CYTOLOGY Regents Biology OBJECTIVES Upon completion of this
CYTOLOGY Regents Biology
OBJECTIVES Upon completion of this unit students will be able to: 1. Recognize that improvements in microscopic techniques have allowed for the development of the cell theory. 2. State the cell theory and the exceptions to the cell theory. 3. Discuss and compare the following relative levels of biological organization: cell tissue organ system organism 4. Describe the appearance and chief functions of the following organelles: • endoplasmic reticulum • nucleus • cytoplasm • nuclear membrane • food vacuole • nucleolus • contractile vacuole • ribosomes • lysosome • mitochondrion • plasma membrane • Golgi apparatus 5. Describe the Fluid Mosaic Model relative to the structure and function of the plasma membrane. 6. Discuss the function of centrioles in animal cells. 7. Discuss the function of chloroplasts and the cell wall in plant cells. 8. Differentiate plant cells and animal cells by giving 3 differences.
INTRODUCTION: THE SIMILARITY AMONG LIVING THINGS • Living things, whether simple or complex, are composed of small, living structural and functional units known as CELLS • Within the living cell are several sub-structures (ORGANELLES) that perform specialized functions for the cell of which they are a part. • Scientists study cell structure in the laboratory with a variety of tools and techniques, and we will be using MICROSCOPES to do just that. • Cytology is the study of CELLS; cyt(o)=CELL and logy= STUDY
A. THE CELL THEORY • The invention and development of the MICROSCOPE has given scientists the ability to discover cells and study their finest details. • The cell theory was developed over many years by scientists working in many parts of the world. • The major tool of early biologists was the MICROSCOPE; either in the form of the simple microscope, or in the form of the compound microscope
• The cell THEORY provides the strongest support for the concept of UNITY (“alikeness”) of living things: 1. ALL LIVING THINGS ARE MADE UP OF CELLS 2. CELLS ARE THE SMALLEST UNIT OF LIFE 3. ALL CELLS COME FROM PRE-EXISTING CELLS; THIS MEANS THAT CELLS DO NOT ARISE SPONTANEOUSLY, BUT ARE PRODUCED BY THE PROCESS OF REPRODUCTION
HOWEVER…. THERE ARE EXCEPTIONS TO THE CELL THEORY: 1. IF ALL CELLS COME FROM PRE-EXISTING CELLS, WHERE DID THE FIRST CELL COME FROM? (WE DON’T KNOW YET) 2. VIRUSES CONTAIN SIMPLE GENETIC MATERIAL AND CARRY OUT A TYPE OF REPRODUCTION, BUT ARE NOT TRUE CELLS. THEY NEED A HOST TO REPRODUCE; THEY CANNOT CARRY OUT ALL LIFE FUNCTIONS ALONE. 3. CERTAIN CELL ORGANELLES (MITOCHONDRIA AND CHLOROPLASTS) BEHAVE LIKE CELLS IN SOME RESPECTS. THEY CONTAIN THEIR OWN GENETIC MATERIAL AND PRODUCE ORGANISMS LIKE THEMSELVES UNDER CERTAIN CONDITIONS.
B. ORGANIZATION OF CELLS IN LIVING THINGS • Organisms are EITHER UNICELLULAR (COLONIAL), OR MULTICELLULAR 1. UNICELLULAR AND COLONIAL ORGANISMS • A cell may exist INDEPENDENTLY (UNICELLULAR) OR IN COLONIES • Unicellular organisms are able to EXIST INDEPENDENTLY (CARRY ON LIFE PROCESSES BY THEMSELVES); BACTERIA, PROTOZOA, MANY ALGAE, SOME FUNGI • The simplest level of MULTICELLULAR organization occurs in COLONIAL ORGANISMS (FEW CELLS TO THOUSANDS OF CELLS ATTACHED TOGETHER)
2. TRUE MULTICELLULAR ORGANISMS • In true multicellular organisms, CELLS ARE FUNCTIONALLY AND STRUCTURALLY SPECIALIZED • How true multicellular organisms are organized:
C. TYPES OF CELLS • There are two types of cells: 1. PROKARYOTIC 2. EUKARYOTIC • Prokaryotic cells DO NOT HAVE A MEMBRANE BOUND NUCLEUS • Eukaryotic cells HAVE A MEMBRANE-BOUND NUCLEUS • We will mainly focus on Eukaryotic Cells, namely PLANT and ANIMAL cells
D. CELL STRUCTURE AND FUNCTION • The cell is extremely complex and is composed of smaller functional parts known as ORGANELLES (“little organs”). • Each of these has special work to do in the survival of a cell: LIFE FUNCTION Respiration Regulation Reproduction Excretion Growth Nutrition Animal Cells Plant Cells Transport Synthesis (proteins) ORGANELLE(S) MITOCHONDRIA NUCLEUS, CELL MEMBRANE, CONTRACTILE VACUOLE NUCLEUS CELL MEMBRANE NUCLEUS CELL MEMBRANE, FOOD VACUOLE, LYSOSOME . . CHLOROPLASTS CELL MEMBRANE, CYTOPLASM, ENDOPLASMIC RETICULUM (ER) NUCLEUS, RIBOSOME, ER, GOLGI APPARATUS
I am an ANIMAL CELL…. . label me!
