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Transcript
Cell Structure 1 Common Cell Traits • A cell is the smallest unit that is capable of performing life functions. • All cells have an outer covering called a cell membrane. • Inside every cell is a gelatin like material called cytoplasm (SI tuh pla zum). • In the cytoplasm of every cell is hereditary material that controls the life of the cell. Cell Structure 1 Comparing Cells • A nerve cell in your leg could be a meter long. • A human egg cell is no bigger than the dot on an i. • A human red blood cell is about one-tenth the size of a human egg cell. Cell Structure 1 Comparing Cells • A bacterium is even smaller—8,000 of the smallest bacteria can fit inside one of your red blood cells. Cell Structure 1 Comparing Cells • The nerve cell has many fine extensions that send and receive impulses to and from other cells. • Though a nerve cell cannot change shape, muscle cells and some blood cells can. • In plant stems, some cells are long and hollow and have openings at their ends. • These cells carry food and water throughout the plant. Cell Types • Scientists have found that cells can be separated into two groups. 1. Prokaryotic 2. Eukaryotic • Brain POP – Cell Specialization Cell Structure 1 Prokaryotic • Cells without a nucleus and membrane-bound organelles. • Found in single-celled organisms such as bacteria. Cell Structure 1 Eukaryotic • Eukaryotic cells have a nucleus that holds the cell’s DNA and membranebound organelles. Many eukaryotes are multicellular. Examples: Protists, Fungi, Plants, and Animals. Cell Structure 1 Cell Wall – Plant Cells • Cell walls are tough, rigid outer covering that protect the cell and provides support and gives shape. • Plants, algae, fungi, and most bacteria are enclosed in a cell wall. Cell Structure 1 Cell Wall - Support and Protection • A plant cell wall is mostly made up of a carbohydrate called cellulose. • Long, threadlike fibers of cellulose form a thick mesh that allows water and dissolved materials to pass into and out of the cell. • Plant cells responsible for support have a lot of lignin in their walls. Cell Structure 1 Cell Membrane- Plant and Animal Cells • Protective layer that has tiny openings or pores around all cells. • In plant cells, the cell membrane is just inside the cell wall. • In animal cells, it forms the outer covering of the cell. Cell Membrane – Similar to A Window Screen. • Provides support and protection for the animal cell. • Regulates movement of materials between the cell and the environment similar to a doorway or window Screen. • Selective Permeable - It allows some things to enter or leave the cell while keeping other things outside or inside the cell. • Move three ways- Diffusion, Osmosis and Active Transport Cell Structure 1 Cytoplasm – Plant and Animal • A clear, thick gelatin like substance that moves constantly in the cell membrane. • Area between nucleus and cell membrane where cell organelles are located. • Throughout the cytoplasm is the cytoskeleton, which helps the cell maintain or change its shape. Cell Structure 1 Cytoplasm • Within the cytoplasm of eukaryotic cells are structures called organelles. • Some organelles process energy and others manufacture substances needed by the cell or other cells. • Most organelles are surrounded by membranes. • The nucleus is usually the largest organelle in a cell. • http://www.classzone.com/books/ml_scien ce_share/vis_sim/chm05_pg7_cell/chm05 _pg7_cell.html • Cell Models: An Interactive Animation Cell Structure Nucleus – Plant and Animal Cell Large, oval structure. • Directs all cell activities and is separated from the cytoplasm by a membrane. • The nucleus contains the instructions for everything the cell does. 1 1 Cell Structure Nucleus – “Brain” of the cell or manager which directs daily operations and passes on information • Contains nuclear membrane, nucleolus and chromosomes. • These instructions are found on long, threadlike, hereditary material made of DNA. • DNA is the chemical that contains the code for the cell’s structure and activities. • Hereditary material coils tightly around proteins to form chromosomes Nucleolus -Found in plant and animal cells. • Dark, round area found within the Nucleus • Produces Ribosomes. • Ribosomes are involved in the protein-making process in the cell. Chromosomes - Found in Plant and Animal Cells • Thick, rod-like strands floating in the nucleus that contains hereditary material, DNA, master