Cell Bio Liam Hendrikse

Front 1

Why do we study cultured cells, rather than studying actual living cells from a live organism?

Back 1

Two reasons: Allows strict control over conditions, and its inefficient to repeatedly take cells from the host being studied. Remember also "Hypothesis driven experiments."

Front 2

What is the difference between studying cells in vivo and in vitro?

Back 2

In vivo refers to studying cells that are part of a whole, live organisms. In vitro refers to the study of cells in culture.

Front 3

Describe the reason why and method that cell clusters are dissociated into single cells prior to culturing.

Back 3

Cells clusters from sampled tissues need to be broken down to allow better growth and observability (remember the goal is to observe effects on single cells). This is achieved using trypsin to cut adhesion proteins, EDTA which acts as a metal ion (Ca 2+) sponge, absorbing the key cofactors for adhesion proteins, and mechanical fragmentation.

Front 4

What are 3 common nutrients in nutrient cell culture?

Back 4

Amino acids, mineral's, vitamins, salts, and glucose.

Front 5

In addition to the various nutrients which are added to create an effective cell culture fluid, _____________ containing ____________ and _____________ are added and the culture is incubated at 37℃ in a carbon dioxide incubator.

Back 5

Serum containing insulin, transferrin and growth factors. Insulin promotes the movement of glucose into the cell, transferrin promotes the movement of iron into the cell.

Front 6

What are the two main types of cell cultures?

Back 6

Adherent or suspension cell cultures.

Front 7

Most animal cells contain cell-surface proteins called cell-adhesion molecules (CAM's), these proteins are used to bind to components of the ECM and cause the cells to form monolayer's of interconnected cells. Bacterial and yeast cells do not have these proteins. Suggest an implication of this associated with growing animal cells in culture.

Back 7

Animal cells generally only grow attached to a solid surface (adherent culture required), whereas bacterial and yeast cells can be grown in a suspension culture.

Front 8

Phenol red is the compound that gives cell cultures the red colour, and is frequently used in cell biology labs. What does it do?

Back 8

Phenol red is a pH indicator. It becomes yellow at pH 6.8, and purple at pH 8.2.

Front 9

What is the Hayflick limit and what implications does it have on cell culturing?

Back 9

The Hayflick limit is the maximum number of times a human primary cell culture will divide before it stops. The limit has led to the development and use of cell line cultures when studying cell biology. Transformed (tumour) cells can replicate indefinitely making them attractive to use in labs for study.

Front 10

What would happen if you accidentally ate HeLa cells?

Back 10

HeLa cells are cancer cells used commonly to create cell line cultures. They came from Henrietta Lacks' cervical cancer. Your stomach acid would likely destroy these cells and nothing would happen.

Front 11

You are studying a culture of cells, and you observe that the cells appear to be growing on top of each other! What are your conclusions?

Back 11

These cells must be transformed cells that do not exhibit contact inhibition. Contact inhibition is the growth mechanism which limits the growth of normal cells to forming a monolayer of cells.

Front 12

Symmetric division of a stem cell leads to:

a) Differentiation of the stem cell, in which the larger cell is the functional cell, and the smaller cell undergoes cell death.

b) Differentiation of the stem cell, in which the larger cell is the functional cell, and both cell undergoes cell death.

c) Renewal of the stem cell

d) Renewal of the stem cell and cell death

Back 12

d) Renewal of the stem cell and cell death

Front 13

The Inner Cell Mass, used for culturing embryonic stem cells, is isolated by micro- pipetting from which of the following:

a) Cell mass

b) Blastocyst

c) Zygote

d) Compacted Morula

Back 13

b) Blastocyst

Front 14

Why is the isolated inner cell mass cultured with fibroblast feeding cells.

Back 14

The feeder cells nourish the embryonic stem cells by providing them with protein hormones.

Front 15

What are the functions of Oct4, Sox2 and Nanog?

Back 15

They are all transcription factors that bind to the promoters of themselves and each other creating a positive auto regulatory loop leading to self renewal of ES cells. In other words, they activate genes for self -renewal (pluripotency) and repress genes that induce differentiation pathways.

Front 16

True or False: The correct direction of cell migration is from the stem-cell niche to the proliferation zone, to the differentiation zone.

