Concept 6.1ALL
ORGANISMS ARE MADE OF
CELLS
THE CELL THEORY 1. All living things are composed of
cells.
2. Cells are the basic unit of structure
and function in living things.
3. All cells come from pre-existing cells.
CELL THEORY DEVELOPMENT
Prior to the development of microscopes, cells could not be seen in any detail
Two types are used Light microscope: first used around 1600 Electron microscope: developed in the
1950s
TYPES OF MICROSCOPES Light Microscopes:
Simplest type
Use visible light
Used to examine living cells
Magnify 1000 X
ELECTRON MICROSCOPES
Use electron beams Magnify 1,000,000 X All specimens must
be killed to view Two types: SEM – used view cell
surface TEM – used to view
internal structures
TYPES OF CELLS Two basic kinds of cells
Classification based on the presence or absence of organelles—parts of cells with specific functions
Prokaryotic cells: have no organelles
Eukaryotic cells: have organelles
PROKARYOTIC CELLS Most primitive cell type
Lack organelles—structures that perform specific functions in cells
First organisms to appear in fossil record
Domains Archaea and Bacteria
PROKARYOTIC CELL
EUKARYOTIC CELLS More advanced cell type
Contain organelles that perform specific functions for the cell
Domain Eukarya
Includes organisms in 4 Kingdoms: Plants Animals Protists Fungi
PROKARYOTIC vs. EUKARYOTIC CELLS
PLANT vs. ANIMAL CELLS
Both contain most organelles Plant cells have 3 structures not seen in
animal cells:
1. Cell wall: surrounds cell membrane
2. Chloroplast: photosynthesis occurs here
3. Central vacuole: large storage area
ANIMAL CELL
PLANT CELL
Concept 6.2MEMBRANES ORGANIZE A
CELL’S ACTIVITIES
MEMBRANE FUNCTIONS
Keeps cell organized
Partitions the cell
Controls movement of substances into and out of cell
Helps maintain chemical environment for cell
- homeostasis - balanced internal
condition of cells
MEMBRANE STRUCTURE
Bilayer structure:
Two layers of phospholipid molecules with protein molecules embedded
Phospholipids are similar to triglycerides—fat molecules
Allows membrane to separate watery inside of cell from watery outside of cell
MEMBRANE STRUCTURE
PHOSPHOLIPID STRUCTURE
Two part molecule:
Hydrophilic polar phosphate group head is attracted to water faces outward towards water
Hydrophobic non-polar fatty acids tails face inward toward each other—away from water
PHOSPHOLIPID MOLECULE
MEMBRANE PHOSPHOLIPIDS
CELL MEMBRANES
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PROTEINS PERFORM MOST MEMBRANE FUNCTIONS
Enzyme activity: catalyze reactions of nearby substrates
Cell-to-cell recognition: surface proteins of other cells are “recognized”
Cell signaling: chemical messengers bind to surface proteins causing change in shape relaying message inside cell
Transport of materials: provide channels for certain solutes
PROTEINS PERFORM MOST MEMBRANE FUNCTIONS
CELL MEMBRANE ACTIVITY
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Concept 6.3MEMBRANES
REGULATE THE TRAFFIC OF MOLECULES
TYPES OF MEMBRANES
Permeable membranes: allow particles freely pass through them
Selectively permeable membranes: allow some substances to cross more easily than others; block some completely
MEMBRANE TRANSPORT
Two main types of transport:
Passive transport: no energy is used by the cell in transporting material
Active Transport: cell must expend energy to move molecules or particles across the membrane
PASSIVE TRANSPORT Three types of passive transport:
Simple diffusion
Facilitated diffusion
Osmosis
DIFFUSION Diffusion: net movement of particles from
area where they are more concentrated to an area where they are less concentrated
Diffusion may occur with or without a membrane—the only requirement is that a concentration gradient must exist
Concentration gradient: difference in the concentration of a substance between one area and another
During diffusion, particles of a substance move through a space until the concentration of the substance is the same in all areas
When diffusion occurs a membrane, particles will continue to move across the membrane until the concentrations are equal on both sides of membrane balance or equilibrium is reached
DIFFUSION
CELL MEMBRANE TRANSPORT
Cell membranes are selectively permeable
O2 and CO2 pass freely
H2O must pass through protein channels
Other molecules pass only under specific conditions
Ions, hydrophilic molecules larger than water, proteins, & large molecules do not move through the membrane on their own.
