1. 3
Biological Molecules 1

2. Chapter 3 At a Glance
3.1 Why Is Carbon So Important in Biological Molecules?
3.2 How Are Organic Molecules Synthesized?
3.3 What Are Carbohydrates?
3.4 What Are Lipids?
3.5 What Are Proteins?
3.6 What Are Nucleotides and Nucleic Acids?

3. OH H HO
CH2OH O
Carbohydrates
energy molecules

4. Carbohydrates are composed of C, H, O
(CH2O)x C6H12O6
Function:
fast energy u energy storage
raw materials u structural materials
Monomer: sugars
ex: sugars, starches, cellulose
(CH2O)x
C6H12O6
carb = carbon
hydr = hydrogen
ate = oxygen compound
sugar

5. Sugars 6 5 3 Most names for sugars end in -ose
Classified by number of carbons
6C = hexose (glucose)
5C = pentose (ribose)
3C = triose (glyceraldehyde)
Glyceraldehyde H OH O C H OH HO O
Ribose
CH2OH OH H HO
CH2OH O
Glucose 6 5 3

6. 3.3 What Are Carbohydrates?
Carbohydrate molecules are composed of C, H, and O in the ratio of 1:2:1
If a carbohydrate consists of just one sugar molecule, it is a monosaccharide
Two linked monosaccharides form a disaccharide
A polymer of many monosaccharides is a polysaccharide
Carbohydrates are important energy sources for most organisms
Most small carbohydrates are water-soluble due to the polar OH functional group

7. 3.3 What Are Carbohydrates?
There are several monosaccharides with slightly different structures
The basic monosaccharide structure is a backbone of 3–7 carbon atoms
Most of the carbon atoms have both a hydrogen (-H) and a hydroxyl group (-OH) attached to them
Most carbohydrates have the approximate chemical formula (CH2O)n where “n” is the number of carbons in the backbone
When dissolved in the cytoplasmic fluid of a cell, the carbon backbone usually forms a ring

8. 3.3 What Are Carbohydrates?
There are several monosaccharides with slightly different structures (continued)
Glucose (C6H12O6) is the most common monosaccharide in living organisms

9. Figure 3-5 Depictions of glucose structure6 5 4 3 2 1
Chemical formula
Linear, ball and stick 6 6 5 5 4 1 4 1 3 3 2 2
Ring, ball and stick
Ring, simplified 9

10. Figure 3-4 Sugar dissolving in water
hydrogen
bond
hydroxyl
group 10

11. ACTIVITY
Build GLUCOSE C6 H12 O6
BUILD RIBOSE C5 H10 O5

12. USE DEHYDRATION SYNTHESIS TO BUILD A DISACCHARIDE
RELEASE THE ENERGY OF THE SUGAR BY BREAKING THE BOND USING HYDROLYSIS

13. 3.3 What Are Carbohydrates?
There are several monosaccharides with slightly different structures (continued)
Additional monosaccharides are
Fructose (“fruit sugar” found in fruits, corn syrup, and honey)
Galactose (“milk sugar” found in lactose)
Ribose and deoxyribose (found in RNA and DNA, respectively)

14. Table 3-1 14

15. Carbon atoms can attach to functional groups - determine characteristics and reactivity of molecule
functional groups- are more reactive than carbon backbone because they are less stable
carboxyl

16. Figure 3-6 Some six-carbon monosaccharides5 5 2 4 1 4 3 3 1 2
fructose
galactose 16

17. Figure 3-7 Some five-carbon monosaccharides5 5 4 1 4 1 3 2 3 2
Note “missing”
oxygen atom
Missing functional
Group- hydroxyl
ribose
deoxyribose 17

18. 3.3 What Are Carbohydrates?
Disaccharides consist of two monosaccharides linked by dehydration synthesis
The fate of monosaccharides inside a cell can be
Some are broken down to free their chemical energy
Some are linked together by dehydration synthesis

19. 3.3 What Are Carbohydrates?
Disaccharides consist of two monosaccharides linked by dehydration synthesis (continued)
Disaccharides are two-part sugars
They are used for short-term energy storage
When energy is required, they are broken apart into their monosaccharide subunits by hydrolysis

20. Figure 3-8 Synthesis of a disaccharide
glucose
fructose
sucrose
dehydration
synthesis 20

21. 3.3 What Are Carbohydrates?
Disaccharides consist of two monosaccharides linked by dehydration synthesis (continued)
Examples of disaccharides include
Sucrose (table sugar)  glucose  fructose
Lactose (milk sugar)  glucose  galactose
Maltose (malt sugar)  glucose  glucose

