ap bio unit 2

cells and transport

integral proteins

penetrate hydrophobic interior of the bilayer. majority span the membrane (transmembrane proteins). hydrophobic regions of integral proteins consist of at least one stretch of nonpolar amino acids (alpha helices)

peripheral proteins

loosely bound to the surface of the membrane

cell fractionation

breaks up cells and separates components using centrifugation based on relative size. enables scientists to determine functions of organelles

isotonic

solute concentration equal

hypotonic

solute concentration greater inside (water greater outside) - water moves in

hypertonic

solute concentration greater outside (water greater inside) - water moves out

prokaryotic characteristics

no nucleus, DNA in nucleoid, no membrane-bound organelles.

eukaryotic characteristics

DNA in nucleus bound by double membrane, membrane-bound organelles, cytoplasm in region between membrane and nucleus

both prokaryotic and eukaryotic characteristics

plasma membrane, cytosol, chromosomes, ribosomes

endosymbiont theory

mitochondria and chloroplasts originated from prokaryotic cells that were engulfed by an ancestor of eukaryotic cells, forming a symbiotic relationship

endomembrane system

nuclear envelope, ER, golgi, lysosomes, vacuoles, plasma membrane. continuous or connected through transfer by vesicles

role of motor proteins

used by vesicles and other organelles to “walk” along the tracks provided by cytoskeleton

free vs attached ribosomes

free float in cytosol, attached are bound to rough ER or nuclear envelope

path of proteins made for export

synthesized in ER. carbs are added to transmembrane proteins to make them glycoproteins. materials are transported to the golgi by vesicles.

in golgi, glycoproteins undergo further carb modification, becoming glycolipid.

the glycoproteins, glycolipids, and secretory proteins transported in vesicles to to plasma membrane.

vesicles fuse w/ membrane, outside face of vseicle becomes continuous w/ inside of membrane, which releases the secretory proteins, and positions the carbs of the membrane glycoproteins and glycolipids on the outside face of the membrane

plant vs animal cells

plants have chloroplasts, cell wall, vacuole. animals have lysosomes and centrioles which are usually absent in plant cells

light vs electron microscopes

light: can magnify about 1000x, visible light is passed through a specimin and then through glass lenses, which refract the light so the image is magnified
electron: study subcellular structures, focus a beam of electrons onto the surface of the specimen (scanning EMs) or through a specimen (transmission EMs). SEMs make a 3d image

volume of plant cells vs animal cells

plants have larger volume b/c of central vacuole. animals are usually 10-30 micrometers wide, plants 10-100

tonicity preferences (animal vs plant)

animal: isotonic

plant: hypotonic

plant cells in different tonicity

hypotonic: swells until wall opposes uptake; turgid

isotonic: cell becomes flaccid (limp), and plant may wilt

hypertonic: lose water, membrane pulls away from wall (plasmolysis)

animal cells in different tonicity

hypotonic: water moves in, cell lyses

isotonic: normal

hypertonic: water moves out, shrivels

how cell wall helps/restricts transport

through plasmodesmata, water and small solutes (sometimes proteins/RNA) can pass from cell to cell. restricts large molecules since it is dense and fibrous

types of membrane transport

active, passive, endocytosis, pinocytosis, phagocytosis, exocytosis, ion pumps/proton pumps, cotransport (downhill diffusion of one and uphill of another coupled—used in proton pump)

why is fluid mosaic structure asymmetrical

groups of certain proteins/lipids may associate in specialized patches

role of phospholipids in membrane fluidity

can move and shift quickly, proteins move more slowly

cold adapted vs warm adapted organisms

cold: cholesterol maintains fluidity by preventing packing, increased proportion of unsaturated fatty acids in membranes to prevent tight packing

warm: cholesterol restrains movement of phospholipids, higher proportion of saturated fatty acids

dynamic equilibrium

same number of molecules cross the membrane in both directions

evolutionary advantage/connectedness of membrane transport

to be inheritable, early metabolism must have led to an increased rate of growth and division of vesicles and, similarly, transport through vesicle boundaries must have supported the evolution of metabolism. transport provided advantages for survival and adaptation in homeostasis and response to environmental changes, increased energy efficiency

chromatin

dna and proteins of chromosomes together

nucleolus

site of rRNA synthesis

smooth ER

lipid synthesis, carb metabolism, detoxes drugs and poisons, stores Ca ions

rough ER

bound ribosomes secrete glycoproteins, distributes transport vesicles, membrane factory for cell

vacuoles

large vesciles derived from ER and golgi - food, contracile, central

peroxisomes

perform redox reactions - produce H2O2 and convert it to water. in liver, detoxes alcohol and other harmful compounds

mitochondria

smooth outer membrane, inner membrane folded into cristae (creates intermembrane space and mitochondrial matrix) - large surface area for enzymes that synthesize ATP

chloroplasts

contain thylakoids (membranous sacs) stacked to form a granum, and stroma (internal fluid)

cytoskeleton

microtubules, microfilaments, intermediate filaments

microtubules

thickest, hollow tubes. maintains cell shape, cell motility (movement), chromosome movements in cell division, organelle movements

microfilaments (actin)

thinnest. maintains cell shape, muscle contraction, cytosplasmic streaming, cell motility, cell division

intermediate filaments

maintains cell shape, anchors nucleus and other organelles, formation of nuclear lamina

centrosomes and centrioles

microtubules grow out from them. centrosome is a microtubule-organizing center, has a pair of centrioles each w/ 9 triplets of microtubles arranged in a ring

cilia and flagella

microtubule containing extensions projecting from cells - flagella is only one or a few, cilia can have large numbers

cell wall

primary cell wall (thin and flexible), middle lamella (thin layer between primary walls of adjacent cells), secondary cell wall (added vbetween cell wall and plasma membrane)

ECM animal cells

made of glycoproteins like collagen, proteoglycans, fibronectin. proteins bind to receptors called integrins