Chapter 7: Structure and Function of the Cell
The Cell Theory
Robert Hooke Observed cork (called them cells)
Antoine Van Leeuwenhoek single-celled organisms "animalcules"
Matthias Schleiden All plants MADE of separate cells
Limitations to Cell Size
Faster passage through small cells
More efficient communication
The Cell Theory
1 All organisms composed of one or more cells
2. Cell is smallest living organizational unit
3. Cells arise only from division of other cells
Increase size, greater increase in volume -surface area
Interaction with outside occurs only at surface
THE STRUCTURE OF EUKARYOTIC CELLS: AN OVERVIEW OF CELL STRUCTURE
The Plasma Membrane Surrounds the Cell- Phospholipid bilayer contains embedded protein
The Central Portion of the Cell Contains the Genetic Material
Genetic material in prokaryotes-Single, circular molecule of DNA
Genetic material in eukaryotes- Contained within the nucleus- Surrounded by two membranes
The Cytoplasm Comprises the Rest of the Cell's Interior- Cytoplasm is a semifluid matrix
Eukaryotes Are More Complex Than Prokaryotes
Key to organization is compartmentalization- Possess internal membrane-bound organelles
Golgi complex and lysosomes created by folding endoplasmic reticulum
Nucleus contains chromatin made of DNA and nucleolus
Mitochondria and chloroplasts associated with cellular energy
Cytoskeleton is an internal scaffold of proteins
Central vacuole in plants stores protein and wastes
Cell walls: cellulose/chitin fibers embedded in polysaccharides, proteins
Vesicles in animals store and transport many materials
THE ENDOPLASMIC RETICULUM: COMPARTMENTALIZATION OF THE CELL
Translate RNA copies of genes into proteins
General Characteristics- Thin membranes not visible in light microscope
Exported proteins contain signal sequences
Divide interior into compartments
Smooth ER: Organizer of Internal Activities
Lipid bilayer with embedded proteins
Lack ribosomes
Rough ER: Manufacturer of Proteins for Export
Contain embedded enzymes
Ribosomes assist manufacture of proteins
Detoxification, carbohydrate and lipid synthesis
Aggregates of protein and RNA
THE NUCLEUS: INFORMATION CENTER FOR THE CELL
The Nuclear Envelope- Double layer of membranes, outer continuous with ERProteins Are Synthesized on the Ribosomes
The Chromosomes of Eukaryotes Are Complex
Read mRNA to direct synthesis of protein
Contain hereditary information
The Nucleolus - Location of ribosome synthesis
Divided into chromosomes
Dark-staining region visible in protein producing cells
associated with histone protein
THE GOLGI APPARATUS: THE DELIVERY SYSTEM OF THE CELL Function in Molecule Collection, Packaging, Distribution
Golgi Bodies- flattened stacks of membranes-Abundant in glandular secretory cells- called the Golgi complex or apparatus
LYSOSOMES: PRODUCERS OF DIGESTIVE ENZYMES FOR THE CELL- Membrane-Bound Organelles Containing Hydrolytic Enzymes
Enzymes catalyze breakdown of macromolecules within cell
Eliminate Other Substances Including Whole Cells
Digest worn-out cell components
Digest pathogens engulfed by white blood cells
Mitochondria: The Cell's Chemical Furnaces- Possesses own genome
Occur in all organisms
Inner membrane is folded into layers called cristae
Bounded by double membrane
Divides into inner matrix and outer compartment
Chloroplasts: Where Photosynthesis Takes Place
Occur in photosynthetic organisms, plants and algae
Centrioles: Microtubular Assembly Plants
Internal membranes form disk-shaped thylakoids
Present in animal cells, NOT plant cells
Photosynthetic pigments on thylakoid surface
Occur in pairs near nuclear envelope, forms the centrosome
Stack of thylakoids called granum
Associated with assembly and organization of microtubules
Possess own genome
Form basal bodies that anchor flagella and cilia
THE CYTOSKELETON: INTERIOR FRAMEWORK OF THE CELL
Network of Protein Fibers
Provide Mechanical Support for Cell
Actin fibers determine cell shape
Rapid changes in filament length changes cell shape quickly
FLAGELLA AND CILIA: MOTILITY FOR THE CELL
Eukaryotic Flagella9+2 structure of microtubules
Cilia and Centrioles Also Show 9+2 Arrangement
Numerous, short projections called cilia
Have functions other than locomotion
SYMBIOSIS AND THE ORIGIN OF EUKARYOTES
Eukaryotes Have Radically Different Cell Structure
Possess organelles that resemble bacteria, endosymbiont theory
Symbionts Provided Metabolic Advantage to Host
Mitochondria are energy factories
Chloroplasts photosynthesize
Evidence Supporting Theory
Mitochondria and chloroplasts surrounded by double membrane
Mitochondria and bacteria have similar size
Mitochondrial ribosomes resemble bacterial ribosomes
Mitochondria and chloroplast DNA circular like bacteria
Mitochondria divide by simple fission