Science 8 - Cells & Cell Organization Notes 1.1 - Characteristics of Living Things Composed of cells Reproduce, grow & repair themselves Require energy o Plants usually from sun o Animals from plants or other animals who got their energy from plants Respond to their environment Have a life span exist for a limited period of time Produce waste Cell Theory All living things are composed of one or more cells All new cells come from previously existing cells 1.3 - Plant and Animal Cells Animal Cell Structures Parts seen with light microscope: Science 8 Cell Notes - Page 1 of 9
Nucleus Control centre directs cells activities Surrounded by a membrane in eukaryotic cells (plants and animals) Not surrounded by a membrane in prokaryotic cells (e.g. one-celled organisms like bacteria) Chromosomes DNA (genetic information) inside nucleus Construction plans for all pieces of cell Duplicated and passed on to other identical cells Cell Membrane Double layer of fat molecules Holds contents of cell in place Controls movement of materials (e.g. nutrients & waste) in/out of cell Cytoplasm Watery fluid Contains everything inside cell membrane but outside nucleus Many chemical activities occur here Allows quick transport of materials between cell structures Stores waste Vacuole Filled with fluid Used to store water & nutrients, waste Used to move excess water out Flagellum Whip-like tail found on some cells Helps cell move Cilia Tiny hairs on special cells that help the move, or move fluids past cell Science 8 Cell Notes - Page 2 of 9
Parts seen with electron microscope: Mitochondria Circular or rod-shaped Power plants of cell Provide cell energy via cellular respiration: sugar + O 2 -> H 2 0 + CO 2 + energy Ribosomes Very small appear as dots Build proteins using information from nucleus and molecules from cytoplasm Endoplasmic Reticulum (ER) Series of folded membranes used for material transport Rough ER has many ribosomes attached Smooth ER has no ribosomes; fats (lipids) made here Golgi Apparatus Looks like stack of flattened balloons Stores proteins in vesicles Vesicles carried to cell surface and released to outside Science 8 Cell Notes - Page 3 of 9
Lysosomes Formed by Golgi Apparatus Contain special proteins that break down large molecules into many smaller molecules that can be used by cell or as building blocks for larger molecules Patrol and clean cytoplasm Important role in destroying harmful substances and invading bacteria Damaged and worn-out cells destroyed by their own lysosomes Plant Cell Structures Same features as animal cells, plus some structures not found in animal cells, seen with light microscope: Vacuole Similar to animal cell, but much larger Cell Wall Protects and supports plant cell Sometimes only one Sometimes a second cell wall for extra support & strength Gases, water & some minerals can pass through pores Chloroplasts Food factories Contain chlorophyll molecules which allow plants to make food from CO 2, H 2 O & sun s energy Science 8 Cell Notes - Page 4 of 9
Plant vs Animal Cells Structure Function Animal Plant cell cell nucleus control centre yes yes directs cell activities chromosome construction plans for cell parts yes yes cell membrane encloses cell yes yes controls movement of materials in/out cytoplasm Watery fluid inside cell chemical activities occur here allows quick transport of materials between cell structures stores waste yes yes vacuole filled with fluid small large used to store water, nutrients & waste used to move excess water out cell wall protects and supports plant cell no yes allows passage of gases, water & some minerals through pores chloroplast food factories contain chlorophyll molecules which allow plants to make food from CO2, H2O & sun s energy no yes flagellum whip-like tail found on some cells some rare helps cell move cilia tiny hairs on special cells that help the move, or move some rare fluids past cell Organization of Living Organisms 2.1 Cells and Cell Systems Multicellular organisms Tissue Organ Group of cells similar in shape and function, e.g. epithelial tissue Several different tissues organized into larger structures, e.g. heart Has at least one function, e.g. pump blood Organ system Group of organs with related functions e.g. circulatory system: heart, arteries, capillaries, veins Other systems include: nervous, excretory, digestive, respiratory, endocrine Science 8 Cell Notes - Page 5 of 9
Levels of Cell Organization in the Human Body Organ system Major organs Major tissues Major functions circulatory nervous excretory digestive respiratory endocrine heart, arteries, capillaries, veins connective, muscle, blood transportatio n of nutrients, dissolved gases, and waste to and from body cells brain, spinal cord, eyes, ears, nerves to and from body parts connective response to environment and control of body activities kidneys, bladder, ureters, urethra connective, muscle removal of waste esophagus, stomach, intestines, liver connective, muscle breakdown of food into molecules small enough to pass into cells lungs, trachea, blood vessels connective, muscle exchange of oxygen and carbon dioxide pancreas, adrenal glands, pituitary gland connective coordination and regulation of body activities Science 8 Cell Notes - Page 6 of 9
2.2 Unicellular Organisms Single-celled micro-organisms (microbes) Can only be seen with a microscope Carry out all of life s functions in a single cell Some cause disease, e.g. some bacteria Many are helpful, e.g. yeast Bacteria Primitive Plentiful Changed little over billions of years Many ways of living, e.g. make own food, parasites, little/no oxygen Exist in almost every environment on earth Prokaryotes no nucleus, mitochondria or ribosomes Protists Neither plant nor animal Eukaryotes Plant-like Protists Diatoms In fresh & salt water Contain chlorophyll Can make own food Encased in two thin shells joined together Science 8 Cell Notes - Page 7 of 9
Euglena Similar to plant and animals Lots of sunlight make own food Little sunlight feed on smaller cells Contractile vacuole expels excess water Animal-like Protists Cannot make own food Must feed on live or dead organisms Have all organelles of animal cells, plus contractile vacuole Food enclosed in food vacuole where it is slowly digested Amoebae Blob-like organism Changes shape as it moves Movement via pseudopod (false foot) o Branch of cytoplasm stretched out, anchored, and then pulls rest of amoeba towards it Feeds by wrapping itself around food Science 8 Cell Notes - Page 8 of 9
Paramecia Cilia used for movement Cilia create current to direct food (bacteria and smaller cells) into oral groove Anal pore expels waste Fungi Yeast One of the few unicellular fungi No chlorophyll Must get energy from other organisms Science 8 Cell Notes - Page 9 of 9