Back 16

True.

Front 17

What is required to revert mature cells into induced pluripotent stem (iPS) cells?

Back 17

Induce Oct4, Sox2, Klf4 and often c-Myc (oncogene). This will turn off the differentiation pathway and turn on self-renewal genes.

Front 18

Why are cancer stem cells (CSC's) a bigger problem than regular cancer cells?

Back 18

CSC's, like stem cells, can differentiate into all cells types, greatly contributing to metastasis. As well CSC's self renew like stem cells.

Front 19

What piece of the modern compound microscope is indicated by each of the coloured arrows? What are these pieces functions?

Back 19

Red arrow: Eye piece (ocular lens, focus light onto the eye)

Blue arrow: Objective Lens (Collect light an magnify)

Green Arrow: Stage (Hold the specimen plate )

Orange Arrow: Condenser (Focus light from light source onto specimen)

Front 20

What is required for an object to be observable by a light microscope?

Back 20

High refractive index.

Front 21

Define resolution.

Back 21

The ability to determine the difference between two close objects as separate identities.

Front 22

Sapphire has a refractive index of 1.762-1.778, while glass has a refractive index of 1.50-1.54. To achieve better resolution which material should be used to observe the specimen through?

Back 22

Sapphire. D = 0.61ƛ / N sin ⍺. Increasing value of N decreases D which is distance resolved between two points.

Front 23

Cellular constituents have refractive properties which slows the passage of light through them. The waves leaving the specimen may be out of phase, causing interference, and looking darker. If the nucleus slows the wavelength by 1/4 𝛌, the mitochondrion slows the wavelength by 1/8 𝛌 and the ribosomes slow by 1/16 𝛌, which organelle will appear the darkest?

Back 23

The nucleus, as it slows the wavelength the most leading to the highest amount of wave interference.

Front 24

What feature of light does phase contrast microscopy rely on to enhance an image?

Back 24

Light wave interference.

Front 25

Which of the following are all parts of the phase contrast microscope?:

a) Phase plate, condenser lens, polariser

b) Phase plate, annular diaphragm, polariser

c) Phase plate, annular diaphragm, condenser lens

d) Lamp, condenser lens, emission filter

Back 25

c) Phase plate, annular diaphragm, condenser lens

Front 26

What key advantage does phase contrast microscopy and differential interference contrast microscopy have over using fluorescence microscopy?

Back 26

Can be used to image live cells, fluorescence microscopy requires the cells be fixed.

Front 27

Mickey is trying to study features of the cell membrane of some animal cells he found. He is using a phase contrast microscope. Liam says Mickey should be using DIC microscopy. Who is right?

Back 27

Liam, DIC microscopy provides a better image of the cell membrane and outlines of organelles, whereas phase contrast microscopy highlights organelles within the cell.

Front 28

What are molecules that can emit visible light following absorption of another wavelength of light?

Back 28

Fluorophores.

Front 29

What is Stoke's shift?

Back 29

The difference in wavelength between the excitation and emission spectra for a particular fluorophore.

Front 30

What is the function of a dichroic mirror?

Back 30

The dichroic mirror is very selectively reflective. Reflecting only a specific wavelength and allowing other wavelengths to pass through it with no reflection.

Front 31

Considering all the steps from translation to arrival in the lysosome for a lysosomal enzyme, how many individual steps require the use of GTP

Back 31

3 steps. GTP is used by SRP and the SRP receptor in the cotranslational translocation of a protein in the secretory pathway. GTP is used to remove the COPII coat proteins following formation of the vesicle for anterograde transport to the cis-golgi. GTP is used to remove the clathrin from a clathrin coated vesicle (and COPI), not mentioned in lecture but the textbook confirms this. UDP is used to attach M6P to the enzyme. ATP is used to unwind the SNARE proteins.

Front 32

How many GTP molecules are consumed in transporting a protein into the mitochondria matrix?

Back 32

None, ATP is used, exact number is irrelevant. BITCHHHHHHHHH!!!!!

Front 33

Mickey got a sweet summer job working in a research lab, experimenting on some very rare cells! He accidentally drop these cells into a cup of deionized water, why is his boss pissed?

