<< Chapter < Page Chapter >> Page >

The functions of proteins

Proteins have a number of functions in living organisms.

  • Structural proteins such as collagen in animal connective tissue and keratin in hair, horns and feather quills, all provide support.
  • Storage proteins such as albumin in egg white provide a source of energy. Plants store proteins in their seeds to provide energy for the new growing plant.
  • Transport proteins transport other substances in the body. Haemoglobin in the blood for example, is a protein that contains iron. Haemoglobin has an affinity (attraction) for oxygen and so this is how oxygen is transported around the body in the blood.
  • Hormonal proteins coordinate the body's activities. Insulin for example, is a hormonal protein that controls the sugar levels in the blood.
  • Enzymes are chemical catalysts and speed up chemical reactions. Digestive enzymes such as amylase in your saliva, help to break down polymers in food. Enzymes play an important role in all cellular reactions such as respiration, photosynthesis and many others.

Research project : macromolecules in our daily diet

  1. In order to keep our bodies healthy, it is important that we eat a balanced diet with the right amounts of carbohydrates, proteins and fats. Fats are an important source of energy, they provide insulation for the body, and they also provide a protective layer around many vital organs. Our bodies also need certain essential vitamins and minerals. Most food packaging has a label that provides this information. Choose a number of different food items that you eat. Look at the food label for each, and then complete the following table:
    Food Carbohydrates (%) Proteins (%) Fats (%)
    1. Which food type contains the largest proportion of protein?
    2. Which food type contains the largest proportion of carbohydrates?
    3. Which of the food types you have listed would you consider to be the 'healthiest'? Give a reason for your answer.
  2. In an effort to lose weight, many people choose to diet . There are many diets on offer, each of which is based on particular theories about how to lose weight most effectively. Look at the list of diets below:
    • Vegetarian diet
    • Low fat diet
    • Atkin's diet
    • Weight Watchers
    For each of these diets, answer the following questions:
    1. What theory of weight loss does each type of diet propose?
    2. What are the benefits of the diet?
    3. What are the potential problems with the diet?

Carbohydrates and proteins

  1. Give the structural formula for each of the following:
    1. A polymer chain, consisting of three glucose molecules.
    2. A polypeptide chain, consisting of two molecules of alanine and one molecule of serine.
  2. Write balanced equations to show the polymerisation reactions that produce the polymers described above.
  3. The following polypeptide is the end product of a polymerisation reaction:
    1. Give the structural formula of the monomers that make up the polypeptide.
    2. On the structural formula of the first monomer, label the amino group and the carboxyl group.
    3. What is the chemical formula for the carbon side chain in the second monomer?
    4. Name the bond that forms between the monomers of the polypeptide.

Questions & Answers

Why does the carboxyl group have acidc properties?
Evi Reply
carboxylic acids
tyrique
Besides improving appearance what is another reason why medal is electro plated
Elizabeth Reply
it is made of metal
Reunity
thanks
Elizabeth
what is different between Dependent variable and independent variables
Elizabeth
difference between A.c and D.c
Gerrard
AC has slip rings DC has split rings commutator
Mohludi
are UV rays dangerous?
Khathutshelo Reply
no
Lianda
what's this?
Lianda
if there is extensive exposure, it can lead to skin cancer
tyrique
i hv a problem with this chapter because i also have problem with Newton's laws of motion
Kearabetswe Reply
what is the wave model of atom ?
Trazy Reply
Can you state the Doppler effect in words
Nombuyiselo Reply
State Coulomb's law in words
Nombuyiselo
the magnitude of the electrostatic force exerted point on each other is directly proportional to the product on magnitude of charges and inversely proportional to the square distance between them
Cassiey
the change in frequency of the sound detected by a listener because sound source and listener have different velocity
Elizabeth
Newton's first law of motion
Nnuso Reply
When an object is at rest or traveling at a constant velocity it will remain at rest unless an unbalanced force acts upon it.
Tumelo
yes that's true
Mphoko
Always know Newton's second law of motion. It appears to be in every question paper
Botho
Is the normal force always 0
Mpilo Reply
no. newtons 3rd law states that if something exerts a force into something else it will experience that same magnitude of force but in the opposite direction. so the net force is equal to the force the object applies to the surface but in the opposite direction
Courtney
define the term rate of reaction in word
David Reply
I think it a chemical process in which substance act mutually on each other.
Sphesihle
how many bones are in the human body?
Asali
it's the rate at which the reactants are able to change to products
Courtney
206 bones
Elizabeth
what is wave lengh
mama Reply
is the de broglie wavelength of the particle
Hope
calcium and magnesium, which one can displace aluminum from its compound?
Markia Reply
how is aluminum ion formed?
Dickens
a substance that has the lower electronegativity which will be in this case the Ca -1.0 this is because the Ca would have a lower ionization energy -needs less energy to fill its outer most shell and therefore will cause a displacement of the Al
Courtney
an Al ion would form when it has lost electrons and will normally be a cation -positively charged (3+)
Courtney
molecules with the same molecular formula but different chain
Malaza Reply
what will be the answer
.angel
chain isomer
Anele
what is structural isomer?
Kearabetswe
Hey if you define an isomer it will come as an organic molecule with the same number of atoms,same molecule formula ,same molecular mass but different STRUCTURAL FORMULA so what we have is only the chain ,positional and functionally isomer.Never heard of STRUCTURAL isomer
Phethego
what does the newton's law says?
there are 3 newtons laws which are newton's law of universal gravitation, law of cooling, law of motion
Imagine
Did the feather or leaf hit the ground first?
Shaloom Reply
leaf
Pradip
both at the same time. air friction ignored
Courtney
2 to 30 minut long distance race 20 km what's the avarage speed for the race
Jamilla Reply

Get the best Siyavula textbooks: gr... course in your pocket!





Source:  OpenStax, Siyavula textbooks: grade 12 physical science. OpenStax CNX. Aug 03, 2011 Download for free at http://cnx.org/content/col11244/1.2
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Siyavula textbooks: grade 12 physical science' conversation and receive update notifications?

Ask