7-1 Life Is Cellular The Discovery of the Cell · 7-3 Cell Boundaries Diffusion Through Cell...
Transcript of 7-1 Life Is Cellular The Discovery of the Cell · 7-3 Cell Boundaries Diffusion Through Cell...
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7-1 Life Is Cellular The Discovery of the CellReviewLife began with the first cell!The cell is the basic unit of life!All living things are composed of cells!Cells only come from other cells!In multicellular organisms, cells make up tissues, organs, organ systems and the organism!
The discovery of the cell depended on the invention of the microscope!
Nucleus(not all cells)
Cytoplasm(Cytosol + Organelles)
Plasma Membrane
Leukocyte (WBC)Colorized Transmission Electron Micrograph (TEM)
Understanding cell structure and function is fundamental to biology!
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The Discovery of the CellThe scientist to the right is Robert Hooke.The material in the micrograph is cork (tree bark).In 1665, Robert Hooke observed and described cells using a primitive microscope, like the one shown here. In doing so, he established cytology (the study of cells).
The scientist at right is Anton van Leeuwenhoek.In 1670, he observed tiny swimming organisms in pond water using his own version of a microscope (above).In doing so, he established microbiology. He called them “animalcules”... Today, microbes.
Early Microscopes
Cork
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The Development Of Cell Theory The Discovery of the Cell
The scientist at right is Matthias Schleiden. In 1838, he observed plant tissues from many species under the microscope. He established that all plants (left) are composed of cells.
The other scientist at right is Theodore Schwann. In 1839, he observed animal tissues from many species under the microscope. He established that all animals (left) are composed of cells.
The scientist below is Rudolph Virchow. In 1855 he observed cells dividing under the microscope (below, right). He established that all cells come from preexisting cells (Omnis cellula e cellula).
Cell Theory1) All living things are composed of cells.2) Cells are the basic unit of structure & function.3) Cells can only come from preexisting cells.
Elodea Leaf (100x)
Pancreatic Tissue (400x)
Cell Division
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Exploring the CellTypes Of MicroscopesThe two major classes of microscopes are light and electron.The electron microscope produces 1000x greater resolution and magnification!
The drawback for the electron microscope is that only dead specimens can be viewed because the process to prepare them is lethal.
The micrograph on the left is a highly magnified, 2D view of a cell nucleus captured using a transmission electron microscope (TEM).The micrograph on the right is a less magnified, 3D view of 2 neurons (nerve cells) captured using a scanning electron microscope (SEM).
Cell Nucleus (TEM) Neurons (SEM)
5HeLa Cells (Henrietta Lacks, 1951)
Exploring the Cell
The micrograph on the left was produced with a special kind of light microscope called a confocal microscope, which uses lasers to visualize specific cellular structures, like the nuclei and cytoskeletons of these cells!
Types Of Microscopes
The micrograph on the right was produced using a scanning tunneling electron microscope that uses a fine probe to trace the surfaces of samples for magnifications capable of seeing molecules, like this DNA!
DNA Molecules (STEM)
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10 m
1 m
Human height
Length of somenerve andmuscle cells
Chicken egg
0.1 m
1 cm
Frog egg
1 mm
100 µm
Most plant andanimal cells
10 µmNucleus
1 µm
Most bacteria
Mitochondrion
Smallest bacteria
Viruses100 nm
10 nm
Ribosomes
Proteins
Lipids
1 nmSmall molecules
Atoms0.1 nm
Unaided eye
Light microscope
Electron microscope
How small are cells?Like the hierarchy of biological organization, this chart ranges from atoms to molecules to organelles to cells.
Nanometer= 1 x 10-9 meter
Micrometer (Micron)= 1 x 10-6 meter
Millimeter= 1 x 10-3 meter
Centimeter= 1 x 10-2 meter
Decimeter= 1 x 10-1 meter
MeterThe base unit!
Prokaryotes!
Eukaryotes!
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All living cells have DNA, Ribosomes, Cytoplasm & Plasma Membrane!
