Tour of the Cell (Ch. 6)

Dead White Men Who Discovered (and were made of) Cells: Anton Van Leeuwenhoek Robert Hooke

Electron Microscopy TECHNIQUERESULTS Scanning electron micro- scopy (SEM). Micrographs taken with a scanning electron micro- scope show a 3D image of the surface of a specimen. This SEM shows the surface of a cell from a rabbit trachea (windpipe) covered with motile organelles called cilia. Beating of the cilia helps move inhaled debris upward toward the throat. (a) Transmission electron micro- scopy (TEM). A transmission electron microscope profiles a thin section of a specimen. Here we see a section through a tracheal cell, revealing its ultrastructure. In preparing the TEM, some cilia were cut along their lengths, creating longitudinal sections, while other cilia were cut straight across, creating cross sections. (b) Cilia 1 µm Longitudinal section of cilium Cross section of cilium 1 µm

The size range of cells Nucleus Most bacteria Measurements 1 centimeter (cm) = 10  2 meter (m) = 0.4 inch 1 millimeter (mm) = 10 –3 m 1 micrometer (µm) = 10 –3 mm = 10  6 m 1 nanometer (nm) = 10 –3 µm = 10  9 m 10 m 1 m 0.1 m 1 cm 1 mm 100 µm 10 µm 1 µm 100 nm 10 nm 1 nm 0.1 nm Human height Length of some nerve and muscle cells Chicken egg Frog egg Most plant and animal cells Mitochondrion Smallest bacteria Viruses Ribosomes Proteins Lipids Small molecules Atoms Unaided eye Light microscope Electron microscope nucleus Most bacteria

Comparing the size of a virus, a bacterium, and an animal cell

Why Cells Are So Small: The SA:V Ratio Surface area increases while total volume remains constant Total surface area (height  width  number of sides  number of boxes) Total volume (height  width  length  number of boxes) Surface-to-volume ratio (surface area  volume)

Prokaryote bacteria cells Types of cells Eukaryote animal cells - no organelles Eukaryote plant cells

Cells gotta work to live! – make proteins proteins control every cell function – make energy for daily life for growth – make more cells growth repair renewal

Proteins do all the work! cells DNA proteins organism

Protein Synthesis Organelles involved – nucleus – ribosomes – endoplasmic reticulum (ER) – Golgi apparatus – Vesicles - cell membrane nucleusribosomeER Golgi apparatus vesicles The Protein Assembly Line The Endomembrane System

nuclear pores nuclear pore nuclear envelope nucleolus Function – Protects (stores) DNA Structure – nuclear envelope double membrane membrane fused in spots to create pores Nucleus What kind of molecules need to pass through?

Nucleolus Function – ribosome production build ribosome subunits from rRNA & proteins Ribosome assembly is completed in cytoplasm small subunit large subunit ribosome rRNA & proteins nucleolus

small subunit large subunit Ribosomes Function – protein production Structure – 2 subunits combine 0.08  m Ribosomes Rough ER Smooth ER

membrane proteins Types of Ribosomes Free ribosomes – suspended in cytosol – synthesize proteins that stay in cytosol Bound ribosomes – attached to endoplasmic reticulum – synthesize proteins for export or membranes

2 types of ER: Smooth ER: Function- Membrane production Metabolic processes – Lipid Synthesis – Glycogen hydrolysis (in liver) – Drug detoxification (in liver)

Rough ER function Produces proteins for export out of cell – protein secreting cells – packaged into transport vesicles for export

Vesicle transport vesicle budding from rough ER fusion of vesicle with Golgi apparatus migrating transport vesicle protein ribosome

proteins transport vesicle Golgi apparatus vesicle smooth ER rough ER nuclear pore nucleus ribosome cell membrane protein secreted cytoplasm The Endomembrane System Putting it together…

LE 6-20 Microtubule Microfilaments 0.25 µm

Cilia and Flagella Microtubules control the beating of cilia (trachea) and flagella (sperm, bacteria) Cilia and flagella differ in their beating patterns

LE 6-31 Tight junctions prevent fluid from moving across a layer of cells Tight junction 0.5 µm 1 µm 0.1 µm Gap junction Extracellular matrix Space between cells Plasma membranes of adjacent cells Intermediate filaments Tight junction Desmosome Gap junctions

1.. In which cell would you expect to find the most smooth endoplasmic reticulum? A.Muscle cell in the thigh muscle of a long-distance runner B.Pancreatic cell that manufactures digestive enzymes C.Macrophage (white blood cell) that engulfs bacteria D.Epithelial cells lining the digestive tract E.Ovarian cell that produces estrogen (a steroid hormone)

3. Of the following, which is probably the most common route for protein flow in the endomembrane system? A.Golgi → lysosome → ER → plasma membrane B.tonoplast → plasma membrane → nuclear envelope → smooth ER C.nuclear envelope → lysosome → Golgi → plasma membrane D.rough ER → vesicles → Golgi → plasma membrane E.ER → chloroplasts → mitochondrion → cell membrane