Cells Review Chapters 7, 8, 12

Microscopes Light microscopes: cells and big organelles Electron microscopes: smaller cells, smaller organelles, bacteria, viruses, small molecules

Prokaryotes vs. eukaryotes No nucleus No membrane bound organelles Small, simple Only ribosomes DNA circular Nucleus Membrane bound organelles Bigger, complex DNA is linear in strands

Nucleus Contains DNA and nucleolus Nucleolus makes ribosomal subunits Nucleus is surrounded by nuclear envelope Envelope has pores through which ribsomes and RNA can exit and messengers can enter

Ribosomes Free ribosomes – float in cytoplasm and make proteins designed to stay in cell Bound ribosomes – located on E.R. and make proteins designed to be exported out of cell Each ribosome is made of 2 subunits Prokaryotes and eukaryotes have different subunits

Endoplasmic reticulum “network within cytoplasm” Smooth E.R. = no ribosomes Make lipids, carbohydrate metabolism, detoxification of drugs and poisons Rough E.R. = ribosomes Makes proteins to be secreted, folds them, and sends them to Golgi

Golgi apparatus Manufacturing, warehousing, sorting, and shipping center Flattened membranous sacs with two sides (receiving/cis and shipping/trans) Ships products in vesicles which can fuse with membrane and be released

Lysosomes Membrane bound sac of hydrolytic enzymes Recycling center Breaks down macromolecules and recycles old, dead organelles

Vacuoles Membrane bound storage sacs Food vacuoles Contractile vacuoles pump water out Central vacuole in plants

Mitochondria Site of cellular respiration (energy!) One large one or hundreds of small ones Double membrane (outer and inner) 2 compartments (intermembrane space and matrix)

Chloroplasts Site of photosynthesis Stacks of membranes called thylakoids = granum (grana) Stroma is fluid filled cavity Thylakoids have the chlorophyll

Cytoskeleton Provides structural support Aids in cell motility Microtubules: cell shape, cilia/flagella, chromosome movement in mitosis, organelle movement) Microfilaments: cell shape, muscle contraction, pseudopodia, cleavage furrow Intermediate filaments: cell shape, organelle anchoring

Plasma membrane Fluid mosaic model Phospholipid bilayer Cholesterol helps maintain fluidity Proteins function as cell surface receptors, channels, enzymes, cell-cell recognition Carbohydrates serve as flags for cell recognition

Transport Passive transport: molecules move down concentration gradient (requires no NRG) Diffusion, osmosis, facilitated diffusion (help of a protein) Active transport: against gradient requires energy Endocytosis (phago, pino, receptor mediated) exocytosis

Osmosis Hypertonic: higher concentration of solutes Water leaves, cell shrivels Hypotonic: lower concentration of solutes Water enters, cell swells and maybe bursts Isotonic: equal solute concentrations

Cell Division Reproduction, growth, repair Results in formation of identical cells with identical DNA Occurs in somatic cells Mitosis: division of nucleus Cytokinesis: division of cytoplasm

DNA and cell division DNA is replicated during S phase of interphase Homologous chromosomes (mom’s and dad’s copy of each chromosome) Sister chromatids: when each chromosome gets copied and connected together to go through mitosis

Cell Cycle Interphase: accounts for most of the cycle (includes growth/gap G1/G2 phase and DNA synthesis S phase) M phase (mitosis) Cytokinesis Cell cycle checkpoints

Mitosis Prophase: chromatin condenses into chromosomes, mitotic spindle forms Prometaphase: centrioles opposite poles, nucleus disappears Metaphase: metaphase plate, chromosomes lined up at center Anaphase: sister chromatids separate Telophase: chromsomes separate to poles, nucleus begins to reform

Cytokinesis Animals: cleavage furrow pinches off cells via contracting ring of microfilaments Plants: cell plate forms between cells and creates new cell wall via delivery from vesicles carrying cell wall parts

Cell Cycle Regulation Checkpoint: critical point where stop and go signals regulate cell cycle Has all DNA been copied? Are there errors? Is the cell big enough? Have all the organelles been copied? Cancer: many mutations cause cells to bypass checkpoints and divide out of control