A Tour of the Cell
Chapter 6
Objectives Distinguish between a prokaryotic and eukaryotic cell Describe the unique structures of a prokaryotic cell Describe the structural differences between plant and
animal cells Describe the complex structural and functional
interconnections among the organelles of the endomembrane system
Describe the structure of the eukaryotic nucleus, mitochondrion and chloroplast
Describe the surface structures of the cell that provide support, protection, and movement in, and communication with, the extracellular environment
Introduction Cell is smallest functional unit of life
cell theory:• all organisms composed of cells• all existing cells arise from pre-existing cells
Common characteristics of all cells: cell contents surrounded by plasma membrane cytoplasm consists of semifluid matrix organelles are embedded in cytoplasm contain genes in the form of DNA
Fundamental Features of Life
Features of cells are characteristic of life cells are highly structured cell structure and function are related cell membranes separate the cell from the
external environment each cell has DNA as the genetic material each cell carries out metabolism
Cell Organization
Two types of cells-prokaryotic and eukaryotic
Prokaryotic: small lacks nucleus; DNA in nucleoid region cytoplasm surrounded by plasma membrane
and outer cell wall flagella and pili may be present
Cell Organization
Eukaryotic Larger than prokaryotic cells complex internal structure with membranous and non-
membranous organelles Membranous components: nucleus, endoplasmic
reticulum, Golgi apparatus,mitochondria, lysosomes and peroxisomes
Non-membranous components: ribosomes, microtubules, centrioles, flagella and cytoskeleton
Plant vs. Animal Cells
Animal cells surrounded by plasma membrane only
Plant cells surrounded by plasma membrane and rigid cell wall; also have central vacuole and chloroplasts
Eukaryotic Cell Organization
Eukaryotic organelles form four functional groups: manufacture breakdown energy processing support, movement and communication
Manufacturing
Nucleus is cell’s genetic control center surrounded by double membrane
contains pores to allow passage of material between nucleus and cytoplasm
DNA normally present as strands of chromatin
During cell division, chromatin coils up to form chromosomes
Nucleolus-organelle within nucleus-responsible for ribosomal RNA synthesis
Endomembrane system
Collection of membranes either inside or Collection of membranes either inside or surrounding the eukaryotic cell, related through surrounding the eukaryotic cell, related through direct physical contact or by transfer of vesiclesdirect physical contact or by transfer of vesicles
Endomembrane system
Endomembrane system: RER and SER
Rough endoplasmic reticulum contains ribosomes; protein synthesis ( RER)
Smooth endoplasmic reticulum synthesizes lipids, processes materials, acts as storage and detoxifies substances (SER)
Golgi Golgi apparatus recieves products from ER
Chemically modifies the products sent to it
Puts “Zip Codes” on products so they know where to go in the cell
Puts these modified products in vesicles and sends them out
Golgi
The Golgi Apparatus is the “UPS” of the cellThe Golgi Apparatus is the “UPS” of the cell
Its recieves, warehouses, sorts, modifies, packs and Its recieves, warehouses, sorts, modifies, packs and reships substancesreships substances
Lysosomes
Lysosomes contain enzymes to digest substances and wastes; defective lysosomes cause fatal diseases
Lysosomes help your cells recycle materials: Each Liver cell recycles half of its synthesized macromolecules per week
Whey else do they do?
Vacuoles
Vacuoles function in general cell maintenance
In plants they can hold organic substances
In protists vacuoles can hold food or water, or act as pumps
Energy Processing
Mitochondria: found in all eukaryotic cells, except anaerobic
protozoans surrounded by double membrane site of cellular respiration Prokaryotes don’t have them… What do they do?? Inner and outer membrane Matrix and Cristae
Chloroplasts Chloroplasts:
found in plants and algae convert solar energy to chemical energy Surrounded by double membrane site of photosynthesis
More on these organelles in Ch 10
Peroxisomes
What is the function of Peroxisomes?What is the function of Peroxisomes?
Read all about them in your bookRead all about them in your book
What is the difference between the terms What is the difference between the terms detoxification and degredation???detoxification and degredation???
Support, Movement, and Communication
Internal cell skeleton-cytoskeleton composed of 3D meshwork of proteins rods of globular proteins-microfilaments
ropelike strands of fibrous proteins-intermediate filaments hollow tubes of globular proteins-microtubules
microtubules provide anchors for organelles, act as conveyor belts and form cilia and flagella
Cilia and flagella function to move whole cell structure consists of 9 microtubule doublets
arranged around central pair (9+2)
Movement of cilia and flagella occurs when arms consisting of the protein dynein move the microtubule doublets past each other
Microfilaments cause contraction of muscle cells
They also function in ameboid movement, cytoplasmic streaming and support for cellular projections
Centrioles
Centrioles, located adjacent to the nucleus, anchor and organize the microtubules that form the spindle during cell division
Eukaryotic Cell Organization
Cell surfaces protect, support and join cells in plants, neighboring cells joined to form
interconnected and coordinated group cell walls multi-layered, composed of mixtures of
polysaccharides and proteins plasmodesmata-channels through cell walls connecting
cytoplasm of adjacent cells- plants
Extracellular Matrix
in multi-cellular animals cells often surrounded by sticky mixture of polysaccharides and proteins
Extends outward from the cell membrane
Lots of collagen is found there……
Eukaryotic Cell Organization
Several type of junctions between cells: tight junctions: leak proof; block movement of
substances
anchoring junctions- join cells and provide structural support; like the rivets in your blue jeans
communicating junctions ( gap junctions)-provide channels between cells; allow rapid transport of materials