Presentation on theme: "INTRODUCTION TO CELLS Cells vary in size and shape and functions! Despite these differences, eukaryotic cells share similar chemistry ! nerve cellParamecium."— Presentation transcript:
INTRODUCTION TO CELLS Cells vary in size and shape and functions! Despite these differences, eukaryotic cells share similar chemistry ! nerve cellParamecium plant stembacterium
CELL THEORY (begin notes) Matthias Schleiden (1838) and Theodor Schwann (1839) recognized that: all living organisms are made of cells; cells form from divisions of existing cells; cell is the smallest unit of life! Robert Hooke, England, 1665 uses a light microscope to examine cork, and names these small chambers “CELLS” THE DISCOVERY OF CELLS Anton van Leeuwenhoek describes various forms of bacteria based on his microscopic observations
CELLS Prokaryotic cells: bacteria, blue-green algae Lack a membrane-bound nucleus DNA is usually one circular chromosome located in an area of the bacterium Lack membrane-bound organelles Eukaryotic cells Single or multicelled DNA encased in a membrane Possess membrane-bound organelles Prokaryotic Eukaryotic
THE PROKARYOTIC CELL EUBACTERIAARCHAEBACTERIA E.coli PROKARYOTES are cells lacking membrane- bound organelles and the internal compartmentalization characteristic of eukaryotes The simplest, most basic type of cell Enormously diverse and occupy most every niche Can be autotrophic or heterotrophic Two domains of prokaryotes – Dramatically different from each other:
THE PROKARYOTIC CELL ●EUBACTERIA more complex true bacteria ARCHAE live in hostile environments Methanogens Halophiles Thermoacidophiles Phile = love E.coli Two domains of prokaryotes – Dramatically different from each other:
THEORY OF ENDOSYMBIOSIS ancestral eukaryotic cell aerobic eubacteria engulfed mitochondrion photosynthetic bacterium chloroplast eukaryotic cell with mitochondrion eukaryotic cell with chloroplast internal membranes
EVIDENCE SUPPORTING ENDOSYMBIOSIS If mitochondria and chloroplasts arose from prokaryotes, then we can predict that: THESE ORGANELLES CONTAIN DNA, RNA, AND RIBOSOMES - Each genome consists of a single, circular molecule of DNA - 70S ribosomes and 23S and 16S rRNA, like prokaryotes THE INNER MEMBRANE OF EACH ORGANELLE CONTAINS ENZYMES AND PROTEINS SIMILAR TO THOSE OF PROKARYOTES - Antibiotics inhibiting transcription or blocking translation (processes used to synthesize proteins) in bacteria similarly affect these processes in chloroplasts and mitochondria. -These antibiotics do NOT affect transcription of nuclear genes or protein synthesis within the cytoplasm of eukaryotes.
The Ribosome is the site of protein synthesis. Ribosomes are usually associated with the endoplasmic reticulum, but some are suspended freely in the cytoplasm. As you will see in this image, ribosomes are structurally different in bacteria and eukaryotes.
THE EUKARYOTIC CELL Eukaryotic cells are larger and more complex than those of the eubacteria and archae Eukaryotes can be single- celled or multicellular organisms Importantly, eukaryotes contain membrane-bound organelles yeast
ORGANELLES THE NUCLEUS Surrounded by a double-membrane known as the nuclear envelope Nuclear envelope Contains pores to facilitate exchange of substances across the nuclear envelope The nucleus contains DNA, usually as chromatin, but this condenses to form chromosomes during cell division. Chromatin: the entire genetic material and associated proteins. Chromosomes: one long molecule of condensed chromatin (humans have 23 pairs = 46)
Chromatin and Chromosomes OrganismGenome # Mb millions of base pairs in haploid state-ova or sperm Chromosome # Haploid-ova or sperm Yeast1216 Corn707 Slime mold1305 Arabidopsis thaliana5,00010 Onion15,0008 Lily50,00012 C. elegans976 Drosophilia1804 Toad3,00018 Chicken50,00039 Mouse3,00020 Cow3,00030 Dog3,00039 Cat3,00038 Human3,00023
ORGANELLES THE NUCLEOLUS Area in nucleus not bound by a membrane Not truly considered an organelle Manufacture ribosomal subunits – the cell's protein-producing factories!
MITOCHONDRIA Contain an outer membrane and an inner membrane folded into cristae in the interior of the organelle Contain DNA, RNA, and ribosomes, all of which are similar to those of prokaryotic cells
MITOCHONDRIA Are THE cellular powerhouses, achieved by producing ATP from the oxidation of food molecules in a process known ascellular respiration Oxidation: process of a compound combining with oxygen and in the process, gives up electrons.
MITOCHONDRIA Cellular Respiration Chemical Equation C 6 H 12 O 6 + 6O 2 CO 2 + H 2 O ATP molecules
CHLOROPLASTS Double membrane-bound organelle, with flattened sacs of membranes, called thylakoids, arranged in stacks, or grana (one stack is a granum) Use radiant energy to produce chemical bond energy Contain DNA, RNA, and ribosomes, sharing features characteristic of prokaryotes
RIBOSOMES Provides structural site of protein synthesis Composed of two units: large and small subunits Ribosomal subunits (large and small) are manufactured in the nucleolus
ROUGH ENDOPLASMIC RETICULUM (ER) Consists of flattened sheets of membranes contiguous with the outer membrane of the nuclear envelope Possesses ribosomes Functions in the synthesis and transport of proteins
SMOOTH ENDOPLASMIC RETICULUM (ER) Consists of flattened sheets of membranes contiguous with the outer membrane of the nuclear envelope Does not contain ribosomes Functions in the synthesis of: cholesterol metabolism, membrane synthesis, detoxification, Ca 2+ storage along with other cellular processes.
SMOOTH ENDOPLASMIC RETICULUM (ER)
GOLGI APPARATUS Comprised of flattened membrane- enclosed sacs Golgi receives and modifies molecules synthesized in the ER and directs them for export or to other cellular locations
LYSOSOMES Small, membrane-enclosed organelles containing enzymes for intracellular digestion PEROXISOMES Small, membrane-enclosed organelles containing oxidative enzymes that generate and destroy hydrogen peroxide VACUOLES Membrane-enclosed organelle can be used for intracellular digestion and for structural support Small, membrane-enclosed spheres mediate the exchange and transport of materials among membrane-enclosed organelles and the exterior of the cell VESICLES
CYTOSKELETON ACTIN FILAMENTS MICROTUBULESINTERMEDIATE FILAMENTS Present in all eukaryotic cells ! CYTOSOL The solution filled environment containing the molecules necessary for essential cellular reactions! Microtubules: provide rapid transport of organellessuch as vesicles and mitochondria in neurons Migrate chromosomes during mitosis and meiosis Actin filaments: provide strength to cell generate locomotion for cells to move generates cytoplasmic streaming in cells Intermediate filaments: constructed of proteins found in hair and nails strengthen long axons of neurons provide mechanical strength to cells
Cell Membranes Cell membranes function : Barrier to prevent loss of intracellular contents to the surrounding medium senses changes in environment and allows the cell to respond
Cell Membranes Cell membranes function : enlarges to enable cell growth and reseals to prevent damage to the cell regulates exchange of nutrients and waste
ANIMAL CELL PLANT CELL YEAST CELL
MODEL ORGANISMS Drosophila melanogaster C. elegansSaccharomyces cerevisae Arabidopsis thaliana humanmouse