The living cell Is a miniature factory where thousands of reactions occur Converts energy in many ways Figure 8.1 Bioluminescence

Metabolism Is the totality of an organism’s chemical reactions Arises from interactions between molecules An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics

Molecular Factory Factories are highly ordered systems which have an input of materials, energy requirements and an expected output There is a design to factories- you don’t get automobiles from a Barbie factory…

Cells as factories Cell has three main functions Make a product through a series of highly ordered steps and guided via an enzymatic and biofeedback process Maintain balance Reproduce All parts of the cell play a role in maintaining the cellular factory.

Size range of cells

The Nucleus and Ribosomes - enclosed by nuclear envelope - contains most of the genes that control the entire cell + DNA organized with proteins into chromatin - nucleolus Nuclear lamina – protein filaments that give structure to the inner nuclear membrane

The Nucleus and Ribosomes (con’t) - build proteins - RNA/protein complexes - free/bound

The Endomembrane System Includes: nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Plasma membrane*

Mitochondria and Chloroplasts energy transformers of cells + double membranes + contain ribosomes/DNA Mitochondrial DNA is only passed on by mom

The Cytoskeleton Cytoskeleton provides structural support for motility and regulation + network of fibers - microtubules - microfilaments - intermediate filaments

Membrane Structure and Function Collagen proteoglycan Fibronectin

Hydrophilic vs Hydrophobic

Membrane Structure and Function (con’t) Fluid Mosaic Model The Fluid Quality of Membranes + held together by hydrophobic interactions - lipids/proteins drift about laterally + unsaturated hydrocarbon tails - maintain fluidity at low temperatures + cholesterol - stabilizes the membrane restrains movement at high temp. hinders close packing at low temp.

Membrane Structure and Function (con’t) Fluid Mosaic Model Membranes as Mosaics + membrane is collage of proteins - integral proteins transmembrane - peripheral proteins appendages

Membrane Structure and Function (con’t) Functions of Membrane Proteins Transport Enzymatic Activity Signal Transduction Intercellular joining Cell-cell recognition Attachment to the cytoskeleton and ECM

Signal Transduction with G proteins

Voltage Gated Ion Channels

Diffusion A.K.A. simple diffusion Movement of small molecules across a selectively permeable membrane from an area of HIGH concentration to an area of LOW concentration w/o the use of energy (DOWN the concentration gradient) e.g. O2, CO2, urea, & alcohol

Traffic Across Membranes (con’t) Passive Transport Osmosis + the diffusion of water - hypotonic,hypertonic, isotonic Tonicity – the ability of a solution to cause a cell to gain or lose water Osmoregulation – the control of water balance e.g. contractile vacuole in paramecium

Osmosis The diffusion of WATER across a selectively permeable membrane OSMOTIC PRESSURE The pressure exerted on plasma membranes in solution Isotonic solution Hypertonic solution Hypotonic solution

Water Potential The physical property predicting the direction in which water will flow, controlled by the solute concentration

Water potential (ψ) = pressure potential (ψp ) + solute potential (ψs )

Plasmolysis A phenomenon in plant cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall when the cell loses water to a hypertonic environment.

Osmotic Potential The tendency of water to move across a selectively permeable membrane into a solution Determined by measuring the pressure required to stop the osmotic movement of water into the solution.

Traffic Across Membranes (con’t) Passive Transport Facilitated Diffusion + diffusion with the help of transport proteins - gated channels

Facilitated Diffusion Protein Channel or Pore

Facilitated Diffusion Protein Carrier

Traffic Across Membranes (con’t) Active Transport energy-requiring process + ATP pumps molecules against concentration gradient + Na+/K+ pump

Active Transport Requires cell energy (ATP) to move molecules AGAINST the concentration gradient; from an area of LOW concentration to an area of HIGH concentration Sodium–Potassium pump (Exchange 3 sodium ions for 2 potassium ions) Hydrogen ion, or proton pump (Pump hydrogen ion against the concentration gradient)

Phosphorylation The addition of a phosphate (PO4) group (From ATP) to a protein or a small molecule This changes the protein shape

Active Transport (Uniport)

Active Transport Na-K Pump

Na-K Pump Antiport

Traffic Across Membranes (con’t) Membrane Potential electrogenic pump + proton pumps (H+) electrochemical gradient + cotransport

Traffic Across Membranes (con’t)

Bulk Media Transport Endocytosis – Vesicle is created from the invagination of the plasma membrane, which pinches off, bringing large molecules into the cell Pinocytosis – Cell drinking (endocytosis) Phagocytosis – Cell eating (endocytosis) Receptor Mediated Endocytosis – Substrate binds to receptor found on the plasma membrane to be brought into the cell Exocytosis – Vesicle binds to the plasma membrane releasing the contents outside of the cell

Traffic Across Membranes (con’t) Transport of Large Molecules Exocytosis + the cell exports macromolecules using vesicles from Golgi apparatus Endocytosis + the cell takes in macromolecules by forming new vesicles from membrane - phagocytosis (“cellular eating”) - pinocytosis (“cellular drinking”) - receptor-mediated endocytosis + ligands