L5. SACCHARIDES PROPERTIES

INTRODUCTION:

On monday, we lerned more about saccharides. This are organic molecules consisting of C, H and O atoms. And are divided in three groups:

- Monosaccharides: Formed by a linear carbon chain, are the building blocks of oligo and polisaccharides. They have a one functional group: cetone or aldehyde. Pentoses and hexoses can swith from acyciclic to cyclic forms called furanoses and pyranoses. Like fructose, glucose or galactose.

- Oligosaccharides: Small polymer containing between 2 and 10 monosaccharides. Like lactose, sucrose or maltose.

- Polysaccharides: big polymers with more tan 10 monosaccharides. Like starch, glycogen, cellulose and chitin.

This molecules give diferent functions in the organisms, energy (starch, glicogen), and structural components (cellulose, ribose, chitin and desoxiribose).

Saccharides yield 4,2 Kcal/gr and are abundant in fruits, sweets, honey... They are a common source of energy in living organisms.

Our objectives in thes case were identify different sugars from its properties, differentiate mono and disaccharides and understand the relation between structure and some properties. 

MATERIALS:

- Test tube rack

- 10mL pipet

- Distilled water

- 5 test tubes

- 1 dropper

- 5 spatula

- Clock glass

- Lactose

- Maltose

- Glucose

- Sucrose

- Starch

- Lugol's iodine

PROCEDURE:

	GLUCOSE (G)	MALTOSE (M)	SUCROSE (SU)	LACTOSE (L)	STARCH (S)
Flavour	Sweet	Sweet	Sweet	No sweet	No sweet
Crystaline form	Crystalline	No crystalline	Crystalline	No crystalline	No crystalline
Colour	White	White	White	White	Cream
Solubility	Soluble	Soluble	Soluble	Soluble	Insoluble
Lugol's iodine	-	-	-	-	+

In the first part of the experiment we tested some phisycal properties of the saccharides: flavour, cristal structure and colour. How?

1. Flavour: Put small amunt of each saccharide in your hand and taste it! it can be sweet or not.
2. Crystals: Observe a small amount of each saccharide on clock glass under magnification.
3. Colour: White, transparent or creamy.

To test solubility:

1. Clean and dry 5 test tubes and label them "G, M, L, SU, S"
2. Put 5mL of water in each test tube.
3. With the aid of a spatula, put small amount of each saccharide inside the labelled test tube and test if they are soluble or insoluble.
4. Observe if each saccharide forms a misture called dissolution or coloidal suspension.

Lugol's iodine test:

Finally, add 2 drops of lugol's iodine to each test tube and test if the reaction is positive or negative. Lugol's is a solution of a elemental iodine (I) and potassium iodine (KI) in water that is use to test a saccharide. The reaction is positive when iodine reactss by turning from yellow to purple, dark-blue/black colour.

RESULTS AND CONCLUSIONS:

We can see that lactose is a disaccharide that don't have sweet flavour. The starch have a cream colour, it's insoluble and it's positive with the Lugol's iodine test because is the only polysaccharide of the experiment. The rest of the saccharides are disaccharides. 

QUESTIONS:

1.- Write the empirical formula of each saccharide that you have use. Show structures of the five saccharides. Classify each one in one group: mono, oligo or polysaccharide.

G: C6H12O6 - monosaccharide.

M: C12H22O11 - oligosaccharide.

SU: C12H22O11 - oligosaccharide.

L: C12H22O11 - oligosaccharide.

S: C6H10O5 - polisaccharide.

2.- Which of the monosaccharides are aldoses and which are ketoses?

ALDOSES: glucose, maltose, lactose, starch.

KETOSES: sucrose.

3.- Which bond links monosaccharides?

Oligosaccharides.

4.- Which saccharide/s is/are sweet? Is this property related to the structure of the molecule?

Glucose, maltose, sucrose

5.- Which saccharide/s is/are soluble? Is this property related to the structure of the molecule?

Starch, It's a big molecule, it have a high molecular weight and is relacionated with the structure.

6.- Which saccharide has reacted with Lugol's iodine solution?

Starch

7.- Which kind of foods contains starch?

Cereals, pasta, rice, legums...                             

8.- Calculate the energy from the nutrition facts labelfrom a cereal

• Calculate the energy that comes from the saccharides.

23gr saccharides

4,2 Kcal => 1g

23x4,2= 96.6Kcal

L4. pH

INTRODUCTION:

The pH is a quantitatively measure to degree of acidity and basicity in a solution. A solution with pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline. Pure water (distilled water) has a pH close to 7, this solution is neutral. 

The equation of pH is this:

                            

pH= -log (H + )

For measuring the pH of a solution at the lab we have different pH indicators:

1. Universal indicator paper: It's an absorbent paper that has been impregnated with universal indicator. This method consists as from about pH 2 to pH 10. 
2. pH-meter: Is an electronic device used for measuring he exact pH af a solution. It consists of a glass electrode connected to an electronic meter that measures and displays de pH reading. 

