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

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:Archaebacteria recently discovered

live in extreme environments (salt lakes, hot springs, deep in ocean)

Eubacteria most commonwell-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 compartmentsExtends through cytoplasmFlattened 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 compartmentsExtends through cytoplasmFlattened 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: H2O2

2H2O2 --> 2H2O + O2

Catalase at high concentration in peroxisome

Catalase

Eukaryotic Cell

NucleusContains cellular DNA (some DNA in mitochondria and chloroplast)

Eukaryotic Cell

NucleusChromosomes = 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 cellMetabolic cells have more mitochondriaMatrix has lots of enzymes and metabolic intermediatesHave their own DNA, RNA and ribosomesDescendants of aerobic bacteria??

Eukaryotic Cell

CytoskeletonMeshwork through cytoplasmProvides structure and organization to cytoplasm and shape to cell

Viruses = Parasites of Cell

Viruses

Replicate themselves in host cellsContain DNA or RNA surrounded by a capsid (protective coat)Outside host cell, virus is nonliving particle (virion)Inside host cell, virus is parasiteUses 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