1. Carbon and Carbohydrates
HL Biology
Cells & Biomolecules

2. Thinking question
What are the basic components you need to
build a living organism?

3. Molecular Biology
• From a purely scientific viewpoint, any living
organism is merely a collection of elements in
the form of atoms, ions an molecules.
• Molecular biology explains living processes in
terms of the chemical substances involved.

4. Basic definitions
Term defintion
Metabolism The web of all the enzyme-
catalysed reactions in a cell or
organism
Anabolism The synthesis of complex
molecules from simpler molecules
Catabolism The breakdown of complex
molecules into simpler molecules.

5. Chemistry revision
• Define the following terms:
– Atom
– element
– Molecule
– Compound

6. Chemistry revision
• Define the following terms:
– Atom
The smallest particle into which an element can be divided without
losing its chemical properties.
– Element
A substance consisting of atoms which all have the same number
of protons - i.e. the same atomic number.
– Molecule
The combination of two or more atoms, eg H2
– Compound
The combination of two or more atoms of different elements, eg
CO2

7. The Molecules of Life
Atoms/Molecules
- we are made of earth elements that are organized
into:
a) inorganic molecules (NaCl, PO4, K+)
b) organic molecules (contain C and H)
All organic molecules contain carbon, but not all
carbon containing molecules are organic, eg. Carbon
dioxide

8. Carbon

9. Carbon
• Carbon is a small, relatively light element with
four single valence electrons.
• It can form up to four stable covalent bonds
with other atoms.
• Carbon atoms attach to each other to form
straight and branched chains and ring
structures of various sizes and complexity that
act as the backbones of biological molecules.

10. Carbon video
• https://www.youtube.com/watch?v=QnQe0x
W_JY4

11. Four Main Types Of Macromolecules
Molecules Monomers
carbohydrates monosaccharides
lipids Glycerol and fatty acids
proteins Amino acids
Nucleic acids nucleotides

12. Macromolecules
• Large molecules formed by joining many subunits
together, make a polymer.
• The smaller subunits are called monomers.
The wall represents:
Each brick represents:

13. You are what you eat!
• http://v.youku.com/v_show/id_XNDU5MDg5
ODky.html

14. carbohydrates
• Carbohydrates contain carbon, hydrogen, and
oxygen atoms in a 1:2:1 ratio.
There are three types of Carbohydrate:
• Monosaccharides = “single sugar”
• Disaccharides = “two sugars”
• Polysaccharides = “many sugars”

15. Monosaccharides
Monosaccharides are sugars that consist of a
single sub-unit (monomer).
Monosaccharide Formula
Glucose C6H12O6
Fructose C6H12O6
Ribose C5H10O5

16. Drawing molecular models of Ribose
and Glucose
Glucose (C6H12O6) Ribose (C5H10O5)

17. Modeling molecules
• Make a model of glucose and a model of
ribose. Take a photograph of each model.

18. Disaccharides
• Disaccharides are pairs of monosaccharides
that are linked together by condensation to
form disaccharides.
Glucose + glucose  maltose + water
Glucose + galactose lactose + water
Glucose + fructose  sucrose + water

19. Disaccharides
• Model condensation reactions between two
glucose molecules. Take photographs of each
step and compile them into a document with
step by step explanations.
• What are the products of this reaction?

20. Condensation Reactions
• Two monosaccharides are joined together to
form a disaccharide with the release of a
water molecule
Glucose + glucose = maltose + water

21. Polysaccharides
• Polymers consisting of chains of
monosaccharide or disaccharide units.
• The bonds are called glycosidic linkages.
• Some polysaccharides serve as energy storage
(eg. Starch and glycogen)
• Some polysaccharides are used for building
and structure (eg. cellulose)

22. Review of glucose
• Glucose is the most common
monosaccharide
• It forms rings in aqueous solution
• The carbon atoms are number 1
– 6 in a clockwise direction,
starting from the carbon
immediately next to the oxygen
atom.

23. Isomers of glucose
• Isomers are compounds with the same
chemical formula but different arrangements
of their atoms.
• Glucose can exist as alpha-glucose or beta-
glucose, depending on the position of the OH
group on carbon1.

24. Polysaccharides
• Polysaccharides form from several hundred to
several thousand monosaccharides joined
together by condensation reactions.
• Condensation reactions usually form
glycosidic linkages between carbon1 of one
glucose to carbon4 of the second glucose.
• 1,4 links form straight chains.
• Occasionally 1,6 links occur, causing branching

25. Cellulose
• Cellulose is a structural material found in the
cell walls of plants.
• It is made up of beta-glucose molecules held
together by 1,4 glycosidic links.
• The beta-glucose monomers alternate, with
each one being upside down compared to its
neighbours. (up, down, up etc)

26. Cellulose

28. Starch
• Starch is a polymer of alpha-glucose, with all
of the glucose monomers in the same
orientation, which makes the chain curved.
• There are two forms of starch:
1. Amylose – 1,4 linkages, un-branched
2. Amylopectin – 1,4 and 1,6 linkages, branched

29. Starch

30. Starch
Starch: a plant polysaccharide. This micrograph shows part
of a plant cell with a chloroplast, the cellular organelle
where glucose is made and then stored as starch granules.
Amylose (unbranched) and amylopectin (branched) are two
forms of starch.

31. Glycogen
• Glycogen is a branched polymer of alpha-
glucose.
• It has even more 1,6 linkages than
amylopectin.

32. Glycogen
Glycogen: an animal polysaccharide. Animal cells stockpile
glycogen as dense clusters of granules within liver and muscle
cells, as shown in this micrograph of part of a liver cell.
Mitochondria are cellular organelles that help break down
glucose released from glycogen. Note that glycogen is more
branched than amylopectin starch.

33. Extra reading
• Still feeling confused? Read chapter 5.2 in
Campbell