Cell Biology Chapter 1.pdf

Cell Biology Notes Chapter 1 Cells: the fundamental Units of Life o The Cell Theory: Cells are the basic units of biology ▪ All organisms consist of one or more cells ▪ The cell is the basic unit of structure for all organisms...

Cell Biology Notes Chapter 1 Cells: the fundamental Units of Life o The Cell Theory: Cells are the basic units of biology ▪ All organisms consist of one or more cells ▪ The cell is the basic unit of structure for all organisms ▪ All cells arise from preexisting cells. That is cells are the basic units of reproduction Important People o Matthias Schleiden ▪ A German botanist and microscopist, was born April 5, 1804 ▪ Published a paper in 1838, called “Beritäge zur Phytogenesis” (Contributions to studies on the origin of plants) o Theodore Schwann ▪ Founder of modern histology and the discoverer of the lemmocyte, was born on December 7, 1810 ▪ In 1839, he published an extensive work on histology: Mikroskopische Untersuchungen über die Übereinstimmung in der Struktur und dem Waschstum der Thiere und Pflanzen (Microscopical Research into the accordance in the structure and growth of animals and plants) Characteristics of life o Order o Regulation o Growth and development o Energy processing o Response to the environment o Reproduction o Evolutionary adaption Living Cells All have a similar Basic Chemistry o Genetic information in the form of genes is carried in DNA  ▪ A gene is the segment of DNA that directs the formation of a protein or RNA. It is a unity of heredity. Dictates the phenotype of an organism ▪ A genome is all the DNA in an organism o In all organisms, DNA is made of four nucleotides (adenine, guanine, cytosine, and thymine) o In all organisms, DNA is transcribed into RNA o In all organisms, mRNA is translated into proteins o The flow of genetic information from DNA to RNA to proteins is called the Central Dogma of Molecular Biology ▪ Central means of significant importance ▪ Dogma means a set of principles set forward by an authority o RNA is made of four nucleotides (adenine, guanine, cytosine, and uracil) o Proteins are made of 20 amino acids All organisms are Bacteria, Archaea, or Eukaryotes o Based on cellular structure organisms are placed into two groups ▪ Prokaryotes (bacteria and archaea) ▪ Pro= before, karyon= kernel or nucleus ▪ Eukaryotes (Plants, animals, fungi, algae, and Protozoa) ▪ Eu= true or genuine, Karyon= kernel or nucleus o Organisms are also classified according to their similarities and differences in ribosomal RNA genes o Genome is all a cell’s DNA o A gene is a DNA sequence that encodes for RNA or protein o Based on comparison of ribosomal RNA sequences of known organisms, there are three domains of organisms ▪ Bacteria ▪ Archaea ▪ Eukaryotes Prokaryotic Cells do not have a nucleus or organelles o Prokaryotic cells are 1-5 micrometers or microns (one-millionth of a meter or 10^-6)  o Prokaryotic cells do have a plasma membrane (phospholipid membrane bilayer) o Prokaryotic cells do not have organelles o Prokaryotic cells do not have a membrane bound nucleus. Prokaryotic DNA is in the nucleoid. A nucleoid is the region in the cytoplasm where the DNA is compacted o Bacteria and archaea DNA is circular, archaea DNA is associated with histone like proteins and bacterial DNA is not. o Prokaryotic cells do not use internal membranes to segregate function o Prokaryotic cells have a cytoskeleton-like structures o Prokaryotic cells do not use endocytosis and exocytosis o Prokaryotic cells don not use mitosis or meiosis to segregate nuclear DNA they divide by binary fission o The size of prokaryotic ribosomes is 70s o Bacteria and archaea have cell walls. Bacteria cell walls contain peptidoglycan. o Archaea cell walls do not contain peptidoglycan Bacteria come in different shapes and sizes o Spherical Cells: round and circular commonly seen in streptococcus o Rod-shaped cells: round with tail like ends commonly seen in Escherichia coli, and salmonella o Spiral cells: looks kind of like a swirly worm commonly seen in treponema pallidum Eukaryotic Cells use the nucleus and additional organelles to compartmentalize cell function o Eukaryotic cells are 10-100 micrometers or microns (one-millionth of a meter or 10-6 ) o Micrometer is a unit of length generally used to measure cells o Eukaryotic cells have a membrane bound nucleus o The majority of the DNA in eukaryotic cells is contained within the nucleus. The DNA is typically linear and associated with proteins called histones o Eukaryotic cells use mitosis or meiosis to segregate nuclear DNA o Eukaryotic cells have organelles o Eukaryotic cells use internal membranes to segregate function o Eukaryotic cells have a cytoskeleton  o Eukaryotic cells use endocytosis and exocytosis o The size of eukaryotic ribosomes is 80S The Eukaryotic Cell: Nucleus o The nucleus is the information store of the cell o Large, prominent, double membrane bound organelle that contains the chromosomal DNA of a eukaryotic cell o DNA replication and transcription occur within the nucleus o The nucleolus is the site of ribosomal RNA (rRNA) synthesis and the site of ribosome assembly o A nucleus has two membranes that form the nuclear envelope, nuclear pores, nucleoplasm, nuclear lamina and nucleolus o The nuclear envelope