22. Simple & complex sugarsOH H HO
CH2OH O
Glucose
Monosaccharides
simple 1 monomer sugars
glucose
Disaccharides
2 monomers
sucrose
Polysaccharides
large polymers
starch

23. Building sugars Dehydration synthesis monosaccharides disaccharide H2O
maltose |
glucose |
glucose |
maltose
glycosidic linkage

24. Building sugars Dehydration synthesis monosaccharides disaccharide H2O|
glucose |
fructose |
sucrose
(table sugar)
sucrose = table sugar

25. GLUCOSE + FRUCTOSE = sucrose

26. 3.3 What Are Carbohydrates?
Polysaccharides are chains of monosaccharides
Storage polysaccharides include
Starch, an energy-storage molecule in plants, formed in roots and seeds
Glycogen, an energy-storage molecule in animals, found in the liver and muscles
Both starch and glycogen are polymers of glucose molecules

27. Figure 3-9 Starch structure and function
starch grains
Potato cells
A starch molecule
Detail of a starch molecule 27

28. 3.3 What Are Carbohydrates?
Polysaccharides are chains of monosaccharides (continued)
Many organisms use polysaccharides as a structural material
Cellulose (a polymer of glucose) is one of the most important structural polysaccharides
It is found in the cell walls of plants
It is indigestible for most animals due to the orientation of the bonds between glucose molecules

29. Animation: Carbohydrate Structure and Function

30. Figure 3-10 Cellulose structure and function
Cellulose is a major
component of wood
A plant cell with
a cell wall
A close-up of
cellulose fibers
in a cell
wall
Hydrogen bonds
cross-linking
cellulose molecules
bundle of
cellulose
molecules
cellulose fiber
Alternating bond
configuration differs
from starch
Detail of a cellulose molecule 30

31. 3.3 What Are Carbohydrates?
Polysaccharides are chains of monosaccharides (continued)
Chitin (a polymer of modified glucose units) is found in
The outer coverings of insects, crabs, and spiders
The cell walls of many fungi

32. Figure 3-11 Chitin structure and function32

33. Polysaccharides Polymers of sugars Function:
costs little energy to build
easily reversible = release energy
Function:
energy storage
starch (plants)
glycogen (animals)
in liver & muscles
structure
cellulose (plants)
chitin (arthropods & fungi)
Polysaccharides are polymers of hundreds to thousands of monosaccharides

34. Breakdown of Polysaccharides
Release of energy
hydrolysis
Polysaccharide + H2O  Monosaccharides
Starch + H2O  Glucose + Glucose + Glucose + Glucose
hydrolysis

35. Polysaccharide diversity
Molecular structure determines function
in starch
in cellulose
isomers of glucose
structure determines function…

36. Cellulose Most abundant organic compound on Earth
herbivores have evolved a mechanism to digest cellulose
most carnivores have not
that’s why they eat meat to get their energy & nutrients
cellulose = undigestible roughage
Cross-linking between polysaccharide chains:
= rigid & hard to digest
The digestion of cellulose governs the life strategy of herbivores.
Either you do it really well and you’re a cow or an elephant (spend a long time digesting a lot of food with a little help from some microbes & have to walk around slowly for a long time carrying a lot of food in your stomach)
Or you do it inefficiently and have to supplement your diet with simple sugars, like fruit and nectar, and you’re a gorilla.
But it tastes like hay! Who can live on this stuff?!

37. Cow Gorilla can digest cellulose well; no need to eat other sugars
can’t digest cellulose well; must add another sugar source, like fruit to diet
The digestion of cellulose governs the life strategy of herbivores.
Either you do it really well and you’re a cow or an elephant (spend a long time digesting a lot of food with a little help from some microbes & have to walk around slowly for a long time carrying a lot of food in your stomach)
Or you do it inefficiently and have to supplement your diet with simple sugars, like fruit and nectar, and you’re a gorilla.
APBioTOPICS/20Biochemistry/MoviesAP/Macromolecule-Lifewire.swf

38. Helpful bacteria Caprophage Ruminants
How can herbivores digest cellulose so well?
BACTERIA live in their digestive systems & help digest cellulose-rich (grass) meals
Caprophage
I eat WHAT!
Tell me about the rabbits, again, George!
Ruminants