Ch. 7: A tour of the cell

So, how do we know what we know about cells????? Methods of study cells and cellular components Microscopes Resolving Power LM vrs EM (TEM, SEM) isolation of organelles cell fractionation techniques

Prokaryote

Eukaryotes, Plant or Animal

So, why aren’t there huge cells out there????? The ratio of cell surface to cell volume determines how large a cell can be. Sufficient surface area to serve their volume e.g. RBC - functional advantage of size

Plasma Membrane Lipid Bilayer (phospholipids) Proteins Carbohydrates Fluid Mosiac Model

Nucleus and Ribosomes Nucleus: Ribosomes Genes, DNA Double membrane (each a lipid bylayer) Nuclear Lamina (mesh lining for shape) Pores, Pore Complex Chromatin Chromosomes Nucleolus (ribosomal RNA made) Ribosomes Build cell proteins (Protein Synthesis) Ribosomal RNA and Proteins Free Ribosomes: suspended in cytosol Bound Ribosomes: attached to outside of ER or Nuclear Envelope. Free R = use inside cytosol Bound R = organelle w/ protein or export

Endomembrane System System of interactive organelles Direct physical contact or Transfer of membrane bound vesicles Nuclear Envelope ER Golgi Lysosomes Vacuoles Plamsa membrane

Endoplasmic Reticulum ½ the total membrane of the cell Network of tubules and cisternae (sacs) Continuous with nuclear membrane Smooth ER Synthesis of lipids Enzymes for detoxification of drugs (liver) Drug Tolerance due to stimulation of sER Rough ER (bound ribosomes) Secretory proteins wrapped in membrane of vesicles Transport Vesicles Makes membrane phospholipids

Golgi Apparatus Manufacturing, warehouse, sorting, and shipping center Receives products of ER Polarity of membrane sacks Cis Face: near ER, receiving side Trans Face: shipping side Modification occur between Cis and Trans Identification Tags added to product

Lysosomes Membrane bound sacks of hydrolytic enzymes Lysosomal Enzymes Low pH (cytosol neutral pH) Phagosytosis Autophagy: recycle their own organic material Apoptosis (programmed cell death) Tadpole’s tail Human fingers

Mitochondria Cellular Respiration (all euK’s) Catabolic process (ATP production Free ribosome make membrane Own DNA for own proteins 2 lipid bilayer membranes Inner membrane w/ folds called Cristae (increase surface area) Intermembrane space Mitochondrial Matix Outer membrane: Smooth

Chloroplasts Stacks of organelles (plastids) Contains pigment, enzymes, for photosynthesis (Chloroplasts have chlorophyll pigment) Thylakoids Granum: stacks of thylakoids Stroma: fluid outside of thylakoids

Peroxisomes Transfer H to O producing H2O2 Contains peroxidase to break down toxic H2O2 Liver: detoxifies alcohol

Cytoskeleton Structural Support Cell Motility Three main Molecules Movement of cell Movement of organelles Three main Molecules

Cilia and Flagella Core of microtubules sheathed in plasma membrane. “9+2” pattern Dynein Arms Radial Spokes Basal Bodies: anchorage to cell

ECM Extracellular Matrix: glycoproteins secreted by the cell. Collagen: ½ total protein of the body Proteoglycans: embedded in collagen, rich in carbohydrates. Fibronectin: glycoprotein of ECM, binds to receptor called Integrins found in cell membrane (in/out). Communication from inside cell to ECM

Intercellular Junctions Cells organized into tissue, organs b/c of Junctions. Types: Plasmodesmata: channels allows for cytosol to pass, unifies plant. Tight Junctions: membranes of neighboring cells fused. Prevents leakage of extracellular fluids. Desmosomes: (anchoring junctions) like rivets. Strong sheet w/ intermediate filaments extending in. Gap Junctions: (communication junction) cytoplasmic channels, proteins around pores to control border.

Lysosome

Cytosol

Nucleus

Ribosomes

Plasma Membrane

Golgi Apparatus

Endoplasmic reticulum

Intercellular junctions: “Just try and figure out who we are!” 1. We are protein “belts” that hold cells so tightly together that we prevent the movement of things between our cells. 2. We are rivets that join cells together in strong sheets, but still allow things to pass between cells. We made of glycoprotein filaments. 3. We allow things to transport between the cytoplasm of adjacent cells. We are membrane proteins. We allow your heart to beat as a unit. Tight junctions Desmosomes Gap Junctions