Cell and Molecular Biology Exam 2

transcription and translation can be happening on the same mRNA molecule in ?

transcription and translation can be happening on the same mRNA molecule in ?

prokaryotes

5’ cap addition funcion

protects mRNA from nucleases

distinguish mRNA from other types of RNA

import for mRNA export

5’ cap definition

guanine molecule that is methylated attached to the 5’ end of RNA through 3 phosphate linkages

knockout

the use of genetic engineering to inactivate or remove one or more specific genes from an organism

Poly A Tail addition function

protects mRNA from nucleases

important for mRNA export

important for translation

allows for the isolation of mRNA in the lab

mRNA splicing function

allows for many proteins to be produced by 1 gene

important for mRNA export

mRNA splicing definition

removal of introns

What will happen if you do not have a 5’ cap?

the protein will be degraded

Where is the poly a tail added?

added to the 3’ end

what is an advantage of rna spilicing?

removing non coding regions and can make more than one protein from one singular gene

after the rna is processed where does it go?

exported from the nucleus into the cytosine through pores in the nuclear membrane

Histones

Can modulate how much RNA you can get from the DNA molecule

When gene regulation happens at the transcriptional level what are the two things involved?

transcriptional regulators

dna methylation

When gene regulation happens at the post transcriptional level what are the two things involved?

1. miRNA: micro RNAs

2. siRNA: small interferring RNAs

Epigenetics

the study of how behaviors and environment can cause changes that affect the way your genes work

epigenetic tags

physically record the cells experiences on the DNA, and stabilize gene expression

Do microRNAs get a 5’ cap and poly A tail?

Yes, because they leave the nucleus and go into the cytosol

they would not be able to be exported without it

Small interferring RNAs (siRNA)

protect cells from infections

Cell membranes 3 steps

1. selective barriers

2. cell communication import and export of molecules, motility

3. compartmentalize eukaryotic cells

What forms cell membranes?

lipids (lipid bilayer, barrier to water soluble molecules) + proteins

Role of plasma membranes

regulate what can enter and exit the cell

what is the most common phospholipid in cell membranes

phosphatidylcholine

true or false

All lipids have a hydrophilic head and hydrophobic tail

true

True or false

All lipids are amphipathic

True

Amphipathic

contain both hydrophobic and hydrophillic parts

Where does membrane assembly begin?

endoplasmic reticulum

Enzymes bound to the cytosolic monolayer of the ER membrane produce new phospholipids from _______ and insert them into the cytosolic monolayer

free fatty acids

Transporters called _____then randomly transfer phospholipid molecules from one monolayer to the other allowing the membrane to grow as a bilayer in which the two leaflets even out continuously in size and lipid composition

scramblases

Scramblase definition

catalyze transfer of random phospholipids from one monolayer to another

True or false

In the ER membrane, phospholipids are randomly distributed

True

Is the plasma membrane symmetric or asymmetric?

asymmetric

When membranes leave the ER and are incorporated in the Golgi, _____ selectively remove phosphatidylserine and phosphatidylethanolamine from the noncytosolic monolayer and flip them to the cytosolic side

fippases

Externalization of phosphatidylserine can be monitored by flow of cytometry using ?

annexin V

what is flow cytometry?

technology that rapidly analyzes single cells as they flow past multiple lasers while suspended in a buffer. Each cell is analyzed for the visible light scatter and one or multiple fluorescence parameters

What are two ways to analyze flow cytometry?

histogram or a contour plot

What carries out most membrane functions?

membrane proteins

Transporter example

Na⁺ pump

Na⁺ pump function

actively pumps Na⁺ out of cells and K⁺ in

Ion channel example

K⁺ leak channel

K⁺ leak channel function

allows K⁺ ions to leave cells thereby influencing cell excitability

Anchor example

integrins

Integrin function

link intrcellular actin filaments to extracellular matrix proteins

Receptor example

platelet derived groth factor (PDGF) receptor

platelet derived groth factor (PDGF) receptor function

catalyzes the production of the small intracellular signaling molecule cyclic AMP in response to extracellular signals

What are three ways transmembrane proteins can extend across the billayer?

single alpha helix

multiple alpha helixes

rolled up beta sheet

What are some membrane proteins anchored to the cytosolic half of the lipid bilayer by?

an amphipathic alpha helix

Other membrane proteins are linked to either side of the bilayer by ?

covalently attached lipid molecules

Many proteins are attached to the membrane only by relatively weak, noncovalent?

interactions with other membrane proteins

Animals exploit the phospholipid asymmetry of their plasma membrane to distinguish between live cells and dead ones. When animal cells undergo a form of programmed cell death called apoptosis, phosphatidylserine— a phospholipid that is normally confined to the cytosolic monolayer of the plasma membrane—rapidly translocates to the extracellular outer monolayer. The presence of phosphatidylserine on the cell surface serves as a signal that helps direct the rapid removal of the dead cell. How might a cell actively engineer this phospholipid redistribution?

(A) by inactivating a scramblase in the plasma membrane

(B) by inverting the existing plasma membrane

(C) by inactivating both a flippase and a scramblase in the plasma membrane

(D) by activating a scramblase and inactivating a flippase in the plasma membrane

(E) by boosting the activity of a flippase in the plasma membrane

D because scramblase active will give phosphate the chance to be translocated in the outer layer of the plasma membrane and the flippase being inactive will keep the phospholipid in the outer membrane

Can membrane proteins be solubilized in detergents?

