13.1

Question 1

Organelle summary - DRAW (p. 283)

Answer 1

RER - synthesis and modification of secretory, membrane-bound and organelle proteins

SER - DETOX, glycogen breakdown in liver, steroid synthesis in gonads (“the detox was smooth”), lipid manufacture/metabolism

Golgi - modification and sorting of proteins, some synthesis - the PACKAGER, also adds sugars to proteins (GLYCOSYLATION)

Peroxisome - metabolize lipids and toxins with hydrogen peroxide; contains enzyme called CATALASE which converts h2o2 to H2O + O2

Lysosomes - contains acid hydrolase (“lysing”) for digestion

Question 2

euchromatin

Answer 2

less dense than heterochromatin

Question 3

nucleolus

Answer 3

the ribosome factory

NO membrane surrounding it

consists of DNA, RNA pol, rRNA, protein components of ribosome

site of transcription of rRNA by RNA pol I

protein ribosome is transported into the nucleus

Question 4

nuclear localization sequence

Answer 4

larger proteins (>60 kDaltons) cannot freely enter the nucleus, they need a sequence of basic amino acids called a NLS - transported inside by specific transport mechanism

Question 5

mitochondria

Answer 5

single circular DNA molecule -> encodes rRNA, tRNA, and several proteins of the ETC

Question 6

all proteins start translation in the…? what is the signal sequence…?

Answer 6

ALL PROTEINS START translation in the cytoplasm

some proteins (secreted proteins, lysosomal proteins) have an amino acid sequence at their N-terminus called a SIGNAL SEQUENCE

the SS recognized by the signal recognition particle (SRP), which binds to the ribosome, forms a ribosome-SRP complex

ER has SRP receptors, the peptide is “pushed” into the ER lumen

after translation, the signal peptide is removed from the polypeptide by SIGNAL PEPTIDASE

for secreted proteins, the signal sequence is REMOVED

Question 7

two sites of protein synthesis

Answer 7

1. free ribosomes in cytoplasm
2. ribosomes bound to rough ER

free ribosomes -> head to peroxisome, mitochondria, nucleus, or cytoplasm

rough ER -> secreted to extracellular environment, or plasma membrane, or membrane or interior of ER, GA, Lysosome (traffic’ed through VESICLES) => interior of ER, Golgi, lysosome, and extracellular environments are in a sense CONTIGUOUS

Question 8

integral membrane proteins have… TD

Answer 8

have hydrophobic amino acid residues called transmembrane domains – these DOMAINS are essentially signal sequences found in the interior of protein (NOT AT N-TERMINUS)

TDs are NOT REMOVED

TDs are threaded through the ER membrane during translation

portion of protein in the ER lumen faces the EXTERIOR

Question 9

ER additional functions

Answer 9

1. post-translational modification of proteins (sometimes glycosylates)
2. disulfide bond formation occurs in ER lumen

Question 10

default target for proteins of secretory path

Answer 10

PLASMA MEMBRANE

targeting signals are needed if a protein ends up elsewhere (GA, ER, lysosomes)

Question 11

disulfide bonds occur in…

Answer 11

oxidative conditions

Golgi, ER, and extracellular are OXIDATIVE

Question 12

a protein produced in secretory pathway that needs to be sent to an organelle outside of the S-pathway needs…

Answer 12

…localization signals

Question 13

Cellular Protein Traffic - DRAW (p. 290)

Answer 13

p. 290

Question 14

GA - 3 purposes

Answer 14

1. modification of proteins made in RER (especially oligosaccharide chains)
2. Sorting and sending proteins (MAIL FACILITY)
3. synthesis of macromolecules to be secreted

Question 15

acid hydrolase

Answer 15

they only function in acidic environments - safety mechanism

a phagocytic vesicle fuses with lysosome

Question 16

cell wall of bacteria, plants, and fungi

Answer 16

1. bacteria -> peptidoglycan
2. plants -> celluose
3. fungi -> chitin

Question 17

colligative property

Answer 17

identity of particle is not important

1. vapor-pressure depression
2. boiling point elevation
3. freezing-point depression - solute causes melting point to decrease
4. osmotic pressure

Question 18

vapor pressure

Answer 18

adding more solute decreases vapor pressure (salt water)

boiling - atmospheric pressure = vapor pressure

Question 19

ion channels

Answer 19

involved in facilitated diffusion, down a EC gradient

Question 20

pores are found

Answer 20

1. double nuclear membrane
2. outer mitochondrial membrane
3. Gram-(-) bacterial outer membrane

