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Transcript
Unit 1: Cells and Systems Section 2: Cells I. Cell Theory 1. All organisms are made up of one or more cells. 2. The cell is the basic unit of life. 3. Cells are reproduced from other cells. Organelles: smaller structures within cells that carry on life functions. • Unicellular: describes a single-celled living thing. • Multicellular: describes a living thing made up of many cells. • Both unicellular and multicellular things are called organisms. • Two main types of cells: Plant Cells Animal Cells II. Cell Structures Three Major Cell Parts • Cell Membrane – thin flexible structure that surrounds the cell. Regulates what enters and exits the cell. • Nucleus - “brain” of the cell. Controls functions of the cell. Contains genetic information – Deoxyribonucleic acid (DNA) • Cytoplasm – jelly-like fluid in which organelles are found. This is where many chemical reactions take place within the cell. Other Major Organelles: • Mitochondrion – converts the energy stored in food into usable energy for the cell (the “powerhouse”) - cellular respiration • Ribosome – manufacture proteins, the building blocks for structures in the cell. • Endoplasmic reticulum – network of flattened tubes that transport proteins within the cell. • Golgi Body – sorts and packages proteins in membrane-wrapped structures called vesicles. • Vesicles - small packages containing proteins, nutrients and water into, out of, and around the cell. • Vacuole – temporary storage areas; assist in regulating water (usually bigger in plant cells) • Lysosomes – contain digestive chemicals that break down food particles, cell wastes, and worn-out cell parts. Additional Plant Cell Structures • Cell Wall - rigid outer wall that provides protection, support and shape. Contains pores to allow substances to pass. • Chloroplast - captures light to synthesize food energy. Contains green pigment chlorophyll. III. Energy for Cells Photosynthesis • Process where plants manufacture their own food • Occurs in the chloroplast, which contains the pigment chlorophyll • chlorophyll absorbs light and converts it into chemical energy. Photosynthesis light energy carbon dioxide + water ---> glucose + oxygen chlorophyll • The glucose (sugar) is then stored for use later Cellular Respiration • cellular respiration takes place in the mitochondria • occurs in both plants and animals glucose + oxygen ---> carbon dioxide + water + energy • the energy released can then be used by the cell IV. Prokaryotic vs. Eukaryotic Cells • Prokaryotic cells contain organelles which are NOT surrounded by a membrane. • Eukaryotic cells contain organelles which ARE surrounded by a membrane. • All multicellular organisms (and some unicellular organisms such as amoeba) are composed of eukaryotic cells. V. Bacteria • smallest and simplest form of life (prokaryotic - no nucleus) • single cells range from 1 nm to 20 nm long • single large DNA strand • Three main types: • bacilli (rod-shaped) • spirilla (spiral-shaped) • cocci (sphere-shaped) Bacteria - Harmful vs. Helpful Harmful • bacteria cause disease by invading the bodies of other organisms and interfering with normal cell functions. • Food spoilage Helpful • food production (yogurt, sourdough bread, cheese) • tanning leather • cleaning up environmental spills • aids our digestive system • Used to produce medicine such as insulin VI. Viruses • lack characteristics of living cells – NON-LIVING! ie. do not use energy, move or grow. • can only be seen by electron microscopes • consist of a piece of DNA, covered by a protective protein coat. • Viruses reproduce by injecting their DNA into a host cell, tricking it into manufacturing new viruses. • The viruses accumulate in the cell preventing the cell from functioning properly (causing disease). Bacteria Viruses Are they considered living? Yes No Composed of…? A single prokaryotic cell A piece of DNA surrounded by protein How do you treat a disease caused by this organism? Antibiotics Bed rest, drink lots of fluids, rarely antivirals Section 1.3 Diffusion, Osmosis, and the Cell Membrane I. Membrane Permeability • Permeable – lets everything through o Cheesecloth is permeable to water • Semi or selectively permeable – lets only some things through o A sieve is selectively permeable to pasta and water • Impermeable – lets nothing through o A plastic bag is impermeable to water II. Concentration • amount of substance in a given space. – The more you have in a given space, the higher the concentration. III. Diffusion • movement of molecules from an area of high concentration to an area of low concentration. Movement of Substances In and Out of the Cell • Nutrients and waste materials must be able to move into and out of the cell. • Cell membrane regulates the passage of substances in and out of the cell. • “Selectively permeable” – permits only certain molecules to enter or leave (semi-permeable). Equilibrium • reached when there is an equal number of particles on either side of a membrane • particles will still move back and forth, but the number of particles on each side stays the same IV. Osmosis • process by which water moves across a membrane. • Water moves across the cell membrane, depending on the relative concentration of water inside and outside the cell. • Water moves from high water concentration to low water concentration (special type of diffusion). Diffusion What type of Nutrients and waste material(s) is/are products transported? How is it used by To bring in food, to the cell? export wastes Which direction High concentration is the flow of the to low material? concentration Osmosis water To maintain a balance of water within the cell High concentration to low concentration