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Cells Objectives: •List scientists who contributed to the cell theory •List the components of the cell theory •Compare prokaryote and eukaryote cells •Label a plant and an animal cell •Know the functions of cell organelles LEVELS OF ORGANIZATION Nonliving Levels: ATOM (element) MOLECULE (compounds like carbohydrates & proteins) ORGANELLES (nucleus, ER, Golgi …) 2 LEVELS OF ORGANIZATION Living Levels: CELL (makes up ALL organisms) TISSUE (cells working together ORGAN (heart, brain, stomach …) ORGAN SYSTEMS (respiratory, circulatory …) 3 ORGANISM (living individual) LEVELS OF ORGANIZATION Living Levels continued: POPULATION (one species in an area) COMMUNITY (several populations in an area ECOSYSTEM (forest, prairie …) BIOME (Tundra, Tropical Rain forest…) BIOSPHERE (all living and nonliving 4 things on Earth) Early Contributions Robert Hooke - First person to see cells and give them their name, he was looking at cork and noted that he saw "a great many boxes” that looked like the cells that monks lived in. (1665) Anton van Leeuwenhoek - Observed first living cells in pond water and scrapings from his teeth, which he called "animalcules" (1673) Early Contributions o Theodore Schwann - zoologist who observed tissues of animals and concluded they had cells. Also the cofounder of the Cell Theory (1839) o Mattias Schleiden - botanist, observed tissues of plants and said they contained cells. Also the cofounder of the Cell Theory ( 1845) o Rudolf Virchow – observed under the microscope, cells dividing and concluded that cells come from pre-existing cells and that all living things are made of cells (1850 ) The Cell Theory 1. Every living organism is made of one or more cells. 2. The cell is the basic unit of structure and function. It is the smallest unit that can perform life functions. 3. All cells arise from preexisting cells. * Why is the Cell Theory called a Theory and not a Fact? Cell Features ALL cells have these parts Ribosomes- make protein for use by the organism Cytoplasm- fluid material within cell DNA- genetic material Cytoskeleton- internal framework of cell Cell Membrane- outer boundary, some things can cross the cell membrane Comprehension Checkpoint Answer true or false 1. Robert Hooke was the first person to see cells. 2. Bacteria cells have a cell membrane. 3. The Cell Theory was developed by a single scientist. 4. Plant cells have cytoplasm 5. Cells taken from fungi do not have DNA. 6. Cells can only come from pre-existing cells. 7. It only took five years to develop the Cell Theory. Prokaryote Cells The first cells to inhabit the earth Simple cells Only example: Bacteria These cells do NOT have a nucleus, their DNA is circular and floats in the cytoplasm Nucleoid region (center) contains the DNA Surrounded by cell membrane & cell wall (peptidoglycan) Contain ribosomes in their cytoplasm to make proteins pilli DNA Ribosomes Some bacteria have a taillike structure called a flagella, that helps it to move A capsule surrounds some bacteria and helps them avoid the body’s immune system Cell wall Cell membrane Bacterial Images Bacteria that causes Anthrax Eukaryotic Cells True Cells Complex Cells found in plants, animals, protists and fungi The cell is composed of 4 main parts: 1. Cell membrane 2. Cytoplasm (cytosol and organelles, except nucleus) 3. Nucleus- “control center” of cell, houses DNA 4. Membrane Bound Organelles- small structures that carry out specific functions (“little organs”). Shape determines function. Other Vocab Protoplasm (nucleus and cytoplasm) Cytosol (fluid part of cytoplasm) Two Main Types of Eukaryotic Cells 13 Plant Cell Animal Cell Cheek Cells Seen Through Microscope Nucleus Controls the normal activities of the cell Usually found at center of cell and the largest organelle in animal cells Has a nuclear membrane/envelope & nuclear pores Contains cell’s DNA in one of 2 forms chromatin - DNA bound to proteins and spread out (non-dividing cell) chromosomes - condensed structures DNA wrapped around proteins, seen in dividing cell Also contains an organelle called nucleolus - which makes the cell’s ribosomes (disappears when cells divide) Cytoplasm • Jelly-like substance enclosed by cell membrane • Provides a medium for chemical reactions to take place • Contains organelles to carry out specific jobs 17 cytoplasm Cell Organelles Mitochondria – this is the cell’s energy center. It turns food into a chemical energy called ATP during Cellular Respiration More active cells like muscle cells have MORE mitochondria The mitochondria is sometimes called the “powerhouse” of the cell Has its own DNA Outer Membrane Interior called Matrix Folded Inner Membrane called Cristae to increase surface area for chemical reactions Interesting Fact --Mitochondria Come from cytoplasm in the EGG cell during fertilization Therefore … 19 You inherit your mitochondria from your mother! Cell Organelles Golgi Apparatus – receive proteins from ER to modify/processes, package and secrete proteins. It is comparable to a factory or a post office. *A vesicle forms with Golgi to transport substances outside cell. Golgi 21 copyright