instructions for building proteins, and passes on traits. The rodlike object is created from hereditary material (nucleic acids) that coils tightly around proteins to form. Cell Structure 1 Chloroplast – Plant Cell only - Energy Producer for the Cell • Large, irregularly shaped green structure floating in cytoplasm • Food for the plant is made here through the process of photosynthesis. • Photosynthesis is the process by which plants and algae use sunlight, carbon dioxide and water to make sugar and oxygen. Cell Structure 1 • • • • Chloroplast- Energy-Processing Organelles Chloroplasts contain the green pigment chlorophyll, which gives many leaves and stems their green color as well as captures light energy (photosynthesis) that is used to make a sugar called glucose. Glucose molecules store the captured light energy as chemical energy. Many cells, including animal cells, do not have chloroplasts for making food. They must get food from their environment. • BrainPop Movies Cell Structure Cell Structure 1 Mitochondria- Powerhouse of the Cell • Rod-shaped structure, somewhat larger than the ribosome. • The energy in food is stored until it is needed and then released by the mitochondria. Mitochondria - Found in Plant and Animal Cells • Energy is released during the break down of food (sugar) into carbon dioxide and water. • This energy is stored in a substance called ATP(adenosine triphosphate). The Cell then uses ATP to do work. Cell Structure 1 Ribosome - Found in Plant and Animal Cells • Tiny, grain like bodies produced in the nucleolus. • Make proteins for the cell. • Proteins are part of cell membranes. Other proteins are needed for chemical reactions that take place in the cytoplasm. Cell Structure 1 Ribosome - Protein Factories of the Cell • Some ribosomes float freely in the cytoplasm; others are attached to the endoplasmic reticulum. • Ribosomes receive directions from hereditary material on how, when, and in what order to make specific proteins. Cell Structure 1 Endoplasmic Reticulum-Found in both Animal and plant cells. Transportation System of the Cell • It is a series of folded, tubular membranes throughout the cell which carries materials such as proteins from one part of the cell to another. • Extends from the nucleus to the cell membrane. Cell Structure 1 ER – Transportation of Materials • The endoplasmic reticulum may be “rough” or “smooth.” • ER that has no attached ribosomes is called smooth endoplasmic reticulum. • This type of ER processes other cellular substances such as lipids that store energy. • Ribosomes attached the ER carry out the job of making proteins. Cell Structure 1 Golgi Bodies - Storage Area • After proteins are made in a cell, they are transferred to another type of cell organelle called the Golgi (GAWL jee) bodies. • The Golgi bodies sort proteins and other cellular substances and package them into membranebound structures called vesicles. Cell Structure 1 Golgi Bodies - Storing Organelle • The vesicles deliver cellular substances to areas inside the cell. • They also carry cellular substances to the cell membrane where they are released to the outside of the cell. • Found in Plant and Animal Cells • Series of closely stacked flattened membrane sacs. Cell Structure 1 Vacuoles – Storage Tank • Cells have membrane-bound spaces called vacuoles for the temporary storage of materials. • Vacuoles can store water, waste products, food, and other cellular materials. • Large, round water filled sac floating in the cytoplasm • Plant cells - one very large vacuole. • Animal cells - small and only have a few. Cell Structure 1 Lysosomes - Recycling Organelles • Contain digestive chemicals called enzymes that break down food molecules, cell wastes, and worn-out cell parts. • When a cell dies, a lysosome’s membrane disintegrates. This releases digestive chemicals that allow the quick breakdown of the cell’s contents. Lysosomes – Cleanup crew for the cell • Common in Animal cells and some in plant cells • Small, round structures Resources • http://library.thinkquest.org/5420/ • http://www.usoe.k12.ut.us/CURR/SCIENCE/scib er00/7th/cells/sciber/orgtable.htm • http://www.biology4kids.com/files/cell_main.html • http://users.rcn.com/jkimball.ma.ultranet/Biology Pages/A/AnimalCells.html • http://micro.magnet.fsu.edu/cells/animalcell.html • http://www.glencoe.com/sites/common_assets/s cience/virtual_labs/E08/E08.html • http://learn.genetics.utah.edu/content/begi n/cells/insideacell/ Cell Structure 