Chapter 4- Cells. Organisms are composed of one to many microscopic cells. Unicellular. Multicellular

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1 Chapter 4- Cells Organisms are composed of one to many microscopic cells Unicellular Multicellular Multicellular organisms are composed of one or more types of tissues Different types of tissues are grouped to form organs The Two Major Types of Cells The Three Domains of Life Domain Bacteria Domain Archaea Prokaryotic cells

2 Domain Eukarya includes all of the eukaryotic organisms. Domain Eukarya Protists (multiple kingdoms) Kingdom Plantae Kingdom Fungi Kingdom Animalia Eukaryotic cells Diagram of a plant cell All eukaryotic cells and prokaryotic cells have at least three components in common: Prokaryotic flagella Nucleoid region (DNA) The plasma membrane Capsule Pili Cell wall Ribosomes Plasma membrane The plasma membrane is composed of phospholipids, proteins, and other materials.

3 The cytoplasm consists of the entire region of the cell between the nucleus and plasma membrane The cytosol is the cellular fluid. Ribosomes, are composed of protein and RNA. Cell Membrane Structure and Function The membranes of cells are composed of: Hydrophilic head Hydrophobic tail Outside cell The lipids belong to a special category called phospholipids Cytoplasm (inside cell) (a) Phospholipid bilayer of membrane Hydrophilic region of protein Phospholipid bilayer Hydrophobic region of protein The cell membrane is described as selectively permeable because it allows free passage of some materials and not others. (b) Fluid mosaic model of membrane -Very small, uncharged molecules can easily pass through the membrane -Larger molecules and ions (molecules with an electrical charge) do not pass through the cell membrane without specific membrane transport proteins.

4 Selective membrane permeability is the basis for osmosis. Osmosis and Water Balance in Cells Osmosis is the diffusion of water across the cell membrane in response to differences in concentrations of solutes (dissolved substances) such as sugars or ions. Diffusion Water, like many substances, will move from where it is more concentrated to where it is less concentrated. If the concentration of solutes inside and outside the cell is the same, then the cell is osmotically balanced. Osmosis and Water Balance in Cells If the solute concentration is lower outside a cell than inside, Prokaryotes, protists, fungi, and plants have cell walls that limit the increase of cell volume through the uptake of water. If the concentration of solutes outside the cells is higher than inside, water leaves the cell and the cytoplasm shrinks.

5 Eukaryotic cells share some features that prokaryotes lack All eukaryotic cells have a: The nucleus is the major site of genetic information (DNA) storage in eukaryotic cells. The nuclear envelope Nuclei also contain nucleoli (nucleolus, sing.), Ribosomes Chromatin Nuclear envelope Nucleolus Pore Eukaryotic nuclear DNA is combined with proteins to form chromosomes. Many of the membranous organelles in the cell belong to the endomembrane system The endoplasmic reticulum (ER) Rough ER The roughness of the rough ER is due to ribosomes that stud the outside of the ER membrane Ribosomes Nuclear envelope Ribosomes Rough ER Smooth ER Small globular structures composed of protein and RNA that generate proteins from amino acids. Transport vesicle buds off 4 Ribosome 3 Secretory protein inside transport vesicle After the rough ER synthesizes a molecule it packages the molecule into transport vesicles 1 2 Protein Rough ER Polypeptide

6 Smooth ER lacks the surface ribosomes of rough ER Nuclear envelope Ribosomes The Golgi apparatus Rough ER Smooth ER Works in partnership with ER The Golgi apparatus of a cell consists of 1 or more Golgi bodies. The cytoskeleton consists of three major types of long, thin, protein fibers: Flagella and Cilia Eukaryotic flagella typically contain a pair of single microtubules, surrounded by a cylinder of nine paired microtubules (9 + 2 arrangement).

7 Mitochondria Each mitochondrion is enclosed by an envelope composed of an outer membrane and a highly folded inner membrane. Peroxisomes -surrounded by single membrane Plant cells Plant cells are distinguished from most other eukaryotic cells by: Components of cell walls: Cellulose - the most abundant organic compound on Earth Cellulose is a polymer of glucose units, but the glucose monomers are linked together in different orientation. Non-cellulose components of plant cell walls Plant cell walls also contain other polysaccharides such as: Hemicellulose is a polymer of glucose and other sugars. Pectin

8 Primary and Secondary Plant Cell Walls Plant cells that are still growing have only a single cell walllayer, or primary cell wall. Secondary cell walls Lignin may be added to the walls of water-conducting cells, so mature cell walls can no longer stretch. Plasmodesmata Large ions and molecules can be transported between the cells.

9 Chloroplasts Leaves and other green parts of plants contain organelles called chloroplasts. The more general term plastid is used to describe Plant and algal cells contain from one to many plastids per cell. Plant cells are enclosed by an envelope composed of 2 membranes. The watery stroma contains other enzymes for photosynthesis. Other types of plastids Amyloplasts Chromoplasts Central vacuole

10 Study outline for Chapter 4-Cells --Understand cell membrane structure and function- What are membranes of cells composed of? -Know the structure of phospholipid bilayer of a membrane -Understand the concept of selectively permeable -Know examples of what can pass easily through membranes and substances that will not pass without specific membrane transport proteins -Understand osmosis and water balance in cells -Know terms-osmosis, diffusion, isotonic, hypotonic, hypertonic, contractile vacuole, plasmolysis -Know the features that eukaryotic cells share but prokaryotes lack -Know structure and function-nucleus, nuclear envelope, nucleolus, chromosomes -Know the membranous organelles that belong to the endomembrane system-er (rough and smooth), ribosomes, Golgi apparatus, Golgi body, cisternae -Know the three major types of fibers in the cytoskeleton-microtubules, microfilaments, intermediate filaments -Understand flagella and cilia arrangement -Know structure and function of mitochondria and peroxisomes Plant cells are distinguished from most other eukaryotic cells by which 4 cellular features? -Know functions of cellulose cell walls -Understand the structure of cellulose -Know the structure and function of non-cellulose components of plant cell walls: hemicellulose, pectin -Know the difference between primary and secondary plant cell walls -Understand the structure and function of plasmodesmata -Understand structure and function of different types of plastids-chloroplast, chromoplast, leucoplast (amyloplast) -Know terms-thylakoid, stroma -Understand structure and function of central vacuole