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Cell Structure and Function Ch. 4 A Look at Cells • Cells are the smallest unit of life that can carry out all the functions of a living thing. They are very specialized. • Living things are unicellular or multicellular. • They vary greatly in shape. • They vary greatly in size. – Bacteria Ostrich Egg All Cells have 3 common features 1. Plasma membrane that separates each cell from environment, permits flow of molecules across membrane, and contains receptors that affect cells activities. 2. Nucleus or nucleoid region that localized herditary material, that is copy and read. 3. Cytoplam contains membrane system, particles, filaments, and semifluid substance. 1.12 Prokaryotes vs. Eukaryotes • Prokaryotes – No nucleus – No membrane bound organelles – Bacteria – Much smaller – Unicellular – Some have cilia (hair-like structures) and some flagella (whip-like tail) for movement. Amoeba • Eukaryotes – Nucleus – Organelles – Unicellular (protists) and multicellular (animal and plants) Plant Cell Diffusion and DNA limit cell size because… • Cells rely on diffusion to carry on proper functions – Cells require a constant supply of glucose and oxygen – Cells must constantly get rid of waste. • DNA is found in all cells. – The larger the cell, the greater number of enzymes – DNA makes enzymes needed for the cell Is bigger better? • Surface Area to Volume Ratio – As the cell size increases, its volume increases 2x faster….why is this a problem? Other ways to solve the problem • If cell size doubled, it would be an 8 fold increase in volume, but the surface area would only increase 4 fold. Therefore, there is not enough membrane for nutrients to flow through to keep the cell alive. Who discovered cells and what did they see? • The invention of the microscope was the key to discovering cells. • Robert Hooke looked at cork cells. (1665) • He thought they looked like “jail cells” and that is why he named them cells. • In the early 1670’s Leeuwenhoek made microscopes that magnified up to 200x and was the first person to see living cells. Other Cell Discoveries • About 150 years later Matthias Schleiden discovered all plants are made up of cells. • At about the same time Theodore Schwann proposed that all living things are made up of cells. • There are cells called “Schwann Cells”. The Cell Theory • In 1858, Rudolf Virchow proposed that plant cells only arise from existing plant cells and new animal cells only come from other animal cells. • The Cell Theory was soon introduced. • 3 principles: 1. Cells are the basic units of all life. 2. All organisms are made up of one or more cells. 3. All cells arise from other cells. Types of Electron Microscopes used to see cells • Scanning Electron Microscope (SEM)– Bounces e- off specimen – Creates 3-D image – Magnifies up to 60,000x • Transmission Electron Microscope (TEM) – E- pass through – Specimens must be very thin – Magnifies up to 2,000,000x Basic Cell Structures • Cell Membrane surrounds all of the structures inside. It is made up of a phospholipid bilayer. • Fluid Mosaic Model. • Lipids are made up of a glycerol, 2 fatty acid chains, and a phosphate group. Cytoplasm The Lipid Bilayer • Hydrophobic tails (the fatty acids) • Hydrophilic heads (the phosphate group) • Proteins are embedded in the lipid bilayer and they allow certain things to pass through and other not. 1.2a All cells are covered by a membrane that controls what enters and leaves the cell. This membrane is made up of a complex network of proteins that provide organization and shape. (In primitive cells, this is not the case). • Hydrophobic tails. • Hydrophilic heads. • Proteins are embedded in the membrane and allow certain things to pass and others not to. Proteins in bilayer • 1. receptors for chemical signals • 2. transport solutes across bilayer • 3. participate in cell identification, defense and communication. 1.3a In cells, there are specialized parts called organelles “little organs” used for the transport of materials, energy capture and release, protein building, waste disposal, information feedback, and movement. • Endoplasmic Reticulum • Golgi Body • Mitochondria • Lysosomes • Vacuoles • 1.3b In most multicellular organisms, these organelles perform some special functions that others do not. Cytoplasm • The semifluid substance made primarily of water and organic compounds. • Organelles and contained with in the cytoplasm. • Within the cytoplasm is a cytoskeleton made up of proteins and fibers. It gives the cell support and shape. The Nucleus • It contains most of the cells genetic material that codes for instructions for making proteins and other molecules. • It is surrounded by a nuclear envelop that is also a lipid bilayer. • Chromosomes keep all of the genetic info. • Nucleolus forms ribosomes. Cell Organelles • Ribosomes-site of protein synthesis • Endoplasmic Reticulum ERInternal membrane system. – Rough- has ribosomes • Makes new cell membranes – Smooth- no ribosomes • Makes lipids, processes carbs and proteins, and modifies toxic chemicals to the cell. The Golgi Body • Golgi apparatus- series