Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Cell Theory All organisms are made of cells The cell is the simplest collection of matter that can live All cells come from other cells

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2 What are cells made of? Cells are mostly water. The rest of the molecules present are: protein nucleic acid carbohydrate lipid others By elements, a cell is composed of: 60% hydrogen 25% oxygen 10% carbon 5% nitrogen

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell structure is correlated to cellular function 10 µm Figure 6.1

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Microscopy To study cells, biologists use microscopes and the tools of biochemistry Scientists use microscopes to visualize cells too small to see with the naked eye

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Types of microscopes Light microscopes (LMs) – Pass visible light through a specimen – Magnify cellular structures with lenses Electron microscopes (EMs) – Focus a beam of electrons through a specimen (TEM) or onto its surface (SEM)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Different types of microscopes – Can be used to visualize different sized cellular structures Unaided eye 1 m 0.1 nm 10 m 0.1 m 1 cm 1 mm 100 µm 10 µ m 1 µ m 100 nm 10 nm 1 nm Length of some nerve and muscle cells Chicken egg Frog egg Most plant and Animal cells Smallest bacteria Viruses Ribosomes Proteins Lipids Small molecules Atoms Nucleus Most bacteria Mitochondrion Light microscope Electron microscope Figure 6.2 Human height Measurements 1 centimeter (cm) = 10  2 meter (m) = 0.4 inch 1 millimeter (mm) = 10 –3 m 1 micrometer (µm) = 10 –3 mm = 10 –6 m 1 nanometer (nm) = 10 –3 mm = 10 –9 m

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Use different methods for enhancing visualization of cellular structures TECHNIQUE RESULT Brightfield (unstained specimen). Passes light directly through specimen. Unless cell is naturally pigmented or artificially stained, image has little contrast. [Parts (a)–(d) show a human cheek epithelial cell.] (a) Brightfield (stained specimen). Staining with various dyes enhances contrast, but most staining procedures require that cells be fixed (preserved). (b) Phase-contrast. Enhances contrast in unstained cells by amplifying variations in density within specimen; especially useful for examining living, unpigmented cells. (c) 50 µm Figure 6.3

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Types of electron microscopes The scanning electron microscope (SEM) – Provides for detailed study of the surface of a specimen TECHNIQUE RESULTS Scanning electron micro- scopy (SEM). Micrographs taken with a scanning electron micro- scope show a 3D image of the surface of a specimen. This SEM shows the surface of a cell from a rabbit trachea (windpipe) covered with motile organelles called cilia. Beating of the cilia helps move inhaled debris upward toward the throat. (a) Cilia 1 µm Figure 6.4 (a)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Types of electron microscopes The transmission electron microscope (TEM) – Provides for detailed study of the internal ultrastructure of cells Transmission electron micro- scopy (TEM). A transmission electron microscope profiles a thin section of a specimen. Here we see a section through a tracheal cell, revealing its ultrastructure. In preparing the TEM, some cilia were cut along their lengths, creating longitudinal sections, while other cilia were cut straight across, creating cross sections. (b) Longitudinal section of cilium Cross section of cilium 1 µm Figure 6.4 (b)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Types of Cells

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Characteristics of ALL cells All cells have several basic features in common – They are bounded by a plasma membrane – They contain a semifluid substance called the cytosol – They contain chromosomes – They all have ribosomes

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Prokaryotic cells – Unicellular – Do not contain a nucleus or membrane bound organelles – Has circular DNA

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Example Prokaryotic cells (b) A thin section through the bacterium Bacillus coagulans (TEM) Pili: attachment structures on the surface of some prokaryotes Nucleoid: region where the cell’s DNA is located (not enclosed by a membrane) Ribosomes: organelles that synthesize proteins Plasma membrane: controls entry and exit of substances Cell wall: rigid structure outside the plasma membrane that protects cell From damage and maintains shape Capsule: jelly-like outer coating of many prokaryotes Flagella: locomotion organelles of some bacteria (a) A typical rod-shaped bacterium 0.5 µm Bacterial chromosome Figure 6.6 A, B Cytoplasm: Fluid component which contains the enzymes needed for all metabolic reactions

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Asexual reproduction: where one individual produces offspring that are genetically identical to itself=clones No fusion of gametes and no mixing of genetic info. Causes disease or illness Live in enormous numbers Soil, rock, oceans and arctic

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mesophiles-act best at moderate temps. Extremophiles-thrives best in extreme environments chaea.html

