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Transcript
The Cell Chapter 3 10 m History of the Cell Robert Hooke first to name cells Van Leuwenhooke First to identify cells as living structures The Cell Theory: Schleiden & Schwann 1. All organisms are made of cells 2. The cell is the simplest collection of matter that can be alive 3. Cell structure is correlated to cellular function 4. All cells are related by their descent from earlier cells Comparing Prokaryotic & Eukaryotic Cells Basic features of ALL cells Plasma membrane Semifluid substance called cytosol within cytoplasm (area between PM and nucleus) Genetic Material Ribosomes Prokaryotic cells are characterized by having No nucleus Free-floating circular DNA No membrane-bound organelles Cell walls Fimbriae Nucleoid Ribosomes Plasma membrane Bacterial chromosome Cell wall Capsule 0.5 m (a) A typical rod-shaped bacterium Flagella (b) A thin section through the bacterium Bacillus coagulans (TEM) Eukaryotic Cells we will focus on plant & animal cells Eukaryotic Cells membrane bound organelles 1. plasma membrane - selectively permeable . 2. Nucleus - surrounded by 2 membranes (nuclear envelope) - interrupted by pores - stores DNA 1 m Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Rough ER Surface of nuclear envelope Pore complex Ribosome Chromatin 1 m 0.25 m Close-up of nuclear envelope Pore complexes (TEM) Nuclear lamina (TEM) 3. endoplasmic reticulum (ER) - continuous with the nuclear envelope - there are two distinct regions of ER Smooth ER Rough ER Smooth ER Nuclear envelope Rough ER ER lumen Cisternae Ribosomes Transport vesicle Smooth ER Transitional ER Rough ER 200 nm Functions of Smooth ER The smooth ER Synthesizes lipids Metabolizes carbohydrates Detoxifies drugs and poisons Functions of Rough ER The rough ER Has bound ribosomes make proteins - glycoproteins - transport vesicles 4. Golgi apparatus consists of flattened membranous sacs Functions Modifies products of the ER Manufactures certain macromolecules Sorts and packages materials into transport vesicles cis face (“receiving” side of Golgi apparatus) 0.1 m Cisternae trans face (“shipping” side of Golgi apparatus) TEM of Golgi apparatus Nucleus Rough ER Smooth ER cis Golgi trans Golgi Plasma membrane 5. lysosome is a membranous sac of digestive enzymes - Undergoes autophagy to digest old, worn-out organelles & macromolecules Nucleus Vesicle containing two damaged organelles 1 m 1 m Mitochondrion fragment Peroxisome fragment Lysosome Digestive enzymes Lysosome Lysosome Plasma membrane Peroxisome Digestion Food vacuole Vesicle (a) Phagocytosis (b) Autophagy Mitochondrion Digestion 6. Vacuoles – diverse maintenance compartments - derived from ER and Golgi apparatus Examples Food vacuoles Contractile vacuoles (found in many freshwater protists pump excess water out of cells) Central vacuoles (found in many mature plant cells hold toxins and water) Central vacuole Cytosol Nucleus Central vacuole Cell wall Chloroplast 5 m Endomembrane System regulates protein traffic and performs metabolic functions in the cell Components Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Plasma membrane These components are either continuous or connected via transfer by vesicles 7. Mitochondria (power house of the cell) - surrounded by a double membrane - cellular respiration - a single cell may have a few hundred 10 m Intermembrane space Mitochondria Outer membrane DNA Free ribosomes in the mitochondrial matrix Inner membrane Mitochondrial DNA Cristae Matrix (a) Diagram and TEM of mitochondrion Nuclear DNA 0.1 m (b) Network of mitochondria in a protist cell (LM) 8. Chloroplasts - contain the green pigment chlorophyll & enzymes that function in photosynthesis - found in leaves & other green organs of plants & algae * Belong to a group of plant organelles called plastids Figure 6.18 50 m Ribosomes Stroma Inner and outer membranes Granum DNA Intermembrane space Thylakoid (a) Diagram and TEM of chloroplast Chloroplasts (red) 1 m (b) Chloroplasts in an algal cell The Endosymbiont theory An early ancestor of eukaryotic cells engulfed a nonphotosynthetic prokaryotic cell, which formed an endosymbiont relationship with its host The host cell and endosymbiont merged into a single organism, a eukaryotic cell with a mitochondrion At least one of these cells may have taken up a photosynthetic prokaryote, becoming the ancestor of cells that contain chloroplasts Endoplasmic reticulum Nucleus Engulfing of oxygenNuclear using nonphotosynthetic envelope prokaryote, which becomes a mitochondrion Ancestor of eukaryotic cells (host cell) Mitochondrion Nonphotosynthetic eukaryote At least one cell Engulfing of photosynthetic prokaryote Chloroplast Mitochondrion Photosynthetic eukaryote 9. cytoskeleton is a network of fibers extending throughout the cytoplasm It organizes the cell’s structures and activities, anchoring many organelles * Technically not an organelle.
