Chapter 6 Nutrition in Humans - Class test prelude

Which of the following enzymes digests polypeptide into amino acids?
A Enterokinase
B Erepsin
C Pepsin
D Trypsin

Ans: B Erepsin

Note:

- Enterokinase activates trypsinogen and converts it to trypsin

- Pepsin digests protein into amino acids

- Trypsin digests protein into polypeptides

Enzymes - Prelude to class test

The figure above shows how the activities of two enzymes X and Y vary with
temperature.

(a) Which enzyme would be best suited to an organism that experiences large
changes in external temperature throughout a 24-hr period? Explain your answer. [2]

(b) State two other factors that influence enzyme activity and explain how each
factor affects the rate of enzyme activity. [4]

And the answers are as follows......

(a) Enzyme Y;
This is because enzyme Y is active over a wider range of temperatures compared to enzyme X.

(b)

1) pH
- When pH is above or below an enzyme's optimum pH, the enzyme becomes denatured and loses its active site and its function.
2) Substrate concentration
- As substrate concentration increases up to a maximum,more active sites could be occupied per unit time, hence more products are formed per unit time, which leads to an increase in enzyme activity.

Mnemonic to remember monosaccharides and disaccharides

Note:
- To form dissacharides, glucose is involved in all 3 reactions.
- Galactose and lactose are obviously in one reaction.

To help you with memorising, I suggest using Mnemonics:
GGM: Go Grand Ma! - Glucose + Glucose --> Maltose
GFS: Go Father Son! - Glucose + Fructose --> Sucrose
GGL: Go Good Luck! - Glucose + Galactose --> Lactose

What are Mnemonics? Read the following links:

http://en.wikipedia.org/wiki/Mnemonic

http://www.bucks.edu/~specpop/mnemonics.htm

Try coming up with your own Mnemonics for other information, be it for your science or humanities subjects! :)

Trans fats

For some of you who would like to read more about trans fats, please look at the following link:

http://www.americanheart.org/presenter.jhtml?identifier=3045792

So yeah, do watch out when you shove french fries into your mouth heartily.
Haha!
*Ms Goh is equally guilty of it*

The one thing some people have been waiting for!

A student was asked to identify the two compounds in each of the three test tubes,
X, Y, and Z. The table above shows the results of the student's tests.


Which of the following statements are true?
A Glucose and starch had been placed in tube Z.
B Albumin and starch had been placed in tube Y.
C Albumin and oil had been placed in tube X.
D Starch and oil had been placed in tube Y.

Answer:
D

Note:
Sodium hydroxide + copper sulphate is actually biuret test. Test for presence of proteins.
Ethanol + water is actually ethanol emulsion test. Test for presence of fats.

=)

Diffusion and Osmosis animations

Dear all,

A few other links to animations that I;ve shown to you in class, in case you would like to relook at them =)

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

Crenation in animal cells

Recall the following (the table that I asked you to copy in your textbook):

Hypotonic solution (compared to the cell)
Plant cell: Become turgid
Animal cell: Swells and burst (Lysis)

Hypertonic solution (compared to the cell)
Plant cell: Becomes plasmolysed
Animal cell: Undergoes crenation

Crenation is the process in which cell shrinks and little spikes appear on the cell surface membrane.

In the following website, drag the mouse to the right and see how crenation occurs.
The more concentrated a solution is, the more hypertonic it is, the lower the water potential, hence water leaves the cell by osmosis to enter the solution.

http://www.yteach.co.uk/page.php/resources/view_all?id=Haemolysis_osmosis_diffusion_Plasmolysis_Facilitated_diffusion_Gradient_Passive_transport_Simple_diffusion_Active_transport_page_5&from=search