Chapter 4 Notes BSC 1005 Mr Tidwell Three principles comprise the cell theory o Every living organism is made of one or more cells o The smallest organisms are single cells and cells are the functional units of multicellular organisms o All cells arise from preexisting cells There are 2 types of microscopes o Light microscope o Electron scan microscope The strongest type of microscope The plasma membrane is composed of phospholipids protein and carbohydrate molecules and regulates the passage of ions and molecules in and out of cells o The phospholipid molecules have hydrophilic likes water tails and hydrophobic avoids water heads The cytoplasm consists of all the fluid and structures that lie inside the plasma membrane but outside of the nucleus the nucleus is not included in the cytoplasm o Cytoplasmic fluid consists of water salts and organic molecules All cells share common features o All use DNA as a hereditary blueprint o All use RNA to copy the blueprint and to guide construction of proteins All energy powering life on Earth originates in sunlight simple form the bodies of bacteria and archaea the simplest forms of life complex form the bodies of animals plants fungi and protists Plant cells are surrounded by a cell wall made of cellulose and polysaccharides o Plant cells also have plastids chloroplasts and a central vacuole not found in animal Two kinds of cells o Prokaryotic o Eukaryotic cells Some animal cells possess centrioles and cilia not found in plant cells Fungal cells are surrounded by a wall of polysaccharides and chitin The cytoskeleton is composed of three types of fibers made of protein o Thin microfilaments o Medium sized intermediate filaments o Thick microtubules The cytoskeleton performs the following functions o Maintaining and changing cell shape o Providing for cell movement o Providing for organelle movement Chapter 4 Notes BSC 1005 Mr Tidwell o Facilitating cell division Cilia and flagella move the cell through fluid or fluid past the cell The nucleus is the control center of the eukaryotic cell and contains three major parts allow proteins pieces of ribosomes and RNA to pass During division chromatin becomes compacted into long strands called o Nuclear envelope Isolates the nucleus from the rest of the cell Double layered Nuclear pore complex through the membrane o Chromatin Chromosomes chromosomes Blueprint for a variety of proteins o Nucleolus The site of ribosome synthesis Ribosome a small particle composed of ribosomal RNA and proteins Consists of ribosomal RNA proteins ribosomes in various stages of synthesis and DNA that carries the genes coding for ribosomal RNA DNA is copied into messenger RNA mRNA and then travels through the nuclear pores to the cytoplasm to direct protein synthesis DNA RNA Protein are membranous sacs that transport substances among the separate regions of the Vesicles membrane system The endoplasmic reticulum ER is a series of interconnected membranes that form a labyrinth of interconnected flattened sacs and channels within the cytoplasm o All proteins and phospholipids of cell membranes are synthesized in the ER o Smooth endoplasmic reticulum has no ribosomes detoxifies drugs and synthesizes lipids like steroid hormones made from cholesterol destined for other membranes for secretion o Rough endoplasmic reticulum is studded with ribosomes and produces proteins The Golgi apparatus sorts chemically alters and packages important molecules Lysosomes serve as the cell s digestive system o Digestive proteins are made in the rough ER travel through the Golgi and are packaged in membrane enclosed vesicles as lysosomes Vacuoles serve as water regulators support and storage o Many freshwater organisms possess contractile vacuoles composed of collecting ducts a central reservoir and a tube leading to a pore in the plasma membrane that carries excess water out of the organism o Vacuoles occupy of the volume of the plant cell Maintain water balance and storage Chapter 4 Notes BSC 1005 Mr Tidwell Store hazardous wastes nutrients or pigments Provide turgor pressure on the cytoplasm to keep cells rigid Evidence for the endosymbiont hypothesis o Both mitochondria and chloroplasts are about the size of prokaryotic cells 1 5 micrometers o Both have a double membrane o Both have enzymes to synthesize ATP o Both possess DNA and ribosomes Mitochondria extract energy from food molecules and store it in high energy bonds of ATP Chloroplasts are the sites of photosynthesis o Light energy is converted to chemical energy in the chloroplasts by photosynthesis Plastids are found only in plants and photosynthetic protists o Plastids are storage containers for various molecules such as pigments and starch o Chloroplasts are highly specialized plastids In prokaryotic cells the central region is called the nucleoid which is separate from the cytoplasm but is not a defined nucleus o Prokaryotic cells have no nuclear membrane or membrane bound organelles present