We made this experiment because this week we studied the dissolutions and dispersions in biology class. The objectives were: measure different pH values of organic and inorganic solutions and prove different methods of measuring pH.

MATERIALS:

- Distilled water

- Milk

- Wine

- Lemon

- Tomato

- Coffee

- Carbonated beverage

- 10% NaOH solution

- 10% HCl solution

- NH3 solution

- Soap solution

- Universal indicator paper (strips)

- pH-meter

- Acetic Acid

- Tongs

- 8 x 100 mL Beakers

- 2 Clock glass

- 1 x 250 mL Beaker

- 5 tests tubes

- test tube rack

- 10 mL pipet

- Funnel

- Graduated Cylinder

PROCEDURE:

To measure de pH of different solutions we are going to put the different solutions in small beakers of 250 mL.

1. Squeeze the lemon and tomato in two clock glasses.
2. Take a pice of indicator paper and place one end of it into the soution. Leave for at least 20 seconds.
3. Remove the indicator paper and compare its colour with the appropriate colour chart. 
4. Repeat points 1 to 2 with as many others solutions as you are provided with.
5. Record your results.

How does concentration affect pH?

Squeeze the rest of the lemon inside a beaker and filter the solution with a funnel and cellulose paper. 

1. Prepare a test tub track with 5 tests tubes cleaned with distilled water. Mark the tubes with the labels: A, A1, A2, A3 and B.
2. Add 10 mL of lemon juice to tubes A and B.
3. Take the A tube and put 5mL of its lemon juice to test tube A1.
4. Take the A1 tube and put 2,5 mL of its lemon juice to tube A2.
5. Take the A2 tube and put 1,2 mL of its lemon juice to tube A3.
6. Add distilled water to each test tube until it has the same volume as test tube B (10 mL).
7. Calculate the concentration of each test tube with the formula you have below

                - Concentration (%)= ( Volume of Juice/ Total Volume) x 100

• Find the pH of the test tube:

TEST	VOLUME OF	TOTAL	CONCENTRATION	pH
B	10 mL	10 mL	100%	3,38
A1	2,5 mL	10 mL	25%	3,37
A2	1,25 mL	10 mL	12’5 %	3,33
A3
A	5 mL	10 mL	50%	3,35

RESULTS AND CONCLUSIONS:

We measure the pH of different substances, and we observed that if the pH was acid the color of the indicator, was red, pink, orange, yellow. LIke the HCl (pH=1) or the wine (ph=3) the tomato (pH=4) and vinegar (pH=2) and the milk that present a neutral- acid pH (pH=6-7) are acid too.

And if the substance present a basic pH, the color of the indicator was more blue and purple like the soap (pH=10), the bleach, that present an a high pH (pH=12-14) and NaOH (pH=14). 
And in a neutral pH is when this solution have pH of seven, the color is more green and this substances present the same number of H+ and oH-, like the distilled water. 

Then we do an other experiment with the lemon juice, with  tubs (A,A1, A2, A3, B) we do a different concentrations of lemon juice and distilled water and with the pH- meter we can calculate, measure the exact pH of the solution. We can see the results in the above table. With this results we can confirm that the lemon juice are acid. It shows a high concentration of hydrogen ions.

QUESTIONS:

1.- Which of the solutions gave an acid pH?

HCl, vinegar, wine, tomato, coffee and milk.

2.- Which of the solutions was alkaline?

Soap, bleach and NaOH.

3.- Which of the solutions were neutral? Did you expect this results? Explain.

Distilled water, because it has the same concentration of H+ and OH, and thats why we expect that water is with a pH neutral.  

                                                                                                  

4.- How does a pH of 3 differ from pH of 4 in terms of H+ concentrations?
10 times large value.

5.- In the second part of the experiment, you have compared the pH of the same product (lemon juice) in different concentrations. In this case explain:

• Which is the dependent variable? The pH.
• Which is the independent variable?The concentration of lemon juice.
• Which is the problem that we want to solve? The problem that we want to solve is equalize the concentrations.
• Which is the control of the experiment? The control is the test B.
• Write the results and conclusions of your experiment: The pH is very similar on the all concentrations, but the normal is that the pH depends of the protons concentrations. 

6.- Which pH do you think that gastric juices might have? Why? Do you think that intestinal pH has the same pH? Why?
They have an acid pH because its used to improve food digestion. I think that all intestinal pH are acid.

7.- Which pH do you think that blood might have? Why?
The blood have an neutral pH, because if is hypotonic the cell bloat, if is an hypertonic the cell crease. The pH causes it to keep the concentration, because we could die.

8.- What is acid rain? Which are the consequences in the ecosystems and how is its formation pattern? Is rain Barcelona acid or alkaline?

