Final - Midterm 2

Question 1

how to manipulate differential centrifugation that results in the largest particles forming a pellet first

Answer 1

an initial slow centrifuge spin for a short amount of time

Question 2

when viewing cells on a microscope, what happens when the wavelength of light hitting the cells on a slide is decreased:

Answer 2

the resolution of the cells is increased

Question 3

microsomes:

Answer 3

the small vesicles that are formed when cells are homogenized, the ER is fragmented and self seals

Question 4

what are 4 parts of the endomembrane system

Answer 4

• lysosomes
• rough ER
• smooth ER
• golgi complex

Question 5

constitutive secretion:

Answer 5

production and transport of materials in secretory vesicles which occurs continuously

Question 6

cell-free system:

Answer 6

studies of cell physiology that occur in test tubes that do not contain whole cells

Question 7

what determines the function of a cell’s smooth ER

Answer 7

protein content

Question 8

autophagy:

Answer 8

the process responsible for organelle turnover in the cell and for the carrying out of regulated destruction of the cell’s own organelles for the purpose of recycling the components of which they are made

Question 9

cisternal maturation model:

Answer 9

suggests that the golgi cisternae are transient structures that form at the cis face of the stack by fusion of membranous carriers from the ER and that each cisterna travels through the golgi complex from the cis to the trans end of the stack, changing in conformation as it progresses

Question 10

what takes place in the golgi apparatus

Answer 10

• O-linked glycosylation
• post-translational processing of the Oligosaccharide precursor
• sorting for transport to other sites in the cell

Question 11

using genetic engineering techniques, which of the following would you do to a protein that is normally constitutively secreted to make it accumulate in the ER

Answer 11

add a KDEL sequence to its C-terminus

Question 12

fusion of late endosomes containing intralumenal vesicles with a lysosome leads to:

Answer 12

the degradation of the contents of late endosomes by lysosomal endosomes

Question 13

clathrin:

Answer 13

is a protein that coats vesicles that contain lysosomal enzymes as they are transported from the TGN

Question 14

if newly synthesized lysosomal acid hydrolases are secreted from the cells rather than being delivered to the lysosomes, what is the most likely reason:

Answer 14

phosphorylated mannose is not added in the cis golgi network

Question 15

which molecules do that AP2 adaptors in a clathrin coat complex connect

Answer 15

the cytoplasmic tails of specific membrane receptors and clathrin molecules

Question 16

carbohydrate chains attached to integral membrane proteins are thought to shield:

Answer 16

lysosomal membranes against attack by their enclosed enzymes

Question 17

substances the enter the cell by receptors-mediated endocytosis bind receptors that collect in specialized domains of the plasma membrane called:

Answer 17

coated pits

Question 18

in an otherwise normally functioning cell, the what impact would the absence of clathrin have on the LDL receptor

Answer 18

would inhibit internalization of the LDL receptor

Question 19

what are the differences between ribosomes that make secretory proteins and those that make proteins intended for the cytosol

Answer 19

there are no differences

Question 20

what effect does the binding of the SRP to the growing polypeptide chain and the ribosome have on protein synthesis

Answer 20

protein synthesis ceases temporarily

Question 21

how do integral membrane proteins enter the lipid bilayer

Answer 21

the translocan channel has a gate that continuously opens and closes, giving each nascent polypeptide segment a chance to partition itself into the lipid bilayer’s hydrophobic core

Question 22

to what residue of a polypeptide are N-linked oligosaccharide chains attached as that polypeptide enters the RER lumen through the translocan

Answer 22

asparagine

Question 23

what happens if the unfolded protein response (UPR) is unsuccessful in relieving the stressful conditions in the cell

Answer 23

apoptosis is triggered and the cell is destroyed

Question 24

proteasomes:

Answer 24

responsible for destroying misfolded proteins in the cytoplasm

Question 25

with respect to proteins that are synthesized in the cytosol but then must be imported into the mitochondrial matrix:

Answer 25

• they must be unfolded
• they will transit through two import complexes
• they will have a signal sequence that directs them to mitochondria

Question 26

what would happen to the movement of vesicles toward their eventual target if a microtubule inhibitor like colchicine were added to the cells

Answer 26

vesicle movement would slow or stop

Question 27

vesicles move along microtubules by attaching to microtubules via

Answer 27

motor proteins

Question 28

noncovalent interactions:

Answer 28

are thought to hold microtubular structure together

Question 29

in cell biology with respect to microtubules, the term ‘dynamic’ means:

Answer 29

ever-changing in structure

Question 30

hydrolysis of ATP:

Answer 30

is the direct source of energy that powers molecular motors