Eukaryotic Cells: organelles, plasma membrane, mitosis, and senescence

Question 1

genes can be genetically mapped by a specific location on that chromosome, a ______

Answer 1

locus

in other words, the locus is the specific location of that gene

Question 2

in addition to providing support and structure, the nuclear matrix also helps regulate gene expression. How does it do so?

Answer 2

the DNA chromosomes are attached to the matrix at specific sites, and these appear to be involved in regulating gene expression

Question 3

the nucleolus functions as the _____ factory

Answer 3

ribosome

hence, the nucleolus is the site of rRNA transcription

Question 4

Name functions of RNA Pol I, II, & III

Answer 4

RNA Pol I: transcribes rRNA

RNA Pol II: transcribes mRNA

RNA Pol III: transcribes tRNA

Question 5

Since ribsome assembly is initiated in the nucleus, where are the protein components of the ribosome made?

Answer 5

the protein components of the ribosome areNOT produced in the nucleolus or the nucles, but rather the cytoplasm (because all transcription occurs in the cytoplasm). These proteins must be shuttled into the nucles from the cytoplasm

Question 6

Why is it that ribosomes are only partially assembled in the nucles before they’re shuttled to the cytoplasm to finish their assembly?

Answer 6

because if ribosomes were to be completely assembled in the nucleus, there is an increased risk of them translating hnRNA before it gets spliced into mRNA.

Question 7

True or False: The ER lumen is isolated from the cytoplasm

Answer 7

True

Question 8

Nuclear pores can freely diffuse molecules

Answer 8

60

Question 9

where is the e- transport chain performed in mitochondria

Answer 9

the inner membrane

Question 10

is the inner membrane or outer membrane of the mitochondria impermeable to the free diffusion of polar substances?

Answer 10

the inner membrane: it must be impermeable to H+ in order to carry out the e- transport chain

Question 11

the space between the inner and outermembrane of the mitochondria is called the ________

Answer 11

intermembrane space

Question 12

How is mitochondrial DNA different from the cellular genome?

Answer 12

mitochondrial DNA more resembles prokaryotic DNA because it is circular DNA with it’s own genetic code. It also has its own unique RNA Pol, DNA replication machinery, ribosomes, and amino-acyl tRNA synthetases compared to the rest of the cell

Question 13

what is the endosymbiotic theory of mitochondrial evolution?

Answer 13

the theory that mitochondria originated as independent unicellular organisms living within larger cells

Question 14

mitochondria are only inherited from the _____

Answer 14

mother

Question 15

the rough ER translates proteins that are targeted from the ____ pathway

Answer 15

secretory

Question 16

function of smooth ER?

Answer 16

has enzymes that are involved in steroid hormone biosynthesis (gonads) and that degrade toxins (liver)

Question 17

What are the 4 destinations of proteins that are transcribed in the cytoplasm?

Answer 17

these proteins are headed toward peroxisomes, mitochondria, the nucleus, or will remain in the cytoplasm

Question 18

What are the main destinations of proteins synthesized in the RER?

Answer 18

proteins secreted into the extracellular environement, incorporated into the plasma membrane, ER, Golgi, or lysosomes,

Question 19

the secreted and lysosomal proteins (made in the RER) have a ___ sequence located at their N terminus, which binds to the _____ particle, forming a complex which can then bind to the ribosome for translation

Answer 19

signal sequence, signal recognition particle

Question 20

when the signal sequence binds to the signal recognition particle, followed by binding to the ribosome, this complex then docks onto a ____ receptor on the cytoplasmic surface of the RER

Answer 20

SRP (signal recognition particle) receptor

Question 21

When and where is the signal peptide (of secreted/lysosomal proteins) removed?

Answer 21

the signal peptide is removed in the RER lumen once translation of that peptide is complete

Question 22

integral membrane proteins have _____ domains, that are essentially signal sequences that are found on the interior of the protein. Are these domains hydrophilic or phobic, and are the located at the N terminus?

Answer 22

transmembrane domains

these domains are hydrophobic (being that they are found on the interior of the protein). because they are found on the interior of the protein, they are not located at the N terminus

Question 23

For a protein destined to integrate into the plasma membrane, the portion of that integral membrane protein that faces the extracellular environment is located in the ______ (ER lumen or cytoplasm) during translation in the RER

Answer 23

ER lumen

Question 24

The gogli and the ____ are responsible for post-translational protein modification

Answer 24

RER

Question 25

For secretory proteins that need to go the Golgi, ER, or lysosome contain ____ signals that help the protein go to those location instead of being excreted.

