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Cell Structure and Function
Chapter 3, Part 2
Eukaryotes & Prokaryotes Cells
CELLS
•The Cell theory states that all living things are composed of cells
– That cells are the functional and structural units of organisms
–That all cells are derived from previously existing cells
Cellular level of organization: Cell size
–Most cells are smaller than 1-100 μm in diameter
–The surface/volume ratio determines the cell’s size
•Nutrients from the cell’s environment must cross the surface to enter the cell
•Cells must be small in order for the surface area to be adequate to supply nutrients
•A small cell has a greater surface/volume ratio than larger cell
•Surface area increases by the cube of the radius
Organization of Life - Organisms are placed into categories based on their evolutionary
relationships. There are 8 major catagories:
1. Domain
5. Order
2. Kingdom
6. Family
3. Phylum
7. Genus
4. Class
8. Species
Each order gets increasingly narrow and specific to groups whose common ancestors is
increasingly recently
Classification of organisms
•There are 3 Domain – that constitute the largest classification category
– Eukarya (eukaryotes)
– Archaea (prokaryotes)
– Bacteria (prokaryotes)
Prokaryotes are single-cell organisms. Example of the classification for human cells.
Domain – Eukarya
Kingdom – Animalia
Phylum – Chordata
Class
– Mammalia
Order – Primates
Family – Hominidae
Genus – Homo
Species – Sapiens
Classification Domain:Eukarya
Protista: Pseudopods - Amoebas
Fungi:
•Cannot move
•Grow rapidly to compensate for lack of mobility
•Obtain their nutrients from other organisms
•Surrounded by cell wall (like plant cell)
The good, the bad and the ugly side of Fungi
•Many antibiotics derive from fungi: for example Penicillins
•Makes wine & beer using yeasts, plus yeasts makes bread rise
•Benefits to the ecology – fungi are the decomposers of the forest floor
Eukaryotic cells
Eukaryotic cells have a membrane-bound nucleus, which contains genetic material
–All plant and animal cells are eukaryotic
– Have Plasma membranes - outer boundary of cell
–Phospholipid bilayer (arrangement of hydrophilic and hydrophobic ends), with embedded
Proteins; Associated glycolipids and cholesterol
The Functions of the cell membrane
–Barrier between the cell and its environment
–Regulate substances transporting in & out of the cell
–Contains receptors that respond to stimuli
–Contains proteins that are vital for immune responses
–Contains a very dynamic, fluid structure
Plant cells- outer cell wall in addition to the plasma membrane, which is composed of cellulose for
rigidity. Some plant cells have a secondary cell wall which is composed of lignin
Eukaryotic cells have:
•Organelles - subcellular structures that perform specific life functions
•Organelles present in animal & plant cells
•Some are found exclusively in plants or animals
–Plants - chloroplasts, central vacuole
–Animals - centrioles
Eukaryotic cells also have:
–Nucleus with genetic material DNA
–Nucleoplasm - semifluid within nucleus
–Chromatin - threadlike DNA (grainy appearance)
–Nucleolus - dark regions of chromatin which produce rRNA which composes ribosomes
–Nuclear membrane- double layered, surrounds nucleus and has large pores
Eukaryotic cells have:
•Ribosomes- site of protein assembly
•Endomembrane system-Includes nuclear membrane, endoplasmic reticulum (er), Golgi apparatus
and vesicles, lysosomes,
•The Energy producing organelles in the eukaryote cells include:
–Mitochondria – exists both in plant and animal cells
–Choloroplast – exists in plant cells – for photosynthesi
Energy related organelles (Chloroplasts - site of photosynthesis)
•The choloroplast captures light energy and converts it to chemical energy in the form of food
molecules
• The choloroplast is surrounded by a Double outer membrane that is filled with fluid called:
stroma
•The choloroplast contains Membranous systems of thylakoids. These are stacked in regions
called grana
Interrelationship between mitochondria and the chloroplasts
–Chloroplasts convert light energy to chemical energy in the form of organic food molecules
(carbohydrates) which can be used by all organisms in cell respiration to make ATP
