Cell Biology

Question 1

which organelles in a eukaryotic cell contain 2 membranes surrounding them

Answer 1

nucleus (called nuclear envelope) and mitochondria

Question 2

What is the RER and what is it’s function. how is it different from SER

Answer 2

RER: rough endoplasmic reticulum: location of synthesis and/or modification of secretory, membrane-bound and organelle proteins. aka packaging station

SER: smooth endoplasmic reticulum: site of detoxification and glycogen breakdown in liver.

Question 3

role of golgi apparatus

Answer 3

sorting and traficking station:

modification of proteins made in RER

sorting of proteins to their correct destinations.

Question 4

peroxisomes degrade what type of macromolecule?

Answer 4

lipids

Question 5

T/F: all of the proteins that enter the secretory pathway contain an ER signal sequence, generally at the N-terminus

Answer 5

true

Question 6

Flowchart of secretory vs non secretory pretien pathways and their signals

Answer 6

Question 7

can a secretory protein be modified during its travel to the PM or lysozome

Answer 7

no, proteins in the secretory pathway are inaccessible to cytoplasmic proteases

Question 8

splicing occurs in nucleus or cytoplasm

Answer 8

nucleus

Question 9

Match the type of organism to the main component in its membrane:

fungi

bacteria

plants

peptidoclygan

titin

cellulose

Answer 9

fungi: titin
bacteria: peptidoglycan
cellulose: plants

Question 10

fluid mosaic model refers to

Answer 10

called fluid because its components are free to move back and forth laterally like a fluid. cannot flip upside down though. only exception is those proteins anchored to cytoskeleton

called mosaic because it is comprised of a variety of components

Question 11

which has greater membrane fluidity and why?

1. phospholipid bilayer composed more of saturated fatty acids
2. phospholipid bilayer composed of more unsaturated fatty acids

Answer 11

unsaturated because the kinks allowing for less van der walls forces allowing more proteins and gases to pass freely within it

Question 12

the ionizability factor (aka van’t Hoff factor) measures what?

Answer 12

how many ions that one unit of a substance will produce in a solution when it dissociates where 1= no ions.

e.g. C₆H₁₂O₆ won’t dissociate so i=1

NaCl will make Na+ and Cl-, so i=2

Question 13

colligative properties refers to:

Answer 13

a property of a solvent that is changed with the addition of a solute where the change is dependent on the number of solute particles rather than on the type of particle.

Question 14

what is vapor pressure and the colligative property of vapor-pressure depression

Answer 14

it is the pressure exerted by the gaseous phase of a liquid that evaporated from the exposed surface of the liquid

volatility : higher the vapor pressure : the more easily it evaporates : the weaker its intermolecular forces

so, when you add a solute, this strengthens the intermolecular forces of the solvent because the solute molecules are attached to solvent molecules > lower vapor pressure

Question 15

what effect does a solute have on the boiling point of a solvent and why?

Answer 15

elevates it (colligative property)

because solutes are attached to solvent particles, making it more difficult for them to break free during boiling (entry into gas phase)

the increase in boiling point : increase in number of solutes

Question 16

what effect does solute have on the freezing point of a solution and why?

Answer 16

depresses it (colligative property)

this occurs because when things freeze, they form solid orderly lattices. solutes disrupt the formation of solid lattices so freezing point is more difficult to acheive and will occur further along the freezing process (ie lower temperature)

increase number of solutes : decrease freezing point

Question 17

osmotic pressure is defined as

Answer 17

the pressure it would take to stop osmosis from occurring. I.e the pressure that must be overcome by solvent in order to move towards concentration equiliubrium

Question 18

diffusion vs osmosis

Answer 18

diffusion refers to any type of movement to fill an available volume in such a way that entropy is increased. Osmosis is a subgroup of diffusion in which the membrane separating the 2 chambers is semipermeable (only permeable to water, not solute)

Question 19

what characteristic allows steroid hormonse to move freely back and forth across the membrane

Answer 19

hydrophobicity

Question 20

T/F: the eukaryotic plasma membrane does not have any pores

Answer 20

true.

this would destroy its function. they exist in the nuclear membrane, the outer mitochondrial membrane, and gram-negative bacterial membrane

Question 21

how do the kinetics of simple diffusion differ from that of facilitated diffusion?

Answer 21

since facilitated diffusion depends on carrier/channel proteins, which are limited in number so they reach saturation

Question 22

how is primary active transport coupled with secondary active transport?

Answer 22

primary active transport uses ATP to fuel transport of molecules against their concentration gradient. This ends up creating a electrochemical gradient. the flow of a molecule along its electrochemical gradient is then coupled with transport of a molecule that must travel against its concentration gradeint

e.g. Na/K pump and glucose transport

Question 23

T/F: when the Na/K pump breaks down and water is drawn into the cell

Answer 23

true, because the net result of the pump is to get 1 positive ion out, thus if this breaks down, that solute particle will stay in the inside and therefore water will move into the cell by the rules of osmosis

Question 24

flowchart of transport mechanisms in cell

Answer 24

Question 25

what is the fate of particles ingested in cell by phagocytosis

Answer 25

they will be fused with lysosome and therefore broken down

Question 26

T/F: clathrin can recognize and bind to lipoproteins

Answer 26

false - it’s on the intracellular side and because a coat on the outside of the endosome

Question 27

clathrin coated pits famously transport what type of macromolecule

Answer 27

large lipoproteins

e.g. cholesterol

Question 28

receptor mediated endocytosis is associated with what protein?

Answer 28

clathrin

it helps sequester cargo and supports proper budding of endosome

Question 29

ligand-gated ion channels open an ion channel upon binding a ______

Answer 29

neurotransmitter ligand

most common example: acetylcholine binds to a receptor, allowing Na+ entry into the cell which rapidly depolarizes it

Question 30

An enzyme-linked receptor, also known as a catalytic receptor, is a transmembrane receptor, where the binding of an extracellular ligand causes

Answer 30

enzymatic activity on the intracellular side. Hence a catalytic receptor is an integral membrane protein possessing both enzymatic catalytic and receptor functions.

e.g. kinase (eg insulin receptor) that phosphorylates a protein to activate it.

Question 31

a kinase _________ a the proteins 1_____, 2______, and 3_____

Answer 31

phosphorylates

1. serine
2. threonine
3. tyrosine

Question 32

all G-protein linked receptors binds a G-protein which binds ___________

Answer 32

GTP, which actives the G protein allowing it to move to activate the next molecule in the signal transduction cascade

Question 33

T/F: a G-protein linked receptor can be inhibitory or excitatory

Answer 33

true