Week 12: The Cell as the Functional Unit Characteristics of cells Characteristics of cells Metabolism Metabolism Reproduction: mitosis and meiosis (text) Reproduction: mitosis and meiosis (text) Recapitulation Recapitulation

Hierarchical Nature of Living Systems Community Population Population Organism Organism Organ Organ Tissue Tissue Cell Cell Organelles Organelles Macromolecules Macromolecules Atoms Atoms

Structural and Functional Characteristics of Cells Cells as the physical infrastructure Cells as the physical infrastructure Cell membranes: gate keeper of outflow and inflow of materials Cell membranes: gate keeper of outflow and inflow of materials Water: medium of cell’s biochemistry Water: medium of cell’s biochemistry Compartmentation via organelles: a good thing! Compartmentation via organelles: a good thing! Major types of cells (see text) Major types of cells (see text)

Cells as the Physical Infrastructure Cell theory Cell theory All organisms composed of cells All organisms composed of cells Cells as smallest unit of organization exhibiting all characteristics of life (e.g., irritability, reproduction, energy) Cells as smallest unit of organization exhibiting all characteristics of life (e.g., irritability, reproduction, energy) Structure Structure Cell Membrane Nucleus Cytoplasm Organelles

Size of Cells Relative to Other Features in the Sciences ~Five orders of magnitude (10 5 ) larger than atoms and visible with light microscope m10 -5 m m

General Features of a Cell Size correlated with function Size correlated with function Upper limit: m (1 x m) Upper limit: m (1 x m) Distance from interior to exterior: critical Distance from interior to exterior: critical Over 1 x m: nonfunctional Over 1 x m: nonfunctional Efficacy of transport/diffusion (diffusion … physics again!) Efficacy of transport/diffusion (diffusion … physics again!) so physics determines upper limit of the cell so physics determines upper limit of the cell

Structural and Functional Characteristics of Cells Cells as the physical infrastructure Cells as the physical infrastructure Cell membranes: gate keeper of outflow and inflow of materials – stop … what is a gate? Cell membranes: gate keeper of outflow and inflow of materials – stop … what is a gate? Water: medium of cell’s biochemistry Water: medium of cell’s biochemistry Compartmentation via organelles: a good thing! Compartmentation via organelles: a good thing! Major types of cells Major types of cells

Membranes: Structure Principal structural components (N=2) Principal structural components (N=2) Lipid Lipid Phosphate group (PO4) Phosphate group (PO4) Lipid bilayer at the molecular level Lipid bilayer at the molecular level Functional property: contrasting chemical characteristics of the two layers Functional property: contrasting chemical characteristics of the two layers Phosphate/ Glycerol (Hydrophilic - polar) Lipid/Fatty Acid (Hydrophobic – non-polar) Lipid Bilayer Hydrophilic (water loving) Hydrophobic (not water loving) Hydrophilic (water loving)

Membranes: Structure Lipid bilayer: “fluid membrane” with floating chunks of proteins and carbohydrates (e.g., icebergs) Lipid bilayer: “fluid membrane” with floating chunks of proteins and carbohydrates (e.g., icebergs) Lipid Bilayer Protein Chunk

The Cell as the Functional Unit Characteristics of cells Characteristics of cells Start with membranes Start with membranes Metabolism Metabolism Reproduction: mitosis and meiosis (text) Reproduction: mitosis and meiosis (text) Recapitulation Recapitulation

Membranes: from Lipid Bilayer to Functional Properties Example of hierarchy theory and emergent properties Example of hierarchy theory and emergent properties “Parts”: lipid, phosphate, proteins, carbohydrates “Parts”: lipid, phosphate, proteins, carbohydrates When combined: unusual/unexpected properties = emergent properties When combined: unusual/unexpected properties = emergent properties Selective permeability (text and lecture) Selective permeability (text and lecture) Active transport (text) Active transport (text) Signaling: cell-to-cell communication (text) Signaling: cell-to-cell communication (text)

Transport through Membrane: Selective Permeability

Signaling in/on Membranes Swine Flu Cystic Fibrosis Allergies

The Cell as the Functional Unit Characteristics of cells Characteristics of cells Water medium Water medium Metabolism Metabolism Reproduction: mitosis and meiosis (text) Reproduction: mitosis and meiosis (text) Recapitulation Recapitulation

Water: Medium for Biochemistry (back to chemistry!) Role of water (H 2 O) Role of water (H 2 O) Liquid medium for cell Liquid medium for cell Physical properties (e.g., polarity, phases) Physical properties (e.g., polarity, phases) Chemical properties (e.g., pH, liquid solution) Chemical properties (e.g., pH, liquid solution) Exquisite and unique properties of H 2 O Exquisite and unique properties of H 2 O Importance in cell metabolism: liquid phase chemistry and pH 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) 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 Characteristics of cells Characteristics of cells Compartmentation Compartmentation Metabolism Metabolism Reproduction: mitosis and meiosis (text) Reproduction: mitosis and meiosis (text) Recapitulation Recapitulation

