Week 12: The Cell as the Functional
Unit
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Characteristics of cells
Metabolism
Reproduction: mitosis and
meiosis (text)
Recapitulation
Hierarchical Nature of Living
Systems
Community
Population
Organism
Organ
Tissue
Cell
Organelles
Macromolecules
Atoms
Structural and Functional
Characteristics of Cells
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Cells as the physical infrastructure
Cell membranes: gate keeper of outflow and
inflow of materials
Water: medium of cell’s biochemistry
Compartmentation via organelles: a good thing!
Major types of cells (see text)
Cells as the Physical Infrastructure
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Cell theory
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All organisms composed of cells
Cells as smallest unit of organization exhibiting all
characteristics of life (e.g., irritability, reproduction, energy)
Structure
Cell Membrane
Organelles
Nucleus
Cytoplasm
Size of Cells Relative to Other
Features in the Sciences
10-10m
10-5m
10+3m
~Five orders of magnitude (105) larger than atoms and visible with light microscope
General Features of a Cell
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Size correlated with function
Upper limit: 0.00001 m (1 x 10-5 m)
 Distance from interior to exterior: critical
 Over 1 x 10-5 m: nonfunctional
 Efficacy of transport/diffusion (diffusion … physics
again!)
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so physics determines upper limit of the cell
Structural and Functional
Characteristics of Cells
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Cells as the physical infrastructure
Cell membranes: gate keeper of outflow and
inflow of materials – stop … what is a gate?
Water: medium of cell’s biochemistry
Compartmentation via organelles: a good thing!
Major types of cells
Membranes: Structure
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Principal structural components (N=2)
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Lipid
Phosphate group (PO4)
Phosphate/ Glycerol
(Hydrophilic - polar)
Lipid/Fatty Acid
(Hydrophobic – non-polar)
Lipid bilayer at the molecular level
Functional property: contrasting
chemical characteristics of the two
layers
Hydrophilic (water loving)
Hydrophobic (not water loving)
Hydrophilic (water loving)
Lipid Bilayer
Membranes: Structure
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Lipid bilayer: “fluid membrane” with floating
chunks of proteins and carbohydrates (e.g.,
icebergs)
Lipid Bilayer
Protein Chunk
The Cell as the Functional Unit
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Characteristics of cells
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Start with membranes
Metabolism
Reproduction: mitosis and
meiosis (text)
Recapitulation
Membranes: from Lipid Bilayer
to Functional Properties
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Example of hierarchy theory and emergent
properties
“Parts”: lipid, phosphate, proteins, carbohydrates
 When combined: unusual/unexpected properties =
emergent properties
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Selective permeability (text and lecture)
Active transport (text)
Signaling: cell-to-cell communication (text)
Transport through Membrane:
Selective Permeability
Signaling in/on Membranes
Swine Flu
Cystic Fibrosis
http://www.youtube.com/watch?v=GW0lqf4Fqpg
Allergies
The Cell as the Functional Unit
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Characteristics of cells
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Water medium
Metabolism
Reproduction: mitosis and
meiosis (text)
Recapitulation
Water: Medium for Biochemistry
(back to chemistry!)
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Role of water (H2O)
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Liquid medium for cell
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Physical properties (e.g., polarity, phases)
Chemical properties (e.g., pH, liquid solution)
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Exquisite and unique properties of
H2O
Importance in cell metabolism:
liquid phase chemistry and pH
Imagine a cell’s functioning in a
medium other than liquid water (say
… water in a gas phase or a solid)
The Cell as the Functional Unit
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Characteristics of cells
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Compartmentation
Metabolism
Reproduction: mitosis and
meiosis (text)
Recapitulation
General Cell Structures:
Compartmentation
Principle of Compartmentation
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Cells are compartmentalized
Elaborate and organized infrastructure
 Analogy to a dorm
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Corridors as endoplasmic reticulum
 Rooms as organelles
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Consequence of not being compartmentalized
… disorder!
Function of individual organelles (text)
Compartmentation: Animal cell
Structural and Functional
Characteristics of Cells
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Cells as the physical infrastructure
Cell membranes: gate keeper of outflow and
inflow of materials
Water: medium of cell’s biochemistry
Compartmentation via organelles: a good thing!
Major types of cells (see text)
Cell Types
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Prokaryotes
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No nucleus
No mitochondria, chloroplasts,
Golgi or endoplasmic reticulum
DNA, enzymes, metabolize, etc.
Example: bacteria
Eukaryotes
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Nucleus and all the organelles
Plant eukaryotes – same except
 Chloroplast for photosynthesis
and cell wall
Animal eukaryotes (this is you!)
Prokaryote: Bacteria
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Flagella
Information
Capsule
Plasma Membrane
Cytoplasm
Cell Wall
Spores
Size of Eukaryote vs. Prokaryote
The Cell as the Functional Unit
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Characteristics of cells
Metabolism (all about
carbon-carbon bonds)
Reproduction: mitosis and
meiosis
Recapitulation
Energy Utilization
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Three related activities: acquisition,
utilization, and storage
Energy Acquisition
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Energy utilization
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Energy capture (autotrophs; heterotrophs)
First law of Thermodynamics
Laws of Thermodynamics (1st and 2nd laws)
ATP (adenosine triphosphate) and ADP
(adenosine diphosphate)
Energy storage
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Chemical bonds (C-C covalent bonds)
Carbohydrates, glycogen and lipids
In humans and other animals, storage as _____?
The Cell’s Energy Currency:
Analogy to Legos!
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Adenosine triphosphate (ATP … high energy)
Adenosine diphosphate (ADP … low energy)
Structure
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3 or 2 phosphate groups
Sugar molecule
Function
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Removal of phosphate group
source
of energy
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Currency analogy in economy
Last 5 seconds in your body: trillions of ATP to
ADP conversions and back again and again and again …!
Cell’s Energy Currency
Biosynthesis = construction of high energy carbon molecules
Catabolism = deconstruction of high energy carbon molecules
ADP
Biosynthesis/
Anabolism
Catabolism
ATP
Remember the analogy to Legos!
Photosynthesis
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Photosynthesis
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Convert sunlight to chemical energy (1st Law of
Thermodynamics)
Process (building high energy carbon molecules)
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Energy + CO2 + H2O  Carbohydrate + O2
Carbon - Carbon
Now the Granola Bar
Energy and the Granola Bar
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First Law of Thermodynamics
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Second Law of Thermodynamics (think ecology)
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Chemistry of bonds (energy stored – First law of
Thermodynamics)
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Uniqueness of carbon atom’s bonding (covalent)
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Immediate energy currency in cells via ATP and ADP
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Release of some energy as heat (Second Law of
Thermodynamics)
Universality of Reproduction:
How the Cell Achieves this Feat
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Reproduction: regenerative process of
making new organisms (not necessarily
copies)
Methods
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Sexual
Asexual (microbes; cell division/mitosis)
Examples
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Siblings
Geranium plants
Dolly (the sheep)
Reproduction: Mitosis (Text)
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Reproduction in general
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Cell to cell reproduction
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Information copying
(DNA)
The Cell as the Functional Unit
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Characteristics of cells
Metabolism
Reproduction: mitosis
Recapitulation