of flat, membranebound sacs where proteins and other molecules from the ER are sorted, modified, packaged, and distributed to their destination for storage or secretion. Lysosomes • Contain digestive enzymes that help break down large molecules of carbs, proteins, and lipids. • They also digest old organelles no longer useful. • Lysosome function – Go to cellular function and structure and click on lysosomes Vacuoles • Saclike structure that stores materials such as water, salts, proteins and carbs. • In plants it takes up 90% of the volume…why? Mitochondria • Change the energy stored in food compounds into a form useful for the cell. (Where ATP is made.) • Also known as “The Power House.” Take a quiz over the organelles here 1.13 Some organelles in modern eukaryotes developed from early prokaryotes: Mitochondria, and chloroplast (in plants). • American biologist Lynn Margulis proposed the endosymbiotic theory. Chloroplast • It suggested that ancient prokaryotes similar to mitochondria and chloroplasts began a symbiotic relationship in a host cell. Eventually these prokaryotes started to function as organelles in the host cells. Plant vs. Animal Cells • Plants • Animals – Have a tough, rigid outer – Cell membrane covering that maintains the cells shape called the Cell Wall. – Smaller vacuoles Support and protection. – Centrioles- help – Chloroplasts enable the plant to organize cell make sugars through photosynthesis. division. – Central vacuole absorb water, store proteins, ions, and waste products. Compare animal Tablecells 3.6 page 70 and plant Photosynthesis vs. Cellular Respiration • Photosynthesis Captures energy (converts light energy into chemical energyATP) Chloroplasts • Cellular Respiration Releases energy (ATP) Mitochondria • C6H12O6 + 6O2 6CO2 + 6H2O • 6CO2 + 6H2O C6H12O6 + 6O2 1.3, 1.4, 1.9, 1.43 Eukaryotic Organelles • Go to the following link for a tutorial on eukaryotic organelles. • Eukaryotic Organelles 1.2b Flagella and Cilia allow some Protista, Monera, and animal cells to move. Flagella in Motion Movement • Cilia- short, hair-like projections that usually occur in large numbers on the surface of certain cells. • Flagella- long, tail-like projections that move in a whip-like motion in eukaryotes and in prokaryotes they spin like a propeller. 1.5 Most cells have a narrow range of temperature and acidity that they can survive. If there are extreme changes in the environment, they may alter the structure of the protein and the cells function. 1.15 In biological systems, STRUCTURE DETERMINES FUNCTION. It is very important to understand the conditions have to be “right” for cells to function properly. If it gets too hot, too cold, too acidic, or too basic, the cell may die or because the conditions denature or alternate the structure of the protein, the function is altered. Cell Membranes and Their Environment • A semipermeable membrane allows certain molecules to pass through and others not. – Passive transport- no energy used – Active- energy used – Active and Passive transport Diffusion • Diffusion is the random movement of molecules from an area of higher concentration to an area of lower concentration. • It always occurs down a concentration gradient. • It continues until the system has reached equilibrium. • Membrane transport- go to cellular transport and click on membrane transport. • Facilitated diffusion is a form of passive transport that uses carrier proteins in the membrane. Will increasing the temp. speed up or slow down diffusion? Osmosis • Osmosis is the diffusion of water across a semipermeable membrane. • 3 types of solutions – Hypertonic- [solutes] are higher on the outside than the inside. – Hypotonic-[solutes] are lower on the outside than the inside. – Isotonic- [solutes]=[on the inside] What do you think will happen in each? Osmosis and Penicillin • Penicillin, one of the most important antibiotic drugs in the history of medicine, depends on osmosis for its killing action. • Pencillin inhibits an enzyme with which many bacteria produce chemical cross-links in their cell walls. • This leads to the formation of a weakened cell wall that cannot stand the stress of osmotic pressure. • The cell wall becomes weaker and breaks. The bacterium bursts under the inrush of water caused by osmosis. Active Transport • Uses energy to move molecules across the membrane against the concentration gradient. Lower to Higher. • It requires carrier proteins and ATP. Bulk Transport of Materials • Exocytosis- movement of materials out of the cell. • Endocytosis- movement of material into a cell. – Pinocytosis- movment of fluids into cell. – Phagocytosis- engulfs food particles into the cell. Cell Specialization • Cells throughout an organism can develop in different ways to perform different tasks. • RBC- transport oxygen • Pancreatic cells- produce insulin • Muscle cells- contract and relax for body movement. • Guard cells- control opening and closing of stomata on leaves for gas exchange. Ch. 7 Review • Click on your biology book, go to Unit 3 cells and click on Links and Self-Test. • Cells Review • Overview of cell and processes