Cell Structure & Function History of the cell Antonie van Leeuwenhoek (1673) – constructed a crude microscope to analyze “animalcules” in pond water & other “tiny things” Robert Hooke (1665) – coined the word “cellulae” (small roon) to describe the boxlike cavities he saw when viewing cork slices under a microscope Both of these individuals observations were discarded for nearly 200 years, due to social standing Development of the CELL THEORY Matthias Schleiden (1838) – using a microscope proposed that all plants are composed of cells Theodor Schwann (1839) – using a microscope proposed that all animals are composed of cells Together they stated: 1. Cells are the elementary particle of all living organisms 2. All cells are alive – independent to the organisms to which they belong

Chapter 3 – Cell Structure & Function Development of the CELL THEORY Rudolf Virchow (1858) – stated 1. Cells never arise from noncellular material 2. Diseases result from changes in specific kinds of cells CELL THEORY 1.All organisms are composed of one or more cells 2.Cells are the basic living unit of organization of all organisms capable of independent existence 3.All cells come from other cells

Chapter 3 – Cell Structure & Function What are cells composed of? All cells are composed of a boundary, a cell body, & a set of genes The plasma membrane is a boundary that separates the contents of the cell from the surrounding environment It is composed of a phospholipid bilayer in which protein molecules are embedded It serves to regulate the passage of materials into & out of the cell, thus maintaining a homeostatic environment for the cell’ life processes

Cell Structure & Function Cells also contain a set of genes, which are composed of DNA Genes contain all of the necessary information for the growth, development, & maintenance of an organism throughout its life cycle In our cells, along with those of plants, fungi (mushrooms), & protists (amoeba), the genes are contained within a membrane bound structure called a nucleus. The presence of this nucleus defines a category of cells called eukaryotic cells Prokaryotic cells (bacteria) do not possess a gene containing nucleus. Its genes occupy a region called the nucleoid. It is not protected by a membrane barrier. The cell body is defined as the area between the nucleus & the plasma membrane It is filled with a semi-fluid substance called cytoplasm Cytoplasm is 90% water & contains dissolved molecules as well as the organelles of the cell

Chapter 3 – Cell Structure & Function

Cell Structure & Function What kind of functions does a cell have to accomplish in order to survive? Organelles & their functions Nucleus – Stores genetic information for the cell. It is surrounded by a double membrane called the nuclear envelope. The nuclear envelope contains nuclear pores to allow the passage of materials between the nucleus & the cytoplasm The nucleus also contains nucleoli which synthesize ribosomes necessary for protein synthesis

Chapter 3 – Cell Structure & Function

Cell Structure & Function The endomembrane system – is composed of the nuclear envelope, endoplasmic reticulum, golgi apparatus, & vesicles Endoplasmic reticulum (ER) – a series of flattened stacks of vesicles (saccules) which are continuous with the outer membrane of the nuclear envelope ER exists as either Smooth ER (SER) or Rough ER (RER) RER is studded with ribosomes, giving the ER its “rough” appearance. It is involved in protein synthesis, packaging the newly synthesized proteins for further modification SER does not have attached ribosomes, hence smooth appearance. It is involved in lipid metabolism, hormone production, detoxification, vesicle formation, & other processes

Chapter 3 – Cell Structure & Function

Cell Structure & Function

Golgi apparatus – a stack of 3 to 20 saccules which are involved in modifying & packaging proteins & lipids delivered to it from the ER Once the molecules have been modified, they exit the Golgi via vesicles which will then migrate to the plasma membrane to secrete the molecule or have them embedded in the plasma membrane Other vesicles will remain in the cytoplasm, becoming organelles like lysosomes & peroxisomes

Chapter 3 – Cell Structure & Function Lysosomes – contain digestive enzymes What kind substances do you think lysosomes digest? Autophagy – digestion of organelles Autolysis – digestion of their host cell Vacuoles – large membranous sacs for storing substances

Cell Structure & Function Mitochondria structure It is a double membrane organelle enclosing a fluid-filled space called the matrix. The inner membrane contains the key enzyme ATP synthase which is used to synthesize ATP from the breakdown of energy rich molecules like carbohydrates

Cell Structure & Function Cytoskeleton It is a network of interconnected filaments & tubules that extends from the nucleus to the plasma membrane It determines cellular shape & movement Composed of microtubules, microfilaments, & intermediate filaments 1) Microtubules are composed of the globular protein tubulin. They are important for maintaining asymmetrical cell shape (neurons) & complex cell movements: A) transportation of secretory vesicles within the cell, B) movement of flagella & cilia, & C) distribution of chromosomes during cell division 2) Microfilaments which are composed of the proteins actin (globular) & myosin (golf- club shaped). They are involved in contractile mechanisms (muscle & cytokinesis) contraction & as mechanical stiffeners for several cellular projections (microvilli) 3) Intermediate filaments are highly stable polymers. They primarily support the nuclear envelope & the plasma membrane

Cell Structure & Function

Centrioles – Form the microtubule organizing centers in cell reproduction / division (mitosis). Involved in assembling & disassembling microtubules necessary for mitosis

Cell Structure & Function Cilia & Flagella – cell movement or the movement of substances along the cell surface Which of your cells contain cilia or flagella?