Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Be smart!
Should I believe all that the advertisements say?
Student’s Version
Table of Contents
Activity 1: Do you require a high protein diet?
P.1
Activity 2: How much protein doesa food product contain?
P.4
Activity 3: Incredible food: Soy (soya) Protein - What does the
advertisement say?
P.8
Appendix 1: Advertisements for extension activity
P.12
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Activity 1
Do you require a high protein diet?
What kind of diet do you need?
Do you require protein supplements? There are many
protein products on the market. Below are the
advertisementsfor two of them:
Source﹕Volleyball Association
of Hong Kong, China
Ad 1
“… the most useful protein supplement ever, it enlarges
every muscle that you want it to… contains the best
quality nutrients, it facilitates protein uptake after
exercise and improves muscle strength, you will
certainly love it ”
Ad 2
P.1
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Q1 Which kinds of people may need the products?
Q2 Why is protein so important to our bodies?
Q3 Those people who want to add volume to their muscles (get larger muscles)
usually eat a high-protein diet or consume protein supplements like the one
in Ad 1. Can all protein consumed be stored in the body for muscle
building? Are there any other factors that could contribute to increasing
muscle size?
P.2
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Q4 Some protein supplements like the product in Ad2 target at vegetarians.
Do you think vegetarians especially need the product or other protein
supplements? Explain.
P.3
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Activity 2
How much protein does a food product contain?
From activity 1, we learnt that some people do require more protein in their diet for various
reasons. However, news reports on health problems caused by low-quality milk are not
uncommon. So, even though you are sure that you need protein supplements, you have to
make sure that the products contain the right amount of proteins that you are looking for.
Imagine that you have just bought a milk product. You want to check if the milk product
contains the same amount of protein as specified on its food label.
Below are two methods for testing protein. Read the information carefully and choose one
which is best suited for the above purpose. Explain your choice. (If necessary, your
teacher may describe the methods to you in greater details using the PowerPoint slides.)
General
information
Detection limit
P.4
Biuret test
Albustix paper
Biuret reagent is a blue solution.
It reacts with protein to give a
purple solution. The intensity of
the purple colour is proportional
to the protein concentration.
Albustix paper is used for testing
the presence of protein in urine.
The paper contains an indicator
dye. At a constant pH, protein
reacts with the dye giving a
green-blue colour. The colour is
proportional to the concentration
of protein.
0.2 – 50 µg
0.15 - 20 g/L
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Biuret test
1. Prepare a set of standard
1.
solutions (0, 2, 4, 6, 8 mg/ml)
by using bovine (cattle) serum 2.
albumin.
2. Pipette 1 ml standard solution (8 3.
mg/ml) to a test-tube containing
2 ml Biuret solution.
4.
3. Repeat the above step for the
Testing procedure
Albustix paper
Dip the Albustix paper into a
solution of the test sample.
Remove excess liquid from the
test paper.
Wait for 60 seconds for the test
paper to dry
Match the colour of the test
paper with those on the standard
rest of the standard solutions
colour chart found on the bottle.
and the test sample.
5. Protein concentration of the
4. Mix the contents inside each of
sample is estimated by
the tubes well. Wait for 15
comparing the colour of the
minutes.
paper with the colour chart
5. The intensity of the purple
provided on the bottle of
colour of the contents inside
Albustix paper.
each of the tubes is determined
by measuring the amount of
light transmitted through the
solution using a colorimeter.
6. A standard curve is plotted with \
light transmittance versus
concentration of protein.
7. Protein concentration of the test
sample can then be determined
from the standard curve after
obtaining the light transmittance
value from the calorimeter.
Limitations
P.5
It is only applicable to soluble
proteins and colourless solution.
The Albustix test is only a
semi-quantitative method. The
result is only an estimated value
since the colour chart provides
only the test results of certain
protein
concentrations.
The
concentration between two values
cannot be measured.
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Discuss the criteria for a scientist to choose a test method.
Which test will you choose to estimate the protein content in the milk product? Explain your
choice below.
Science-Technology-Society
Albustix paper is used for testing the presence of protein in
urine. Normally, urine contains no protein but kidney diseases
may result in the presence of protein in urine. The invention of
the Albustix paper has provided a convenient assay for doctors
to measure protein in urine. People can even perform the test at
home. So, science and technology are affecting our lives!
Science is ever improving
Scientists have developed many methods to determine
protein concentration accurately e.g. the Kjeldahl method,
and the Bradford Assay. Scientists often try to improve their
methods of investigation. They improve or develop new
techniques to get more reliable and accurate results.