Question 21

Na/K ATPase

Answer 21

the driving force behind secondary active transport

1. maintains osmotic balance between interior/exterior
2. establish resting potential
3. provide sodium concentration gradient used to drive secondary active transport

Question 22

secondary active transport

Answer 22

the transport process is not coupled directly to ATP hydrolysis; ATP is used to create a gradient, which is used to drive the transport of another molecule (coupling)

Question 23

chloride and calcium are…

Answer 23

preferentially extracellular

Question 24

clathrin

Answer 24

inside the cell involved in receptor-mediated endocytosis

Question 25

ligand and 3 types of signal transduction

Answer 25

ligand = key ("ligkey"), usually a hormone or neurotransmitter the response = signal-transduction 1. ligated-gated ion channels - an ion channel opens when binding a neurotransmitter 2. catalytic receptors - enzymatic active site on the cytoplasmic side; enzyme activity initiated by ligand binding at the extracellular surface 3. G-protein linked receptor - uses a secondary messenger to communicate with enzymes in the cytoplasm (cAMP is important, which AMPLIFIES the signal)

Question 26

G-protein epinephrine pathway (DRAW - p. 309)

Answer 26

...

Question 27

cytoskeleton (3 components)

Answer 27

1. microtubules - thickest (25 nm) 2. intermediate filaments (10 nm) 3. microfilaments - thinnest (7 nm) made of noncovalently polymerized proteins example of QUATERNARY structure

Question 28

microtubule

Answer 28

hollow rod, alpha and beta-tubulin ONLY 1 end can elongate the other end is anchored to MICROTUBULE ORGANIZING CENTER (MTOC) -- within MTOC is a pair of centrioles, which are organized into 9 microtubule triplets aster - star-shaped, radiate out from the centrioles (Aster = MTOC). Fungi/plants do NOT have MTOC polar fibers - connect chromosome to the aster mitotic spindle - whole thing Also: transport substances within the cell (railroad analogy) - driven by proteins that hydrolyze ATP and act as molecular motors 9+2 arrangement found in flagellum and cilia (9 pairs of MTs form a ring around two lone microtubules in the center). Prokaryotes have different structure.

Question 29

what connects microtubules?

Answer 29

each microtubule is bound to its neighbor by contractile protein called DYNEIN causes the movement of filaments past one another

Question 30

what attaches MTs to plasma membrane?

Answer 30

basal body (same structure as centriole)

Question 31

microfilaments

Answer 31

rods formed in cytoplasm from polymerization of globular protein ACTIN, which form a chain and wrap each other to form ACTIN FILAMENT PINCHES the parent cell AMOEBOID movement

Question 32

intermediate filaments

Answer 32

heterogenous, wide range of polypeptides more permanent provides strong cell structure

Question 33

tight junctions and desmosomes

Answer 33

epithelial cells in the gut the seal is completed by desmosomes desmosome -> hold cells together at concise points, not bands, composed of fibers that span the plasma membranes of two cells (anchored to plasma membrane by a plaque formed by protein keratin) - found at mechanically-stressed locations (bladder, cardiac)

Question 34

gap junctions

Answer 34

heart muscle cells holes called gap junctions that allow ions to flow back and forth

Question 35

apical and basolateral

Answer 35

apical - facing the intestinal lumen basolateral - facing the tissues

Question 36

gap junctions

Answer 36

pore-like connections between adjacent cells (cytoplasms can MIX ions, AAs, carbs, but not polypeptides or organelles) allow membrane depolarization of action potential to pass from cell to cell

Question 37

prophase

Answer 37

1. nucleolus disappears 2. spindle and kinetochore fibers appear 3. centriole pairs move to opposite ends 4. nuclear envelope converts into tiny vesicles

Question 38

cleavage furrow

Answer 38

ring of actin filament that contracts

Question 39

Benzene

Answer 39

a mutagen, as is UV

Question 40

what kills a cell?

Answer 40

stressors include 1. nitric oxide, 2. toxin 3. cytokines also, p53 -> apoptosis

Question 41

caspases

Answer 41

a type of protease, carries out apoptosis cysteine in active site cleave target proteins at aspartic acid sites (cleave-asp) grouped into initiators and effectors initiators - respond to extra- or intracellular death signals by clustering together and activating each other activation of initiators leads to activation of effector caspase to trigger APOPTOSIS (see illustration p. 318)