Exam 1 questions/concepts

Question 1

What are the nonpolar amino acids?

Answer 1

Alanine, Valine, Leucine, Isoleucine, Methionine, Phenylalanine (F), and Tryptophan (W).
- FILMWAV

Question 2

What are the polar uncharged amino acids?

Answer 2

Serine (S), Threonine (T), Glutamine (Q), Asparagine (N), and Tyrosine (Y).
- STQNY
(Stony with a Q)

Question 3

What are the polar charged amino acids?

Answer 3

Aspartic acid - (D), Glutamic acid - (E), Lysine + (K), Arginine + (R), and Histidine (H).

• DEKRH
• HERDK

Question 4

Is Phosphotidyl choline (PC) positive, neutral, or negative?

Answer 4

Neutral.

Question 5

Is phosphotidyl serine (PS) positive, neutral, or negative?

Answer 5

Negative

Question 6

Is phosphotidyl ethanolamine (PE) positive, neutral, or negative?

Answer 6

Neutral

Question 7

Is phosphotidyl inositol (PI) positive, neutral, or negative?

Answer 7

Negative

Question 8

What molecules experience simple diffusion?

Answer 8

1. Small gases (O2 and CO2)
2. Small polar molecules (H2O and Ethanol)
3. Large hydrophobic molecules (Estrogen)

Question 9

What molecules must go through active transport/facilitated diffusion?

Answer 9

Large polar molecules (glucose)
Charged molecules (amino acids, ions)

Question 10

What is unique to eukaryotes?

Answer 10

ER: Endoplasmic reticulum

Question 11

Amino acids buried inside the protein complex are likely _____.

Answer 11

Hydrophobic

Question 12

What is the major component of lipid droplets found in adipocytes (fat cells)?

Answer 12

Triglyceride

Question 13

How do non-transmembrane proteins associate with the plasma membrane?

Answer 13

1. Lipid-anchored proteins covalently bonded to a lipid group that resides within the membrane.
2. Peripheral proteins noncovalently bonded to polar head groups of the lipid bilayer.
3. Peripheral proteins noncovalently bonded to an integral membrane protein.

Question 14

Cells exposed to heat shock increase expression of chaperones. How, exactly, are these events linked?

Answer 14

Hsp70, a chaperone, binds to nascent polypeptides and aids in proper folding. When exposed to
heat shock, nascent polypeptides do not fold as easily and previously folded polypeptides begin to
denature. So, under conditions of heat shock, more chaperones are required and the previously
“extra” Hsp70 that had been bound to and sequestering Hsf1 is now required. Hsp70 releases from
Hsf1. Hsf1 trimerizes and acts as a transcription factor for the up-regulation of chaperones.

Question 15

What is mediated by a non covalent bond?

Answer 15

Stabilization of protein secondary structures.

Question 16

What is needed regarding protein folding in the cell?

Answer 16

A protein may require the assistance of both Hsp70 chaperones and chaperonins to
reach its native conformation.

Question 17

Which process is the slowest?
A. Phospholipid flex (rotating).
B. Lateral diffusion of phospholipids.
C. Transverse diffusion of phospholipids.
D. B and C are similar in speed.

Answer 17

C. Transverse diffusion of phospholipids

Question 18

What serves as an “eat-me” signal for the engulfment of dead cells by phagocytes?

Answer 18

Externalization of phosphatidylserine.

Question 19

What is a form of active transport?

Answer 19

Transport of glucose by Na+/glucose cotransporters.

Question 20

Briefly explain how neurotransmitters released from presynaptic terminals trigger action
potentials on postsynaptic membranes.

Answer 20

Neurotransmitters released from presynaptic terminals bind ligand-gated Na+ channels on
the post-synaptic membranes resulting in Na+ influx (into the cell). If depolarization is
sufficient, the action potential is triggered as the voltage-gated Na+ channels open.

Question 21

Detergents are commonly used to solubilize integral membrane proteins. Explain why.

Answer 21

Amphipathic detergents interact with membrane lipids to disrupt the membrane. The
hydrophobic transmembrane domains of integral membrane proteins (transmembrane
proteins) are stabilized by the hydrophobic regions of the detergent, and hydrophilic
regions interact with the aqueous environment, allowing the protein to be solubilized.

Question 22

Some strong detergents can also denature proteins (induce protein unfolding/misfolding). Explain
why.

Answer 22

Strong detergents are charged (as well as amphipathic) and they interfere with noncovalent
bonds in proteins (R-group interactions). This forces apart charged regions of the protein
and can even expose hydrophobic regions leading to misfolding.

Question 23

Glucocorticoids (hydrophobic molecules) is a type of hormone. In what manner does it interact with its target cell to elicit a cellular response. What is that response?

Answer 23

Glucocorticoids diffuse freely through the PM and interact with receptors inside the cell.
These receptors act as transcription factors (in the nucleus) to increase and/or decrease
expression of certain genes.

Question 24

Glutamates (amino acids) is a type of hormone. In what manner does it interact with its target cell to elicit a cellular response. What is that response?

Answer 24

Glutamates bind transmembrane receptor proteins externally and a signal is transduced
into the cell. Transcription factors will then be activated/repressed and the general response
of hormone binding will be to increase and/or decrease expression of certain genes.