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Transcript
Chapter 2 Cells Section 1 cell structure • Common cell traits – – smallest unit of life – all cells have an outer covering cell membrane – every cell has cytoplasm and a nucleus Comparing cells • Come in many sizes • Nerve cells are long and send and receive messages throughout the body • Cells in plants carry food and water thru the plant Cell types • Group 1 – no membrane bound structures or organelles (bacteria) – called prokaryotic cells • Group 2 –has membrane bound structures – called eukaryotic cells Cell organization • Each cell has a specific function • Cells take in nutrients • Cells secrete and store chemicals • Cells break down substances 24 hours a day • Cell wall – found only in plant cells • Tough, rigid outer covering that protects the cell and gives it its shape • Made mostly of cellulose • Responsible for support and protection of the plant Cell membrane • protective layer around all cells • Regulates what enters and leaves cell – waste, food, water Cytoplasm • Gelatin like substance that fills the cell • Contains a cytoskeleton to give cell its shape, change its shape or move Organelles • Found in eukaryotic cells only • Each has a specific job within cell • Similar to organs in animals Nucleus • Controls all cell activities – brain of cell • Separated from rest of cell with its own membrane • Nucleus contains DNA that is the instructions for each cell • DNA is the code for the cell’s structure and activities Energy processing organelles • Chloroplasts – – only in plant cells – Organelle where food is made for plant – Contain green pigment chlorophyll that captures light energy for photosynthesis • Mitochondria – Help release energy by breaking down food into CO2 and water – Some more active cells have more mitochondria than other cells (muscles) • Ribosome – – helps make the cell’s proteins – Some float freely, others are attached to the ER – Receive directions from DNA in nucleus Processing, transporting and storing organelles • Endoplasmic reticulum (ER) – Series of folded membranes in which materials can be processed and moved around inside the cell – Can be rough or smooth • Golgi bodies – Stacked and flattened – Sort proteins and other cellular substances and package them into membrane bound structures called vesicles – Vesicles deliver substances to areas inside cell and to cell membrane to release materials out of the cell Recycling organelles • Lissome – – Contain digestive chemicals that help break down food molecules, cell waste, and worn out cell parts – Surrounded by membrane that prevents chemicals leaking into the cell and destroying it From cell to organism • Many 1 celled organisms perform all their life functions by themselves • Cells in many celled organisms do not work alone – Each cell does its own job, while depending in some way on other cells • Cells grouped together to do a job are called tissues • Example – cardiac cells together form cardiac tissue • Organs are made of a group of two or more tissues working together • An organ system is a group of organs working together to perform a function • Ex. Nervous system, excretory system, respiratory system,etc. Section 2 • • viewing cells Cells are microscopic in size We use microscopes to magnify the cell using different lenses Early microscopes In the 1600’s, Leeuwenhoek developed the 1st simple microscope using 1 lens Modern microscopes • If a microscope has more than one lens, we say it is a compound mic. • Compound mic, has an eyepiece lens and an objective lens – usually has between 2-4 objective lenses. Magnification • The total magnification is found by multiplying the power of the eyepiece times the power of the objective lens being used – Ex. Eyepiece = 5x and objective lens =10x • Therefore, 5x10=total mag. of 50x Electron microscope • Used to see things that are too small for other mic. to see • Can magnify up to 1,000,000 x • Scanning electron mic. – produces realistic 3d image Cell theory • Cells were discovered in 1665 by Robert Hooke • All organisms are made of one or more cells • The cell is the basic unit of organization in organisms • All cells come from other cells Section 3 viruses WHAT IS A VIRUS • A STRAND OF DNA SURROUNDED BY A PROTEIN COAT • DON’T HAVE NUCLEUS, CELL MEMBRANE OR ORGANELLES • HAVE A VARIETY OF SHAPES HOW DO VIRUSES MULTIPLY • USE A HOST CELL TO MAKE COPIES OF THEMSELVES • SOME VIRUSES CAN BE STORED FOR YEARS AND SUDDENLY COME ALIVE AND MULTIPLY QUICKLY • A VIRUS CAN BE ACTIVE OR LATENT ACTIVE VIRUSES WHEN IT ENTERS THE CELL AND IS ACTIVE IT MAKES NEW VIRUSES IMMEDIATELY, DESTROYING THE HOST CELL LATENT VIRUSES • HEREDITARY MATERIAL OF HOST CELL AND VIRUS COMBINE • DOES NOT MAKE NEW VIRUSES RIGHT AWAY • CAN STAY LATENT FOR YEARS, AND UNDER CERTAIN CONDITIONS CAN ACTIVATE THE VIRUS HOW DO VIRUSES AFFECT ORGANISMS • VIRUSES ATTACK PLANTS, FUNGI, PROTISTS, ETC. • A VIRUS CAN NOT MOVE BY ITSELF • IT CAN BE CARRIED BY WIND OR INHALED • MOST VIRUSES AFFECT ONLY ONE KIND OF CELL • VIRUSES CAN INFECT BACTERIA – CALLED BACTERIOPHAGES • THEY ATTACH TO BACTERIUM, INJECT DNA AND WITHIN 20 MINUTES EACH INFECTED CELL RELEASES AN AVERAGE OF 100 VIRUSES FIGHTING VIRUSES VACCINES FROM WEAKENED VIRUS PARTICLES TREATING VIRAL DISEASES • ANTIBIOTICS ARE EFFECTIVE AGAINST BACTERIAL INFECTIONS, BUT NOT VIRUSES • BODY MAKES INTERFERONS TO HELP UNINFECTED CELLS CREATE DEFENSES • ANTIVIRAL DRUGS PREVENTING VIRAL DISEASES • VACCINATIONS • IMPROVE SANITATION METHODS • QUARATINING INFECTED PATIENTS RESEARCH WITH VIRUSES USED IN GENE THERAPY TO SUBSTITUTE NORMAL DNA FOR THE CELL’S DEFECTIVE DNA, TO CHANGE VIRAL CELLS – USED TO FIGHT CANCER