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Domain Archaea wasn't recognized as a major domain of life until quite recently. Until the 20th century, most biologists considered all living things to be classifiable as either a plant or an animal. But in the 1950s and 1960s, most biologists came to the realization that this system failed to accomodate the fungi, protists, and bacteria. By the 1970s, a system of Five Kingdoms had come to be accepted as the model by which all living things could be classified. At a more fundamental level, a distinction was made between the prokaryotic bacteria and the four eukaryotic kingdoms (plants, animals, fungi, & protists). The distinction recognizes the common traits that eukaryotic organisms share, such as nuclei, cytoskeletons, and internal membranes. The scientific community was understandably shocked in the late 1970s by the discovery of an entirely new group of organisms -- the Archaea. Dr. Carl Woese and his colleagues at the University of Illinois were studying relationships among the prokaryotes using DNA sequences, and found that there were two distinctly different groups. Those "bacteria" that lived at high temperatures or produced methane clustered together as a group well away from the usual bacteria and the eukaryotes. Because of this vast difference in genetic makeup, Woese proposed that life be divided into three domains: Eukaryota, Eubacteria, and Archaebacteria. He later decided that the term Archaebacteria was a misnomer, and shortened it to Archaea. The three domains are shown in the illustration above at right, which illustrates also that each group is very different from the others. Further work has revealed additional surprises, which you can read about on the other pages of this exhibit. It is true that most archaeans don't look that different from bacteria under the microscope, and that the extreme conditions under which many species live has made them difficult to culture, so their unique place among living organisms long went unrecognized. However, biochemically and genetically, they are as different from bacteria as you are. Although many books and articles still refer to them as "Archaebacteria", that term has been abandoned because they aren't bacteria -- they're Archaea.

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Eukaryotic cells Eukaryotic cells have internal membranes that compartmentalise their functions. They – Contain a true nucleus, bounded by a membranous nuclear envelope – Are generally quite a bit bigger than prokaryotic cells – Have extensive and elaborately arranged internal membranes, which form organelles

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Types of Eukaryotic cells Can be unicellular (protists) Or multicellular (fungi, plants & animals) Have a membrane bound nucleus Contain organelles Have linear DNA

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Unicellular eukaryotes that are not animals, plants or fungi. There are 4 subgroups.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Different organisms living together usually benefiting both Can be unicellular (eg. Yeasts) or multicellular (mushrooms) Sexual reproduction- when gametes(sex cells) from each parent join and genetic info. mixes to produce offspring with different chromosomes

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A plant cell In plant cells but not animal cells: Chloroplasts Central vacuole and tonoplast Cell wall Plasmodesmata CYTOSKELETON Ribosomes (small brwon dots) Central vacuole Microfilaments Intermediate filaments Microtubules Rough endoplasmic reticulum Smooth endoplasmic reticulum Chromatin NUCLEUS Nuclear envelope Nucleolus Chloroplast Plasmodesmata Wall of adjacent cell Cell wall Golgi apparatus Peroxisome Tonoplast Centrosome Plasma membrane Mitochondrion Figure 6.9

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Most are multicellular. Unicellular eg is amoeba

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A animal cell Rough ERSmooth ER Centrosome CYTOSKELETON Microfilaments Microtubules Microvilli Peroxisome Lysosome Golgi apparatus Ribosomes In animal cells but not plant cells: Lysosomes Centrioles Flagella (in some plant sperm) Nucleolus Chromatin NUCLEUS Flagelium Intermediate filaments ENDOPLASMIC RETICULUM (ER) Mitochondrion Nuclear envelope Plasma membrane Figure 6.9

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The Cell: A Living Unit Greater Than the Sum of Its Parts Cells rely on the integration of structures and organelles in order to function 5 µm Figure 6.32

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cell organelle table r00/7th/cells/sciber/orgtable.htmhttp://utahscience.oremjr.alpine.k12.ut.us/scibe r00/7th/cells/sciber/orgtable.htm

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Degrade and digest pathogens and cellular components

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Energy converting Organelles Mitochondria and chloroplasts change energy from one form to another Mitochondria – Are found in nearly all eukaryotic cells – Are the sites of cellular respiration Chloroplasts – Found only in plants, are the sites of photosynthesis – Contains the green compound, chlorophyll

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mitochondria Mitochondria are enclosed by two membranes – A smooth outer membrane – An inner membrane folded into cristae Mitochondrion Intermembrane space Outer membrane Free ribosomes in the mitochondrial matrix Mitochondrial DNA Inner membrane Cristae Matrix 100 µm Figure 6.17

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chloroplasts – Are found in leaves and other green organs of plants and in algae Chloroplast DNA Ribosomes Stroma Inner and outer membranes Thylakoid 1 µm Granum Figure 6.18

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cilia and Flagella Cilia and flagella – Contain specialized arrangements of microtubules – Are locomotor appendages of some cells 15 µm 1 µm Flagella on sperm cells Cilia on protozoan cell

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Different classification Systems List the 6 groups that we have classified organisms so far. Go to Taonga/Science-Ideas-and-Concepts/Classification-systemhttp://sciencelearn.org.nz/Contexts/Hidden- Taonga/Science-Ideas-and-Concepts/Classification-system 1.Who published a system for classifying living things in the 18 th Century? 2.What did this system show? 3.List this naming structure 4.Why do some scientists say there are 5 kingdoms? 5.What is a possible 7th group? What is the argument against this? 6.Are these groups going to remain like this? Why?