1. Chapter 3 Molecules of Life (Sections 3.1 - 3.3)

2. 3.2 Molecules of Life— From Structure to Function
Only living things make the molecules of life—complex carbohydrates and lipids, proteins, and nucleic acids
All of these molecules are organic
organic
Type of compound that consists primarily of carbon and hydrogen atoms

3. Carbon and Hydrocarbons
Carbon chains or rings form the backbone of molecules of life
An organic molecule that consists only of hydrogen and carbon atoms is a hydrocarbon
hydrocarbon
Compound or region of one that consists only of carbon and hydrogen atoms

4. Modeling an Organic Molecule

5. Functional Groups
Most molecules of life have at least one functional group
functional group
A group of atoms bonded to a carbon of an organic compound
Gives a specific chemical property such as polarity or acidity. The following table gives examples of functional groups. One example is a phosphate group, found on DNA and the energy molecule, ATP.

6. Common Functional Groups
Figure 3.3 Common functional groups. Such groups impart specific chemical characteristics to organic compounds.
Stepped Art
Fig. 3.3, p. 38

7. What Cells Do
Metabolic activities (mediated by enzymes) help cells stay alive, grow, and reproduce
metabolism
All enzyme-mediated chemical reactions by which cells acquire and use energy as they build and break down organic molecules

8. Building and Breaking Down
Condensation reactions build polymers from monomers of simple sugars, fatty acids, amino acids, and nucleotides
Hydrolysis reactions release monomers by breaking apart polymers
monomers
Molecules that are subunits of polymers
polymer
Molecule that consists of multiple monomers

9. Condensation Builds a large molecule from smaller ones
Enzyme removes –OH group from one molecule and -H atom from another
Covalent bond forms between two molecules – water also forms
Figure 3.4 Two common metabolic processes by which cells build and break down organic molecules.

10. Hydrolysis
Splits a large molecule into smaller ones by a water-requiring reaction
Enzyme attaches –OH group and -H atom from water at cleavage site

11. Hydrolysis
A Condensation. Cells build a large molecule from smaller ones by this reaction. An enzyme removes a hydroxyl group from one molecule and a hydrogen atom from another. A covalent bond forms between the two molecules, and water also forms.
B Hydrolysis. Cells split a large molecule
into smaller ones by this water-requiring
reaction. An enzyme attaches a hydroxyl group and a hydrogen atom (both from water) at the cleavage site.
Figure 3.4 Two common metabolic processes by which cells build and break down organic molecules.
Stepped Art
Fig. 3.4, p. 39

12. Animation: Condensation and hydrolysis
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13. Key Concepts Structure Dictates Function
We define cells partly by their capacity to build complex carbohydrates and lipids, proteins, and nucleic acids
All of these organic compounds have functional groups attached to a backbone of carbon atoms

14. 3.3 Carbohydrates
Enzymes assemble complex carbohydrates such as cellulose, glycogen, and starch from simple carbohydrate (sugar) subunits
Cells use carbohydrates for energy, and as structural materials
carbohydrate
Molecule that consists primarily of carbon, hydrogen, and oxygen atoms in a 1:2:1 ratio

15. Simple Sugars
Monosaccharides (one sugar unit) are the simplest type of carbohydrate
Components of the nucleic acids DNA and RNA have five carbon atoms
Glucose has six

16. Short-Chain Carbohydrates
Disaccharides consist of two sugar monomers
Lactose (glucose + galactose)
Sucrose (glucose + fructose)

17. Synthesis of a Sucrose Molecule
Sucrose (common table sugar) is synthesized from monomers of glucose and fructose in a condensation reaction
Figure 3.5 The synthesis of a sucrose molecule is an example of a condensation reaction. You are already familiar with sucrose—it is common table sugar.

18. Complex Carbohydrates
Polysaccharides, are straight or branched chains of many sugar monomers—often hundreds or thousands
Common polysaccharides: cellulose, glycogen, and starch
All consist of glucose monomers
Each has different chemical properties due to different patterns of covalent bonds that link glucose monomers

19. Cellulose Tough structural component of plants
Chains of glucose units stretch side by side and hydrogen bond at many -OH groups
Hydrogen bonds stabilize chains in tight bundles of long fibers

20. Starch (the Amylose part)
Main energy reserve in plants, which store it in roots, stems, leaves, fruits, and seeds
In amylose, a series of glucose units form a coiled chain

21. Glycogen
In humans and other animals, glycogen stored in muscles and liver functions as an energy reservoir

22. Chitin Monomers are glucose with nitrogen-containing carbonyl group
Long, unbranching chains linked by hydrogen bonds.
Strengthens hard parts of many small animals, such as crabs
Figure 3.7 Chitin. This polysaccharide strengthens the hard parts of many small animals, such as crabs.

23. Key Concepts Carbohydrates
Carbohydrates are the most abundant biological molecules
They function as energy reservoirs and structural materials
Different types of carbohydrates are built from the same sugars, bonded in different patterns