A lesson on the structure and function of large biological molecules

2. The Molecules of Life
Given the rich complexity of life on Earth, the most
important large molecules found in all living things can
be sorted into just four main classes: carbohydrates,
lipids, proteins, and nucleic acids.
On the molecular scale, members of three of these
classes—carbohydrates, proteins, and nucleic acids—
are huge and are therefore called macromolecules.

3. Macromolecules are polymers, built
from monomers
A polymer is a long molecule consisting of many
similar or identical building blocks linked by
covalent bonds.
Monomers - The repeating units that serve as
the building blocks of a polymer are smaller
molecules.

6. Carbohydrates – C,H,O;
1:2:1 – CH2O
•oxidize easily and are the most readily-available
energy/heat source
•serve as important structural material in some
animals and all plants
•literally means ‘hydrated carbon’
•made up of repeating units called sugars.
•Excess CHO-- glycogen or fat (stored in liver or
muscles)
Note :
The larger the carbohydrate molecule,
the less soluble it is in water.
Organic Compounds

7. Carbohydrates
serve as fuel and building material
simplest carbohydrates are the monosaccharides
Disaccharides - consisting of two monosaccharides
joined by a covalent bond
Polysaccharides – carbohydrate macromolecules
composed of many sugar building blocks

8. Classification of Sugars according
to size and solubility
1.Monosaccharides- simple sugars; CHO in a ratio
of 1:2:1
•Basic units of carbohydrates
•Examples:
Glucose, Fructose, galactose- C6
H12
O6

9. 2. Disaccharides- double sugars; made up of two
monosaccharides joined together by dehydration synthesis
•Have to be hydrolyzed to be broken down to
monosaccharides
•Examples:
glucose + fructose = sucrose (table sugar)
2C6
H12
O6
---- C12
H22
O11
+ H2
O
lactose( milk sugar)= gluc + gal
maltose(malt sugar)= gluc + gluc
Classification of Sugars according
to size and solubility

11. 3. Polysaccharides- long
chains of simple sugars
(polymers) linked together
by dehydration synthesis
•large, insoluble molecules
•lack sweetness of mono-
and disaccharides
Examples:
Starch- storage form of
CHO in plants (made up of
long glucose chains)
Classification of Sugars according
to size and solubility

12. Glycogen- storage CHO of animal tissues
- large molecule and highly branched
- can easily be broken down to yield glucose
Cellulose – most abundant organic molecule in the planet
- chief structural material in plants; provides rigidity
- indigestible in man due to complex arrangement of
glucose
- provides bulk and stimulates bowel movement
- enzyme cellulase from bacteria and protozoans digest
cellulose to yield glucose

13. Chitin
•Second most abundant organic compound on earth.
•Makes up the hard outer skeletons of certain animals
ex. Insects, crabs, lobsters
•Resistant to breakdown by bacteria and animals

14. Lipids
They mix poorly, if at all, with water.
-CHO, but with less O and more C atoms-- more
heat

15. Three forms of Lipids
1.Fats or triglycerides; Fatty acids
and glycerol as building blocks
(3:1 ratio)
- non-polar
and do not mix with water
•may be solid (fats) or liquid
(oils) according to length of
fatty acid chains and degree
of saturation

16. •Saturated- with single bonds between C atoms
-longer fatty acid chains; solid at 20o
C
- animal fats as butter fat and meat fats
- encourage build-up of plaques in walls and vessels

17. •Unsaturated- with double/triple bonds between C atoms
- short FA chains; liquid at room temperature
- plant sources as olive, peanut, corn

18. 2. Phospholipids-modified
triglycerides with two FA
chains + 1 phosphorus-
containing group
- with polar heads and
non-polar (hydrocarbon)
tails
- phosphate groups in
heads attract water and ions
- in cell membrane;
regulates transport

19. Steroids are lipids characterized by a carbon
skeleton consisting of four fused rings.
Different steroids are distinguished by the
particular chemical groups attached to this
ensemble of rings.
Steroids

20. Cholesterol
- from animal products; CV
disorders
- component of cell membranes
- raw material for Vitamin D
synthesis, other steroid hormones
( estrogen, progesterone,testosterone,
cortisol and aldosterone)
- manufactured in liver, most
abundant in brain
- attaches to protein to form
lipoprotein before it can circulate

21. Two types of Lipoproteins
High Density Lipoproteins (HDL)
- more CHON, less lipid
- brings cholesterol to liver for elimination
-‘good cholesterol
Low Density Lipoproteins (LDL)
- less CHON, more lipid
-clogs blood vessels
- ‘bad cholesterol’

22. •CHON, sometimes sulfur, phosphorus and trace metals as iron
and copper; second most abundant (10-20% of cell mass)
•Building blocks: amino acids-- about 20 aa
•Essential aa ( 8)- taken in with food
•Non-essential (12)- synthesized by body
•aa can be a base (proton acceptor) or an acid (proton donor)
•linked by peptide bonds which break during hydrolysis
•Deficiency: brittle nails, rough scaly skin, rough lackluster hair
•Extreme deficiency: kwashiorkor
Proteins

23. Proteins account for more than 50% of the dry
mass of most cells, and they are instrumental in
almost everything organisms do.
Some proteins speed up chemical reactions,
while others play a role in defense, storage,
transport, cellular communication, movement, or
structural support.

25. •Nucleic acids are polymers made
of monomers called nucleotides.
•nucleotide- nitrogen base, pentose
sugar, phosphate group
•DNA –chief hereditary material
•RNA- important in protein
synthesis
Nucleic Acids

26. • DNA is the genetic material that organisms
inherit from their parents.
• Each chromosome contains one long DNA
molecule, usually carrying several hundred or
more genes.
• When a cell reproduces itself by dividing, its
DNA molecules are copied and passed along
from one generation of cells to the next.

27. NUCLEOTIDE
- a five-carbon sugar (a pentose), a nitrogen-containing
(nitrogenous) base, and one to three phosphate groups

28. Pyrimidine - has one six-membered ring of carbon and
nitrogen atoms. The members of the pyrimidine family
are cytosine (C), thymine (T), and uracil (U).
Purines are larger, with a six-membered ring fused to
a five-membered ring. The purines are adenine (A) and
guanine (G).
Adenine, guanine, and cytosine are found in both DNA
and RNA; thymine is found only in DNA and uracil
only in RNA.