Yes

The detergent disrupts the lipid bilayer and interacts with ?

the membrane hydrophobic portion

Triton X-100 is used for?

cell permeabilization

HeLa cells (epithelial cells) stained with anti-Ki-67 (cellular marker for proliferation) and CF®488A goat anti-mouse (green). Actin filaments were stained with CF®633 phalloidin (magenta)

What are HeLa cells?

cell line that can be used as a model

isolated from cervical cancer, human epithelial cells

first cell line

HeLa cells (epithelial cells) stained with anti-Ki-67 (cellular marker for proliferation) and CF®488A goat anti-mouse (green). Actin filaments were stained with CF®633 phalloidin (magenta)

In what species the primary antibody anti-Ki-67 was produced?

primary antibody was produced by mouse because the secondary is antimouse

HeLa cells (epithelial cells) stained with anti-Ki-67 (cellular marker for proliferation) and CF®488A goat anti-mouse (green). Actin filaments were stained with CF®633 phalloidin (magenta)

In what species the secondary CF488A was produced?

Goat

HeLa cells (epithelial cells) stained with anti-Ki-67 (cellular marker for proliferation) and CF®488A goat anti-mouse (green). Actin filaments were stained with CF®633 phalloidin (magenta)

Actin was stained with CF633 phalloidin. Is this an antibody?

Not an antibody because there is no anti in front of phalloidin

What is the cell surface coded with?

carbohydrate

Most membrane proteins have what linked to them?

oligosaccharides

ex: glycoproteins

other proteins have what linked to them?

polysaccharides

ex: proteglycans

Glycocalyx

the carbohydrate layer formed by glycoproteins, proteoglycans and glycolipids

What does the glycocalyx protect?

the cell surface from mechanical damage and is important in cell-cell recognition and adhesion

carbohydrates on _____ allow migration out of the blood into infected tissues

neutrophils

Lectins

transmembrane proteins in endothelial cells

What do lectins bind to in the neutrophil membrane?

oligosaccharides

Lectins to oligosaccharides are not very strong but it will lead to what?

another much stronger protein-protein interaction that helps the neutrophil slip between the endothelial cells

What are leucocytes?

white blood cells

Sodium ions, oxygen (O2), and glucose pass directly through lipid bilayers at dramatically different rates. Which of the following choices presents the correct order, from fastest to slowest?

(A) oxygen, glucose, sodium ions

(B) sodium ions, oxygen, glucose

(C) glucose, sodium ions, oxygen

(D) glucose, oxygen, sodium ions

(E) oxygen, sodium ions, glucose

A

What are lipid bilayers impermeable to?

ions and most uncharged polar molecules, all charged substances

The rate at which a solute crosses a protein-free artificial lipid bilayer by simple diffusion depends on?

size and solubility

The charges on these solutes and their strong electrical attraction to water molecules prevents what?

prevents them from crossing the membrane

Differences in ion concentrations are crucial for?

cells survival and function

For a cell to avoid being torn apart by electrical forces, the quantity of + charge inside the cell must be very different or similar to the quantity of the - charge

similar

Differences in the concentration of inorganic ions across a cell membrane create what?

a membrane potential

True or False

Although the electrical charges inside and outside the cell are generally kept in balance, tiny excesses of positive or negative charge can occur

True

Such electrical imbalances generate what across the membrane called the membrane potential?

voltage difference

resting membrane potential between -20 and -200 mv

voltage difference across the cell membrane in steady state conditions

What are the two classes of membrane transport proteins

transporters and channels

what does a channel form?

a pore across the bilayer through which specific molecules can diffuse- size and electric charge

True or false

Ion channels can exist in only a closed conformation and they transport only in the open conformation.

False

they can exist in bother an open or closed conformation

Channel opening and closing are usually controlled by ?

an external stimulus or by conditions within the cell

A transporter undergoes a series of conformational changes to transfer small solutes across ?

the lipid bilayer

Transporters are very selective for the solutes that they bind and they transfer them at much slower or faster rate than channels?

slower

Solute cross membranes by either passive or active transport?

Both

Both concentration gradient and membrane potential influence the passive transport of ?

charged solutes

Each cell membrane has its own characteristic set of ?

transporters

Conformational changes in a transporter mediate the passive transport of a solute such as?

glucose

The transition between the states occur randomly/ non randomly is completely reversible/irreversible and does not depend on whether the solute binding site is occupied?

randomly, reversible

If the solute concentration is higher on the outside of the bilayer, the solute will bind more often to the transporter in the outward open conformation than in the inward open conformation and there will be a net transport of ?

glucose down its concentration gradient

What are the 3 ways pumps carry out active transport in?

gradient driven pump, atp driven pump, and light driven pump

The Na⁺ pump uses energy of ATP hydrolysis to pump Na⁺ out of animals cells and K⁺ in or out?

in

Gradient-driven pumps

transfer solutes either in the same direction in which case they are called symports, or in opposite directions which are antiports

Two types of glucose transporters enable gut epthelial cells to transfer glucose across the ?

epithelial lining of the gut

The Na+-K+ATPase is also known as the Na+-K+pump. It is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration. What happens immediately after the pump hydrolyzes ATP?

(A) Na+ is bound

(B) ADP is bound

(C) The pump is phosphorylated

(D) The pump changes conformation

C

ATP molecules binds to the pump and the phosphorylation allows the conformation to be changed. So, phosphorylation has to happen first

Signal transduction

the process whereby one type of signal is converted into another

Cell signaling

mechanisms b which cells send signals and interpret the signals they receive

Receptors

Proteins that recognize and respond specifically to a signal molecule

can signals act over a long or short range?

yes

Extracellular signal molecules

proteins, peptides, amino acids, nucleotides, steroids, fatty acids, derivatives, and dissolved gases

hormones produced in _____ glands are secreted into the bloodstream and are distributed widely throughout the body

Endocrine