General Cell Structures: Compartmentation

Principle of Compartmentation Cells are compartmentalized Cells are compartmentalized Elaborate and organized infrastructure Elaborate and organized infrastructure Analogy to a dorm Analogy to a dorm Corridors as endoplasmic reticulum Corridors as endoplasmic reticulum Rooms as organelles Rooms as organelles Consequence of not being compartmentalized … disorder! Consequence of not being compartmentalized … disorder! Function of individual organelles (text) Function of individual organelles (text)

Compartmentation: Animal cell

Structural and Functional Characteristics of Cells Cells as the physical infrastructure Cells as the physical infrastructure Cell membranes: gate keeper of outflow and inflow of materials Cell membranes: gate keeper of outflow and inflow of materials Water: medium of cell’s biochemistry Water: medium of cell’s biochemistry Compartmentation via organelles: a good thing! Compartmentation via organelles: a good thing! Major types of cells (see text) Major types of cells (see text)

Cell Types Prokaryotes Prokaryotes No nucleus No nucleus No mitochondria, chloroplasts, Golgi or endoplasmic reticulum No mitochondria, chloroplasts, Golgi or endoplasmic reticulum DNA, enzymes, metabolize, etc. DNA, enzymes, metabolize, etc. Example: bacteria Example: bacteria Eukaryotes Eukaryotes Nucleus and all the organelles Nucleus and all the organelles Plant eukaryotes – same except Plant eukaryotes – same except Chloroplast for photosynthesis and cell wall Chloroplast for photosynthesis and cell wall Animal eukaryotes (this is you!) Animal eukaryotes (this is you!)

Prokaryote: Bacteria Flagella Flagella Information Information Capsule Capsule Plasma Membrane Plasma Membrane Cytoplasm Cytoplasm Cell Wall Cell Wall Spores Spores

Size of Eukaryote vs. Prokaryote

The Cell as the Functional Unit Characteristics of cells Characteristics of cells Metabolism (all about carbon-carbon bonds) Metabolism (all about carbon-carbon bonds) Reproduction: mitosis and meiosis Reproduction: mitosis and meiosis Recapitulation Recapitulation

Energy Utilization Three related activities: acquisition, utilization, and storage Three related activities: acquisition, utilization, and storage Energy Acquisition Energy Acquisition Energy capture (autotrophs; heterotrophs) Energy capture (autotrophs; heterotrophs) First law of Thermodynamics First law of Thermodynamics Energy utilization Energy utilization Laws of Thermodynamics (1 st and 2 nd laws) Laws of Thermodynamics (1 st and 2 nd laws) ATP (adenosine triphosphate) and ADP (adenosine diphosphate) ATP (adenosine triphosphate) and ADP (adenosine diphosphate) Energy storage Energy storage Chemical bonds (C-C covalent bonds) Chemical bonds (C-C covalent bonds) Carbohydrates, glycogen and lipids Carbohydrates, glycogen and lipids In humans and other animals, storage as _____? In humans and other animals, storage as _____?

The Cell’s Energy Currency: Analogy to Legos! Adenosine triphosphate (ATP … high energy) Adenosine triphosphate (ATP … high energy) Adenosine diphosphate (ADP … low energy) Adenosine diphosphate (ADP … low energy) Structure Structure 3 or 2 phosphate groups 3 or 2 phosphate groups Sugar molecule Sugar molecule Function Function Removal of phosphate group source of energy Removal of phosphate group source of energy Currency analogy in economy Currency analogy in economy Last 5 seconds in your body: trillions of ATP to ADP conversions and back again and again and again …! Last 5 seconds in your body: trillions of ATP to ADP conversions and back again and again and again …!

Cell’s Energy Currency Catabolism Biosynthesis/ Anabolism ADP ATP Remember the analogy to Legos! Biosynthesis = construction of high energy carbon molecules Catabolism = deconstruction of high energy carbon molecules

Photosynthesis Photosynthesis Photosynthesis Convert sunlight to chemical energy (1 st Law of Thermodynamics) Convert sunlight to chemical energy (1 st Law of Thermodynamics) Process (building high energy carbon molecules) Process (building high energy carbon molecules) Energy + CO 2 + H 2 O  Carbohydrate + O 2 Energy + CO 2 + H 2 O  Carbohydrate + O 2 Carbon - Carbon

Now the Granola Bar

Energy and the Granola Bar First Law of Thermodynamics Second Law of Thermodynamics (think ecology) Chemistry of bonds (energy stored – First law of Thermodynamics) Uniqueness of carbon atom’s bonding (covalent) Immediate energy currency in cells via ATP and ADP Release of some energy as heat (Second Law of Thermodynamics)

Universality of Reproduction: How the Cell Achieves this Feat Reproduction: regenerative process of making new organisms (not necessarily copies) Reproduction: regenerative process of making new organisms (not necessarily copies) Methods Methods Sexual Sexual Asexual (microbes; cell division/mitosis) Asexual (microbes; cell division/mitosis) Examples Examples Siblings Siblings Geranium plants Geranium plants Dolly (the sheep) Dolly (the sheep)

Reproduction: Mitosis (Text) Reproduction in general Cell to cell reproduction Information copying (DNA)

The Cell as the Functional Unit Characteristics of cells Characteristics of cells Metabolism Metabolism Reproduction: mitosis Reproduction: mitosis Recapitulation Recapitulation