Cell Biology:Cell Structure and Function Lesson 1 – Eukaryotic Cells and Organelles (Inquiry into Life pg. 49-62)
Today’s Objectives • Analyze the functional inter-relationships of cell structures, including: • Describe the major cell structures and their functions • State the balanced chemical equation for cellular respiration • Describe how the Endomembrane System functions to compartmentalize the cell and move materials through it • Identify cell structures depicted in diagrams and electron micrographs
The Cell • The cell is the structural and functional unit of an organism. • It is the smallest structure capable of performing all the functions necessary for life.
The study of cells • The study of cells had its birth with the invention of the microscope, but it became a product of the 19th century. As biologists became increasingly familiar with the detailed microscopic features of organism they were able to make certain generalizations about cells.
In the late 1830’s two German biologists, Schleiden( a botanist) and Schwann, (a zoologists) made similar claims. They realized that all organisms they were studying were composed of cells. Their discoveries are now generalized as “ The cell is the building block of all organisms.”
A few years later, Rudolph Virchow added the observation that cells “come from pre-existing cells.” These two statements comprise what is now known as the Cell Theory.
Cell Theory • Cell theory states: • All organisms are composed of one or more cells. • Cells are the basic unit of structure and function in an organism. • All cells come from other cells.
Cell Size • Cells are very small. Most cells are between 1 micrometer (1 thousandth of a millimeter) and 100 micrometers.
Cell Size • Small cells are advantageous to multicellular organisms. • Nutrients and wastes are passed through the cell at its surface, therefore the amount of surface area affects the ability to material in and out of the cell. • As cells increase in volume, the proportionate amount of surface area decreases. Surface Area: 96 cm2 192 cm2 384 cm2
Types of Cells • There are two overall classifications of cells: • Prokaryotic cells (simple cells) • Do not contain nucleus or membrane enclosed organelles • Found in Bacteria, Archaea • Usually exist as single celled organisms (unicellular) • Eukaryotic cells (complex cells) • possess nucleus and organelles • Contains internal membranes • Multicellular organisms
Examples of Eukaryotic cells include Plants, Animals, Protists, Fungi. Prokaryotic cells are considered to be less efficient than Eukaryotic cells because the chemical reactions occur all over the cytoplasm rather than in areas of specialization.
Nucleus • Largest Organelle. • Surrounded by a double-layered membrane (the nuclear envelope). • Membrane has pores through which larger molecules pass. (Nuclear Pores) • Control center for the cell’s functions. (The brain). • Contains a fluid called the nucleoplasm. • Contains chromatin (DNAstrands which forms chromosomes during cell division.)
Nucleolus • Dark region in the Nucleoplasm. • One or more found in the nucleus. • Site where ribosomal RNA (rRNA) is produced or stored. • Involved in interactions between the nucleus andthe cytoplasm.
Chromatin • The hereditary materialof the cell. • Condenses to form chromosomes during cell division. • Composed of Protein and DNA
Chromosomes • Condensed chromatin • Contains the hereditary information.(genes) • Rod-shaped bodies in the nucleus, particularly during cell division
Each eukaryotic species has a characteristic number of chromosomes A typical human cell has 46 chromosomes, but sex cells (eggs and sperm) have only 23 chromosomes.
Cytoplasm • A semifluid (like a gel) medium composed of water, salts and dissolved organic molecules • Contains and supports all the cells organelles.
Plasma Membrane • All cells are surrounded by a plasma membrane. • The material inside of a cell is the cytoplasm. • The plasma membrane regulates what enters and exits a cell.
Plasma Membrane (cell membrane) • Composed of proteins and phospholipids (fats with Phosphorus). • Acts as skin around the cells contents. • Acts as a selectively permeable membraneto allow movement of materials in and out of the cell. • Located around the outside of the cell. • Single membrane around the vacuoles/vesicles, lysosomes, E.R., Golgi Apparatus. • Double membrane around the nucleus and mitochondria
End of Part 1 • Cell Organelle Jigsaw • Half of groups research organelles on front side • Half of groups research organelles on back side • Half way through, 2 groups join to teach other group about their organelles • Location in cell • Structure • Function
The Endomembrane System • Consists of: • Nuclear Envelope • Endoplasmic reticulum • Golgi apparatus • Vesicles • This system compartmentalizes the cell so that particular enzymatic reactions are restricted to specific regions • Organelles of the endomembrane system are connected directly or by transport vesicles
Smooth Endoplasmic Reticulum (Smooth ER) • System of interconnected flattened tubes, sacs, or canals. • Begins at the nuclear envelope and branches throughout the cytoplasmto the cell membrane. • Moves moleculesfrom one area to another.
-Location of lipid manufacture. Cells that produce steroid hormones, have an abundant smooth ER. -Section of both types of ER can break free “blebbing” to produce small membrane bound sacs of either proteins or lipids called vesicles. -Contains enzymes that synthesize lipids and related products such as steroids.
