basic features that all cells share

• plasma membrane (selective barrier that bounds the cell)
• cytosol (semifluid jellylike substance)
• chromosomes (carry genes in the form of DNA)
• ribosomes (tiny complexes that make proteins according to instructions from the genes)

prokaryotic cells

• lack nuclei and other membrane-enclosed organelles
• small

"before nucleus"

eukaryotic cells

• membrane-enclosed nucleus, contains cell's linear chromosomes
• membrane bound organelles in cytoplasm
• larger (cell-wise)

"true nucleus"

what do prokaryotic and eukaryotic cells have in common?

• plasma membrane
• ribosomes

cytoplasm

• the interior of the cell that contains, within the cytosol, organelles
• in eukaryotic cells - refers to the region between nucleus and the plasma membrane

organelle

• a subcellular structure that have specialized forms and functions

plasma membrane

• forms a boundary for the cell
• selectively permeable
• permits the passage of selected materials into and out of the cell

what is the plasma membrane made up of?

• phospholipids
• proteins
• associated carbohydrates

(these molecules determine the function of the membrane)

what is going on inside the eukaryotic cell?

• extensive, elaborately arranged internal membranes divide cell into compartments (organelles)
• compartments provide different local environments that support specific metabolic functions
• this allows incompatible processes to occur simultaneously in a single cell

how do the plasma membrane and organelle membranes participate in the cell's metabolism?

• many enzymes are built right into the membranes

what is the basic fabric of most biological membranes?

• a double layer of phospholipids and other lipids
• embedded in bilayer/attached to surface are diverse proteins

membrane and composition

• each type of membrane has a unique composition of lipids and proteins suited to that membrane's specific functions

example: enzymes in mitochondria membranes function in cellular respiration

cell wall (prokaryotic cell & plant cell)

• rigid structure outside of the plasma membrane
• in plants, protects and helps maintain their shape
• provides a barrier for some substances to enter the plant cell
• primary component: cellulose

bacterial chromosome (prokaryotic cell)

• carries genes in the form of DNA

nucleoid (prokaryotic cell)

• region where the cell's DNA is located (not membrane bound)

endoplasmic reticulum

• network of membranous sacs and tubes
• active in membrane synthesis and other synthetic + metabolic processes
• has rough and smooth regions

plasmodesmata (plant cell)

• perforate the cell wall
• channels that connect plant cells
• allow communication and movement of materials between cells

which two cellular components are involved in the genetic control of the cell?

• nucleus
• ribosomes

nucleus

• houses most of the cell's DNA
• template to make messenger RNA (mRNA), which contains the code to produce protein
• most noticeable organelle in cell due to large relative size

nuclear envelope

• a double membrane that surrounds the nucleus
• continuous with the rough ER
• has pore structures that regulate what may enter or leave the nucleus

chromatin

• complex of DNA and protein housed in the nucleus that forms chromosomes
• diffuse threads of this condense into visible chromosomes as cell gets ready to divide

nucleolus

• region of the nucleus where ribosomal RNA (rRNA) is synthesized and complexes with proteins to form ribosomal subunits

ribosomes

• complexes that synthesize protein
• composed of rRNA and protein
• sites of protein synthesis within the cell
• consist of a large and small subunit

free ribosomes

• float in cytosol
• produce proteins that are used within the cell

bound ribosomes

• attached to the ER
• make proteins destined for export from the cell

endoplasmic reticulum (ER)

• network of membranes and sacs
• makes up more than half the total membrane structure in many cells
• two types of ER: smooth and rough

cisternal space

• internal area of the ER

smooth ER

• synthesis of lipids
• detoxification of drugs and poisons
• metabolism of carbohydrates
• storage of calcium ions

rough ER

• aids in synthesis of secretory and other proteins on bound ribosomes
• adds carbohydrates to proteins to make glycoproteins
• produces new membrane

what does the endomembrane system consist of?

ER (rough and smooth), golgi apparatus, lysosome, vacuole

golgi apparatus

• stacks of flattened membranous sacs
• has polarity (cis and trans faces)
• modifies proteins, carbohydrates on proteins, and phospholipids
• synthesizes polysaccharides
• sorting of "golgi" products - released into vesicles

lysosomes

• membranous sac of hydrolytic enzymes
• breakdown ingested substances, cell macromolecules, and damaged organelles for recycling

vacuole

• large membrane-bound vesicle
• assist in digestion, storage, waste disposal, water balance, cell growth, and protection

what does the endomembrane system do?

• organelles that work together to modify, package, and transport lipids and proteins

mitochondrion

• bounded by double membrane
• inner membrane has infoldings
• function: cellular respiration

chloroplast

• two fluid membranes around fluid stomata (contains thylakoids stacked into grana)
• function: photosynthesis

peroxisome

• specialized metabolic compartment bounded by a single membrane
• contains enzymes that transfer H atoms from substrates to oxygen, producing hydrogen peroxide, which is converted to H2O

cytoskeleton

• functions in structural support for the cell and in mobility and signal transmission

microtubules

• shape the cell
• guide organelle movement
• separate chromosomes in dividing cells

cilia and flagella

• motile appendages containing microtubules
• primary cilia play sensory and signaling roles

microfilaments

• thin rods that function in muscle contraction, amoeboid movement, cytoplasmic streaming, and support of microvilli

intermediate filaments

• support cell shape
• fix organelles in place

what are plant cell walls made of?

• cellulose fibers imbedded in other polysaccharides and proteins

extracellular matrix

• animal cells secrete glycoproteins and proteoglycans that form this
• functions in support, adhesion, movement, and regulation

cell junctions

• connect neighboring cells

how do plant cells connect?

• plasmodesmata

how do animal cells connect?

• tight junctions
• desmosomes
• gap junctions

the cell is...

• a living unit greater than the sum of its parts

endosymbiotic theory

• mitochondria and chloroplasts descended from prokaryotic cells once engulfed by ancestors of eukaryotic cells

EVIDENCE: double membrane structure, own ribosomes and circular DNA molecules, reproduce independently within the cell