TYPES OF PASSIVE TRANSPORT
Simple diffusion: passage of substance directly through the membrane
O2, CO2
TYPES OF PASSIVE TRANSPORT
Facilitated diffusion Substances pass
through a channel in a transport protein in membrane
Sugars, H2O, some ions
PASSIVE TRANSPORT
DIFFUSION
Diffusion.url
OSMOSIS Osmosis: passive transport of H2O across
a selectively permeable membrane
Aqueous solutions: solutions in which water is the solvent
Aqueous solutions can be classified into 3 categories called osmotic solutions
TYPES OF OSMOTIC SOLUTIONS
Hypotonic: lower solute concentration outside cell than inside
Water moves into cell
Hypertonic: higher solute concentration outside cell than inside
Water moves out of cell
Isotonic: same solute concentration outside cell as inside cell
Water moves in equal amounts in and out
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Cell in Hypotonic Solution
CELLCELL
10% NaCL90% H2O
20% NaCL
80% H2O
What is the direction of water movement?
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Cell in Hypertonic Solution
CELLCELL
15% NaCL85% H2O
5% NaCL95% H2O
What is the direction of water movement?
ENVIRONMENTENVIRONMENT
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Cell in Isotonic Solution
CELLCELL
10% NaCL90% H2O
10% NaCL
90% H2O
What is the direction of water movement?
The cell is at _______________.equilibrium
ENVIRONMENTENVIRONMENT
NO NET MOVEMENT
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CYTOLYSIS & PLASMOLYSISCYTOLYSIS & PLASMOLYSIS
Cytolysis Plasmolysiscopyright cmassengale
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Isotonic Solution
NO NET MOVEMENT OF H2O
(equal amounts entering & leaving)
Hypotonic Solution
CYTOLYSIS cell swells and bursts
Hypertonic Solution
PLASMOLYSIS cells shrink and shrivel
copyright cmassengale
OSMOSIS
Osmosis.url
OSMOSIS & PLANT CELLS
Hypotonic environment: plant cells are firmest and healthiest cell wall prevents membrane from bursting (CYTOLYSIS)
Isotonic environment: non-woody plants wilt
Hypertonic environment: membrane pulls away from cell wall (PLASMOLYSIS)
- kills the cell
ACTIVE TRANSPORT Two major types of active transport:
1. Solute ions are “pumped” across the membrane
2. Large particles are transported into or out of the cell
ACTIVE TRANSPORT
Requires energy or ATP
Moves materials from LOW to HIGH concentration
AGAINST concentration gradient
Specific transport protein pumps a solute across a membrane.
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Sodium-Potassium Pump
3 Na+ pumped in for every 2 K+ pumped out
LARGE MOLECULE TRANSPORT
Some particles are too large to move through the membrane
Must be packaged in membrane sacs called vesicles
Particle fuses with plasma membrane and is moved either into (endocytosis) or out of (exocytosis) the cell
Both processes require energy
ENDOCYTOSIS Material is brought into the cell
TYPES OF ENDOCYTOSIS Phagocytosis: cell membrane engulfs and
takes in particle of solid material; - “cell eating”
Pinocytosis: cell membranes engulfs and takes in small droplet of liquid;
- “cell drinking”
EXOCYTOSIS Product of cell is exported
ENDOCYTOSIS & EXOCYTOSIS
05_09Endo_Exocytosis.swf
Concept 6.4THE CELL BUILDS
A DIVERSITY OF PRODUCTS
NUCLEUS Directs the activities of the cell
Contains most of cell’s DNA in the form of chromatin
Chromatin: long fibers of DNA;
- attached to proteins
- organized when cell divides
NUCLEUS Nuclear envelope:
double membrane surrounding nucleus
Membrane contains tiny nuclear pores
Substances made in nucleus exit through these pores
Contains nucleolus
NUCLEOLUS Nucleolus: round structure made of fibers
and granules inside nucleus
Produces ribosomes—tiny organelles involved in protein synthesis
RIBOSOMES Made of proteins and nucleic acids
NOT surrounded by a membrane
Produce all the proteins for the cell
Float free in cytoplasm or are attached to membrane network within the cytoplasm
ENDOPLASMIC RETICULUM
