Loading presentation...

Present Remotely

Send the link below via email or IM


Present to your audience

Start remote presentation

  • Invited audience members will follow you as you navigate and present
  • People invited to a presentation do not need a Prezi account
  • This link expires 10 minutes after you close the presentation
  • A maximum of 30 users can follow your presentation
  • Learn more about this feature in our knowledge base article

Do you really want to delete this prezi?

Neither you, nor the coeditors you shared it with will be able to recover it again.


Biological molecules

No description

Alvin Tay

on 16 March 2014

Comments (0)

Please log in to add your comment.

Report abuse

Transcript of Biological molecules


1. As a source of ENERGY...
Why do we need food?
2. For Growth, Repair or Replacement of worn and damgaed tissues...
3. To maintain HEALTH...
Food contains a store of
called potential chemical energy
When digested food (eg. Glucose) is oxidised during respiration, the energy is released and used for
vital activities
to keep our body alive such as movement, heart beat and nerve impulses; and to maintain a
constant internal body temperature
Food provides the substances needed for synthesising new protoplasm, cells and tissues.
Food such as some vitamins and minerals, is required to prevent deficiency diseases.
Taking in useful substances is called feeding or
7 types of NUTRIENTS
Mineral Salts
Dietary Fibre
Provide energy
Growth and Repair
Keep us healthy
70% of our body is water
Help form cytoplasm and nucleus
reagent for digested food substances, excretory products and hormones
Helps in chemical reactions of an organism
Needed for hydrolytic reactions (
Helps to regulate body temperature
Water is best known solvent for both inorganic salts and many organic compounds
Food Tests
Iodine test for starch
2 drops of iodine solution
onto any substance
Iodine solution changes from
if starch is present.
Add 2cm3 Benedict’s solution
Red precipitate
Heat in water bath
About 2cm3 of test solution
The different colours indicate presence of reducing sugar in increasing amounts:
green ppt
for trace amount;
yellow ppt
for small amount,
orange ppt
for moderate amount and
brick-red ppt
for high amount
Blue – Green – Yellow - Red
Add 2cm3 Benedict’s solution to 2cm3 of test solution in a test tube.
Shake the mixture.
Put the test-tube in a beaker of boiling water for 5 minutes.
If reducing sugars are present, a brick-red precipitate will be formed.
Benedict’s Test for Reducing Sugars
2cm3 of ethanol
to test solution.
Shake the mixture thoroughly
2cm3 of water
to solution.
cloudy, white emulsion
is formed if fats are present.
Violet colour
Allow mixture to stand for 5min
Shake after each drop
Shake mixture thoroughly
Add 1% copper (II) sulphate solution drop by drop
Add 1cm3 of sodium hydroxide
Sample to be tested: in this case, Egg white (2cm3)
Biuret test for proteins
Ethanol emulsion test for fats
Oil droplet
2 layers of immiscible liquid
White emulsion
Add 2cm3 of water
Add 2cm3 of ethanol
Shake mixture thoroughly
1cm3 of sodium hydroxide solution
of test solution .
Shake well.
1% copper (II) sulphate solution

drop by drop
, shaking after each drop.
Allow mixture to stand for
5 minutes
violet colouration
is formed if protein is present.
Quick check!
What do you add to test for starch?

What is the colour of the precipitate formed if reducing sugars are present?

What is the colour change you will observe if proteins are present?
Iodine solution
Brick-red precipitate
Blue to Violet
These enzymes act like chemical ‘scissors’ to cut up large molecules into small molecules until they become small enough to pass through the cell membrane.
Enzymes are
biological catalysts
made of
They change the rate of chemical reactions without themselves being chemically changed at the end of the reaction.
No enzyme?
Biochemical reactions in the body will otherwise process
too slowly
to sustain life!
Digestive enzymes
are enzymes that help in digestion.
Different types of digestive enzymes break down different nutrients into smaller and soluble molecules during digestion.
Each enzyme is specific; it acts only on one type of food.
3 Main Types of
Digestive Enzymes!
Groups of enzymes that digest
Carbohydrases break down large carbohydrates into
simple sugars.
Groups of enzymes that digest
Proteases break down large protein molecules into small
amino acid
Groups of enzymes that digest
Lipase break down big fats molecules into small molecules called
fatty acids.
Simple sugars, amino acids, fatty acids and glycerol are simple and soluble substances that are small enough to diffuse into the bloodstream.
Hence, nutrients can be absorbed and used by the body.
What are enzymes?

What is the product of protein digestion?

What is the product of carbohydrate digestion?

What are the products of fats digestion?
1.) Biological catalysts made of proteins
2.) They change the rate of chemical reactions without themselves being chemically changed at the end of the reaction
Amino acids
Simple sugars
Glycerol + Fatty Acids

Specific shape of an enzyme that binds the substrate
Substance on which an enzyme acts on i.e. the things we want to digest
Each enzyme has its
specific active site.
Each active site has a certain shape.
The specificity of an enzyme is due to its
three-dimensional shape.
The enzyme acts like a lock. The substrate acts like a key.
Only substrates with the
correct exact complementary shape
can fit into the enzyme like a ‘lock and key’ to form an
enzyme-substrate complex
The enzyme then acts on the substrates to form new products. The enzyme itself
does not
take part in the reaction.
The new product leaves the active sites.
The enzyme is now free to take part in another reaction.
Quick check
Identify the substrate, the enzyme and the products:
Amylase breaks down starch to form sugars
Protease breaks down protein in egg white to form amino acids
Lipases break down fats, to form fatty acids and glycerol
At low temperatures, enzymes are
As temperature increases, its activity
This is both the substrate and enzyme molecules gain
kinetic energy
and move about more rapidly, increasing the chance of collision between substrate and enzyme’s active site.
The enzyme is about twice as active for every
10 degree celsius
rise in temperature until the optimum temperature is reached.
Effect of temperature on enzymes
It is the temperature at which enzyme activity is
Enzyme works best and fastest at this temperature.
Different enzymes have different optimum temperatures (
30oC - 70oC
Most enzymes in our body work best at
(body temperature).
Optimum temperature
At high temperatures, enzyme activity
Enzymes are
as they are protein molecules.
The enzyme
loses its unique shape
of its active site.
The active site is altered or lost.
is the
change in a three-dimensional structure
of an enzyme and loss in active site specific shape. This can be caused by heat or chemicals.
Hence, the enzyme loses its ability to function permanently.
Effect of temperature on enzymes
At high temp, enzyme is denatured
Enzymes are inactive
Increasing temp, increase enzyme activity
Most alkaline
Least alkaline
Least acidic
Most acidic
pH is a measure of how
a solution is
What is pH?
Enzymes are affected by the acidity or alkalinity of the solution in which they act in.
Optimum pH is the pH at which enzyme activity is
Enzyme works best at this pH.
Different enzymes have different optimum pH.
Most enzymes work best in neutral conditions.
Extreme changes in pH may
some enzymes.
Effect of pH on enzymes
Enzymes in the stomach

Enzymes in the small intestine

Enzymes in the mouth
Quick Check
Optimum pH: 2 (acidic conditions)
Optimum pH: 8 (alkaline conditions)
Optimum pH: 7 (neutral conditions)
Above optimum pH, decrease enzyme activity
Increasing pH, increase enzyme activity
Extremely LOW and HIGH pH reduces enzyme activity
pH of solutions can affect enzyme activity.
Full transcript