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Transcript
Biology 1- Chapter 7 Notes Prentice Hall (pg. 168-193) • 7–1 Life Is Cellular • A. The Discovery of the Cell 1. Early Microscopes 2. The Cell Theory B. Exploring the Cell C. Prokaryotes and Eukaryotes 1. Prokaryotes 2. Eukaryotes • 7–2 A. B. C. D. E. F. G. H. Cell Boundaries A. Cell Membrane B. Cell Walls C. Diffusion Through Cell Boundaries 1. Measuring Concentration 2. Diffusion D. Osmosis 1. How Osmosis Works 2. Osmotic Pressure E. Facilitated Diffusion F. Active Transport 1. Molecular Transport 2. Endocytosis and Exocytosis Eukaryotic Cell Structure Comparing the Cell to a Factory Nucleus Ribosomes Endoplasmic Reticulum Golgi Apparatus Lysosomes Vacuoles Mitochondria and Chloroplasts 1. Mitochondria 2. Chloroplasts 3. Organelle DNA I. Cytoskeleton 7–3 • 7–4 The Diversity of Cellular Life A. Unicellular Organisms B. Multicellular Organisms 1. Specialized Animal Cells 2. Specialized Plant Cells C. Levels of Organization 1. Tissues 2. Organs 3. Organ Systems 7.1: The History of the Cell Theory • Before microscopes were invented, people believed that diseases were caused by curses and supernatural spirits. • As scientists began using microscopes, they quickly realized they were entering a new world–one of microorganisms. • Microscopes enabled scientists to view and study cells, the basic units of living organisms. Development of Light Microscopes • The first person to record looking at water under a microscope was Anton van Leeuwenhoek. • The microscope van Leeuwenhoek used is considered a simple light microscope because it contained one lens and used natural light to view objects. • Compound light microscopes use a series of lenses to magnify objects in steps. • These microscopes can magnify objects up to 1500 times. The Cell Theory • Robert Hooke was an English scientist who lived at the same time as van Leeuwenhoek. • Hooke used a compound light microscope to study cork, the dead cells of oak bark. • Cells are the basic building blocks of all living things. The cell theory is made up of three main ideas: • All organisms are composed of one or more cells. • The cell is the basic unit of structure and function of organisms. • All cells come from preexisting cells. Three Scientists contributed to the Cell Theory: • 1838- Schleiden: plants are made of cells • 1939- Schwann: animals are made of cells • 1855- Virchow: New cells are produced from the division of old cells Development of Electron Microscopes • The electron microscope was invented in the 1940s. • This microscope uses a beam of electrons to magnify structures up to 500,000 times their actual size. There are two basic types of electron microscopes. • The scanning electron microscope scans the surface of cells to learn their three dimensional shape. • The transmission electron microscope allows scientists to study the structures contained within a cell. Scanning Probe Microscope • Discovered in the 1990’s • Produces images by tracing the surfaces of samples with a fine probe • Can observe single atoms in the air or in solution Natural laws limit cell size • Large cells have a smaller ratio of surface area to volume than small cells • cells must be small enough to have a surface area which can supply nutrient needs • cells must be large enough to hold all required molecules and organelles Two Basic Cell Types Cell membrane Cytoplasm Prokaryotic Cell Cell membrane Cytoplasm Nucleus Eukaryotic Cell Organelles Prokaryotic and Eukaryotic Cells Prokaryotic Cells • Cells that do not contain internal membrane-bound structures and do not have a nucleus are called prokaryotic cells. Prokaryotic Cell • Unicellular organisms such as bacteria are very simple. • They still carry out all of life’s activities such as respiration, cell reproduction, growth, etc. Eukaryotic Cells • Cells containing membrane-bound structures and a nucleus are called eukaryotic cells. • Most of the multicellular plants and animals are made up of cells that are very specialized and diverse in their structures and functions Eukaryotic Cell 7.2 Eukaryotic Cell Structure Organelles • The membrane-bound structures within eukaryotic cells are called organelles. • Each “little organ” has a specific function that contributes to cell survival. • Separation of organelles into distinct compartments benefits the eukaryotic cells. • Lysosomes • Nucleus • Plasma Membrane • Endoplasmic Reticulum • Mitochondrion Biologists divide the cell into two major parts • The nucleus is the central membrane-bound organelle that manages cellular functions. • Everything between the cell membrane and the nucleus is called the cytoplasm. Nucleus - Nuclear envelope – double layered membrane surrounding nucleus; contains small pores - Nuclear pores- allow transport of materials in and out of nucleus - Chromatin-granular material visible within the nucleus; consists of DNA tightly coiled around proteins - Chromosomes – threadlike Nucleolus Chromatin structure within the nucleus containing the genetic information that is passed from one generation of cells to the next (chromosomes are formed when chromatin condenses during cell division) Nuclear - Nucleolus – dense material Envelope in nucleus; makes ribosomes which make proteins Nuclear Pore Ribosomes • Ribosomes are made in the nucleolus. • They travel in and out of the nucleus throught he nuclear pores. Ribosomes • Ribosomes are small particles within the cell on which proteins are assembled; made of RNA and protein • They can be free (in the cytoplasm) • They are also attached to the rough endoplasm reticulum Endoplasmic reticulum • The endoplasmic reticulum (ER) is responsible for assembly, transport, and storage of molecules within cell. • There are two types • Rough ER- contains ribosomes and makes proteins • Smooth ER- lacks ribosomes; has enzymes that make membrane lipids and detoxifies drugs • Liver cells contain many smooth ER for detoxification Golgi Apparatus • Stacks of membranes in the cell that modifies, sorts, and packages proteins from the endoplasmic reticulum • The Golgi apparatus is like a customization shop where finishing touches are added to proteins. Lysosomes • Lysosomes are organelles that contain digestive enzymes. They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria. • The lysosomes are the clean-up crew of the cell • Tay-Sachs disease is caused by excess lipid accumulation on the brain. The cause of this disease has been traced to lysosomes that failed to function properly Vacuoles • Vacuoles are membrane-bound spaces used for temporary storage of materials (such as water, salts, proteins, and carbohydrates) • Notice the difference between vacuoles in plant and animal cells. Plant Vacuole Animal Cell Cell • Paramecium have a contractile vacuole that pumps excess water out of the cell, which aids with homeostasis Mitochondria • Mitochondria are • Cellular respiration is the membrane-bound process that converts organelles in plant and chemical energy stored in animal cells that transform food into ATP energy for energy for the cell. cells to use. • A mitochondria, like the • Muscles cells (needed for endoplasmic reticulum, has a highly folded inner movement) contain a large membrane. number of mitochondria for • The folds increase the energy production surface area of the mitochondrion in order to make more energy (ATP) • Cellular Respiration takes place in the mitochondria of cells Chloroplasts • Chloroplasts are found in cells of plants and some other organisms • Chloroplasts are organelles that capture light energy and produce food to store for a later time. • Photosynthesis takes place in the chloroplasts • Chloroplasts contain green pigment called chlorophyll. • Chlorophyll traps light energy and gives leaves and stems their green color. • Chloroplasts acts like a solar power plant Cytoskeleton • Cells have a support structure called the cytoskeleton within the cytoplasm. • It is a network of proteins that help maintain cellular shape and movement • The cytoskeleton is composed of microtubules and microfilaments. Cell membrane Endoplasmic reticulum Microtubule Microfilament Ribosomes Mitochondrion • Microtubules are thin, hollow cylinders made of protein that maintain cell shape • Microfilaments are thin solid protein fibers that help cells move (amoeba) Centrioles • Made of microtubules • one of two tiny structures located in the cytoplasm of animal cells near the nuclear envelope • help to organize cell division (helps cells split into two) • only found in animal cells Cilia and Flagella Cilia • Some cell surfaces have cilia and flagella, which are structures that aid in locomotion or feeding. Cilia and flagella can be distinguished by their structure and by the nature of their action. • Cilia are short, numerous, hair-like projections that move in a wavelike motion. • Flagella are long projections that move in a whip-like motion. Flagella and cilia are the major means of locomotion in unicellular organisms. Flagella The Plasma Membrane • All living cells must maintain a balance regardless of internal and external conditions. Survival depends on the cell’s ability to maintain the proper conditions within itself. Why cells must control materials • The plasma membrane is the boundary between the cell and its environment. It is the plasma membrane’s job to: • allow a steady supply of glucose, amino