1 From Cell to Organism • A tissue is a group of similar cells that work together to do one job. • Tissues are organized into organs. Cell Structure 1 From Cell to Organism • An organ is a structure made up of two or more different types of tissues that work together. • Your heart is an organ made up of cardiac muscle tissue, nerve tissue, and blood tissues. Cell Structure 1 From Cell to Organism • A group of organs working together to perform a certain function is an organ system. Your heart, arteries, veins, and capillaries make up your cardiovascular system. Section Check 1 Question 1 Which of these cells is found in a bacterium? Section Check 1 Answer Prokaryotic cells are only found in one-celled organisms, such as bacteria. Prokaryotic cells are cells without membrane-bound structures. Section Check 1 Question 2 Which part of the cell protects the cell and gives it shape? Answer Cell walls are tough, rigid outer coverings that protect the cell and give it shape. The cells of plants, algae, fungi, and most bacteria are enclosed in a cell wall. Section Check 1 Question 3 In what part of the cell is the cytoskeleton found? Answer Cytoplasm is the gelatinlike substance within the cell. The cytoskeleton is found throughout the cytoplasm. Viewing Cells 2 Magnifying Cells • To see most cells, you need to use a microscope. • A microscope has one or more lenses that enlarge the image of an object as though you are walking closer to it. Viewing Cells 2 Early Microscopes • In the late 1500s, the first microscope was made by a Dutch maker of reading glasses. • In the mid 1600s, Antonie van Leeuwenhoek, a Dutch fabric merchant, made a simple microscope with a tiny glass bead for a lens. Viewing Cells 2 Early Microscopes • His microscope could magnify up to 270 times. • Today you would say his lens had a power of 270. Viewing Cells 2 Modern Microscopes • Depending on how many lenses a microscope contains, it is called simple or compound. • A simple microscope is similar to a magnifying lens. • It has only one lens. A microscope’s lens makes an enlarged image of an object and directs light toward your eye. • The change in apparent size produced by a microscope is called magnification. Viewing Cells 2 Modern Microscopes • The compound light microscope has two sets of lenses—eyepiece lenses and objective lenses. • The eyepiece lenses are mounted in one or two tubelike structures. • Compound light microscopes usually have two to four movable objective lenses. Viewing Cells 2 Magnification • The powers of the eyepiece and objective lenses determine the total magnifications of a microscope. • If the eyepiece lens has a power of 10 and the objective lens has a power of 43, then the total magnification is 430 (10 times 43). Viewing Cells 2 Electron Microscopes • Things that are too small to be seen with other microscopes can be viewed with an electron microscope. • Instead of using lenses to direct beams of light, an electron microscope used a magnetic field in a vacuum to direct beams of electrons. Viewing Cells 2 Electron Microscopes • Scanning electron microscopes (SEM) produce a realistic, three-dimensional image. • Only the surface of the specimen can be observed using an SEM. Viewing Cells 2 Electron Microscopes • Transmission electron microscopes (TEM) produce a two-dimensional image of a thinlysliced specimen. • Scanning tunneling microscopes (STM) are able to show the arrangement of atoms on the surface of a molecule. Viewing Cells 2 Electron Microscopes • A metal probe is placed near the surface of the specimen and electrons flow from the tip. • The hills and valleys of the specimen’s surface are mapped. Viewing Cells 2 Cell Theory • Cells weren’t discovered until the microscope was improved. • In 1665, Robert Hooke cut a thin slice of cork and looked at it under his microscope. • To Hooke, the cork seemed to be made up of empty little boxes, which he named cells. Viewing Cells 2 Cell Theory • In the 1830s, Matthias Schleiden used a microscope to study plants and concluded that all plants are made of cells. • Theodor Schwann, after observing different animal cells, concluded that all animals are made up of cells. • Eventually, they combined their ideas and became convinced that all living things are made of cells. Viewing Cells 2 Cell Theory • Several years later, Rudolph Virchow hypothesized that cells divide to form new cells. • His observations and conclusions and those of others are summarized in the cell theory.