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CHAPTER 4 CELLS LIVING ORGANISMS are HIGHLY ORGANIZED • Cells, the simplest collection of matter that can live, were first observed by Robert Hooke in 1665 • Antoni van Leeuwenhoek later described cells that could move – He viewed bacteria with his own hand-crafted microscopes Copyright © 2009 Pearson Education, Inc. The CELL THEORY: • The early microscopes provided data to establish the cell theory – All living things are composed of cells – All cells come from other cells (NO Spontaneous Generation) Copyright © 2009 Pearson Education, Inc. INTRODUCTION TO THE CELL Copyright © 2009 Pearson Education, Inc. Microscopes reveal the world of the cell • A variety of microscopes have been developed for a clearer view of cells and cellular structure • The most frequently used microscope is the light microscope (LM)—like the one used in biology laboratories • We will use a COMPOUND LIGHT MICROSCOPE – Light passes through a specimen then through 2 glass lenses into the viewer’s eye – Specimens can be magnified up to 400 times the actual size of the specimen Copyright © 2009 Pearson Education, Inc. Enlarges image formed by objective lens Eyepiece Magnifies specimen, forming primary image Objective lens Focuses light through specimen Ocular lens Specimen Condenser lens Light source Microscopes reveal the world of the cell • Microscopes have limitations – Both the human eye and the microscope have limits of RESOLUTION—the ability to distinguish between small structures – Therefore, the light microscope cannot provide the details of a small cell’s structure – SO…we can stain the specimen – Can you think of a problem with this??? Copyright © 2009 Pearson Education, Inc. 10 m Length of some nerve and muscle cells Chicken egg 10 mm (1 cm) 100 µm 10 µm 1 µm 100 nm 10 nm 1 nm 0.1 nm Frog egg Most plant and animal cells Nucleus Most bacteria Mitochondrion Mycoplasmas (smallest bacteria) Viruses Ribosome Proteins Lipids Small molecules Atoms Electron microscope 1 mm Light microscope 100 mm (10 cm) Human height Unaided eye 1m Prokaryotic cells are structurally simpler than eukaryotic cells • Bacteria and archaea are prokaryotic cells • All other forms of life are eukaryotic cells – Both prokaryotic and eukaryotic cells have a plasma membrane and one or more chromosomes (DNA) and ribosomes – Eukaryotic cells have a membrane-bound nucleus and a number of other organelles, whereas prokaryotes have no nucleus and no true organelles Copyright © 2009 Pearson Education, Inc. Prokaryotic Cells • Prokaryotic cells are like a studio (oneroom) apartment – All functions take place within the plasma membrane of the cell Pili Nucleoid Ribosomes Plasma membrane Bacterial chromosome Cell wall Capsule A typical rod-shaped bacterium Flagella A thin section through the bacterium Bacillus coagulans (TEM) Eukaryotic cells are partitioned into functional compartments • Eukaryotic cells are like a multiple room apartment – Different functions take place in different organelles Copyright © 2009 Pearson Education, Inc. Eukaryotic cells are partitioned into functional compartments • Manufacturing of protein molecules involves the nucleus, ribosomes, endoplasmic reticulum, and Golgi apparatus Copyright © 2009 Pearson Education, Inc. The nucleus is the cell’s genetic control center • It contains the information (DNA) to make protein molecules • The nuclear envelope is a double membrane with pores that allow material (messenger RNA) to flow out of the nucleus – It is attached to a network of cellular membranes called the endoplasmic reticulum Copyright © 2009 Pearson Education, Inc. Two membranes of nuclear envelope Nucleus Nucleolus Chromatin Pore Endoplasmic reticulum Ribosomes Ribosomes make proteins for use in the cell and outside of the cell • Ribosomes are involved in the cell’s protein synthesis –Ribosomes are synthesized in the nucleolus, which is found in the nucleus Copyright © 2009 Pearson Education, Inc. Ribosomes ER Cytoplasm Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit TEM showing ER and ribosomes Diagram of a ribosome Small subunit The endoplasmic reticulum is a biosynthetic factory • There are two kinds of endoplasmic reticulum—smooth and rough • Smooth ER lacks attached ribosomes • Rough ER lines the outer surface of membranes – They differ in structure and function – However, they are connected Copyright © 2009 Pearson Education, Inc. Nuclear envelope Ribosomes Smooth ER Rough ER The endoplasmic reticulum is a biosynthetic factory • Smooth ER is involved in a variety of diverse metabolic processes – For example, enzymes produced