The acid rain is a phenomenon, that have a pH levels lower than normal. Is mainly due to the mixture of water with molecular products of sulfur and nitrogen in the combustion incurred, such as nitrous oxide NO2, NO3 nitric oxide or sulfur dioxide SO2 which when combined with the water generated nitrous acid HNO2, HNO3 nitric acid and sulfuric acid H2SO4. 
Acid rain can have harmful effects on plants, animals and buildings. Causes corrosion of metal structures such as bridges or erosions in stone buildings. It also burns the leaves of vegetation and ecosystems it affects mainly vegetables, such as forests, but can also affect lakes and reservoirs acidifying them.
In Barcelona this rain, is alkaline. 

L3. OSMOSIS

INTRODUCTION:

We do an osmosis experiment to know about the osmosis phenomena, that is the spontaneous movement of solvent molecules through a semipermeable membrane into a region of higher solute concentration in the direction that tends to equalize the solute concentrations on the two sides. Now, we understand the process of osmosis in plasmatic membranes. The membranes are semipermeable. The water travel through the plasma membrane in order to the intra and extra cellular concentrations. The important of this practice, is to know when it produce hypertonic concentration that becomes  the plasmolysis, the water moves out to the cell, and hypotonic concentration, that becomes turgid, because the water moves inside the cell. 

MATERIALS:

- Egg

- Potato

- Salt

- Distilled water

- Acetic acid

- Spatula

- 600 mL Beaker

- 3 Clock glass

- Pen

- Spoon

- Knife

PROCEDURE:

EGG: 

The experiment is divided in two parts:  

1). 
We watch that under the hard outer shell of a chicken egg, there is a semipermeable membrane that allows air and moisture to pass throgh. Because water molecules can move into and out of the egg but larger molecules cannot, the semipermeable egg membrane allows for an exploration of concepts of diffusion and osmosis. 

- Before the egg osmosis experiment could begin, the egg's hard outer shell must be removed. Let's start with this:

• Take a 600mL beaker and put inside the egg. And we wait a few minutes to dissolve the shell.  
• Cover the egg with vinegar and make note of what's happening, remembering our experiment of last week.

Once the egg's shell is removed and the egg is rinsed dry and clean, measure and weigh the egg. Record the dimensions off each egg on the paper sheet on the table.

• Clean the beaker and put the egg inside again
• Cover with distilled water. Make note of the volume of solution inside the beaker.

2).

• Left the egg one day in the distilled water. After about a day, carefully remove the egg using a spoon. Rise the egg with water and let it dry.
• Measure again the dimensions and record its weight.
• Make note of the solution volume in the beaker and notice if there has been any difference.
• Observe the results and write your conclusions. 

POTATO:

•  Lay out three watch glass
•  Slice the potato in three parts lengthwise. Each slice must be 1,5cm thick
•  Place each slice onto a watch glass and make a hole in the middle of each slice. (the hole doesn't have to cross the slice).
• In the first hole, don't put anything. In the second one fill it with salt and in the third, put distilled water
• left this preparation 30 minutes approximately, and make note of what is happening.

RESULTS AND CONCLUSIONS:

In our first experiment, with the egg we have observed that when we put the egg with acetic acid the shell that was covering the egg, would undoing. the egg with distilled water bloat, the water is directed toward the semipermeable membrane of the egg. The egg with the pass of the days it becomes viscous. At the end, the dimension of the egg increased for the hypotonic concentration. 

FInally our hypothesis of the last experiment that we made with potatoes, we thought that in the firs slice, with nothing in the hole, there would be no reaction. In the second one, with salt the potato will be flaccid, because the water inside will go out because the potato is a hypotonic and the salt is a hypertonic. And the potato with distilled water, it becomes turgid. In this case the potato it's a hypertonic and the water hypotonic. The objective is to compare the appearance and the turgid of the slices.

QUESTIONS:

EGG EXPERIMENT:

1.- What is happeningwhen the shells are soaking of acetic acid? 
(Ca(CH3COOH)2) and CO2 are produced. This makes bubbles loss.

2.- Write the results of the dimensions and weigh of the egg before and after immersing it in distilled water. Write and draw a simple diagram of the water direction.
Before: 156'0g
after: 186'0g

POTATO EXPERIMENT:

3.- Explain the results of the experiment.

In the first potato was nothing so there have been no changes. 
In the second one we put salt, we can observe that the water  that is inside of the potato has gone out. The cell of the potato has become flaccid. 
In the third one we put distilled water, this water have been disappear and the cell become turgid. 

4.- Why have we left the first slice without any treatment ( salt or distilled water)?
To compare all the results. 

5.- Which are the dependent and independent variables?
The independent variable, we can modify, i mean are the potato with salt and the potato with distilled water.
The dependent isn't modify. 

GENERAL QUESTIONS:

6.- How can you explain (through osmosis) the ability of plant roots to draw water from the soil?
Plants are made up of water and the salt concentration is higher, the water is directed where it is found in the highest concentration of salt.

7.- What will it happen if a saltwater fish is placed in a fresh water (low concentration of salts) aquarium?
It will die. 

8.- Look at the image you have below and explain what is happening to the erythrocytes in each situation:

1. PLASMOLYZED (hypertonic)
2. ISOTONIC (flaccid)
3. TURGID (hypotonic)