S4N. Biology
Carolina Moore
Bio molecules
Glossary
 Biological molecules: Organic molecules that make up living cells. They are
the cells’ building blocks.
 Metabolism: Sum of all the chemical reactions occurring in living cells.
 Catabolism: Reactions that involve breaking down molecules into
smaller units. Energy is released
 Anabolism: Reactions by which living organisms synthesize complex
molecules of life from simpler ones. Uses energy.
 Organic molecules: Compounds that contain carbon hydrogen bonds.
 Macromolecules: “giant molecules”
Examples: Polysaccharides, proteins(polypeptides), and nucleic acids.
 Polymers: Poly means “many”. Macromolecules made of many repeating
subunits that are similar or identical to each other.
Monomer: The repeating subunits that make up polymers.
The bio molecules are: Carbohydrates, proteins, nucleic acids and lipids.
1_ Carbohydrates
They are classified depending on the amount of sugar units that form it.
The word saccharide means “sugar”:
Monosaccharide: Consist of a single sugar unit (Ex: Glucose, fructose)
Disaccharide: Consist of two sugar units (Ex: Maltose, sucrose)
Polysaccharide: Consist of many sugar units. (Starch, glycogen, cellulose)
The smaller units, or monomers, of carbohydrates are the monosaccharides.
S4N. Biology
Carolina Moore
The most common monosaccharide is glucose (C6H12O6) but there are other sugars
(fructose, for example, is the monomer that makes up sucrose, the sugar that you
eat)
Glucose molecule
Formula: C6H12O6
Two glucose molecules can react together to form a disaccharide.
The reaction is called a condensation reaction, because water is formed in the
process, as shown in the diagram. The resulting bond is called: glyosidic bond.
The reverse reaction (to break the bond) is called a hydrolysis reaction, and water is
used.
Monosaccharides and disaccharides taste sweet, they are called
sugars.
S4N. Biology
Carolina Moore
Role of sugars in living organisms:
Commonly used as source of energy in respiration. Also building blocks of larger
molecules.
If many sugars are linked together, a polysaccharide is formed.
Polysaccharides don´t taste sweet.
So they are NOT called sugars.
Examples of polysaccharides are: Starch, glycogen and cellulose.
The three are polymers of glucose.
Cellulose: Makes up the cell wall of plant cells.
Starch and glycogen: Very important for glucose storage.
 Starch is glucose storage in plants,
 Glycogen is glucose storage in animals.
S4N. Biology
Carolina Moore
S4N. Biology
Carolina Moore
Storage. In
chloroplasts in
plant cells
Storage. In animals,
Structure. Makes
liver and muscle cells
the cell wall
of plant cells
Because glucose is the main source of energy for many living cells, it is very
important to store it.
Glucose cannot be stored as a monosaccharide for two main reasons:
 It dissolves too easily and would make the cell content too concentrated
(Osmotic problems)
 It is a very reactive molecule, so it would interfere with normal cell chemistry.
When glucose is linked to others, to form starch or glycogen, it is not soluble and
not reactive.
S4N. Biology
Carolina Moore
Starch is found in chloroplasts of
Glycogen is found in liver and
photosynthetic cells in plants.
muscle cells of animals.
In your mouth starch is digested into maltose (a sugar).
Using a cracker and your mouth design an experiment to measure how long it takes
for starch to be digested in your mouth:
……………………………………………………………………………………………
……………………………………………………………………………………………
…………………………………………………………………………………………….
…………………………………………………………………………………………….
…………………………………………………………………………………………….
…………………………………………………………………………………………….
…………………………………………………………………………………………….
…………………………………………………………………………………………….
Fill in the blanks:
Plants produce their own glucose, by a process called_____________ The energy
needed for this reaction is obtained from_______________. The elements needed to
build glucose are Carbon Hydrogen and Oxygen, these elements are obtained
from___________ and ___________
When a plant cell needs energy, it would obtain the ___________ needed for cellular
respiration, by a _____________ reaction of __________stored in its chloroplasts.
Animals, instead, need to eat the glucose. We can obtain it as sugars or as
polysaccharides, such as starch. Glucose needs no digestion; it can be directly
absorbed in the________ _____________. Starch needs to be digested, so that the
resultant ……………………. can be absorbed.
S4N. Biology
Carolina Moore
We have no digestive enzymes for cellulose, so the glucose in cellulose of eaten
plant cells cannot be …………………….. by us.
Food tests:
Nutrient
Reagent
Positive result
Negative result
Sugar
Benedict and double boil
Green or Orange red
Blue
Starch
Iodine
Blue black
Yellow brown
Food source for carbohydrates.
The main source of carbohydrates for humans are the foods that contain starch.
Starch is used by plants as glucose storage.
Seeds such as wheat have plenty of starch, other seeds that have starch are rice
and maize.
Cereals, in general are a very good source of starch.
