ENDURING UNDERSTANDING 2.B GROWTH, REPRODUCTION AND DYNAMIC HOMEOSTASIS REQUIRE THAT CELLS CREATE AND MAINTAIN INTERNAL ENVIRONMENTS THAT ARE DIFFERENT FROM THEIR EXTERNAL ENVIRONMENTS. ESSENTIAL KNOWLEDGE 2.B.3 EUKARYOTIC CELLS MAINTAIN INTERNAL MEMBRANES THAT PARTITION THE CELL INTO SPECIALIZED REGIONS. BIG IDEA II BIOLOGICAL SYSTEMS UTILIZE FREE ENERGY AND MOLECULAR BUILDING BLOCKS TO GROW, TO REPRODUCE AND TO MAINTAIN DYNAMIC HOMEOSTASIS.

ESSENTIAL KNOWLEDGE 2.B.3: EUKARYOTIC CELLS MAINTAIN INTERNAL MEMBRANES THAT PARTITION THE CELL INTO SPECIALIZED REGIONS. Learning Objectives: (2.13) The student is able to explain how internal membranes and organelles contribute to cell functions. (2.14) The student is able to use representations and models to describe differences in prokaryotic and eukaryotic cells.

OVERVIEW: THE FUNDAMENTAL UNITS OF LIFE All organisms are made of cells The cell is the simplest collection of matter that can live Cell structure is correlated to cellular function All cells are related by their descent from earlier cells Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

TYPES OF CELLS The basic structural and functional unit of every organism is one of two types of cells: prokaryotic or eukaryotic Eukaryotic cells have internal membranes that compartmentalize their functions Protists, fungi, animals, and plants all consist of eukaryotic cells Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

COMPARING PROKARYOTIC AND EUKARYOTIC CELLS Basic features of all cells: Plasma membrane Semifluid substance called cytosol Chromosomes (carry genes) Ribosomes (make proteins) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

PROKARYOTES VS. EUKARYOTES Prokaryotes: NO NUCLEUS, but do have nucleoid region with DNA present Small and Simple – few organelles Have cell membranes and cytoplasm Ex. Bacteria and Archaea Eukaryotes: Contain nuclei Contains organelles that perform specialized functions Unicellular or multicellular Ex. Plants, animals, protists, fungi

Fig. 6-6 Fimbriae Nucleoid Ribosomes Plasma membrane Cell wall Capsule Flagella Bacterial chromosome (a)A typical rod-shaped bacterium (b)A thin section through the bacterium Bacillus coagulans (TEM) 0.5 µm

EUKARYOTIC CELLS Eukaryotic cells are characterized by having DNA in a nucleus that is bounded by a membranous nuclear envelope Membrane-bound organelles Cytoplasm in the region between the plasma membrane and nucleus Eukaryotic cells are generally much larger than prokaryotic cells Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

A VIEW OF THE EUKARYOTIC CELL A eukaryotic cell has internal membranes that partition the cell into organelles Plant and animal cells have most of the same organelles- Not in Animal Cells: Chloroplasts | central vacuole | tonoplast | cell wall | plasmodesmata Not in Plant Cells: Lysosomes | centrioles | flagella Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 6-9a ENDOPLASMIC RETICULUM (ER) Smooth ERRough ER Flagellum Centrosome CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Microvilli Peroxisome Mitochondrion Lysosome Golgi apparatus Ribosomes Plasma membrane Nuclear envelope Nucleolus Chromatin NUCLEUS

Fig. 6-9b NUCLEUS Nuclear envelope Nucleolus Chromatin Rough endoplasmic reticulum Smooth endoplasmic reticulum Ribosomes Central vacuole Microfilaments Intermediate filaments Microtubules CYTO- SKELETON Chloroplast Plasmodesmata Wall of adjacent cell Cell wall Plasma membrane Peroxisome Mitochondrion Golgi apparatus

ORGANELLES: EMERGENT PROPERTIES All biological systems are composed of parts that interact with each other. These interactions result in characteristics not found in the individual parts alone. In other words, “THE WHOLE IS GREATER THAN THE SUM OF ITS PARTS.” This phenomenon is referred to as emergent properties. All biological systems from the molecular level to the ecosystem level exhibit properties of biocomplexity and diversity. Together, these two properties provide robustness to biological systems, enabling greater resiliency and flexibility to tolerate and respond to changes in the environment. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

INTERNAL MEMBRANES FACILITATE CELLULAR PROCESSES. Internal membranes facilitate cellular processes by minimizing competing interactions and by increasing surface area where reactions can occur. Membranes and membrane-bound organelles in eukaryotic cells localize (compartmentalize) intracellular metabolic processes and specific enzymatic reactions. Archaea and Bacteria generally LACK internal membranes and organelles and have a cell wall.