Rough Endoplasmic Reticulum (Rough ER) • Like Smooth E.R., but with attached ribosomes. • Folds and processes proteins and packages them in transport vesicles • Abundant in cells that produce large amounts of protein for export from the cell.
Golgi Apparatus (Golgi Body) • Stack, of a half dozen or more flattened sacs. • On one side receives protein-filled vesicles from the E.R. • Sorts the proteins and packages them in vesicles at the other side. From here the vesicles move to different locations in the cell. • Like the post office of the cell.
Many transport vesicles from the ER travel to the Golgi apparatus for modification of their contents. • The Golgi is a center of manufacturing, warehousing, sorting, and shipping. • The Golgi apparatus is especially extensive in cells specialized for secretion.
Vesicles and Vacuoles Vesicles and vacuoles (larger versions) are membrane bound sacs with varied functions. Vacuoles • Storage areas for water, nutrients, and salts. Vesicles • A small vacuole • Storage sites in various kinds of molecules. • Transport and secretory vesicles move their contents within the cell and in and out of the cell. • Can be made by the Golgi Apparatus or from an infolding of the cell membrane
Lysosomes • Special vacuoles formed by the golgi body. • Contain powerful digestive enzymesthat break down unwanted, foreign substances or worn-out parts of cells
Ribosomes • Contain rRNA and protein subunits. • Function as sites for protein synthesis. • Found on ER (proteins for export) or in the cytoplasm (proteins for use in the cell). - Several ribosomes together in a line, all producing the same protein is called a polyribosome.
Mitochondria (singular – Mitochondrion) • Burn glucose to produce adenosine triphosphate (ATP). • Use up oxygen and give off carbon dioxide (this process is called cellular respiration). • C6H12O6 + 6O2→ 6CO2 + 6H2O + Energy • Composed of two membranes.
-Considered the powerhouse of the cell. • Their inner membranes loop back and fourth through • the inner fluid, matrix, of the mitochondria • increasing its surface areaand producing shelf-like • structures called cristae. • This inner • membrane is the • site of cellular • respiration
Cytoskeleton • Protein components of cytoskeleton provide internal structure to maintain the cell’s shape, anchor the organelles, and allows them to move when appropriate. • Composed of microfilaments (actin filaments) and microtubules. • Like the “bones and muscles” of the cell
Cytoskeleton – Microfilaments (Actin Filaments) • Primarily functions to maintain cell structure and cell movements • Extremely thin protein fibers usually occurring in bundles. • Similar in composition to the protein in the muscle (allows for muscle contraction).
Cytoskeleton - Microtubules • Maintain the shape of the cell and act as tracks that organelles can move on. • Thin cylinders several times larger than microfilaments. • Found in both cytoplasm and certain organelles. • Used to construct material to make up Cilia, Flagella and Centrioles. Tubulin
Other Organelles • Centrioles: • short cylinders with a 9+0 pattern of microtubule triplets • Two centrioles lying at right angles form the centrosome which is the microtubule organizing center (MTOC) • Cilia and Flagella: • Hair like projections that can move in undulating fashion (like a whip) or stiffly (like an oar) • Cells with cilia and/or flagella are capable of movement • Cilia also line the respiratory system and help remove foreign material from the lungs
A cell is a living unit greater than the sum of its parts • While the cell has many structures that have specific functions, they must work together. • The enzymes of the lysosomes and proteins of the cytoskeleton are synthesized at the ribosomes. • The information for these proteins comes from genetic messages sent by DNA in the nucleus. • All of these processes require energy in the form of ATP, most of which is supplied by the mitochondria. • A cell is a living unit greater than the sum of its parts.
ABCD Quiz! • I believe you all know how to play this game: • Groups of 4 • 1 scorekeeper • 4 contestants • I will show a clue about an organelle, each team member will guess one of the 4 choices provided • Team with highest score wins • No notes or books allowed
Question 1 • I am the largest organelle in a cell, and I contain hereditary material. I am a: • A) Ribosome • B) Mitochondrion • C) Nucleus • D) Golgi Apparatus • Answer is C
Question 2 • I am composed of phospholipids and proteins and I control what enters and exits the cell. I am a: • A) Plasma Membrane • B) Lysosome • C) Vesicle • D) Smooth ER • Answer is A
Question 3 • I am kind of like the subway system of the cell because I transport molecules from one place to another. I am a: • A) Rough ER • B) Vesicle • C) Lysosome • D) Mitochondrion • Answer is B
Question 4 • I receive protein filled transport vesicles from the ER which I then sort and repackage for use inside the cell. I am the: • A) Ribosome • B) Vacuole • C) Cytoplasm • D) Golgi Apparatus • Answer is D