Cells Structural and functional units of living organisms

Eukaryotic (“true nucleus”) vs. Prokaryotic (“before nucleus”) cells Proks - nucleoid is not separated from cytoplasm by a membrane Euks - nuclear material is enclosed in a double membrane - nuclear envelope

Prokaryotic vs. Eukaryotic Cells

Changes from Proks to Euks: (1)DNA size and compactions (2)Cell size and organization (3)Early euk cells were endosymbiotic

Development of Eukaryotic Cells

Prokaryotic (bacterial) Cell

Prokaryotic Cells Two groups: Archaebacteriarecently discovered live in extreme environments (salt lakes, hot springs, deep in ocean) Eubacteria most common well-studied (Escherichia coli/E. coli) inhabit soil, surface water, organisms

Eukaryotic Cell Animal cell Plant cell

Eukaryotic Cell Plasma membrane

Eukaryotic Cell Plasma membrane

Eukaryotic Cell Endoplasmic Reticulum (ER) Membrane-enclosed compartments Extends through cytoplasm Flattened branches = cisternae Smooth ER (lipid biosynthesis, drug metabolism) - Ribosome free Rough ER (LOTS OF PROTEIN SYNTHESIS) - Ribosomes attached ALSO free ribosomes - synthesize proteins that will remain in cytosol

Eukaryotic Cell Golgi Complex Membrane-enclosed compartments Extends through cytoplasm Flattened branches = cisternae Site of processing, packaging and targeting of proteins Modifications - sulfate, carbohydrate, lipids, etc. Modification tags protein for its destination

Eukaryotic Cell Lysosomes Animal cells only Contain enzymes that digest proteins, polysaccharides, nucleic acids, lipids Enzymes kept inside by membrane Lysosome pH - ATP-fueled proton pump keeps pH in lysosome at ~5.0 rather than 7.0 (in cytosol) Enzymes within lysosome act best at lower pH

Eukaryotic Cell Peroxisomes Purpose - take up reactive chemical species that could otherwise damage cell machinery Example: H 2 O 2 2H 2 O 2 --> 2H 2 O + O 2 Catalase at high concentration in peroxisome Catalase

Eukaryotic Cell Nucleus Contains cellular DNA (some DNA in mitochondria and chloroplast)

Eukaryotic Cell Nucleus Chromosomes = 2 chromatids Chromatin mass = 50% DNA, 50% histones DNA of single human chromosome forms ~1,000,000 nucleosomes

Eukaryotic Cell Most cells (somatic cells) have 2 copies of each chromosome Gametes, germline cells (egg and sperm) have only 1 copy of each chromosome

Eukaryotic Cell Mitochondria Diameter of ~1 µm (bacterial cells) 100s-1000 per cell Metabolic cells have more mitochondria Matrix has lots of enzymes and metabolic intermediates Have their own DNA, RNA and ribosomes Descendants of aerobic bacteria??

Eukaryotic Cell Cytoskeleton Meshwork through cytoplasm Provides structure and organization to cytoplasm and shape to cell

Viruses = Parasites of Cell Viruses Replicate themselves in host cells Contain DNA or RNA surrounded by a capsid (protective coat) Outside host cell, virus is nonliving particle (virion) Inside host cell, virus is parasite Uses host cells’ machinery to make more virus particles Turnip yellow mosaic virus (spheres) Tobacco mosaic virus (cylinders) Bacteriophage T4 HIV Poliovirus

Secretory cells of pancreas Skeletal muscle cell Sperm cells Red blood cells Human embryo at 2-cell stage