Two Major Cell Types
- Evolved ~4bya- 1μm - 10μm- No Membrane-bound Nucleus or Organelles- Domains: Archaea & Bacteria Kingdoms: Archaebacteria & Eubacteria
Prokaryotes were first and set up the system we all live within!
Prokaryotes
Nucleus
Organelles
Plasma Membrane
Cell Wall
Plant Cell
Eukaryotes
- Evolved ~2bya (Endosymbiosis!)- 10μm - 100μm- Membrane-bound Nucleus and Organelles- Domain: Eukarya Kingdoms: Protista Fungi Plantae Animalia
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Prokaryote S & F
“Simple” cells can perform all basic life functions!
E. Coli(ChemoheterotrophicConsumer)
Cyanobacteria(PhotoautotrophicProducer)
Cytoplasm
Ribosomes
Plasma Membrane
Cell Wall Capsule
Nucleoid (DNA)
Mesosome (ER-like) Pili
Plasmid(DNA)
Flagellum
Thylakoid Membrane
(Chloroplast-like!)
You must LISTEN to note the functions!
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Diffusion Through Cell Boundaries7-3 Cell Boundaries
An aqueous solution is that in which water is the solvent.The cytosol is the aqueous solution portion of the cell cytoplasm.Plasma is the aqueous solution component of blood that the cells are bathed in.So the environments both inside and outside the cells are aqueous solutions!The plasma membrane is the barrier that separates these environments in every living cell!The plasma membrane is also selective, allowing only certain things to pass in or out of the cell. Life is in aqueous solution!
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Example Calculations (mass/volume)100 g NaCl in 1 L H
2O = ______ g/L
10 g NaCl in 100 ml H2O = _____ g/ml or
_____ g/L since there are 1000 ml in a L
Diffusion Through Cell BoundariesMeasuring Concentration
In this example, salt is the solute dissolved in water, which is the solvent. This is an aqueous solution.
Review
The concentration ([S]) of a solution indicates the amount of solute dissolved in the solvent.
Water is the “universal solvent” because it is polar and easily dissolves sodium chloride because it is an ionic compound.
A solution with more solute is more concentrated relative to a solution with less solute (dilute).
Concentration is measured and calculated as the mass (g) or number of particles (moles) per unit volume (L).
Mass or Number of Particles/Volume
A solution is a mixture where the solute is completely and evenly distributed (dissolved) within the solvent. The solute is the substance dissolved in the solvent. The solvent is the fluid in which the solute is dissolved.
1000.1
100
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Diffusion
The person in this diagram is placing one drop of dye into water.Relative to the rest of the container, the dye concentration is very high only where the drop first enters the water.Concentration gradient ([ ]
g) is a difference in concentration between locations.
As time passes, dye molecules move along their [ ]g from high concentration to
low concentration.Diffusion is the movement of solute particles in solution along their [ ]
g until they
are evenly distributed, as at the end of this example.
Red Dye
WaterTime
Equilibrium is when solute particles are evenly distributed within the solvent and there is no [ ]
g.
Particles diffuse along their [ ]g to equilibrium!
Diffusion Through Cell Boundaries
[D] [D] =[D]
[D]g
[D] [D]
[D]g
No [D]g
Equilibrium
Aqueous Dye Solution
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The Cell MembraneReviewAll cells have DNA, Cytoplasm, Ribosomes and a Plasma Membrane.The Plasma Membrane is a flexible, fluid, selective barrier between the aqueous solutions inside and outside the cell.
The Cell Wall is a rigid structure outside the plasma membrane.Cells of Kingdoms Archaebacteria, Eubacteria, Protista, Fungi and Plantae have cell walls.
The Plasma Membrane functions as a selective barrier, while the Cell Wall functions in protection, support, and to maintain shape.
The plasma membrane is a selective barrier!
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The Plasma Membrane
Cells are largely made of membrane.The molecule in the top left diagram is a phospholipid.The two major regions of a phospholipid molecule are the polar, hydrophilic head, and the non-polar, hydrophobic tails.Because water is polar, polar compounds are hydrophilic (“water loving”) and non-polar compounds are hydrophobic (“water fearing”), meaning they won’t dissolve or interact with water molecules.Liposomes form when phospholipids are placed in water. They resemble cells.A phospholipid bilayer is two layers of phospholipid molecules that forms due to the outward interaction of the hydrophilic heads with water, and the inward repulsion from water of the hydrophobic tails.