by the smooth ER are involved in the synthesis of lipids, oils, phospholipids, and steroids Copyright © 2009 Pearson Education, Inc. The endoplasmic reticulum is a biosynthetic factory • Rough ER makes proteins –Once proteins are synthesized, they are transported in vesicles to other parts of the endomembrane system Copyright © 2009 Pearson Education, Inc. The Golgi apparatus finishes, sorts, and ships cell products • The Golgi apparatus functions in conjunction with the ER by modifying products of the ER – Products travel in transport vesicles from the ER to the Golgi apparatus – One side of the Golgi apparatus functions as a receiving dock for the product and the other as a shipping dock – Products are modified as they go from one side of the Golgi apparatus to the other and travel in vesicles to other sites Copyright © 2009 Pearson Education, Inc. Transport vesicle buds off 4 Ribosome Secretory protein inside transport vesicle 3 Sugar chain 1 Polypeptide 2 Glycoprotein Rough ER “Receiving” side of Golgi apparatus Golgi apparatus Transport vesicle from ER New vesicle forming “Shipping” side of Golgi apparatus Transport vesicle from the Golgi Golgi apparatus PROTEIN SYNTHESIS • In the nucleus, DNA information for protein synthesis is copied into messenger RNA (mRNA) • mRNA leaves the nucleus; goes to the ribosomes • Proteins are synthesized at the ribosomes • Proteins leave the ribosomes in transport vesicles headed for the Golgi apparatus • Proteins are modified at the Golgi apparatus • Modified proteins leave the Golgi apparatus in transport vesicles headed for their destination (inside or outside of the cell) Nucleus Nuclear membrane Rough ER Smooth ER Transport vesicle Transport vesicle Golgi apparatus Lysosome Vacuole Plasma membrane Lysosomes are digestive compartments within a cell • A lysosome is a membranous sac containing digestive enzymes – The enzymes and membrane are produced by the ER and transferred to the Golgi apparatus for processing – The membrane serves to safely isolate these potent enzymes from the rest of the cell – These enzymes can be used to: – Digest dead cells – Digest “food” for unicellular organisms – Destroy pathogens (WHITE BLOOD CELLS) Copyright © 2009 Pearson Education, Inc. Vacuoles function in the general maintenance of the cell • Vacuoles are membranous sacs that are found in a variety of cells and possess an assortment of functions – Examples are the central vacuole in plants – Water is stored here Copyright © 2009 Pearson Education, Inc. Chloroplast Nucleus Central vacuole Mitochondria harvest chemical energy from food • Cellular respiration is accomplished in the mitochondria of eukaryotic cells – Cellular respiration involves conversion of chemical energy in foods (GLUCOSE) to chemical energy in ATP (adenosine triphosphate) Copyright © 2009 Pearson Education, Inc. Mitochondrion Outer membrane Intermembrane space Inner membrane Cristae Matrix Chloroplasts convert solar (sunlight) energy to chemical energy • Chloroplasts are the photosynthesizing organelles of plants –Photosynthesis is the conversion of light energy to chemical energy of sugar molecules Copyright © 2009 Pearson Education, Inc. Chloroplast Stroma Inner and outer membranes Granum Intermembrane space Cilia and flagella move when microtubules bend • While some protists have flagella and cilia that are important in locomotion, some cells of multicellular organisms have them for different reasons – Cells that sweep mucus out of our lungs have cilia – Animal sperm are flagellated Copyright © 2009 Pearson Education, Inc. Cilia Flagellum Eukaryotic cells are partitioned into functional compartments • Although there are many similarities between animal and plant cells, differences exist – Lysosomes and centrioles are not found in plant cells – Plant cells have a rigid cell wall, chloroplasts, and a central vacuole not found in animal cells Copyright © 2009 Pearson Education, Inc. NUCLEUS: Nuclear envelope Smooth endoplasmic reticulum Chromosomes Nucleolus Rough endoplasmic reticulum Lysosome Centriole Peroxisome CYTOSKELETON: Microtubule Intermediate filament Microfilament Ribosomes Golgi apparatus Plasma membrane Mitochondrion Review of Cell Types Bacterial Cell Plant Cell Animal Cell Ten times smaller (1-10 micrometers) 10-100 micrometers 10-100 micrometers One “Naked” Chromosome Multiple Chromosomes Multiple Chromosomes Cell Wall Cell Wall No Cell Wall No Nucleus Nucleus Nucleus No Organelles Organelles Organelles No Organelles Chloroplasts; Central Vacuoles No Chloroplasts or Central Vacuoles No Organelles No Centrioles or Lysosomes Centrioles and Lysosomes