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Life and Cells Characteristics of Life Organisms are living things All share similar life functions Life functions: the many activities carried out by all living things Metabolism: all the chemical reactions that occur within a living thing Homeostasis: the maintenance of a stable internal environment Scientists Robert Hooke : looked at a thin slice of cork (oak cork) through a compound microscope and observed tiny, hollow, roomlike structures and called these structures 'cells' because they reminded him of the rooms that monks lived in. He only saw the outer walls (cell walls) because cork cells are not alive. Anton van Leeuwenhoek (around the same time as Hooke, 1676) He observed living cells called bacteria, which are single-cell organisms. . Matthias Schleiden (1838) who viewed plant parts under a microscope and discovered that plant parts are made of cells. Theodor Schwann (1839) viewed animal parts under a microscope and discovered that animal parts are also made of cells. This helped propel the idea that cells were common building blocks of normal and possibly abnormal bodies. Rudolph Virchow (1855), who stated that all living cells come only from other living cells. Robert Brown: Discovered an organelle called the nucleus, at the center of most cells. Louis Pasteur: Proved that tiny microscopic organisms (microbes) cause disease. Pasteruization: sterilizing food to inhibit microbe growth and preserve shelf life. Life Functions 1. Nutrition: obtaining materials from the environment and processing them for use 2. Transport: absorption and movement of materials in an organism 3. Respiration: processes that provide the energy needed for life 4. Excretion: removal of waste products 5. Synthesis: formation of large molecules from smaller ones 6. Regulation: the control and coordination of an organism’s activities 7. Growth: an increase in size and/or cell number 8. Reproduction: the production of new individuals to allow the species to survive Chemical Composition Organisms share similar chemical compositions Made of mostly carbon, hydrogen, nitrogen, and oxygen Organic molecules contain both carbon and hydrogen Ex: glucose (C6H12O6) Inorganic molecules do not contain both carbon and hydrogen Ex: carbon dioxide (CO2), water (H2O) Organization Organisms share the same basic building plan Most cells contain specialized structures called organelles The cell is the smallest structural and functional unit of life Organisms can either be single-cellular or multicellular In multicellular organisms, groups of specialized cells are organized into tissues Different kinds of tissues can be combined to make an organ that performs a life function Organs work together to form an organ system that also performs a life function Levels of organization: Atom – Molecule – organelle – cell – tissue – organ – organ systems – organism Cells Two types of cells: prokaryotic and eukaryotic Prokaryotic = bacteria Do not have a nucleus or other organelles Eukaryotic = animal and plant cells Have a nucleus and other organelles Cell Theory 1. All organisms are made up of one or more cells. 2. The cell is the basic unit of structure and function of all living things. 3. All cells arise from previously existing cells. Exceptions to the Cell theory Exception to "every cell came from another cell": The first cell ever. (Controversial) Exception to "a cell is the smallest unit of life"/"all life is made of cells": viral matter. Mitochondria and Chloroplast contain their own DNA so they can reproduce on their own. Theory: The cell is a unit and will reproduce as a unit Cytoplasm The cytoplasm is the jelly-like substance inside the cell Contains specialized structures Transports materials Most of the reactions of metabolism occur here Nucleus nucleus controls the cell’s metabolism and stores genetic information Genetic information = DNA in chromosomes Often found in the center of the cell Contains a dark area called the nucleolus The Makes ribosomes Protected by an outer covering called the nuclear envelope Nuclear envelope contains small openings called nuclear pores Vacuoles Vacuoles are storage sacs in the cytoplasm Surrounded by a membrane Contain food, water, or wastes May be specialized to digest food or pump excess water out of the cell Larger in plant cells than in animal cells Contractile Vacuole: A specialized organelle designed to pump out excess water. Useful only in fresh water protozoa. Salt water protozoa do not need them. Salt dehydrates the cell. Endoplasmic Reticulum The endoplasmic reticulum (ER) is a series of interconnecting channels that makes lipids Lipids = fats Can also transport proteins Rough ER = small structures called ribosomes are attached Smooth ER = no ribosomes Ribosomes Ribosomes are tiny structures that make proteins Can be floating free in the cytoplasm (“free ribosome”) Can be attached to the rough ER Golgi Apparatus The Golgi