Cell membranes are phospholipid bilayers!
14Passive diffusion REQUIRES NO CELLULAR ENERGY!
Extracellular
Intracellular
Plasma
This membrane is permeable to this solute, it allows the solute to diffuse.
Passive Diffusion
Extracellularis outside the cell, and intracellular is inside the cell.
The extracellular concentration of the solute is very high compared to the intracellular concentration. This is a concentration gradient [S]
g.
Time
Over time, the solute diffuses through the membrane along its concentration gradient (from high to low).
The final distribution of solute is equal concentrations across the membrane, however solute particles continue to diffuse in both directions at equal rates. This is known as a dynamic equilibrium.
[S]
[S]
[S]
[S]
=[S]
=[S]
[S]g
[S]g
No[S]g
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A membrane is impermeable when nothing can pass through, semipermeable when only water can pass through, and selectively permeable when water and only certain small solute particles can pass through.
The solute particles are not the only particles in solution? Water molecules are particles! The diagram shows the concentration difference between solutions as the number of sugar molecules on each side of the membrane.The more solute particles, the fewer “free” water molecules because water molecules interacting with solute particles are not “free” to diffuse.Because the membrane is not solute permeable, only water will diffuse.Tonicity is the “osmotic power” of a solution to draw water to itself.
Osmosis is the diffusion of water through membranes!
The membrane above is impermeable to sugar and permeable to water.
Movement of water
Dilute sugar solution (100ml)
Concentrated sugar solution
Sugar molecules
Semipermeable Membrane
(Water molecules not shown)
Time
125ml 75ml100ml 100ml
[S] [S][S]
g
[H2O][H
2O]
[H2O]
g
Osmosis
Hypertonic ([S]), Hypotonic ([S]), Isotonic (=[S]).
HypotonicHypertonic
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Osmosis
The significant difference between this example and the previous is a lid with pressure gauges.
Osmotic pressure is the pressure produced in a closed system by the diffusion of water through a membrane (osmosis).In a closed system (lid), the pressure on the hypotonic side of the membrane will decrease and on the hypertonic side will increase.
Either condition can be catastrophic for a living cell!!! Osmolarity must be precisely regulated in living systems (osmoregulation to maintain homeostasis).
Osmotic pressure is dangerous!
[S][S]
[S]g
[H2O] [H
2O]
[H2O]
g
Hypotonic Hypertonic
Pressure Pressure
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Plasmolysis Turgid (Normal)
OsmosisThe animal cells in this example are RBCs.
The solution surrounding the cells is hypertonic when [S] [H
2O].
Plant cells prefer a hypotonic environment to maintain turgor pressure so they do not become flaccid (wilt).
Plant cells have a cell wall and central vacuole. Animal cells do not.
For both cell types, water will diffuse along it’s concentration gradient OUT of the cell causing the RBCs to crenate (shrivel) and the plant cell to plasmolyze (plasma membrane shrinks away from the cell wall).The solution surrounding the cell is hypotonic when [S] [H
2O].
For both cell types, water will diffuse along it’s concentration gradient INTO the cell causing the RBCs to cytolyze (swell & burst) and the plant cell to become turgid (increased osmotic turgor pressure).
Animal cells prefer an isotonic environment.
Osmoregulation is crucial!
If your hospital IV solution (saline) is hypertonic, your RBCs will crenate. If it is hypotonic, they will cytolyze. Either is fatal and requires medical technicians to mix their concentrations VERY PRECISELY!
Interstitial fluid is the aqueous solution that baths all of our (animal) cells.Osmoregulation is the homeostatic system to maintain isotonic interstitial fluid. In animals, this is performed primarily by the excretory system (kidneys).