When wheat is powered we produce flour, so foods made with flour are a very good
source of carbohydrates. Name food made with flour which are a very good source
of carbohydrates: …………………………………...............................
…………………………………………………………………………………………….
2_ Proteins
Are also called polypeptides.
A polypeptide is a molecule made of many amino acids linked together.
So proteins are long chains (polymers) of amino acids (monomers).
Amino acid structure
All amino acids share a basic structure, but have a part (R ) that is different
There are 20 different amino acids.
S4N. Biology
Carolina Moore
Proteins differ in the amino acids that make it and their sequence (just like
different words can be made by different combinations of the different letters of the
alphabet)
The amino acids join together by a condensation reaction. The resulting bond is
called peptide bond.
S4N. Biology
Carolina Moore
The peptide bond is very strong. It is not broken by changes in temperature or PH.
To break the peptide bond a hydrolysis reaction done by enzymes is needed (such
as it occurs in digestion)
The types of amino acids contained in a chain, and the sequence in which they are
joined makes up the primary structure of proteins.
Secondary structure: The polypeptide often folds, this is due to attraction between
amino acids in the chain.
Tertiary structure: A protein coils to form a precise 3 dimensional shape.
Quaternary structure: Many proteins are made of 2 or more polypeptide chains.
All the bonds that maintain secondary, tertiary and quaternary structure can be
disrupted by high temp or PH changes.
Protein denaturation: A protein needs it specific 3D shape to function well. So high
temp and PH changes, which break bonds that hold 2ry, 3ry structure in shape,
causes the protein to go back to its primary structure. The protein is said to be
denatured and is not active (not able to perform its function)
S4N. Biology
Carolina Moore
Role of proteins in living cells:
Part of cell membranes, enzymes, make up the structure, antibodies.
Crucial building blocks of cells. Required for growth and repair (building new cells,
muscle build up for ex)
Food tests for proteins:
Nutrient
Reagent
Positive result
Negative result
Protein
Biuret
Violet
Blue
Food sources for proteins:
……………………………………………………………………………………………
……………………………………………………………………………………………
……………………………………………………………………………………………
……………………………………………………………………………………………
Fill in the blanks
How do we obtain our proteins?
Probably you have heard that you need to eat proteins to grow and to be strong.
In a sense this is true, BUT the proteins that you eat are NOT the ones your cells
use.
When you eat proteins, these are digested in the ___________ and the __________
__________, by the enzymes: ______________ .
S4N. Biology
Carolina Moore
The resultant ________ _________ are then absorbed and travel by the blood to the
cells in your body. The cell will use these amino acids to produce its own proteins.
The information of the primary structure of the proteins you have to build is in the
_________ of your cells. Which proteins are going to be synthesized, depends on
the cell activity.
For example, white blood cells produce their own antibodies, but if there are not
enough amino acids, less antibodies than needed can be built. So, not eating
enough proteins might cause you to become sick more often.
Plants produce their own bio molecules. So, after producing glucose by
photosynthesis, they transform it into the amino acids they need, so that each cell
has the amino acids needed to build its own proteins.
Which element, needed to synthesize amino acids is missing from glucose?
_______________
How do plants obtain that missing element?
_______________________________________________________________
3_ Lipids
Lipids are not polymers. Even though they are made of smaller molecules, they are
not a chain of repeating units.
The most common are triglycerides. They are made of 1 glycerol and 3 fatty acids.
Cell membranes are made of a bi layer of phospho lipids.
Role in living organisms: Energy reserves. Insulator
Fatty acids
S4N. Biology
Carolina Moore
Triglyceride: 1 Glycerol + 3 Fatty acids
4. Nucleic acids
Polymers of nucleotides.
Nucleotide: Phosphate + sugar + base
S4N. Biology
Carolina Moore
Nucleic acids are chains of nucleotides linked to each other
DNA is a double helix structure, made of two chains of nucleotides.
Each chain of the double helix is joined to each other by complementary bases.
S4N. Biology
Carolina Moore
DNA is used for making proteins.
The cell “reads” the DNA and translate it into proteins
S4N. Biology
Carolina Moore
The DNA is read in codons.
Codons are like the DNA “words” each codon codes for a specific amino acid. By
reading all the codons together, the cell puts the amino acids together in the correct
sequence therefore building the protein primary structure, according to the cell´s
DNA “instructions”
S4N. Biology
Carolina Moore
Remarkably ALL living cells /from bacteria to complex organisms) read the DNA in
the same way. They all share the same genetic code (all cells use the same
“genetic” language).
Discuss implications of this fact for:
Common ancestor theory of evolution………………………………………………
…………………………………………………………………………………………………
……………………………………………………………………………………….
Genetically modified organisms…………………………………………………
…………………………………………………………………………………………………
……………………………………………………………………………………….
ATP: Energy currency of the cell