CrazCo

Hi,

I am confused on how the difference in pH and membrane potential of the inside of the cell and the outside of the cell is measured.

Specifically, how does using a lipophilic cation help measure membrane potential? and how does measuring the concentration of weak acids and bases on each side of the membrane help measure the pH?

Thanks!

Hi,

During the transpeptidation reaction in peptidoglycan biosynthesis when the peptides are cross-linked, is the terminal D-alanine lost [i.e. in E. coli when DAP forms a peptide bond with D-ala of the new disaccharide]? Or does the terminal D-alanine remain and is later cleaved by the carboxypeptidation reaction.

Essentially, I'm confused by the difference between transpeptidation and carboxypeptidation.

If someone could help me clear it up that'd be great!

Thanks!

There are only two resonance structures that don't involve an oxygen atom taking a +1 formal charge. Do electronegative elements enjoy being electron deficient?

My idea of resonance structures must be Wrong

As is the central atom with two (-O-H), one =O and one -O(-) off it.

That is the Lewis structure. Couldn't the (-) charge be on any oxygen, making a minimum of 4 resonance structures?

in H2AsO4-.

I figured it was four, but I am mistaken. Any pointers?

All the terms are confusing me. How do histones, nucleosomes, solenoids and looped domains all fit into DNA packaging?

:S:S

Yeah you've got it. But be careful with the terms strong and weak, something can only be truly strong if it dissociates into its constituent ions 100% in aqueous solution. So [ce]HCO_{3}^{-}[/ce] is technically not a strong base but it is a "stronger-weak base", same goes for [ce]F^{-}[/ce].

 

 

 

Here's a hint: [ce]HF[/ce] is one of the strongest of the common weak acids.

Thanks!

Does this look good?

Least to Most Basic: I-,F-, HCO3- LiH

Remember that the conjugate base of a weak acid is a strong base. Inversely, the conjugate base of a strong acid is a weak base.

 

-One of the bases you listed is the conjugate base of a very strong acid...that means that species is a very weak base.

 

-The conjugate acid of [ce]HCO_{3}^-^[/ce] is [ce]H_{2}CO_{3}[/ce] is that a strong acid, a weak acid, or a "stronger-weak" acid?

 

-One of the species you listed yields a quite basic metal hydroxide in aqueous solution. Think about the Arrhenius definition of a base.

 

-You could always look up a table of [math]pK_{a}[/math] values if you know what those are.

Thanks!

So hydrofluoric acid is a weak acid, therefore F- is a strong base!

Hydroiodic is a strong acid, therefore I- is a weak base!

Carbonic acid is a weak acid, therefore HCO3- is a strong base!

I am not sure about LiH, but I don't know how to determine whether HF is weaker or stronger than HCO3-

HCO3-, F-, I- and LiH.

I do not know how to approach it.

I could guess, but I have no method of finding this.

i don't know how to answer this without going to the lab!

1. What is a benefit and one disadvantage of observing bacteria in Yogurt using a live whole mount compared to a Gram stain slide?

cholesterol (adjusts fluidity)

integral

peripheral

transmembrane protein

proteins

chains [glycoproteins]

makes absolutely zero sense to me how a misfolded protein without any instruction from nucleic acid can infect cells. can someone help?

http://fya.dal.ca/Files/science.pdf

At least at Dalhousie it appears as if I don't need to take any physics for a major in biology.

Biology. I just wanted to not take any physics ever again!

i took hard courses, i just hated physics, for some reason i could never grasp it.

anyways thank you for re-assuring me!

So by not taking physics in my senior year there is no way that alone will impact me in being accepted into the B.Sc program? Thank the Lord!

I heard schools often give you the option to take different classes. Like instead of physics you can take say.. Earth Sciences or Geology. I hope Dal is like this.

I asked my teachers and they weren't sure, and Google is giving me mixed results. I was going to call the University I wish to attend but they aren't available during this time - and I need to know for Monday. I took eleventh grade physics but didn't take 12th grade. I am worried I will need it to go for my B.Sc. Is it required?

I have taken Chemistry, Biology and Environmental science to the highest levels possible.

Thanks

And I guess I should also inquire if you wish to pursue be awarded a Bachelor of Science do you need to take any physics classes?

cusp = limit is a different finite number from both sides

corner = limit is a infinity from one side and negative infinity from the other

i think it's a cusp because when you derive it you get

y = x^2 - |x-4|

y=x^2 + x - 4

y= x^2 -x + 4

y' = 2x+1

y'= 2x-1

as it approaches 4

y' = 9

y' = 7

im lost..

i know, but i think im doing it wrong because it looks completely continuous but apparently it has a corner meaning it has a different limit from each side at x=4

we have to use algebra

thank you, i now understand

Merged post follows:

is there such thing as chlorine channels in the neural membrane? and is the concentration greater on the inside or outside of it when we're talking about chlorine ions. i am thinking if one binded to a chlorine receptor depending on which side is more concentrated it would diffuse and cause it to either be excited or depressed? is this true

y = x^2 - abs(x-4)

at x = 4 how do i tell if it has a discontinuity, cusp, vertical tangent or corner using algebra

im soooo lost.

je t'aime

That doesn't make sense at all, they're opposite :S

i heard that estrogen and progesterone virutally prevent other hormones, lh / gnrh, etc.. from being produced. i don't see the benefits, why is this so needed