Chemical reactions more efficient Dynamic selective barrier 8 Slide 10 Major differences Prokaryotes No nucleus Nucleoid region Simple No membrane bound organelles Smaller (1-5 nm) Evolutionarily older 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 9 Slide 11 Views of Prokaryote Cells 10 See Fig. 27.2 Slide 12 The Origin of Eukaryotic Cells 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 11 Slide 13 Eukaryotes: Animal & Plant Cells Animal cell structures: Plasma membrane Nucleus Cytosol Ribosomes Endoplasmic reticulum Golgi apparatus Mitochondria Cytoskeleton Vacuoles Peroxisome Not typically found in plants: Centrosome Lysosomes Flagella See Fig. 6.9 Animal cell 12 Slide 14 Views of Animal Cells 13 Cheek cells (400X) Cardiac muscle cells Intestinal (smooth) muscle cells Brain cells (astrocytes) Slide 15 Eukaryotes: Animal & Plant Cells Plant cell structures: Plasma membrane Nucleus Cytosol Ribosomes Endoplasmic reticulum Golgi apparatus Mitochondria Cytoskeleton Peroxisome Not found in animals: Cell Wall w/plasmodesmata Plastids (Chloroplasts, Amyloplasts, Chromoplasts) Central vacuole Fig. 4.6 Animal cell 14 See Fig. 6.9 Plant cell Slide 16 Views of Plant Cells 15 Leaf cells Leaf cells w/chloroplasts Plant cell Root cell w/amyloplasts Leaf epidermal (surface) cells Slide 17 Cytosol Cytoplasm Area between the nucleus and the plasma membrane Cytosol Fluid of the cytoplasm 16 Slide 18 Nucleus Functions Store genes on chromosomes Regulate gene expression Transport regulatory factors and gene products Produce messages (mRNA) that code for proteins Produce the components of ribosomes Replication of genetic material 17 Slide 19 Nucleus Nuclear envelope Double membrane Pore complexes Gatekeepers Nuclear lamina Protein filaments Maintains shape of nucleus Fig. 6.10 18 Slide 20 Nucleus Chromosomes Discrete units of DNA Chromatin - Association of DNA molecules and proteins One chromatin = one chromosome Nucleolus Ball-like mass of fibers & granules Produces ribosomal RNA (rRNA) Assembles components of ribosomes Fig. 6.10 19 Slide 21 Ribosomes Complex of proteins & rRNA Function: 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 proteins for membranes or exportation from cell Free ribosomes make proteins that stay in cytosol 20 Fig. 6.11 Slide 22 DNA Control of the Cell DNA Protein production 1.mRNA synthesis 2.mRNA travels to ribosomes 3.Ribosomes use mRNA to synthesize proteins 21 Slide 23 Endomembrane System 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 22 Slide 24 Endoplasmic Reticulum Function: manufacturing of many cellular products Large more than of all membrane in cell Continuous with nuclear envelope Cisternae Membranous tubules & sacs Cisternal space 23 Fig. 6.12 Slide 25 Endoplasmic Reticulum Smooth ER No ribosomes Functions: Lipid production E.g., steroids, phospholipds Metabolism of carbohydrates Detoxification of drugs Calcium ion storage 24 Fig. 6.12 Slide 26 Endoplasmic Reticulum Rough ER Ribosomes bound to ER Function: Produces secretory proteins Glycoproteins Transport vesicles Produces membrane proteins Makes phospholipids for membrane 25 Fig. 6.12 Slide 27 The Golgi Apparatus Function: Receives products from ER Modifies products Stores products Delivers products Other parts of cell Other cells (secretion/exportation) Manufactures some macromolecules 26 Fig. 6.13 Slide 28 The Golgi Apparatus Cis face receiving Trans face shipping Products identified and tagged e.g., phosphate groups added to products e.g., recognition proteins on transport vesicles Cisternal maturation model Dynamic process Cisturnae move from cis to trans Products modified as cisturnae move 27 Fig. 6.13 Slide 29 Lysosomes 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 28 Fig. 6.14 Slide 30 Lysosomes Function: Nutrient digestion Part of phagocytosis Destroy harmful bacteria Recycle damaged organelles Autophagy Embryonic development 29 Fig. 6.14 Slide 31 Vacuoles: Animal Cells Membrane bound sacs that form (bud) from the ER, Golgi apparatus or plasma membrane. Function: Contain material Food vacuole Water pumps Contractile vacuoles 30 Slide 32 Central Vacuole: Plant Cells 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 31 Slide 33 Endomembrane System 32 Fig. 6.16 Slide 34 Mitochondria Function: 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 DNA Has a double membrane Membrane proteins made by free ribosomes Cristae infoldings of inner membrane 33 Fig. 6.17 Slide 35 Chloroplasts Function: 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 34 Fig. 6.18 Slide 36 Other Plastids Plastid Organelle with 2 membranes Has its own DNA & RNA Found in plants, some protists Three main types Chloroplasts Chromoplasts Function: Stores lipid soluble pigments Usually colored Amyloplasts Function: Stores starch 35 Slide 37 Peroxisomes Specialized membrane compartment Single membrane Function: 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 36