cmassengale Cell Organelles Lysosome – Contains digestive enzymes, breaks down food, bacteria and worn out cell parts Programmed for cell death (autolysis), "suicide sac” Lyse (break open) and release digestive enzymes to break down and recycle cell parts Cell Organelles Endoplasmic Reticulum (ER) – Connects to nuclear envelope and cell membrane Functions in Synthesis of cell products and Transport, "intracellular highway". -Rough ER contains many ribosomes & is involved in protein synthesis -Smooth ER (ribosomes not found on surface) Makes membrane lipids (steroids) Regulates calcium (muscle cells) Destroys toxic substances (Liver) Cell Organelles Ribosomes are made of proteins and rRNA where protein synthesis occurs by joining amino acids together Can be attached to Rough ER or be Free (unattached) in 24 the cytoplasm Cell Organelles Cytoskeleton – Helps cell maintain support & shape; movement microtubules-hollow structures; also -help build cilia flagella microfilaments-threadlike Cell Organelles Centrioles are found only in animal cells Paired structures near nucleus Made of bundle of microtubules Appear during cell division forming mitotic spindle Help to pull chromosome pairs apart to opposite ends of the cell 26 Centrioles & the Mitotic Spindle Made of MICROTUBULES (Tubulin) 27 Cell Organelles Cilia are shorter and more numerous on cells Flagella are longer and fewer (usually 1-3) on cells Function in moving cells, in moving fluids, or in small particles across the 28 cell surface Cell Movement with Cilia & Flagella 29 Cilia Moving Away Dust Particles from the Lungs Respiratory System 30 Cell Membrane Selectively permeable ; it regulates what comes into the cell and what leaves the cell It is composed of a double layer of phospholipids with proteins embedded throughout Cell or Plasma Membrane Composed of double layer of phospholipids and proteins Surrounds outside of ALL cells Controls what enters or leaves the cell Living layer Outside of cell Proteins Carbohydrate chains Cell membrane 32 Inside of cell (cytoplasm) Protein channel Lipid bilayer Phospholipids Heads contain glycerol & phosphate and are hydrophilic (attract water) Tails are made of fatty acids and are hydrophobic (repel water) Make up a bilayer where tails point inward toward each other Can move laterally to allow small molecules (O2, CO2, & 33 H2O to enter) The Cell Membrane is Fluid 34Molecules in cell membranes are constantly moving and changing Cell Membrane Proteins Proteins help move large molecules or aid in cell recognition Peripheral proteins are attached on the surface (inner or outer) Integral proteins are embedded completely through the membrane 35 GLYCOPROTEINS Recognize “self” Glycoproteins have carbohydrate tails to act 36 as markers for cell recognition Cell Membrane in Plants Cell membrane • Lies immediately against the cell wall in plant cells • Pushes out against the cell wall to maintain cell shape 37 Plant Cells Have additional structures CELL WALL – surrounds membrane & provides additional support CHLOROPLASTS – contain green pigment, function in photosynthesis CENTRAL VACUOLE – large water container in center of cell LACK Centrioles Plant Cell Can you identify all the parts? Anacharis Cells Viewed With a Microscope Cell Organelles o Cell Wall- Nonliving layer found in plants, fungi, & bacteria o Made of cellulose in plants, peptidoglycan in bacteria and chitin in Fungi o Supports and protects cell o 41Found outside of the cell membrane Cell wall Chloroplasts Found only in producers (organisms containing chlorophyll) Use energy from sunlight to make own food (glucose) Energy from sun stored in the Chemical Bonds of Sugars 42 Chloroplasts Surrounded by DOUBLE membrane Outer membrane smooth Inner membrane modified into sacs called Thylakoids Thylakoids in stacks called Grana & interconnected Stroma– gel like material 43 surrounding thylakoids Chloroplasts Contains its own DNA Contains enzymes & pigments for Photosynthesis Never in animal or bacterial cells Photosynthesis – food making 44 process Cell Organelles Vacuole – storage area for sugars, proteins, minerals, lipids, wastes, salts, water, and enzymes, plant cells usually have a large central vacuole Small or absent in animal cells Contractile Vacuole Found in unicellular protists like paramecia Regulate water intake by pumping out excess (homeostasis) Keeps the cell from lysing (bursting) 46 Contractile vacuole animation Organelles with DNA In 1970, American biologist, Lynn Margulis, provided evidence that some organelles within cells were at one time free living cells themselves Supporting evidence- Mitochondria and chloroplasts have their own DNA (separate from the nucleus) This supports the ENDOSYMBIOSIS THEORY which states that eukaryotic cells evolved when prokaryote cells engulfed or absorbed other cells. Multicellular Organisms Cells in multicellular organisms often specialize (take on different shapes & functions) 48 Cell Specialization Cells in a multicellular organism become specialized by turning different genes on and off This is known as DIFFERENTIATION 49 Specialized Animal Cells Muscle cells Cheek cells 50 Red blood cells