Answer 25

targeting signals

Question 26

proteins made in the cytoplasm but need to go to an organelle (hence, proteins that are not part of the secretory pathway) contain sequences called ____ signals to help direct them

Answer 26

localization

Question 27

Which proteins have a signal sequence?

Which proteins have transmembrane domains?

Which proteins have localization signals?

Answer 27

signal sequences: Proteins made in the RER/secretory pathway: excreted, plasma membrane, RER, Goli, lysosomes.

Only plasma membrane proteins have a transmembrane domain

localization signals: proteins made in the cytoplasm (with the exception of cytoplasmic proteins): perioxisomes, nucleus, mitochondria

Question 28

Which proteins have targeting signals?

Answer 28

proteins designated to the RER, Golgi, and lysosomes

note that these are all secretory pathway proteins, but of the secretory pathway proteins, excreted and plasma membrane proteins do not have these targeting signals

Question 29

glycolysis enzymes are translated in the _____ (cytoplasm or the RER)

Answer 29

cytoplasm because they are cytoplasmic proteins (note glycolysis occurs in the cytoplasm)

Question 30

where are histone proteines and proteins that make up DNA and RNA Polymerase synthesized?

Answer 30

in the cytoplasmic ribosomes

Question 31

Kreb cycle enzymes are proteins synthesized in the ______

Answer 31

cytoplasm

note that kreb cycle enzymes are destined to go to the mitochondria, and mitochondrial proteins are synthesized in the cytoplasmic ribosomes

Question 32

Where is catalase synthesized?

Answer 32

in the cytoplasmic ribosomes

note that catalase is a peroxisome enzyme

Question 33

The golgi has mostly a unidirectional pathway. What is the directionality of this pathway?

Answer 33

RER → cis Golgi → medial Golgi → trans Golgi

Question 34

In addition to modifying proteins, the Golig also synthesizes certain ____ to be secreted

Answer 34

macromolecules i.e polysaccharides

Question 35

distinguish between the constitutive secretory pathway and the regulated secretory pathway

Answer 35

constitutive secretory pathway refers to proteins that are sent in vesiscles from the Golgi immediately to the cell surface (they are not held and released at certain times)

the regulated secretory pathway refers to the proteins that are stored in the secretory vesicles and released only at certain times, usually in response to a change or signal from the environment

Question 36

Distinguish between the function of lysosomes and peroxisomes

Answer 36

lysosomes: degrade biological macromolecules (both intra and extracellular) via acid hydrolases. they perform autophagy, phagocytosis, and crinophagy (digestion of unneeded/excess secretory products)
peroxisomes: essential for lipid breakdown and contains catalse, which converts H₂O₂ into H₂O and O₂. In the liver they assist in detoxification of drugs and chemicals

Question 37

What does the lysosome do with the molecular building blocks once it breaks the macromolecules down via hydrolysis?

Answer 37

they will release the molecular building blocks into the cytoplasm for reuse

Question 38

why is it important that acid hydrolases in the lysosome only work at a low pH?

Answer 38

this is a protective mechanism so that if a lysosome bursts, their hydrolases won’t continue to degrade cellular components, as the cellular environment has a pH of slightly over 7, whereas the lysosome has a pH of 5

Question 39

Free FA form ____ whereas phospholipids form ____

Answer 39

FA = micelles

phospholipids = bilayers

Question 40

why do phospholipids form bilayers?

Answer 40

because its the lowest energy state for these molecules, as the hydrophobic components are conglomerated together away from the hydrophilic components

Question 41

What types of molecules can freely diffuse accross the plasma membrane?

Answer 41

small, nonpolar molecules i.e. CO₂, O₂, and steroid hormones

Question 42

Name whether the following will increase or decrease membrane fluidity:
1) saturated FA

2) unsaturated FA
3) cholesterol

Answer 42

1) decrease fluidity d/t increased van der Waals interactions
2) increase fluidity d/t decreased van der Waals
3) increased fluidity at cold temperatures (i.e. acts like antifreeze) and decreased fluidity at high temperatures

Question 43

What molecules do channel proteins allow to pass through the plasma membrane?