COMPARTMENTALIZATION IN CELLS Subcellular Structures that Function in Control: Nucleus (plant and animal) Centrosome (plant and animal) Subcellular Structures that Function in Assembly, Transport, and Storage: Endoplasmic reticulum (plant and animal) Ribosomes (plant and animal) Golgi apparatus (plant and animal) Vacuoles (plant -1 large, and animal - many) Lysosomes (animal) Leucoplasts (plant only) Subcellular Structures that Function in Energy Transformations: Chloroplasts and Chromoplasts (plant only) Mitochondria (plant and animal) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig – The Nucleus Nucleolus Nucleus Rough ER Nuclear lamina (TEM) Close-up of nuclear envelope 1 µm 0.25 µm Ribosome Pore complex Nuclear pore Outer membrane Inner membrane Nuclear envelope: Chromatin Surface of nuclear envelope Pore complexes (TEM)

THE ENDOMEMBRANE SYSTEM The endomembrane system regulates protein traffic and performs metabolic functions in the cell Internal membranes facilitate cellular processes by minimizing competing interactions and by increasing surface area where reactions can occur. Components of the endomembrane system: Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Plasma membrane These components are either continuous or connected via transfer by vesicles Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

FIGURE 7.16: RELATIONSHIPS AMONG ORGANELLES OF THE ENDOMEMBRANE SYSTEM

LYSOSOMES: DIGESTIVE COMPARTMENTS A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids Some types of cell can engulf another cell by phagocytosis; this forms a food vacuole A lysosome fuses with the food vacuole and digests the molecules Lysosomes also use enzymes to recycle the cell’s own organelles and macromolecules, a process called autophagy Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

FIGURE 7.14 THE FORMATION AND FUNCTIONS OF LYSOSOMES (LAYER 1)

FIGURE 7.14 THE FORMATION AND FUNCTIONS OF LYSOSOMES (LAYER 2)

FIGURE 7.14 THE FORMATION AND FUNCTIONS OF LYSOSOMES (LAYER 3)

Fig Nucleus 1 µm Lysosome Digestive enzymes Lysosome Plasma membrane Food vacuole (a) Phagocytosis Digestion (b) Autophagy Peroxisome Vesicle Lysosome Mitochondrion Peroxisome fragment Mitochondrion fragment Vesicle containing two damaged organelles 1 µm Digestion In phagocytosis, large substances are taken up by a cell and digested by lysosome enzymes. In autophagy, lysosomes also use enzymes to recycle the cell’s own organelles and macromolecules.

APOPTOSIS – PROGRAMMED CELL DEATH Programmed destruction of cells (apoptosis) by their own lysosomal enzymes is important in the development of many multicellular organisms (such as tadpoles into frogs). This even occurs in the hands of human embryos (which are webbed until lysosomes digest the tissue between the fingers). Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

LYSOSOMAL DISORDERS A variety of inherited disorders called lysosomal storage diseases affect lysosomal metabolism. In Pompe’s disease, the liver is damaged by an accumulation of glycogen due to the absence of a lysosomal enzyme needed to break down that polysaccharide. In Tay-sacs disease, a lipid-digesting enzyme is missing or inactive, and the brain becomes impaired by an accumulation of lipids in the cells. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Golgi Complex cis face (“receiving” side of Golgi apparatus) Cisternae trans face (“shipping” side of Golgi apparatus) TEM of Golgi apparatus 0.1 µm

Fig. 6-11: Ribosomes Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Small subunit Diagram of a ribosome TEM showing ER and ribosomes 0.5 µm

Fig Smooth ER Rough ER Nuclear envelope Transitional ER Rough ER Smooth ER Transport vesicle Ribosomes Cisternae ER lumen 200 nm

FUNCTIONS OF SMOOTH ER The smooth ER Synthesizes lipids Metabolizes carbohydrates Detoxifies poison Stores calcium Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

FUNCTIONS OF ROUGH ER The rough ER Functions to compartmentalize the cell, serves as mechanical support, provides site-specific protein synthesis with membrane-bound ribosomes. Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates) Distributes transport vesicles, proteins surrounded by membranes Is a membrane factory for the cell Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

PATHWAY OF PROTEIN-BASED SECRETION Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

MITOCHONDRIA & CHLOROPLASTS Mitochondria and chloroplasts change energy from one form to another Mitochondria are the sites of cellular respiration, a metabolic process that generates ATP Chloroplasts, found in plants and algae, are the sites of photosynthesis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

MITOCHONDRIA AND CHLOROPLASTS Mitochondria and chloroplasts Are not part of the endomembrane system Have a double membrane Have proteins made by free ribosomes Contain their own DNA Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig Free ribosomes in the mitochondrial matrix Intermembrane space Outer membrane Inner membrane Cristae Matrix 0.1 µm

Fig Ribosomes Thylakoid Stroma Granum Inner and outer membranes 1 µm

A Living Unit is Greater than the Individual Sum of Its Parts 5 µm