Prokaryotic Cells Eukaryotic Cells domains Bacteria & Archaea 1-10 μm DNA located in nucleoid region cell wall capsule pili flagella domain Eukarya (protists, fungi, plants, & animals) 10-100 μm DNA located in nucleus organelles plasma membrane cytosol/cytoplasm ribosomes chromosomes

Limits on Cell Size as a cell increases in size, its volume grows proportionally more than its surface area cells need a surface area large enough to accommodate its volume if the surface area : volume ratio is too great, the rate of chemical exchange with the environment may be too slow to meet the cell’s needs

Generalized Animal Cell

Generalized Plant Cell

Nucleus contains most of the cell’s genes directs protein synthesis by synthesizing mRNA surrounded by a porous double membrane called the nuclear envelope DNA is organized into chromosomes (made up of chromatin) nucleolus – sythesizes rRNA (ribosomal subunits)

Ribosomes made of rRNA and protein carry out protein synthesis free ribosomes make proteins that function within cytosol bound ribosomes make proteins destined for insertion into membranes, for packaging within organelles, or for secretion

Endomembrane System consists of membranes related through direct physical continuity or by vesicles includes: nuclear envelope endoplasmic reticulum Golgi apparatus lysosomes vacuoles & vesicles plasma membrane

Endoplasmic Reticulum continuous with nuclear envelope rough ER has ribosomes attached to surface makes secretory proteins makes membrane smooth ER lacks ribosomes synthesizes lipids metabolizes carbohydrates detoxifies drugs/poisons stores calcium ions

Golgi apparatus consists of flattened membranous sacs two poles: cis = receiving end trans = shipping end modifies products of ER, stores them, “tags” them, & sends them to other destinations manufactures macromolecules (ex: polysaccharides)

Lysosome contains hydrolytic enzymes fuse with vesicles or vacuoles to… digest macromolecules recycle organic material (ex: old organelles) break down food destroy invaders

Vacuoles similar to lysosomes because they carry out hydrolysis in plant & fungal cells food vacuoles store & break down food contractile vacuoles pump excess water out of cell central vacuole of plant cells stores organic compounds & ions, acts as a disposal site for waste, contains pigments, and may contain poisons for defense against predators

Mitochondrion site of cellular respiration enclosed by 2 membranes: outer is smooth & inner is convoluted (cristae) between membranes is intermembrane space interior is called the matrix contains its own DNA & ribosomes number in cell is related to cell’s level of metabolic activity

Chloroplast site of photosynthesis contains chlorophyll found in leaf cells & cells of other green organs enclosed by 2 membranes with a narrow intermembrane space interior fluid is called the stroma stroma contains stacks of membranous sacs called thylakoids (a stack of thylakoids is called a granum) contains its own DNA & ribosomes

Peroxisome bound by a single layer of phospholipids contains enzymes that catalyze oxidation reactions producing hydrogen peroxide (H2O2) as a by-product additional enzymes break down the H2O2 which is toxic to the cell

Cytoskeleton network of fibers extending throughout cytoplasm provides mechanical support to the cell maintains the shape of the cell anchors organelles involved in cell movement (cilia & flagella) may also be involved in the regulation of biochemical activities

Components of the Cytoskeleton microtubules shape & support the cell serve as tracks for the movement of organelles separate chromosomes during cell division “9+2” arrangement and dynein arms cause cilia & flagella to beat grow out from centrosome (which includes a pair of centrioles in animal cells) continued

microfilaments (actin filaments) built from molecules of actin helps cell bear tension (pulling forces) play a role in cell motility works with myosin to cause muscle cell contraction in animals & cytoplasmic streaming in plant cells intermediate filaments helps cell bear tension reinforces shape of cell helps anchor organelles make up nuclear lamina (lining on nuclear side of nuclear envelope)

Cell Wall protects & maintains shape of plant cell prevents excessive uptake of water composed primarily of cellulose in plants & chitin in fungi perforated by channels called plasmodesmata that connect adjacent cells

Extracellular Matrix consists primarily of glycoproteins (carbohydrate attachments to membrane proteins) most abundant glycoprotein is collagen

Intercellular Junctions Plant Cells plasmodesmata = cytoplasmic channels between adjacent plant cells Animal Cells tight junctions = bind cells tightly together to prevent fluid from leaking into surrounding tissues desmosomes = anchoring junctions (fasten cells together) gap junctions = cytoplasmic channels between adjacent animal cells