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 Animation: Lysosome Formation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

A lysosome fuses with the food vacuole and digests the molecules 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 For the Cell Biology Video Phagocytosis in Action, go to Animation and Video Files. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

two damaged organelles 1 µm Fig. 6-14 Nucleus 1 µm Vesicle containing two damaged organelles 1 µm Mitochondrion fragment Peroxisome fragment Lysosome Digestive enzymes Lysosome Lysosome Plasma membrane Peroxisome Figure 6.14a Lysosomes Digestion Food vacuole Mitochondrion Digestion Vesicle (a) Phagocytosis (b) Autophagy

Nucleus 1 µm Lysosome Digestive enzymes Lysosome Plasma membrane Fig. 6-14a Nucleus 1 µm Lysosome Digestive enzymes Lysosome Figure 6.14a Lysosome—phagocytosis Plasma membrane Digestion Food vacuole (a) Phagocytosis

two damaged organelles 1 µm Fig. 6-14b Vesicle containing two damaged organelles 1 µm Mitochondrion fragment Peroxisome fragment Lysosome Figure 6.14b Lysosomes—autophagy Peroxisome Mitochondrion Digestion Vesicle (b) Autophagy

The Endomembrane System: A Review The endomembrane system is a complex and dynamic player in the cell’s compartmental organization Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Nucleus Rough ER Smooth ER Plasma membrane Fig. 6-16-1 Figure 6.16 Review: relationships among organelles of the endomembrane system Plasma membrane

Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi Fig. 6-16-2 Nucleus Rough ER Smooth ER cis Golgi Figure 6.16 Review: relationships among organelles of the endomembrane system Plasma membrane trans Golgi

Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi Fig. 6-16-3 Nucleus Rough ER Smooth ER cis Golgi Figure 6.16 Review: relationships among organelles of the endomembrane system Plasma membrane trans Golgi

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

Mitochondria: Chemical Energy Conversion Mitochondria are in nearly all eukaryotic cells They have a smooth outer membrane and an inner membrane folded into cristae The inner membrane creates two compartments: intermembrane space and mitochondrial matrix Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix Cristae present a large surface area for enzymes that synthesize ATP Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

in the mitochondrial matrix Fig. 6-17 Intermembrane space Outer membrane Free ribosomes in the mitochondrial matrix Inner membrane Cristae Figure 6.17 The mitochondrion, site of cellular respiration Matrix 0.1 µm

Chloroplasts: Capture of Light Energy The chloroplast is a member of a family of organelles called plastids Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis Chloroplasts are found in leaves and other green organs of plants and in algae Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Chloroplast structure includes: Thylakoids, membranous sacs, stacked to form a granum Stroma, the internal fluid Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Inner and outer membranes Fig. 6-18 Ribosomes Stroma Inner and outer membranes Granum 1 µm Thylakoid Figure 6.18 The chloroplast, site of photosynthesis

Overview: Life at the Edge The plasma membrane is the boundary that separates the living cell from its surroundings The plasma membrane exhibits selective permeability, allowing some substances to cross it more easily than others Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cellular membranes are fluid mosaics of lipids and proteins Phospholipids are the most abundant lipid in the plasma membrane Phospholipids are amphipathic molecules, containing hydrophobic and hydrophilic regions The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it For the Cell Biology Video Structure of the Cell Membrane, go to Animation and Video Files. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

WATER Hydrophilic head Hydrophobic tail WATER Fig. 7-2 Figure 7.2 Phospholipid bilayer (cross section) Hydrophobic tail WATER

Phospholipid bilayer Hydrophobic regions of protein Hydrophilic Fig. 7-3 Phospholipid bilayer Figure 7.3 The fluid mosaic model for membranes Hydrophobic regions of protein Hydrophilic regions of protein

Fig. 7-7 Fibers of extracellular matrix (ECM) Glyco- Carbohydrate protein Carbohydrate Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Figure 7.7 The detailed structure of an animal cell’s plasma membrane, in a cutaway view Cholesterol Microfilaments of cytoskeleton Peripheral proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE

Discussion Questions A Panoramic View of the Cell Distinguish between prokaryotic and eukaryotic cells. Explain why there are both upper and lower limits to cell size. Explain the advantages of compartmentalization in eukaryotic cells.

Chapter Review Inside of every cell there is some type of organization that allows cells to perform it’s life functions. Some cells are more complicated that others. In this assignment you will need to explain: a. the process by which a cell takes mRNA (a code for an enzyme) from the nucleus . b. converts it to an enzyme. c. and transports it outside the cell. a. the process by which Starch is taken into the cell. b. Broken down (digested). c. What organelle is it taken to and Why? a. What is the difference between Eukaryotes and Prokaryotes. b. In what type of cell would you find Plastids, Vacuoles and what’s their function. c. In what type of cells would you find Cilia and Flagella and what’s their function. Unicellular Multicellular Levels of Organization Metabolisms Organelles Eukaryotes Prokaryotes Ribosomes Endoplasmic Reticulum Golgi Bodies Mitochondria Nucleus Vacuoles Centrioles Plastids Chloroplasts Chlorophyll Lysosomes Cilia Flagella Symbiotic Theory

Vacuoles? Fluid filled, membrane bound structures for storage.

Cytoskeleton? Gives support and shape to the cell. 2 Parts 1. Microfilaments = protein strands (actin & myosin) - Contractile proteins – support and help in cell movement. 2. Microtubules = long thick proteins that stretch form the cell membrane to the nucleus. Help organelles move with in the cell

Centrioles – Cilia / Flagella Centrioles = used in cell division (made of microtubules) Play Cilia and Flagella – microtubules surrounded by the cell membrane extending outside the cell used for locomotion

Evolution of Eukaryotes Symbiotic Theory? Symbiosis? 2 organisms living in close association. Prokaryotic Characteristics? No Nucleus DNA = single, double stranded, circular chromosomes No membrane bound organelles, but do have ribosomes (smaller) Mitochondria and Chloroplasts? Contain their own DNA, RNA and ribosomes that are similar to Prokaryotes. Ribosomes? Smaller in Prokaryotes yet similar enzymes for making proteins and Nucleic Acids It’s Logical but incomplete. Why? Nuclear Membrane? Various Membrane bound structures? And other eukaryotic structures?

Symbiotic Theory