apparatus (or Golgi complex) processes proteins and lipids Processes = modifies and packages Acts as the cell’s post office Made of membrane-bound sacs that look like a stack of curved plates Mitochondria Singular, mitochondrion; plural, mitochondria Uses enzymes to extract energy from nutrients Most of the cell’s energy comes from the mitochondria Energy is called ATP (adenosinetriphosphate) “Powerhouse of the cell” Chloroplasts Chloroplasts are only found in plant cells Contain the green pigment chlorophyll Chlorophyll captures light, which plants use to make their own food Photosynthesis Other Organelles Lysosomes are sacs that contain digestive enzymes Centrioles are cylindrical structures involved in cell reproduction Found only in animal cells Mitochondrion Golgi apparatus Nucleolus DNA Smooth ER Centrioles Lysosome Rough ER Cytoplasm Nucleus Vacuole Ribosomes Cell membrane Nuclear pore Nucleus Cell wall Nuclear pore Cell membrane Golgi apparatus Ribosomes Lysosome Rough ER Cytoplasm Vacuole Mitochondrion Smooth ER Chloroplast The Cell Membrane The cell membrane (a.k.a. plasma membrane) is a thin bilayer that surrounds the outside of the cell Bilayer = double layer Separates the inside of the cell from the environment Allows the cell to communicate with its surrounding and respond to chemical signals Regulates the movement of materials in and out of the cell Both animal and plant cells have a cell membrane Plant cells also have a cell wall on the outside of the cell membrane The cell wall is made of cellulose and gives the plant cell strength and rigidity Cell wall is non-living Structure of the Cell Membrane Made of phospholipids Phospholipids have a head and a tail Heads are hydrophilic “Water-loving”; like to be in contact with water Tails are hydrophobic “Water-hating”; avoid contact with water Phosphate head Fatty acid tails Hydrophilic Hydrophobic Heads are on the outside and tails are on the inside Heads are in contact with water Tails are protected from water Proteins are also in the membrane Some proteins go through the entire bilayer; others only go through one layer This structure of the cell membrane with proteins floating in a double-layer sea of phospholipids is called the fluid mosaic model Proteins Bilayer Hydrophilic heads Hydrophobic tails Hydrophilic heads Transport Across the Membrane The cell membrane is selectively permeable It only lets certain substances in or out of the cell Some small molecules can pass through the bilayer Others use proteins to cross the membrane Passive Transport Passive transport requires no energy Two forms: diffusion and osmosis Diffusion: the movement of molecules from an area of high concentration to an area of low concentration (movement is with the gradient high to low) A concentration gradient occurs when there are different amounts of the same substance on either side of a membrane There is a concentration gradient here. There are more squares outside the cell than inside the cell. In diffusion, substances move from high concentration to low. Some of the squares from outside the cell moved inside. Osmosis: the movement of water molecules from a high concentration to a low concentration Water loves to dilute substances Plasmolysis When plant cells lose water from osmosis, the contents of the cells shrink The plant cell’s cell membrane will peel away from the cell wall This is plasmolysis Occurs when you place plant cells in a concentrated salt solution Water leaves the cell to dilute the outside salt Normal plant cells Plasmolysis Plasmolysis can be reversed if you put the cells in fresh water Water moves back into the cell to dilute its contents If animal cells take in too much water, they can burst If This happens if they are put in a solution that contains more water than the cell does (distilled water) animal cells lose too much water, they shrivel Normal blood cell Tap water Took in too much Lost too much water water Distilled water (pure water) Salt solution Active Transport In active transport, substances move from areas of low concentration to areas of high concentration ( against the gradient) This requires energy Special proteins in the cell membrane act as pumps The protein pumps use energy to move substances against their concentration gradient There are more triangles in the cell than outside the cell. The protein pump (blue) is going to use energy to pump more triangles into the cell. Energy was used to force the triangles into the cell. Energy Differences between Plant and Animal cells 1. Plant cells have a cell wall, animal cells do not. 2. Plant cells have large vacuoles for water storage and chloroplasts for photosynthesis animal cells do not. 3. Plant cells are squared off and green in color animal cells are not. 4. Animal cell have centrioles, plant cells do not. Nucleus Cell wall Nuclear pore Cell membrane Golgi apparatus Ribosomes Lysosome Rough ER Cytoplasm Vacuole Mitochondrion Smooth ER Chloroplast