Answer 43

they selectively allow ions or molecules to cross the membrane

Question 44

integral plasma lipids and proteins are free to diffuse ____ (tranversely or laterally)

Answer 44

laterally

*they can only move in a 2D direction; they are not allowed to flip flop

Question 45

all glycosylations are found on the ____ of the plasma membrane

Answer 45

exterior

Question 46

some _____ are anchored to the cytoplasm and cannot move in any direction

Answer 46

proteins

Question 47

Equation for Molarity (M)

Answer 47

mol of sollute / #L of solution

⇒ M = mol/L

Question 48

Equation for molality (m)

Answer 48

molality = #mol solute / #kg of solvent

m = mol/kg

Question 49

which values can fluctuate with changes in temperature: molarity or molality. Why?

Answer 49

molarity can vary with changes in temperature because the volume of a solution can increase or decrease as temperature increases or decreases (assuming that pressure of the solution remains constant)

molality does not change with temp because it doesn’t involve volume. it involves mass

Question 50

Equation for mole fraction (X_S)

Answer 50

X_S = #mol of substance S / total # mol in solution

it expresses the fraction of moles of a given substance relative to the total amount of moles of solution. is used when >1 solute is present

Question 51

distinguish between strong, weak electrolytes, and nonelectrolytes

Answer 51

strong electrolytes are ions that dissociate completely in solvent

weak electrolytes are ions that do not dissociate completely in solvent; some remain ion paired to some extent

nonelectrolytes are covalent compounds that don’t dissociate into ions

Question 52

what is the van’t Hoff factor?

Answer 52

aka the ionizability factor: tells us how many ions one unit of substance will produce in a soltion

i.e. glucose (C₆H₁₂O₆) = 1

NaCl = 2

HNO₃ = 2

CaCl₂ = 3

Question 53

What are colligative properties?

Answer 53

refers to vapor pressure, BP, MP/FP, and osmotic pressure

Question 54

colligative properties depend on the ____ in the solution, not the ___ of the particle

Answer 54

depends on the number of solute particles, not the identity/type of particle

hence, colligative properties does not depend on the size, type, or charge of the solute particles

Question 55

will adding an ionic solute to a solvent increase or decrease the vapor pressure. Why?

Answer 55

it will decrease the vapor pressure because adding solute increases the intermolecular forces within the solution

Question 56

The boiling poing (BP) is the temperature at which the vapor pressure of the solution is equal to the ____ pressure over the solution

Answer 56

atmospheric

Question 57

if you add ionic solute to a solution, will it increase or decrease the BP?

Answer 57

it will increase the boiling point because there will be more molecular interactions and therefore more forces that need to be overcome to transition from liquid to gas state

Question 58

Equation for ∆T_b

Answer 58

∆T_b = k_bim

k_b = solvent’s BP elevation constant

i = van’t Hoff factor

m = molality concentration of solution

k_b ≈ 0.5C˚/m

Question 59

If you add ionic solute to a solvent, will in increase or decrease the FP/MP.

Answer 59

it will decrease the FP/MP

Question 60

Equation for ∆T_f

Question 61

Distinguish between diffusion and osmosis

Answer 61

diffusion refers to passage of solutes along their concentration gradient (high to low)

omosis refers to passage of solvent (H₂O), not solutes, across a semipermeable membrane (flows from areas of low solute concentration to high solute concentration)

Question 62

what is osmotic pressure?

Answer 62

the pressure it would take to stop osmosis from occuring

Question 63

equation for osmosis (Π)

Answer 63

Π = MiRT

M = molarity

i - van’t Hoff factor

R = universal gas constant = 0.0821 L·atm/K·mol

T = temp in Kelvins

Question 64

distinguish between simple and facilitated diffusion

Answer 64

simiple diffusion occurs without the help from an integral membrane protein

facilitated diffusion is a diffusion of a solute down its concentration gradient through an intergral membrane protein

Question 65

listed which type of signal/response the following channel proteins respond to:

voltage-gated ion channels

ligand-gated ion channels

Answer 65

voltage gated opens in response to a change in the electrical potential across the membrane

ligand-gated open in response to the bindingn of a specific molecules i.e. neurotransmitter

Question 66

can ion channels move ions against their concentration gradient?

Answer 66

no

Question 67

how to carrier proteins differ in their transport of molecules compared to ion channels?