acids, and lipids to come into the cell no matter what the external conditions are. • remove excess amounts of these nutrients when levels get so high that they are harmful. • allow waste and other products to leave the cell. Cell membrane • This process of maintaining the cell’s environment is called homeostasis. • Selective permeability is a process used to maintain homeostasis in which the plasma membrane allows some molecules into the cell while keeping others out. Plasma Membrane Water Structure of the Plasma Membrane • The plasma membrane is composed of two layers of phospholipids back-to-back. • Phospholipids are lipids with a phosphate attached to them. Phosphate Group Glycerol Backbone Two Fatty Acid Chains • The lipids in a plasma membrane have a glycerol backbone, two fatty acid chains, and a phosphate group. Makeup of the phospholipid bilayer • The phosphate group is critical for the formation and function of the plasma membrane. • Phosphate Group The fluid mosaic model describes the plasma membrane as a flexible boundary of a cell. The phospholipids move within the membrane. Other components of the plasma membrane: Cholesterol • Cholesterol plays the important role of preventing the fatty acid chains of the phospholipids from sticking together. Molecule • Transport proteins allow needed substances or waste materials to move through the plasma membrane. Cellular Boundaries • The plasma membrane acts as a selectively permeable membrane. • The cell wall is a fairly rigid structure located outside the plasma membrane that provides additional support and protection. Diffusion • process by which molecules tend to move from an area where they are more concentrated to an area where they are less concentrated • Equilibrium- when the concentration of a solute is the same throughout the solution Osmosis • diffusion of water through a selectively permeable membrane Hypertonic Solution • concentration of solutes in solution is higher than the concentration of solutes inside the cell • causes water to diffuse out of the cell; may cause cell to shrivel and shrink; disrupts metabolism and may kill cell Hypotonic Solution • concentration of solutes is lower than the concentration inside the cell • causes water to diffuse into the cell • animal cells may burst in a hypotonic solution • plant cells do not burst because they are surrounded by a rigid cell wall Isotonic Solution • the concentration of solutes equals the concentration of solutes inside the cell • does not result in the net diffusion of water into or out of the cell • kidneys and skin help to maintain isotonic conditions in your body Facilitated Diffusion • movement of specific molecules across cell membranes through protein channels • passive - does not require an input of energy • always moves particles down a concentration gradient • because these molecules re polar they must travel through channels in transport proteins; ex: glucose Glucose molecules High Concentration Cell Membrane Low Concentration Protein channel Active Transport • energy-requiring process that moves material across a cell membrane against a concentration difference • requires energy from ATP molecules • can move particles up a concentration gradient (from low to high) • requires carrier proteins to “pump” particles across membrane • ex: Na-K pumps in nerve cells, movement of nutrients into plant roots Molecule to be carried Energy Molecule being carried Endocytosis • process by which a cell takes material into the cell by infolding of the cell membrane Two Types • Phagocytosis-process in which extensions of cytoplasm surround and engulf large particles and take them into the cell • Pinocytosis-process by which a cell takes in a liquid from the surrounding environment Exocytosis • wastes and cell products leave the cell by fusing with membrane; products packaged by Golgi apparatus and excreted from cell 7.4- Diversity of Cellular Life Unicellular Organisms • Sometimes single cells are the organism • Grow, respond to the environment, transform energy, and reproduce • • • • Multicellular Organisms Made up of many cells Very diverse Depend on communication and cooperation between specialized cells Cell specialization Cells throughout an organism can develop in different ways to perform different tasks Cell Specialization Animal cells • Red Blood Cells • Pancreatic Cells • Muscle Cells Plant Cells • Guard cells Levels of Organization Muscle cell Smooth muscle tissue Stomach Digestive system • Many multicellular organisms have structures called organs that have a specific function and work with other organs. • Working together, these organs carry out the life processes of the entire organism.