Lab Exam 1

Question 1

Procedure and what Benedicts Assay Tested

Answer 1

• The presence of a reducing sugar by searching for carbonyl group in the chain form of a sugar
  
  • Not found in ring form as carbonyl group is lost due to bonds
  • Copper bydroxide was mixed in an alkaline pH and heated for 3 mins and tested for solubility; cloudy illustrates it was insoluble and therefore shows a reducing sugar as Copper hydroxide reduced is cuprous oxide which is insoluble in water

Question 1

Samples tested in Carbohydrate Experiment

Answer 1

• Glucose(reducing monosaccharide)
  • Fructose(Reducing Monosaccharide)
  • Galactose(Reducing Monosaccharide)
  • Lactose(reducing disaccharide)
  • Maltose(Reducing Disaccharide)
  • Sucrose(Non reducing disaccharide)
  • Starch(non-reducing disaccharide)

Water

Question 2

Procedure and what Barfords Assay Tested For:

Answer 2

• The presence of a monosaccharide

Copper hydroxide was mixed in an acidic pH where only monosaccharide reducing sugars can work; a positive reaction of slightly turbid or color change indicates a monosaccharide

Question 3

Procedure and what Iodine Assay Tested for:

Answer 3

• The presence of Starch

2 drops of Iodine was mixed with samples an interactions of the covalently linked coiled glucose units was watched; if interacts with coils it forms a blue black complex and if not remains yellowy

Question 4

Relationship between reducing sugars and type of sugar

Answer 4

All monosaccharides are reducing sugars, but not all disaccharides are reducing sugars

Question 5

Substances and Procedure in Biuret Assay

Answer 5

• Egg Albumin
  
  • Gelatin
  • Sucrose
  • Water

15 drop of biuret regent(copper sulfate in alkaline solution mixed in each solution with the goal of denaturing tertiary and secondary protein structure to highlight primary structure which exposes peptide bonds by causing the reagent to change to a violet color

Question 6

Substances in Lipid Tests

Answer 6

• Vegetable oil(lipid,
  
  • Olive oil(lipid)
  • Gelatin
  • Sucrose
    Water

Question 7

Procedure and What Miscibility Assay tested for:

Answer 7

• 3mL of mixture was mixed with 3mL of water and vigorously mixed

Looking for the hydrophobic/hydrophilic nature of substances: if substances did not mix, indicating they are hydrophobic and therefore a lipid

Question 8

Procedure and what Sudan Black Tested For

Answer 8

• 3mL of mixture and water were vigorously mixed
• 4 drops of Sudan black were added; as it is a hydrophobic it gets homogenously mixed with other hydrophobic substances; if the substance on top is stained black then it is hydrophobic

Question 9

Summary of Cellular Respiration Equation

Answer 9

Glucose + 6O2 -> 6 Co2 + 6H2O + energy(heat and 36-38 ATP)

Question 10

Procedure of Cellular Respiration Prac

Answer 10

• Prepared respirometers by adding an absorbent cotton ball at the bottom before adding 20 drops of 1m KOH
  
  • A non absorbent cotton ball was added on top before the subjects were placed inside
  • Cork was applied with inserted pipets before being placed in water baths
• Oxygen consumption was measured by water movement in respirometer away

Question 11

Purpose of KOH in CR

Answer 11

• Potassium hydroxide will react with Co2 to produce solid potassium carbonate which will remove all co2 produced during cellular respiration in order to accurately show how much O2 is being consumed
• As any gaseous volume change in respirometer is now due to O2

Question 12

Results of Cellular Respiration Prac

Answer 12

• Germinating peas had the highest rate of oxygen consumption compared to crickets but crickets had high metabolic rate as they produced more O2 relative to their weight
• Oxygen consumption in living things should show a linear positive trend

Question 13

Photosynthesis Equation

Answer 13

6CO2 + 12 H2O + light energy-> 2 C3H6O3 + 6O2 + 6H2O

Question 14

Purpose of Photosynthesis Lab

Answer 14

1. To examine the effect of light intensity(number of photons per time) on the rate of photosynthesis
2. To separate pigments of chloroplast extract from spinach leaves by paper chromatography
3. To then construct an absorption spectrum of chlorophyll solution using a spectrophotometer

Question 15

Experiment 1 Photosynthesis: Light Intensity Procedure and Results

Answer 15

• Placed 3 elodea algea leaves into a test tube and filled the rest with sodium bicarbonate(Co2 and water)
• Then placed it a stopper on top with a bent piece of glass tubing which as oxygen is produced, pushing the liquid further out of it.
• We placed the tube in front of a lamp with a level of watts and with a water beaker in between to regulate the amount of light energy being absorbed by the algae
• We measured the time it took for 0.1ml of oxygen to be produced before converting that time into the respiration rate for an hour.

The greater the light intensity, the greater the rate of respiration

Question 16

Experiment 2 Photosynthesis: paper chromotography procedure and results

Answer 16

• Cut a piece of paper about the length of the test tube, cut a triangle shape at the bottom, poked a thin hole at the top, and drew a mark above the triangle to mark a constant location
• Added 25 drops of chloroplast to the marked spot, blowing in between to let it dry,
• Then placed the tip of the triangle into the solution at the bottom for over 20 mins, letting the solvent move up the paper
• Once the solvent reaches the pigment, the pigment is dissolved by the moving solvent and carried up the paper based on their characteristics
• Once the solvent moved as high as it could we then drew marker points at points where each different color(pigment) reached its brightest and then measured the distance it travelled from the origin point
• We then calculated the Rf for each pigment which was dividing the distance it travelled by the total distance travelled by the solvent.

Order of distance travelled from furtherst to shortest:
- Carotenes
- Xanthrophylls
- Chlorophyl A
Chlorophyll B

Question 17

Experiment 3 Photosynthesis: Absorption Spectrum procedure and results

Answer 17

• We placed a chlorophyll pigment solution in a spectrophotometer which passed light of specific wavelengths through the solution to measure the degree of absorption by the pigment solution
• Before measuring the absorbance level at each wavelength, the spectrometer had to be calibrated with the B solution
• The absorbance was then measured, producing data seen in the tables

The resulting data produced a graph with two peaks at 420nm and 540-560nm. The greater peak being 420 nm