Back 33

Dropping cells in a hypotonic solution will cause an influx of water into the cell and lyse them. You just destroyed some very rare cells.

Front 34

Sodium dodecyl sulfate (SDS) is an anionic detergent, it disrupts membranes and denatures proteins by disrupting non-covalent bonds. With that in mind, what else should be included in the SDS-PAGE solution to ensure complete denaturation of any protein?

Back 34

A reducing agent to disrupt all the disulfide bonds.

Front 35

The DXE signal sequence (di-acidic) is found on _________, and is recognized by __________. The KDEL signal sequence is found on __________, and is recognized by ___________. The KKXX signal sequence is found on __________, and is recognized by ____________.

Back 35

The DXE signal sequence (di-acidic) is found on ER-resident membrane proteins, and is recognized by COPII coat proteins. The KDEL signal sequence is found on ER-reseident enzymes, and is recognized by the KDEL receptors. The KKXX signal sequence is found on KDEL receptors, and is recognized by COPI coat proteins.

Front 36

A cell has a mutation that causes dolichol carriers to be synthesized incorrectly and therefore not functional. What are possible consequences of this mutation?

Back 36

The dolichol carrier is required to attach oligosaccharides to newly translated proteins (via oligosaccharyl transferase). Therefore glycosylation will not function in the ER and this will negatively affect protein folding and ability of the protein to adhere to other proteins.

Front 37

The lumen of the ER is hydrophilic. While proteins are being translated into the lumen, hydrophobic regions of the polypeptide chain tend to aggregate together (and even with other hydrophobic regions on different polypeptides), which can cause misfolding. What protein ensures this does not occur and how does it work?

Back 37

BiP. BiP binds to exposed hydrophobic regions to prevent them from binding to other hydrophobic regions.

Front 38

Proteins are imported into the mitochondrial matrix by going through TIM and TOM's donut holes. What is the space between TIM and TOM called?

Back 38

Contact site.

Front 39

Importation of proteins the the mitochondrial matrix is an example of _______________, whereas importation of proteins the ER is an example of _________________.

Back 39

Translocation, cotranslational translocation.

Front 40

True or False: The order of locations for a secreted protein is ER -> medial golgi -> cis golgi

-> trans golgi -> trans golgi network -> secretion.

Back 40

False. ER -> cis golgi -> medial golgi

-> trans golgi -> trans golgi network -> secretion.

Front 41

True or False: The golgi apparatus is connected to the ER.

Back 41

False.

Front 42

What feature of the KDEL receptor allows it to bind a KDEL sequence in the cis golgi?

Back 42

The KDEL receptor binds KDEL sequences in the golgi due to lower pH that in the ER. Once the KDEL receptor is back in the ER it releases the KDEL sequence due to higher pH.

Front 43

AP1 is associated with vesicles made from the ___________, whereas AP2 is associated with vesicles made from the _____________.

Back 43

AP1 is associated with vesicles made from the trans-golgi network, whereas AP2 is associated with vesicles made from the plasma membrane. (Think of it in order we learned about it)

Front 44

Binding of an M6P signal to the M6P signal receptor causes the recruitment of which of the following:

a) AP1

b) AP2

c) AP1 and clathrin triskellions

d) AP2 and clathrin triskellions

e) COP1 coat proteins

f) COP2 coat proteins

Back 44

c) AP1 and clathrin triskellions

Front 45

What causes M6P to unbind from M6P receptors in the late endosome?

Back 45

Low pH.

Front 46

I-cell disease is caused by lacking an important enzyme associated with vesicle trafficking. What enzyme is absent in people with I-cell disease?

Back 46

GlcNAc phosphotransferase.

Front 47

The absence of GlcNAc phosphotransferase in I-cell disease means M6P is not attached to lysosomal enzymes. Without this sorting signal, where do the enzymes end up?

a) Lysosome

b) Proteosome

c) ER

d) Remain in the TGN

e) Secreted out of the cell

Back 47

e) Secreted outside of the cell

Front 48

Retrograde transport can occur between the cis-golgi and the ER. Can retrograde transport occur between the trans-golgi network and other levels of the golgi apparatus?

Back 48

Yes.