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•Suppose a protein in the nucleus of a cell is present at a concentration of 1 X 10-9 M (moles/L). How many molecules/nucleus if the nucleus has volume of 500 μm3 ?Recall that Avogadro’s Number is 6 X1023 molecules/mole, 1 L = 103 mL, 1 mL = 1 cm3, and 1 cm = 104 um.

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Irving Heathcote
Irving HeathcoteLv2
28 Oct 2019

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Related questions

Hello, I am doing homework and I am not sure if my answers are correct, can someone help me verify if I am doing this right or wrong? My responses are underneath the questions.

You are given a protein solution with a concentration of 0.25 mg/ml. Answer these questions.

A.) We need 20 µg for an experiment. What volume of the protein solution do we need?

Convert 20 μg and you will get 0.02 mg C = M/V rearrange for Volume V= M/C , V= (0.02 mg)/(0.25 mg/ ml) = 0.08 ml or 80 μl

B.) Suppose we want to prepare a solution containing 150 µg of the protein at a concentration of 0.50 mg/ml. To do this we will first dry down enough protein solution to get 150 µg. How much solution do we need to start with? How much H2O do we add to get the desired concentration?

You will convert 150 μg to 0.15 mg and divide by 0.25 mg/ ml to get 0.60 ml that needs to be dried down to obtain 0.5 mg/ml, then you will add enough water so that the total volume is 0.5 ml.

C.) If the protein has a M.W. = 15,000, express its initial concentration in moles/liter, in µmoles/ml and in µmoles/µl. If we want 2 µmoles for a reaction, what volume do we need?

Convert 0.25 mg/mL = 0.00025 g/mL = 0.00025 g/0.001 L = 0.25 g/L If M.W. of the protein is 15,000 g/mol then 0.25 g = 0.25/15,000 moles = 1.67 x 10^-5 moles. This many moles is contained in a liter (L) therefore concentration is 1.67 x 10^-5 moles/L = 1.67μmoles/L = 1.67 μmoles/1000 mL = 1.67 x 10^-3 μmoles/mL = 1.67 x 10^-3 μmoles/1000 μL = 1.67 x 10^-6 μmoles/μL. The concentration of the solution is 1.67 x 10^-6 μmoles/μL, 1 μmole is present in 1/(1.67 x 10^-6) μL and if 2 μmoles are present in 2/(1.67 x 10^-5) μL = 1.20 x 10^-5 μL = 1.20 L

D.) Suppose we want 1 ml of a 10 µg/ml solution. How much H2O and protein stock must we add to get this?

C1V1 = C2V2 (250 μg/ μl)(V1) = (10 µg/ml)(1ml) V1= 0.04 ml or 40 μl (Volume of protein stock for solution) Volume of water 1.0 ml- 0.04ml = 0.96 ml

E.) Suppose we want 100 µl of a 0.1 µg/µl solution. How much H2O and protein stock must we add to get this?

C1V1 = C2V2 (0.25 μg/ μl)(V1)= (0.1 μg/ μl)(100 μl) V1=40.0 μl (Volume of protein stock for solution) Volume of water 100 μl- 40.0 μl = 60.0 μl

Chemistry 1215 Experiment 5: Determination of Avogadro’s Number, Pre-lab Name ____________________________________________ 1. How many moles of stearic acid are contained in 0.25 mL of a hexane solution containing 5.4 X 10-4 g stearic acid/L? 2. How many nm2 are there in 20.0 cm2 ? 3. Calculate the surface area in nm2 of a water solution contained in a Petri Dish with a diameter of 9.0 cm. The area of a circle is calculated as A = πr 2 . 4. If a molecule of stearic acid covers an area of 0.21 nm2 , how many stearic acid molecules will it take to cover the surface of the Petri dish in question 3?

A fictional cubed-shaped bacterium, Bacterius cubis, occupies a volume of 2.3 femtoliters. This particular type of bacteria is known to communicate with its own species by secreting a small molecule called bactoX (MW = 116.0 g/mol). Answer the following questions regarding this bacterium.

A) Each bacterium contains 4.960 × 103 bactoX molecules that can be secreted. How many moles of bactoX are present in a 2.8-μL sample volume that contains 3682000 bacterial cells?

B) Calculate the molarity (mol/L) of bactoX in the 2.8-μL sample volume if all of the bacteria were to simultaneously secrete all of the bactoX molecules contained within their cell bodies into the vial.

C) Scientists discovered that bactoX will induce a luminescence response in B. cubis when the concentration in a sample reaches 5.00 × 10-12 M. How many molecules of bactoX must be present in solution to initiate luminescence in a 1.8-μL sample? How many individual bacteria cells does this represent (the number of bactoX molecules per cell is given in part A)?

D) What volume (in nanoliters) would the bacteria cells in part C occupy if tightly packed (assume there is no space between the cells)?

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