P.6
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Having decided on which test you will be using to estimate the protein content of the milk
product, now work out the detailed procedure in the space below to show how you are going
to estimate if the milk product contains the same amount of proteins as specified on its food
label. (Hint: Dilution of the milk product may be required.)
Now, try to estimate the protein content in the milk product! Is it the same as stated in the
food label?
P.7
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Activity 3
Incredible food: Soy (soya) Protein - What does the
advertisement say?
Soya has been one of the most popular foods in Asia (China and Japan) and is said to be a
good protein source for vegetarians. The proteins in Soya have been investigated for many
years for benefits to health apart from muscle building. Recently, a new food supplement
made from Soya has been produced. Advertisements in a local newspaper are shown below.
(The brand name is covered.)
Optional exercise:
People talk about different kinds of cholesterols. Do you know about them? Are all
cholesterols bad? Find it out from the following website!
http://www.bbc.co.uk/health/conditions/cholesterol1.shtml (English)(Last visited on 2/3/2006)
http://www.healthcare2u.com/cd_chole.html (Chinese) (Last visited on 2/3/2006)
P.8
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Let’s take a look into the suggestions by U.S. Food and Drug Administration (FDA)
about soy protein!
The Soy Health Claim – 1999
In October 1999, FDA approved a health claim that can be used on labels of soy-based 1
foods to support their healthy-heart benefits. The agency reviewed research from 27
studies that showed soy protein's value in lowering levels of total cholesterol and
low-density lipoprotein (LDL, or "bad" cholesterol).
Food marketers can now use the following claim, or a reasonable variation, on their 5
products: "Diets low in saturated fat and cholesterol that include 25 grams of soy
protein a day may reduce the risk of heart disease.”
Foods made with the whole soybean, such as tofu, may qualify for the claim if they
have no fat other than that present naturally in the whole bean.
Q1 Does the FDA allow the health claims made in the advertisement for the product?
Is soy protein so
Q2 What evidence did the FDA use to decide on approving
the health claim?
incredible?
Now, look at the following statement about the effects of soy protein.
Soy protein shows little effect on "bad" cholesterol - 2006
News
Soy protein in the diet or from nutritional supplements has little or no effect on the risk
factors for heart disease, according to a new American Heart Association scientific
1
statement published in 2006.
After analyzing 22 studies, it is found that large amounts of soy protein in the diet
reduced low-density lipoproteins (LDL) or “bad cholesterol” by only 3 percent and had
no effect on high-density lipoproteins (HDL), or “good cholesterol”, no effect on
lipoprotein or blood pressure.
In a statement released in the year 2000, adding soy protein to a diet low in saturated fat
and cholesterol was recommended. However, the statement is re-evaluated after the
recent, well-controlled studies, noted above were added to the knowledge base.
P.9
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
5
10
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Q3 Compare the statements made by the FDA and the American Heart Association. Why has
the knowledge about the health effects of soy protein been re-evaluated?
Q4 This kind of change is common in the scientific world. Can you name another scientific
knowledge/theory that has ever changed?
Q5 Soy is regarded as a healthier source of protein than meat since it contains little or no
cholesterol. But are there any drawbacks from eating so much soy? Think!
-
P.10
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Extension activity: Are advertisements about food products always true?
Many health products, just as that in activity 3, have made a number of health claims. Are
they really true? How can you verify the claims?
You are scientists working for the Consumer Council. Your task is to design an investigation
to assess the health claims made by the products. Present the design of your investigation to
the class. In your presentation, include possible problems and limitations of the design.
(Technical procedures are not required.)
Include ethical considerations in your design. How do scientists overcome such concerns?
P.11
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Appendix 1: Advertisements for extension activity
Extension activity: Are advertisements about food products always true?
Advertisement for a vitamin C product (Brand name is covered.)
You may include the following questions in your discussion.
1. What is vitamin C? What are its functions in the body?
2.
What are the claims in the advertisement?
3.
Are the claims valid based on your knowledge?
4.
How to test the effect of the product on health?
P.12
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Advertisement for a sliming product (Brand name is covered.)
You may include the following questions in your discussion.
1. What is chitosan?
Chitosan (蟹殼素/殼聚糖) is a
polysaccharide produced
commercially from chitin which
comprises the exoskeleton of
crustaceans (e.g.crabs and shrimp).
2. What are the claims in the advertisement?
3. How to test the effect of the product on health?
P.13
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say? (Protein)
Advertisement for a collagen product (Brand name is covered.)
You may include the following questions in your discussion.
1. What is collagen (膠原蛋白)? What are its functions in the body?
2.
What are the claims in the advertisement?
3.
Are the claims valid based on your knowledge?
4.
How to test the effect of the product on health?
P.14
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.