Crenation Cytolysis
Flaccid(wilted)
Normal
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Extracellular
Cell membrane
Intracellular (cytoplasm)
Protein channel
Proteins
Phospholipid bilayer
Carbohydrate chains
Cell Membrane Constituents
The fluid mosaic model of the plasma membrane describes the phospholipid bilayer as very dynamic (fluid) with a wide variety of protein molecules embedded in it (mosaic).Attached to some proteins are carbohydrate polymers forming glycoproteins that function in cell to cell recognition (Ex. Self vs. Non-self immunity).Membrane proteins can also transport particles across the membrane, be enzymes catalyzing metabolic reactions, and be receptors for signal molecules that bind causing a change in the cell.The plasma membrane phospholipid bilayer alone is a selectively permeable barrier to large, charged particles.Certain proteins embedded in the bilayer increase membrane permeability and selectivity. There are also passive facilitated carrier proteins, passive cotransport
proteins, and active transport pumps, all very specific.
Membrane function depends on proteins!
Passive Facilitated Transport
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Facilitated Diffusion
Protein channel or carrier
Glucose molecules
Facilitated diffusion requires a concentration gradient, is a passive form of channel or carrier transport.
Phospholipid bilayer permeable solute particles are:1. Small 2. Uncharged 3. Non-polar
Channel proteins create a pore of the proper size and properties to facilitate the passive transport of specific particles.
Gated channels can alter permeability by being opened or closed.Gated channels can be either chemically gated and open/close when a signal molecule binds to them, or electrically gated and open/close in response to a change in charge across the membrane.
Passive transport is diffusion of particles across a membrane along their concentration gradient, without requiring cellular energy (ATP).
Facilitated diffusion is a passive form of channel/carrier transport!
Carrier proteins bind specific solute particles and through conformational change facilitate their passive translocation across the membrane.
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Active TransportMolecule or ion to be pumped
High Solute Concentration
Low Solute Concentration
PUMP
Active transport is the pumping of particles across the membrane AGAINST their concentration gradient using cellular energy.
Active transport does NOT require a concentration gradient.
Active transport proteins are also known as pumps.
The energy for active transport is supplied by Adinosine Triphosphate (ATP), the energy currency of all living cells.
Unlike passive transport, active transport enables cells to concentrate specific particles in the cytoplasm or within other cellular compartments (organelles).
Active transport uses ATP to pump particles against their [ ]g!
ATP
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The other indication of active transport is ATP (energy)!
[Na+]g [K+]
g
If membrane permeable, each ion would diffuse along their concentration gradient.
Both ions are being pumped AGAINST their [ ]
g indicating
that this is active transport.
The sodium-potassiium pump pumps 3 sodium ions out and 2 potassium ions in.
Pumping more positive charge out than in results in a slight intracellular negative charge,
Active Transport
making this an electrogenic pump.
The phospholipid bilayer is impermeable to these ions because they are charged.
The sodium-potassium pump is a ubiquitous electrogenic pump!
The direction of the [Na+]g is
extracellular to intracellular (Out to in). The [K+]
g is intracellular
to extracellular (In to out).
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“cell eating”“cell drinking” Highly specific!
Active TransportBulk Transport
Bulk transport is the active endomembrane (vacuole or vesicle) transport of large particles, many particles, or a high volume of solution all at once.It is a form of active transport because it requires ATP (not shown).Endocytosis (“inside cell”) generally refers to intracellular bulk transport.Phagocytosis (“cell eating”) is bulk transport involving pseudopodia surrounding and engulfing large extracellular particles (food) forming a phagocytic vacuole.Pinocytosis (“cell drinking”) is bulk transport involving the engulfment of extracellular solution by infolding the plasma membrane forming a vesicle.Receptor-mediated endocytosis is bulk transport involving infolding of the plasma membrane lined with extracellular, solute specific receptors and intracellular coat proteins forming a coated vesicle. The contents of a phagocytic vacuole will be
Plasma membrane actively engulfs large quantities!
digested and diffuse into the cytosol. The contents of a pinocytotic vesicle will diffuse into the cytosol. The contents of a coated vesicle will be delivered to an intracellular location specified by the coat proteins (like an address).
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Active TransportBulk Transport
Plasma membrane actively secretes large quantities!
