Name____________________ Lab Day/Time_________
Lab Partner’s Name____________________
Buffers Activity
Learning Objectives:
- Understand the role of buffers in homeostasis
- Observe effect of carbon dioxide on pH
- See the effect of pH on protein structure pH in the Body: Our bodies are extremely sensitive to shifts in pH. If the pH of our bodily fluids falls outside of 7.35 to 7.45 range, then our body will not function properly. Homeostasis is the term used to describe the process by which our body maintains a stable internal environment and pH is an important factor. Questions:
1. Is the pH of blood acidic, basic, or neutral? Briefly explain your reasoning. (2pts)
The pH is basic. Alkalinity or acidity of something is expressed in pH scale, which is number from 0 to 14 where acidity decreases from 0 to 6.9 and alkalinity increasing from 7.1 to 14. A pH of 7 shows the neutral part located at the center of scale. Therefore, blood having a pH scale of 7.35 to 7.45 is means that blood is slightly alkaline.
2. A patient has their blood drawn and the concentration of hydronium is found to be 5.01 x 10-8 M. Is this patient’s blood pH within the healthy range? Show your calculation. (2pts)
Kw = [H3O+][OH-], where Kw = 1.0 × 10-14 is a constant
At neutral, the concentration of both H3O+ and OH-
is 1.0 × 10-7 M
The concentration of OH- is;
= 2.0 × 10 -7
This means that, the concentration of OH- is greater than 1.0 × 10-7 M thus the blood is bases. For healthy person, the concentration of should be greater than 1.0 × 10-7 M.
3. Carbon dioxide, a product of metabolism, reacts with water to release protons. Complete the below chemical equation. (2pts)
___CO2__ (aq) + H2O (l) H2CO3 (aq) H+ (aq) + __HCO3-___ (aq) carbonic acid
4. In the titration lab, you used an indicator to see the change in pH when the end point was reached. In this experiment we will be using the indicator bromothymol blue to observe the effect of carbon dioxide on pH. This indicator is blue under basic conditions and yellow under acidic conditions.
a) Use a graduated cylinder to add 10mL of DI water to a 125mL Erlenmeyer flask.
b) Label the flask “water test”.
c) Add 10 drops of bromothymol blue indicator to the flask and record your observations.
d) Use a straw to gently bubble your breath through the water for about 1 minute. Do not drink the water or suck it up the straw! Record your observations.
Observations: (2pts)
When the bromothymol blue indicator is added to the flask with water, the solution changes colour from colourless to green.
When the breath is bubbled through the solution, for one minute, the colour of solution changes from green to yellow.
5. Did the water become acidic? Support your response with data. (2pts)
After bubbling breath in the solution, the water becomes acidic. this is because, animals and human being exhale CO2 which combines with water to form carbonic acid.
CO2(aq) + H2O (l) H2CO3 (aq)
Buffers in the Body:
Buffers are chemical mixtures that resist pH change when exposed to acids or bases. They contain both a weak proton donor and weak proton acceptor. The former neutralizes any strong bases added and the latter neutralizes any strong acids added to the buffer. Our bodies rely upon a combination of three different buffers to maintain stable pH: the bicarbonate buffer system, the phosphate buffer system and the protein buffer system. Although they involve different chemicals, all three systems function as discussed here.
Questions:
6. Bicarbonate buffer testing:
a) Use a graduated cylinder to add 10mL of DI water to a different 125mL Erlenmeyer flask.
b) Label the flask “bicarbonate test”.
c) Add a small amount of sodium bicarbonate to the flask (about the size of a pea) and swirl it around until dissolved.
d) Add 10 drops of bromothymol blue indicator to the flask and record your observations.
e) Use a straw to gently bubble your breath through the water for about 1 minute. Do not drink the water or suck it up the straw! Record your observations.
Observations: (2pts)
When drops of bromothymol blue indicator are added to the flask containing sodium bicarbonate solution, the solution turn into blue.
After bubbling the breath through the solution, the colour of the solution remain the same.
7. Did the combination of carbonic acid and bicarbonate function as a buffer? Support your response with data. (2pts)
Yes, the combination of carbonic acid that is from the breath and bicarbonate from sodium bicarbonate function like a buffer. Buffer controls the pH of the blood to remain in between 7.35 and 7.45. this is why the colour of the solution of sodium bicatbonate does not change after bubbling the breath through. When the pH of the sodium bicarbonate reaches 7.35, the bicarbonate ions (HCO3-) control the increase of the hydrogen ions (H+) which are responsible for acidity.
The chemical reaction below shows buffer system
CO2(aq) + H2O (l) H2CO3 (aq) H+ (aq) + HCO3-(aq)
Denaturation of Proteins:
The proteins in our bodies are composed of long, highly folded chains of amino acids. Protein shape is absolutely critical to protein function so changes in this folding reduce or stop protein function. Protein folding is delicate and can be disrupted by things such as temperature, presence of certain chemicals and changes in pH. This disruption of protein folding is known as denaturation.
Questions:
8. Observe the egg white that was exposed to acid at the start of lab note any changes. Do you think protein folding has been affected? Do you think protein function has been affected? Briefly explain your reasoning and support your response with data. Hint: Consider the signs of chemical reaction (2pts)
When the egg white is exposed to acid, the egg white changes from translucent to white. This means that the folding of the protein has been affected by causing the denaturing of protein in egg white. Therefore, the function of egg is also affected.
Denaturation of protein (lysine) by acid and bases
9. Our kidneys perform several critical functions for regulating blood pH including controlling the concentration of bicarbonate in our blood. When damaged, the kidneys can sometimes excrete too much bicarbonate in the urine.
a) Would blood pH increase or decrease if this happened? Would the blood become more basic or more acidic? Explain your reasoning (2pts)
The blood pH decreases thus blood becoming more acidic. this because, when the kidneys excrete too much bicarbonate in the urine, the level of bicarbonate in the blood decreases thus the concentration of acid increasing leading to decrease in Ph.
b) How might the proteins in our body be affected by our kidneys expelling too much bicarbonate? (2pts)
The bicarbonate is responsible of neutralizing the excess acidic during the folding of protein by acid. Therefore, when the kidneys expel a lot of bicarbonate, it result to unfolding of protein due to lack of enough bicarbonate to neutralize the excess acid.