Answer 67

carrier proteins don’t form a tunnel/channel; rather, they bind to the molecules being transported at one side of the membrane, which induces a conformational change of the carrier protein, causing the molecule to be transferred from one side of the membrane to the other

Question 68

distinguish between uniport, symport, and antiport carrier proteins

Answer 68

uniport: carry one molecule across the membrane
symport: carry >1 molecule across the membrane in the same direction
antiport: carry 2 molecules in opposite directions

Question 69

distinguish between a channel and a pore in a membrane

Answer 69

a channel is selective or which type of molecule it allows to pass

a pore is not selective, and will allow any molecule under a certain size from passing through the membrane

Question 70

what are porins?

Answer 70

they are the polypeptides that form pores

Question 71

does simple diffusion exhibit saturation kinetics?

Answer 71

no. it is only limited by surface area and the size of the driving force (gradient)

Question 72

does facilitated diffusion exhibit saturation kinetics?

Answer 72

yes. the increase in driving force will increase the flux (rate of diffusion), but only to a certain extent. Once all transport proteins become saturated, no further increase in flux is possible.

Question 73

Active transport is movement of solutes ____ their concentration gradient, which requires _____

Answer 73

against, energy

Question 74

Distinguish between primary and secondary active transport

Answer 74

primary: transport is coupled to ATP hydrolysis
secondary: transport is not directly r/t ATP hydrolysis; ATP is first used to create a gradient, then the potential energy in that gradient is used to drive the transport of some other molecules across the membrane i.e. the glucose/Na+ pump is connected to the Na+/K+ ATPase

Question 75

Na+/K+ ATPase:

1) How many Na+ ions does it pump and in which direction?
2) How many K+ ions does it pump and in which direction?
3) what is the purpose of the K+ leak channels?

Answer 75

1) 3 Na+ out of the cell
2) 2 K+ into the cell
3) allows movement of K+ down it’s concentration gradient (K+ flows out of the cell), which then creates an electrical potential accross the plasma membrane with a net negative charge on the interior of the cell (this is the resting membrane potential)

Question 76

What are the 3 main functions of Na+/K+ ATPase?

Answer 76

maintain osmotic balance between interior and exterior of cell

establish the resting membrane potential

provide Na+ concentration gradient used to drive secondary active transport

Question 77

where are the Na, K, and Cl concentrations highest, inside or outside the cell?

Answer 77

Na+ and Cl- are highest on outside of cell

K+ is highest on the inside of the cell

Question 78

Distinguish between phagocytosis, pinocytosis, and receptor-mediated endocytosis

Answer 78

phagocytosis: nonspecific uptake of large particulate matter into a phagocytic vesicle, which later merges with a lysosome. No invagination occurs with this process

Pinocytosis: nonspecific uptake of small molecules & extracellular fluid via invagination

Receptor-mediated endocytosis: very specific uptake of molecules. inside the cell are pits coated with clathrin, which are attached to receptors that bind to a specific molecule outside the cell. i.e. a lipoprotein that is carrying cholesterol binds to the exracellular receptor, the complex internalizes, and then taken into a vesicle that is termed an endosome, which gets taken to a lysosome for digestion.

Question 79

what is a ligand?

Answer 79

a molecule that serves as the key for a given receptor, which once bound will trigger a response within a cell via a process called signal transduction

Question 80

what is a catalytic receptor?

Answer 80

a receptor with an enzymatic active site, that once bound to it’s ligand, this enzymatic active site (which is present on the cytoplasmic side of the membrane) will carry out a catalytic role of an enzyme inside the cell i.e. protein kinase, which attaches phosphate groups to proteins, which then regulates that protein’s activity

Question 81

G-protein linked receptor:

1) ____ binds to G-protein receptor on extracellular surface
2) G-proteins (on cytoplasmic side of receptor), dissociate from ____ and bind to _____
3) the activated G protein then diffuses across the plasma membrane to activate ____

Answer 81

1) ligand
2) GDP, GTP
3) adenylyl cyclase

Question 82

In the G-protein receptor cascade, once adenylyl cyclase is activated, it makes ___ from ____.