–Only plants and algae have chloroplasts
–All cells, plant and animal, contain mitochondria
In the Eukaryotic cells:
Photosynthesis – is best summarized as following:
Light energy + carbon dioxide + water  carbohydrate + oxygen
Cellular respiration – is best summarized as:
Carbohydrate + oxygen  carbon dioxide + water + energy (ATP)
** The chemicals required by cell respiration are produced in photosynthesis, and vice versa
Prokaryotic cells are found in the: Archae and Bacteria Domains
–They are Smaller that eukaryotes, unicellular, Extremely abundant and Lack a nucleus
• He Nucleoid - contains a single (looped) chromosome
•The Genetic material is not enclosed like in the eukaryote cells
•They lack a mitochondria, golgi, ER, choloroplast
Domain: Archaea Prokaryotes
•Unicellular organism
•Nucleus with no membrane
•Simple structure
•Complex metabolic system
•live in aquatic, salty, acidic, or very hot environments or lack oxygen
Archae and Bacteria Domains cell structure:
–Cell wall - contains peptidoglycans
–Some have cell walls encapsulated - slime layer (biofilms)
–Flagellum or fimbriae
–Plasma membrane
–Ribosomes – for protein synthesis
–Food granules – glycogen storage
–Thylakoids – a sac with a granum containing chlorophyll
Bacterial cells (also Prokaryote cells)
Archae and Bacteria are aerobic or anaerobic
–Aerobic – require O2
–Anaerobic – O2 not required
–Metabolize inorganic molecules (ammonia, iron, sulfur, nitrite, hydrogen)
–Divide & reproduce by binary fission
–Affect other living organism (Eukaryotes)
•Help obtain nutrients, metabolize, recycle waste, debris dead organisms
•Deadly diseased – produce toxins
Prokaryotes
•Differences exist among the Prokaryotes.
•Endospores: resistant to extreme environmental conditions
–Variant temperature: like very hot (hot springs) or very cold (Artic)
–Exreme high pressures, like areas below the deep surface of Earth.
–Variant pH conditions that are Acidic (vinegar) – or basic(salty waters) conditions
CELL Review
The Nucleus and Nuclear Envelope of the Eukaryotic cells
•Endomembrane system (cont.’)
–Rough endoplasmic reticulum (rer)
•Complex system of sacs and channels
•Has attached ribosomes
•Serves as site of assembly of proteins for export
•Assembled proteins enter channels for processing
–Addition of sugar chains to form glycoproteins
•Released in vesicles
–Smooth endoplasmic reticulum (ser)
•Synthesizes lipid products such as phospholipids and steroids
•Released in vesicles
The Endoplasmic Reticulum
Eukaryotic cells
•Golgi apparatus
–packaging and processing center for cell products
–Receives the vesicles from er
–Vesicles fuse with Golgi and products are released inside
–Further modification of glyoproteins occurs
–Golgi also produces lysosomes-protein containing vesicles within cells
The Endomembrane System
Eukaryotic cells
•Lysosomes
–Contain hydrolytic enzymes
–Fuse with vesicles from cell membrane containing macromolecules
–Digestion occurs and nutrients released to cell
–Also may be involved in programmed cell death - “suicide sacs”
•Lysosomal membranes in old or damaged cells rupture and enzymes digest the cell
Eukaryotic cells
•Mitochondria - another energy related organelle
–Site of aerobic cell respiration; production of ATP
–Outer double membrane surrounds fluid-filled matrix
–Inner folded membrane-folds are called cristae
–Cristae provide increased surface area for the production of ATP
Eukaryotic cells
•The Cytoskeleton
–Maintains cell shape
–Allows cells and organelles to move
–Components include actin filaments, intermediate filaments, and microtubules
•Actin filaments interact with motor molecule myosin in muscles
•Intermediate filaments support the nuclear membrane
•Microtubules protrude from the centrosome and form centrioles, cilia, and flagella
The Cytoskeleton
Eukaryotic cells
•Centrioles
–Short tubules with 9+0 pattern of microtubule triplets
–In animal cells, centrosome is composed of 2 centrioles
–Believed to be involved in microtubule formation including mitotic spindle
Eukaryotic cells
•Cilia and flagella - Hair-like projections,
•cilia is generally multiple
•flagella is single or double: Whip-like action; Used for motility