Network of membranes within cytoplasm
Connected to the nucleus One of the main manufacturing and
transportation facilities of the cell Two distinct regions:
1. Rough ER
2. Smooth ER
ENDOPLASMIC RETICULUM
ROUGH ER Has ribosomes attached
Ribosomes produce proteins and insert them into or through ER membrane
Some proteins are packaged in vesicles and exported
Cells that secrete many proteins are rich in rough ER
SMOOTH ER No attached ribosomes functions:
Lipid synthesis
Detoxification
Carbohydrate metabolism
Cells of ovaries and testes (produce sex hormones) are rich in smooth ER
GOLGI APPARATUS Series of flattened
sacs receive chemical products in vesicles
Modifies, stores, and repackages cell products in vesicles
Routes repackaged vesicles with chemical products to their destinations
LYSOSOMES Membrane-bound
sacs containing digestive enzymes
SEVERAL FUNCTIONS:
Fuse with food vacuoles and digest them
Digest harmful bacteria Recycle material from
damaged organelles
LYSOSOMES
Lysosomes (492.0K).url
VACUOLES Membrane-bound sacs having different
functions in different organisms:
Storage vacuole: stores food or wastes
Contractile vacuole: pumps out excess water in unicellular freshwater organisms
Central vacuole: large vacuole found in plants
CENTRAL VACUOLE Found in plant cells
and algae
Contribute to growth by absorbing water and causing cells to expand
Contain pigments in flower cells that attract insects
Concept 6.5CHLOROPLASTS
AND MITOCHONDRIA
ENERGIZE CELLS
CHLOROPLASTS Most living organisms run on energy
provided by photosynthesis
Photosynthesis: process of converting light energy to chemical energy
Chloroplasts: organelle in cells of plants and algae where photosynthesis occurs
CHLOROPLAST STRUCTURE
Enclosed by two membranes
Inner membrane divides chloroplast into two compartments
CHLOROPLAST STRUCTURE
One compartment is fluid-filled stroma
Other compartment contains thylakoids
- membrane-bound disks that trap light energy and convert it to chemical energy
MITOCHONDRIA “Powerhouse of the cell” site of
cellular respiration
Cellular respiration: process used to access energy from food by organisms
Releases energy from food and uses it to form another organic molecule—ATP
ATP (adenosine triphosphate): main energy molecule used by cells
STRUCTURE OF MITOCHONDRIA
Enclosed by two folded membranes
Folds greatly increase number of sites where cellular respiration can occur
Inner membrane—aerobic cellular respiration occurs here
Concept 6.6AN INTERNAL
SKELETON SUPPORTS THE CELL AND
ENABLES MOVEMENT
CYTOSKELETON Network of protein
fibers that extend throughout cell
Structural pattern changes constantly
Made up of 2 main types of fibers: microtubules and microfilaments
MICROTUBULES Straight, hollow tubes of proteins
Give rigidity and shape to cell
Provide “tracks” along which other organelles can move
MICROFILAMENTS Thinner, solid rods made of protein
Enable cell to move or change shape
Contribute to oozing movements of some cells—amoeba and white blood cells
FLAGELLA
Long, thin, whip-like structures projecting from cell
Wave in “S” shaped motion
Enable some cells to move around in their environment
Made up of microtubules
CILIA Hair-like structures projecting from cell
Shorter and more numerous than flagella
Composed of microtubules
Have a back-and-forth motion—like oars on a rowboat
Move a cell through its surroundings or move substances over cell surface
THE CELL FUNCTIONS AS A COORDINATED UNIT Each membrane-bound organelle
performs its own unique function
However, no organelle works alone
The cooperation of organelles makes the cell a living unit that is greater than the sum of its parts
THE END
ORGANELLE REVIEW
Cell Structure and Function.url
Origin of Organelles
The Evolution of Cellular Organelles.url
05_03Passive_diffusion.swf
05_03Diffusion.swf
ENDOCYTOSIS & EXOCYTOSIS
Endocytosis and Exocytosis (720.0K).url
SODIUM-POTASSIUM PUMP
Sodium-Potassium Exchange Pump (682.0K).url