Chapter 7 Vocab Quiz: Thursday Test: Friday Cell Project: Th. 2/22/07 A Tour of the Cell Chapter 7 Vocab Quiz: Thursday Test: Friday Cell Project: Th. 2/22/07

How Do We Study Cells

Light Microscopes Definition: two important powers: Advantages: magnification (magnifying power) resolution (resolving power) Advantages: Disadvantages:

Electron Microscopes Definition: Advantages: Disadvantages:

Cell Fractionation two steps: homogenization differential centrifugation: tool-ultracentrifuge

All cells have: plasma membrane DNA (not necessarily in a nucleus) cytoplasm

Limits on Cell Sizes lower limits upper limits: surface area-to-volume

Compartmentalization Internal membranes allow eukaryotic cells to battle the surface area-to-volume ratio problem that limits cell size. Eukaryotic cells can form “compartments” which segregate certain reactions that interfere with each other (local environments) These internal membranes participate directly in the cells metabolism (enzymes) Each membrane has a unique composistion (enzymes for cellular respiration - mitochondria)

Nucleus: Cell’s Genetic Library contains most of the genes in a eukaryotic cell nucleus is enclosed by the nuclear envelope separates nuclear DNA from the cytoplasm envelope is a double membrane, each is a lipid bilayer with associated proteins envelope is perforated by nuclear pores, lined by a pore complex which regulates transport

Nuclear Organization DNA Proteins - histones Chromatin Chromosomes Nucleolus

Ribosomes build a cell’s proteins sites of protein synthesis = translation cells with high rates of protein synthesis have …large numbers of ribosomes free ribosomes - suspended in the cytosol; make proteins that work in the cytosol bound ribosomes - attached to the outside of the membranes of the nuclear envelope and ER; make proteins that are (1) included in the membrane; (2) packaging within an organelle; (3) exported from the cell

Endoplasmic Reticulum extensive membranes which may account for over half of the cell’s total membrane Rough ER - ribosomes on surface bound ribosomes make secretory proteins cells that are specialized for secretion often have tremendous amounts of rough ER also the membrane factory of the cell - synthesis of phospholipids

Smooth ER - lack ribosomes different functions in different cells phospholipid, steroid, and sex hormone synthesis metabolism of carbohydrates detoxification of drugs and poisons (increased smooth ER production in liver cells is the basis for drug tolerances) storage and release of calcium ions during muscle contraction

Golgi Apparatus products are modified as they move from region to the next products are sorted into vesicles, pinch off from the Golgi surface molecules on the vesicle direct its movement through the cell

Lysosomes contains hydrolytic enzymes for digestion of macromolecules lysosomes fuse with food vacuoles that are formed during phagocytosis some cells recycle their own cell parts - autophagy apoptosis - programmed cell death - sometimes uses lysosomes for destruction of the cell

Vacuoles food vacuoles contractile vacuoles central vacuole

Mitochondria site of cell respiration, catabolic processing of fuels to produce ATP “Powerhouse of the Cell” respiratory enzymes are found throughout the mitochondria glucose + oxygen ----> carbon dioxide + water + ATP

Chloroplasts one of a group of organelles called plastids Site of photosynthesis - organic molecules are created from carbon dioxide and solar energy

Cytoskeleton Three parts (classified by size): Microtubules; Intermediate Filaments; Microfilaments mechanical support maintain or change cell shape anchor and direct organelle movement control movement of cellular appendages muscle contraction

Prokaryotes vs. Eukaryotes compare: contrast:

Animal Cells vs. Plant Cells compare: contrast:

Summary