is composed of two concentric membranes: the outer membrane and the inner membrane o The outer membrane of the endoplasmic reticulum The Endoplasmic Reticulum or the ER o Endoplasmic mean within the plasma o Reticulum means network o The ER has cisternae (flatted sacs) that are interconnected, a lumen (the space within the ER membrane o It is a single membrane organelle o The ER is continuous with the outer membrane of the nucleus o There are two types of ER, rough and smooth ER o Rough endoplasmic reticulum or RER has ribosomes on the side of th membrane that faces the cytosol o The rough ER is the site of secretory protein and membrane protein synthesis o The smoother ER is the site of lipid synthesis and steroid synthesis, calcium storage, drug detoxification (Leydig cells of the testicles make testosterone and follicular cells of the ovaries make estrogen, so they have lots of SER) The Golgi Apparatus o Nicknamed the postmaster of the cell o The Golgi apparatus is made uo of stacks of membrane enclosed sacs called cisternae o Golgi modifies proteins that it receives from the ER. It makes sugars to add to proteins and lipids o Once the Golgi apparatus modifies the proteins (or lipids) it will ship them to other parts of the cell. Hence the nickname postmaster of the cell.  o The side of the Golgi apparatus that faces the ER is called the cis face o The side of the Golgi apparatus that face the plasma membrane is called the trans face Endomembrane System o Digestive enzymes are synthesized on ribosomes and travel through the rough ER o The enzymes are packages into vesicles and travel to the Golgi apparatus o The Golgi apparatus modifies the enzymes for export to the lysosomes o The enzymes are delivered to the lysosome in vesicles o A lysosome fuses with a food vacuole, and the enzymes digest the food Eukaryotic Cells engage in continual endocytosis and exocytosis across their plasma membrane o Endocytosis is the uptake of material from outside the cell (extracellular) by the infoldings of the plasma membrane, followed by pinching off the vesicles o Exocytosis is the process by which material is released or secreted from the eukaryotic cell in vesicles. The vesicles fuse with the plasma membrane and release the material to the outside of the cell (extracellular) o Eukaryotic cells engage in continual endocytosis and exocytosis across their plasma membrane The Cytoplasm o Cytoplasm is the portion of the cell that is not occupied by the nucleus. It includes the organelles and cytosol o The cytosol is a concentrated aqueous gel of large and small molecules. It’s the semifluid substance in which organelles are suspended. It contains the cytoskeleton, ribosomes and molecules of the cell o Lysosomes single membrane organelle that contains digestive enzymes that can degrade or breakdown all biological molecules within the cell. The lysosome clean, recycle and dispose of macromolecules within the cell o Peroxisome a single membrane organelle that provide a safe space withi the cell to carry out reactions that generate and remove harmful reactive oxygen species such as hydrogen peroxide and superoxide The Powerhouse of the Cell: Mitochondria o Mitochondria generate useable chemical energy (ATP) by the oxidation of food molecules (sugar)  o Mitochondria are nicknamed the powerhouse of the cell because they produce energy in the form of adenosine triphosphate (ATP) o Site of aerobic respiration-oxygen and ADP used to produce chemical energy in the form off ATP. The process generates carbon dioxide (CO2). Aerobic respiration is also called cellular respiration o Sugar is consumed and ATP is produced during cellular or aerobic respiration o Contains as outer and inner membrane (double membrane organelle), an intermembrane space, the inner membrane folds to form cristae, small circular DNA, mitochondria ribosomes and a matrix o Mitochondria have their orn genome, can duplicate, and divide independent of cell division but cannot function for long outside of the cell because they are endosymbionts The Cytoskeleton o The cytoskeleton is responsible for support, structure, motility, organization, directed organelle and cell movements and vesicle transport o The cytoskeleton is composed of: ▪ Microtubules (25nm in diameter) ▪ Intermediate filaments (8-12nm in diameter) ▪ Actin filaments (7 nm in diameter) o Microtubules- chromosome movement and cell movement. The thickest element of the cytoskeleton o Intermediate filament- strength and support to cells o Actin filament or microfilament- contraction Unique Features of Plant Cells o Plant cells have: ▪ A cell wall made of cellulose ▪ A central vacuole ▪ Chloroplasts o The central vacuole stores water and solutes o The vacuole pushes the contents of the cell against the cell wall and consequently maintains turgor pressure The Eukaryotic Cell: Chloroplasts o The site of photosynthesis in plants and algae o Chloroplasts capture energy from sunlight to make sugars and oxygen o Chloroplasts are surrounded by a double membrane (outer and inner membrane), thylakoids (flattened sacs, considered third membrane), stroma  thylakoids (connect thylakoids), grana (stacks of thylakoids), chlorophyll, small circular DNA, chloroplast ribosomes, and stroma o Chlorophyll is in the internal thylakoid membrane