Answer 82

cAMP from ATP

Question 83

Once cAMP is made in the G-protein cascade, cAMP activates ____ in the cytoplasm, which ____ certain enyzmes, with the end result being mobilization of energy

Answer 83

cAMP-dependent kinases, phosphorylates

Question 84

distinguish between G_s and G_i G receptor proteins

Answer 84

G_s refers to G protein activation that stimulates adenylyl cyclase (and increases production of cAMP)

G_i refers to G protein activation that inhibits adenylyl cyclase (and therefore decreases the production of cAMP)

Question 85

Some G protein linked receptors are not always associated with cAMP. Some activate ______, which ulitmately increases cytoplasmic Ca++ levels

Answer 85

phospholipase C

Question 86

Distinguish between microtubules, microfilaments, and intermediate filaments

Answer 86

microtubules: made of alpha tubulin and ß tubulin, which together form an alpha-ß tubulin dimer, which forms tubes. the tubes can be extended only from one end, with the other end attached to the MTOC (microtubule organizing center). *note the MTOC contains the centrioles (a ring of 9 microtubule triplets) essential to mototic divisions. microtubules also form cilia and flagella
microfilaments: made of globular protein called actin, which forms 2 chains wrapped around each other to form the filament. responsible for gross movement of the cell.

intermediate filaments are comprised of a variety of polypeptides (heterogenous); they provide strong cell structure and help to resist mechanical stress

Question 87

eukaryotic flagella are made of microtubules, which differs from prok. flagella in that euk flagella have a ____ arrangement

Answer 87

9+2 arrangement of microtubles

Question 88

Distinguish between tight-junctions, desmosomes, and gap junctions

Answer 88

tight-junctions: aka occluding junctions. they are bands between cells that block the flow of molecules across the entire cell layer and also block flow of molecules w/in the plane of the plasma membrane i.e. membrane proteins on apical surface of intestinal lining cannot transport laterally to basolateral surface of of the cell.

desmosomes: do not form a seal like tight-junctions, rather they are concise points that the plasma membranes between cells are anchored via a plaque called keratin. these points do not freely diffuse laterally across a plasma membrane; they are anchored in place by intermediate filaments of the cytoskeleton

gap junctions: form pore-like connections between adjacent cells, allowing passage of ions, AA, and carbs, but not polypeptides and organelles i.e. allow for membrane depolarization of an action potential in smooth and cardiac muscle

Question 89

In what phase of a cell cycle does DNA replication occur

Answer 89

S phase, which is in the interphase portion of a cell cycle

Question 90

when does the cleavage furrow form during mitosis?

Answer 90

during anaphase

Question 91

distinguish between sister chromatids and nonhomologous chromosomes

Answer 91

sister chromatids are identical copies of a chromosome, attached to each other by 1 centromere

nonhomologous chromosomes are equivalent but not identical and do not come anywhere near eachother during mitosis

Question 92

what is a karyotype?

Answer 92

a display of an orgnamism’s genome

Question 93

Distinguish between a protooncogene, and oncogene, and tumor suppressor genes

Answer 93

protooncogenes: normal versions of genes that allow for regular growth patters, but can be converted into oncogenes under the right circumstances (i.e. mutation or exposure to mutagen)
oncogene: mutated genes that induce cancer

tumor suppressor genes: code for proteins that prevent conversion of cells into CA cells. they detect damage to genome and halt cell growth and division until the damage can be repaired; or can trigger apoptosis if damage is too severe to fix i.e. p53 is a protein scaled up when genetic damage or oncogene is detected, & if repair is not possible, it induces apoptosis

Question 94

which enzymes are responsible for carrying out apoptosis?

Answer 94

caspases

Question 95

explain how initiator caspases and effector caspases work in apoptosis

Answer 95

initiator caspases will cluster together when they detect cellular death signals. Their clustering activates each other, which then activates effector caspases.

effector caspases cleave a variety of cellular proteins to trigger apoptosis

Question 96

what is oxidative stress?

Answer 96

occurs when levels of reactive O₂ species increase to the point where it outstrips the cell’s ability to detoxify them, ultimately generating free radicals and casuing damage to DNA, proteins, & lipid bilayers

Question 97

phagocytes may produce nitric oxide or superoxide to kill pathogens. hence, the immune system uses _____ stress to kill pathogens

Answer 97

oxidative

Question 98

what is regenerative capacity?

Answer 98

refers to an organisms ability to restore damage tissues and depends on stem cells w/in an organism i.e. newts can regrow their tails if chopped off, or multipotent stem cells w/in bone marrow regenerate blood and immune system

Question 99

what is senescence?

Answer 99

refers to biological aging, which can occur through shortening of telomeres throughout time, or can be caused by environmental exposures and behavioral factors

Question 100

distinguish between retrograde and anterograde

Answer 100

retrograde means moving in the backwards direction

anterograde means moving in the forwards direction