u2: cell structure and function

fundamental units of life

cell theory #1: cells are ________________

are composed of cells

cell theory #2: all organisms ________________

come from preexisting cells

cell theory #3: all cells ________________

mitochondria

made of an outer and inner membrane

fluid filled matrix contains enzymes, dna, ribosomes

important in cellular respiration

chloroplast

contains chlorophyll, is site for photosynthesis

enclosed within 2 membranes with internal membranes called thylakoids

vacuole

in some eukaryotes (mainly plants & fungi)

storage of waste and toxic compounds

structure for plant cells (turgor pressure)

contractile vacuoles

freshwater protists get rid of excess water using _____

cytoskeleton

maintains cell shape and organelle positioning

made of microfilaments, intermediate filaments, microtubules

microfilaments

made of actin, determines cell structure

dynamic instability —> actin can grow and shorten

microtubules

largest, show dynamic instability

made from tubulin dimers

polymerization —> rigid structure

cilia

short, abundant, move stiffly and are flexible

often on bacteria to help them navigate

flagella

long, 1-2, snakelike waves

also helps organisms move

9+2 arrangement

9 doublts fused microtubules on the outside

2 unfused microtubules in the center

dynein

drives sliding of doublets

nexin

crosslinks doublets to prevent sliding

kinesin

motor protein that walks cargo on microtubules

ribosomes

sites of protein synthesis

in mito/chloroplast

also free-floating in cytoplasm/rough er

nucleus

DNA combines to form chromatin in long threads of chromosomes

endomembrane system

group of membranes and organelles in eukaryotic cells

modify, package, and transport lipids and proteins

rough ER

bumpy ribosomes attached to cytoplasmic surface

proteins fold and modify

packaged into vesicles to ship to golgi apparatus

smooth er

few/no ribosomes

synthesizes carbs, lipids, steroid hormones

detoxifies meds and poisons

golgi apparatus

receiving side = cis, opposite side = trans

proteins and lipids undergo further modification

sorts and packages vesicles that bud off from trans face

lysosome

breaks down old structures to reuse molecules (using enzymes)

phagocytosis —> breaks down pathogens

• makes phagosome (food vacuole)

• waste secreted by exocytosis

plant cell wall

semi-rigid structure outside plasma membrane

supports cell structure and protects cell

also has transport in plasmodesmata

extracellular matrix

holds cells together in tissues

filters materials

orients cell movement in growth and repair

plasmodesmata

plasma membrane lined channels allow water, ions, rna to move between adjacent plant cells

= gap junctions in animal cells

tight junctions

completely prevents substances from moving between cells

desmosomes

holds cells together but allows materials to move

good when cells need to be tightly bound but still transport

gap junctions

channels that run between membrane pores in adjacent cells for substances to pass between cells

= plasmodesmata in plants

small nonpolar molecules

what can pass through membrane?

cholesterol

helps bilayer stay fluid

holds phospholipids together and regulates how tight they pack

requires atp, against concentration gradient

active transport…

sodium-potassium pump

forms electrogradient

secondary active transport

secondary active transport

transport that depends on the active transport but doesn’t require atp

endocytosis

receptor mediated endocytosis

membrane forms a vesicle that separates from membrane

exocytosis

vesicle merges with membrane, releases contents inside

passive transport

facilitated diffusion, ligand gated channels, carrier protein are examples of: ______

hypertonic

water moves to ____ side