Exocytosis (“outside cell”) is active, extracellular bulk transport involving the fusion of transport vesicles with the plasma membrane, emptying their contents outside the cell.When the cell is specialized to manufacture and release compounds through exocytosis, it is known as secretion. For example the secretion of hormones from endocrine glands.The endoplasmic reticulum may produce proteins for exocytosis.In this process, the golgi receives the contents of the transport vesicle, modifies and repackages it in a secretory vesicle.
The secretory vesicle membrane fuses with, and becomes part of the plasma membrane, secreting its contents extracellularly.
This series of organelles are part of the endomembrane system.
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The Diversity of Cellular Life
The organism in the TEM is a spirilli Eubacteria, indicated by its small size.Is it microscopic, again indicated by its small size and use of a TEM.It is unicellular, as are all bacteria, indicated by not seeing multiple cells.
Microorganisms dominate life on Earth, especially prokaryotes (bacteria)!
Because they are microscopic, unicellular organisms are collectively known as microorganisms (microbes).
The Kingdoms that include unicellular organisms are: Archaebacteria, Eubacteria, most Protista, & some Fungi.
We live within the system setup and run by microbes!
Unicellular Organisms
Colorized TEM
10µm
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All multicellular organisms have common ancestry with, or arose from, unicellular organisms of the Kingdom Protista!
The Kingdoms that include multicellular organisms are some Protista, most Fungi, Plantae, and Animalia.
This is a photo of a fertilized egg (zygote) completing its first cleavage (division) to become a 2-cell embryo.A short time before this photo was taken, there would have been only one cell. This is how all multicellular organisms start out!These cells will continue to divide and develop from an embryo to a fetus. Cells will differentiate and become specialized to function within the tissues, organs and organ systems of the organism.
We all developed from one cell that divided and differentiated!
The Diversity of Cellular LifeMulticellular Organisms
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Multicellular Organisms
Cell differentiation is the process during multicellular development by which cells become different from other cells, eventually expressing only a specific 30% of their genes.
Differentiation & Specialization
Cell specialization is the result of cell differentiation, where different cell types have a unique structure to perform specialized functions in specialized tissues, organs, and organ systems.
Red Bood Cells (SEM)
Red blood cells are specialized to be packed full of hemoglobin (no nucleus) so they can carry as much oxygen as possible. Muscle cells are packed full of contractile proteins (visible striations) so they can contract (shorten). Pancreatic cells are glandular, specialized to secrete specific protein enzymes and hormones (packed with ER & blue secritory vesicles).
We are made up of over 200 specialized cell types!
Muscle Cells (LM) Pancreatic Cell (TEM)
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Multicellular Organisms
All multicellular organisms have specialized cells!
Differentiation & Specialization
This micrograph shows the epithelium (outer covering) of a leaf.
The small openings are stomata (singular, stomate).
The two cells on either side of each opening are called guard cells.
Guard cells are specialized to regulate the opening and closing of the stomate.
This regulates gas exchange in the plant (CO
2 in, O
2 out)
and the rate of transpiration (H
2O out, drawing everything
up from the roots).
Stomate
Guard cells
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Levels Of Multicellular Organization(Hierarchy of Biological Organization)
Examples
1. Cardiac Muscle
2. Epithelial Tissue
3. Proximal Tubule
4. Follicular Tissue
Smooth muscle tissueMuscle cell Stomach Digestive system
Level & Definition Level & Definition Level & Definition
Level & Definition
7-4 The Diversity of Cellular Life
Examples
1. Cardiac Cell
2. Skin Cell
3. Tubule Cell
4. Oocyte (Egg)
Examples
1. Heart
2. Skin
3. Kidney
4. Ovary
Examples
1. Circulatory
2. Integumentary
3. Excretory
4. Reproductive
Cellular Level - A cell is the basic unit of life, structure & function. A plasma membrane enclosing cytoplasm including DNA and specialized organelles.
Tissue Level - A group of specialized cells functioning together to perform a specialized function as part of an organ.
Organ Level - A collection of specialized tissues functioning together to perform a specialized function as part of an organ system.
Organ System Level - A collection of specialized organs functioning together to perform a specialized life function as part of an organism.