1. NUCLEUS • The nucleus is the CONTROL CENTER OF THE CELL • It contains all of the DNA of the cell and helps to maintain HOMEOSTASIS by regulating all of the life functions of the cell (R-R-R-E-G-N-T-S) • “The Brain” of the cell also has a MEMBRANE to control what enters and leaves the nucleus 2. NUCLEOLUS • Involved in CELL REPRODUCTION and is a dark body inside the nucleus • Primarily involved in RNA SYNTHESIS
3. CYTOPLASM • Fills the cell as it is JELLY-LIKE • All ORGANELLES are located in the cytoplasm and many liquids are dissolved in it. 4. ENDOPLASMIC RETICULUM (ER) • Often referred to as the ER of the cell. • The ER is a SYSTEM OF FLUID FILLED TUBES THAT FORM A NETWORK THROUGHOUT THE CELL • There are two types of ER: a. SMOOTH (s. ER) – OUTER SURFACES ARE SMOOTH b. ROUGH (r. ER) – LOOKS ROUGH BECAUSE RIBOSOMES ARE ATTACHED TO THEM
• The tubes of the ER provide a path of TRANSPORT of materials throughout the cell. • At some spots the membrane of the ER and the CELL MEMBRANE connect, allowing for materials to pass in and out of the cell. 5. RIBOSOMES • Look at the dots on the Rough ER…. those are RIBOSOMES • They are also found floating free in the CYTOPLASM • Proteins that cells need are made by protein synthesis and the RIBOSOMES HELP TO MAKE PROTEINS
6. LYSOSOMES • Contain HYDROLYTIC AND DIGESTIVE ENZYMES • In unicellular organisms, they digest food within the cell. • In multicellular organisms, they HELP DESTROY OLD ORGANELLES, FIGHT INFECTION, AND DIGEST FOREIGN MATTER 7. GOLGI APPARATUS (aka GOLGI BODY) • The Golgi Body is made up of a STACK of membranes. Its function is to PACKAGE AND STORE MATERIALS which will eventually be secreted from the cell.
8. VACUOLE • Vacuoles are FLUID-FILLED organelles surrounded by a membrane. • Plant cell vacuoles are usually HUGE compared to animal cells’. • There are two types of vacuoles: a. CONTRACTILE – HELP TO REMOVE EXCESS WATER AND WASTE b. FOOD – TAKE IN AND STORE FOOD
9. MITOCHONDRIA • The mitochondrion is often referred to as the POWERHOUSE of the cell because it provides the cell with its ENERGY through the life process of RESPIRATION • The “mighty-might” is oval in shape with two membranes surrounding it. • The inner membrane is called CRISTAE which are highly folded. • Mitochondria • CONTAIN THEIR OWN DNA AND CAN REPLICATE BY THEMSELVES
10. PLASMA MEMBRANE (aka CELL MEMBRANE) • The three main functions of the cell membrane are to: 1. SEPARATE THE CELL FROM ITS ENVIRONMENT (BARRIER) 2. CONTROLS WHAT COMES IN AND OUT OF A CELL 3. MAINTAINS HOMEOSTASIS • The cell membrane is a two-layered(BILAYER) structure composed of PROTEINS, LIPIDS, AND CARBOHYDRATES • The proteins of the membrane are believed to be important in CONTROLLING THE PASSAGE OF SUBSTANCES THROUGHOUT THE MEMBRANE; PROTEIN RECEPTORS • The cell membrane is SELECTIVELY PERMEABLE • Through its selective permeability, THE CELL MEMBRANE REGULATES THE CHEMICAL COMPOSITION OF THE CELL
Diagram of the Fluid Mosaic Model:
E. THE THREE C’S 1. CENTRIOLES • Look like BARRELS that are usually found near the NUCLEUS • They are involved in CELL REPRODUCTION • They are ONLY FOUND IN ANIMAL CELLS 2. CELL WALL • The cell wall is a RIGID STRUCTURE made of CELLULOSE • It provides SUPPORT AND PROTECTION for the cell • They are ONLY FOUND IN PLANT CELLS 3. CHLOROPLASTS • Chloro = GREEN and plast = FORMED BODY • Chloroplasts are pigment-containing structures that aid in PHOTOSYNTHESIS • Therefore, chloroplasts are only found in PLANT CELLS
F. DIFFERENCES BETWEEN PLANT AND ANIMAL CELLS 1. ONLY PLANT CELLS HAVE CELL WALLS 2. ONLY PLANT CELLS HAVE CHLOROPLASTS 3. ONLY ANIMAL CELLS HAVE CENTRIOLES Use the animal cell on page 7 to help with labeling the PLANT CELL:
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