41

Chemistry / What is the water equivalent of blood glucose concentration?

« on: 07/09/2020 19:42:16 »

Hello

I put 1 gram of glucose in 1 litre of water to produce a concentration of 100mg/dl.

I used a regular blood glucose meter to measure the concentration and it showed a "too low" indication which is less than 20mg/dl.

Why this happened? What am I missing? I was hoping that I can use a blood glucose meter to measure glucose in drinks or other solutions but it seems not possible.

Also, what is the glucose concentration in a water solution that is equivalent to the blood glucose concentration of 100mg/dl?

Any idea?

Thanks

42

Chemistry / How can I adjust the pH?

« on: 04/09/2020 11:38:23 »

Hello

I have bought a buffer salt to add to a water container.

The pKa of the salt is 7.2. Does that mean that after I add the salt to the water, the pH will be 7.2?

If I want to adjust that pH, what materials can I use to do that? NaOH and HCl are dangerous so I want to use safer alternatives preferably something I can get from the supermarket like vinegar and baking soda.

Thanks!

43

Physics, Astronomy & Cosmology / What is the 3D shape with the maximum surface area?

« on: 26/08/2020 17:28:39 »

Hello

Two cylinders with the same volume but different radius, have the same surface area?

If not, how much is the difference between two 5mL cylinders with radius 10mm and 1mm?

44

Science Experiments / What is the right type and amount of buffer?

« on: 24/08/2020 14:29:13 »

Hello

I want to conduct an experiment with a chemical reaction that will take place in a neutral pH solution but it will produce 100mmol of protons.

What type and amount of buffer do I need to add to the solution so that the pH will stay the same?

If you can point me to a cheap buffer to buy online it would be best as my budget is limited.

Thanks!

45

Physiology & Medicine / Why artificial vascular grafts are not used in coronary bypass?

« on: 08/08/2020 14:18:00 »

Hello!

Why artificial vascular grafts are not used in coronary bypass?

Thanks!

46

Chemistry / Does enzyme immobilisation result in increase or decrease of reactivity?

« on: 06/08/2020 14:13:53 »

Hello

Does enzyme immobilisation result in increase or decrease of reactivity?

I find contradicting references.

Thanks

47

Physics, Astronomy & Cosmology / Are there liquid electrodes?

« on: 06/08/2020 13:52:47 »

Hello

When a molecule gets oxidised and loses an electron, is it possible for this electron to move in the solution and go to another molecule that will get reduced? Is it possible this move of electrons that will take place without an electrode?

If yes, how exactly? And is there a chance the electron gets lost in the wider solution and not be transferred to the reductant?

48

Physics, Astronomy & Cosmology / Is it possible to use low pressure to maintain flow?

« on: 06/08/2020 12:09:21 »

Hello

Let's say we have three chambers with pressure P1, P2, P3.

If P1<P2<P3, is it possible to maintain a flow from P2 to P3 using P1 assuming the pressures stay constant?

Thanks!

49

Physics, Astronomy & Cosmology / Are proton/hydroxide membranes permeable to hydrogen/oxygen/water?

« on: 04/08/2020 08:38:37 »

Hello

There seem to be many proton/hydroxide selective membranes but I am not sure how they work.

Do they block water/oxygen/dihydrogen and only allow protons/hydroxides or they allow all of these molecules to pass?

Thanks!

50

Chemistry / Can enzymes bind permanently substrates?

« on: 03/08/2020 19:50:50 »

Hello

I know that enzymes bind to substrates temporarily, they chemically convert them and they then release the product.

Is it possible that enzymes act as molecules that permanently bind substrates?

Any examples? Does this have any applications?

Thanks!

51

Physics, Astronomy & Cosmology / Is hydrogen burned when it is produced?

« on: 23/07/2020 13:33:53 »

Hello

Is it the case that when hydrogen is produced via electrolysis, the oxygen present burns some of that hydrogen produced?

If yes, how is this managed in real applications?

Thanks!

52

Physics, Astronomy & Cosmology / How is diffusion affected by the cross sectional area?

« on: 11/07/2020 10:27:02 »

Hello

I came across this interesting video:
Diffusion of two chemicals between two chambers attached with a narrow constriction

How is the time to equalise the concentration in the two chambers relates with the cross sectional area and the length of the connecting tube?

Thanks

53

Chemistry / What is the rate of concentration replenishment?

« on: 10/07/2020 19:20:35 »

Hello

I still have not been able to find out how to calculate the concentration replenishment when a catalytic particle converts the substrate of a solution.

What is the mass transport via diffusion that the catalytic particle receives assuming that the substrate concentration does not change in the solution?

This mass transport will determine the maximum theoretical reaction rate.

Thanks!

54

Chemistry / How fast do buffers work?

« on: 28/06/2020 00:00:03 »

Hello

When you have a buffered solution and you put a base or acid, does this become instantly neutralised by the buffer or you need to wait for it to diffuse into the whole solution and then become neutralised? In other words, how fast does the buffer react?

Thanks

55

Chemistry / What is the surface parameter in Fick's Law?

« on: 27/06/2020 23:56:37 »

Hello

With Fick's Law you get a result of moles per cm2 per second.

That cm2 unit of area is a geometrical/macroscopic or microscopic surface area?

The human intestine has a macroscopic length of 7m and perimeter 10-15cm. This means that it is about 1m2.

However due to the microscopic wrinkles its surface is 250m2.

Which area would you consider in Fick's Law? And what if the microscopic wrinkles are in the magnitude of nanometers?

Thanks!

56

Chemistry / What is the meaning of specificity constant kcat/KM?

« on: 26/06/2020 13:41:34 »

Hello

I do not understand what specificity constant kcat/KM represents.

Its units are e.g. 10/M*s

I cannot make sense of units like 1/M*s

Can anyone explain what that really represents please?

Is it 10 substrate 'conversions' per second when the substrate is at concentration of 1M ?

Or what exactly?

Thanks!

57

Physics, Astronomy & Cosmology / Is Coriolis force real?

« on: 26/06/2020 11:50:26 »

Hello

I am confused by Coriolis force.

Is it real? Does it really act on objects?

I read that it is not a real force however how can it then be a result of earth's movement onto objects and not be a real force?

The earth's movement exerts force on the objects on the planet and it supposedly creates and maintains their kinetic energy in respect to the earth's rotation.

Thanks!

58

Physiology & Medicine / How to convert LDL cholesterol concentration to LDL particle concentration?

« on: 26/06/2020 11:14:26 »

Hello!

Can you tell me please how to convert LDL cholesterol concentration values to LDL particle concentration values?

The regular LDL results we get from the lab denote the cholesterol grams per litre of the LDL proteins.

However, I want to know the amount of actual LDL particles that this value corresponds to.

Particularly the small LDL particles that pass through endothelium and cause atherosclerosis.

Thanks!

59

Physics, Astronomy & Cosmology / How to calculate the mass transport on an electrode?

« on: 25/06/2020 12:43:59 »

Hello

I want to calculate the mass transport via diffusion for an electrode.

This is the current density that can be achieved if diffusion replenishes the concentration of a solute that reacts on an electrode.

Can you describe the inputs that I need and the steps to calculate it?

I know the concentration of the solute in the solution and we can assume that this is stable.

I am struggling to apply Fick's law as I am not sure about the dφ/dx.

Thanks!

60

Physics, Astronomy & Cosmology / Are there materials that allow light to pass from one side?

« on: 21/06/2020 10:17:41 »

Hello!

Are there materials that allow light to pass from one side? And not the other?

Thanks!