1. The Chemical Composition of Cells
Chapter 2
The Chemical Composition of Cells

2. Learning Objectives- 1
Understand the Structure of the Molecular Components of Living Organisms
Carbohydrates, which supply and store energy and serve as structural building blocks, include sugars and polymers of sugars.
Proteins, which catalyze reactions and are structural building blocks, are polymers of amino acids.
The nucleic acids DNA and RNA, which code and express genetic information, are polymers of nucleotides.
Lipids are membrane components consisting mainly of carbon and hydrogen atoms derived from acetates and other molecules.
Secondary metabolites such as phenolics, alkaloids, and terpenoids often protect or strengthen plants.

3. Learning Objectives -2 To Understand Energy and Chemical Reactions
Energy can be stored and can move or change matter .
Chemical reactions involve either a net input or a net output of free energy.
The movement of electrons is the basis of energy transfer through oxidation and reduction reactions.
The terminal phosphate bond in ATP releases energy when broken.
NADH, NADPH, and FADH2 are universal carriers of energy-rich electrons in living organisms.

4. Learning Objectives -3
To Understand the Nature of Chemical Reactions and Enzymes
Enzymes position reactants, allowing reactions to occur with minimal activation energy or increase in temperature.
Cofactors such as coenzymes interact with enzymes to assist reactions and indirectly provide energy in the form of electrons for biochemical reactions.
Competitive and noncompetitive inhibition can slow or stop enzymatic reactions and pathways.
Enzymatic reactions are linked together into metabolic pathways.

5. Learning Objective
Know the basic structure of atom, and know the role of ionic, covalent and hydrogen bonds.

6. Key Terms: Atoms Proton Neutron Electron
positive electric charge, small mass
Neutron
uncharged, about same mass as proton
Electron
negative charge, extremely small mass

7. A Carbon Atom

8. Electrons Move around the nucleus at different energy levels
Allow elements to combine chemically to form chemical compounds
Ions are atoms which tend to gain or lose electrons

9. Electron Configurations

10. Acids and Bases
Acids dissociate in water to form hydrogen ions (protons, H+)
Bases dissociate in water to yield negatively charged hydroxide ions (OH-)

11. pH Scale
A measure of the relative concentrations of H+ and OH- in a solution
A solution’s acidity or alkalinity is expressed in terms of the pH scale

12. KEY TERMS
IONIC BOND
An electrostatic attraction between oppositely charged ions

13. Ionic Bonding

14. KEY TERMS COVALENT BOND
A chemical bond involving one or more shared pairs of electrons

15. Covalent Bonding in Hydrogen

16. Covalent Bonding in Methane

17. KEY TERMS HYDROGEN BOND
An attraction between a slightly positive hydrogen atom in one molecule and a slightly negative atom (usually oxygen) in another molecule

18. Animation: How Atoms Bond
CLICK TO PLAY

19. LEARNING OBJECTIVE
Discuss the properties of water, and explain the importance of water to life

20. Water Has a strong dissolving ability
Molecules form hydrogen bonds with one another (cohesion)
Molecules form hydrogen bonds to substances with ionic or polar regions (adhesion)
Adhesion & Cohesion are particularly important for transport
All living things require water to survive
Almost all chemical reactions that sustain life occur in aqueous solution
High Melting & Freezing Points
Insulation Property after freezing (e.g., lakes)

21. Water Structure

22. Animation: Structure of Water
CLICK TO PLAY

23. LEARNING OBJECTIVE
Describe the chemical compositions and functions of carbohydrates, lipids, proteins, and nucleic acids

24. KEY TERMS CARBOHYDRATE
An organic compound containing carbon, hydrogen, and oxygen in the approximate ratio of 1C:2H:1O

25. Carbohydrates 1 Include sugars, starches, cellulose
Important fuel molecules, components of molecules (nucleic acids) and cell walls

26. Carbohydrates 2 Monosaccharides Disaccharides Polysaccharides
simple sugars
Disaccharides
two monosaccharide units
Polysaccharides
many monosaccharide units

27. Common Monosaccharides

28. Sucrose Synthesis

29. Starch: A Storage Polysaccharide

30. Cellulose: A Structural Polysaccharide

31. KEY TERMS
LIPID
Any of a group of organic compounds that are insoluble in water but soluble in fat solvents

32. Lipids 1 Have a greasy consistency, do not readily dissolve in water
Important fuel molecules, components of cell membranes, waterproof coverings over plant surfaces, light-gathering molecules for photosynthesis

33. Lipids 2
A neutral fat or oil molecule is composed of a molecule of glycerol plus one, two or three fatty acids

34. Formation of a Neutral Fat or Oil

35. KEY TERMS
PROTEIN
A large, complex organic compound composed of amino acid subunits

36. Protein
A macromolecule composed of amino acids joined by peptide bonds
Order of amino acids determines structure and function of a protein molecule
Enzymes: Proteins that increase the rate of chemical reactions

37. Amino Acids

38. Peptide Bonds

39. Protein Synthesis Animation

40. Organization of Protein Molecules

41. KEY TERMS
NUCLEIC ACID
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)
Large, complex organic molecules composed of nucleotides

42. Nucleic Acids Control the cell’s life processes
Deoxyribonucleic acid (DNA)
Transmits information from one generation to the next
Ribonucleic acid (RNA)
Involved in protein synthesis

43. Nucleotides Repeating units that form nucleic acids
Order of nucleotides in a nucleic acid chain determines the specific information encoded
Adenosine triphosphate (ATP)
A modified nucleotide compound important in energy transfers in biological systems

44. Nucleic Acids

45. Nucleic Acids

46. Nucleic Acids

47. DNA Replication Animation

48. KEY TERMS ADENOSINE TRIPHOSPHATE (ATP)
An organic compound of prime importance for energy transfers in biological systems

49. ATP
ATP is a nucleotide that performs many essential roles in the cell.
It is the major energy currency of the cell, providing the energy for most of the energy-consuming activities of the cell.
It is one of the monomers used in the synthesis of RNA and, after conversion to deoxyATP (dATP), DNA.
It regulates many biochemical pathways.

50. LEARNING OBJECTIVE
Discuss the role of enzymes in cells

51. KEY TERMS ENZYME ACTIVATION ENERGY
An organic catalyst, produced within an organism, that accelerates specific chemical reactions
ACTIVATION ENERGY
The energy required to initiate a chemical reaction

52. Enzymes
Speed up a chemical reaction by lowering its activation energy (energy needed to initiate the reaction)
Most enzymes are highly specific and catalyze only a single chemical reaction
Without enzymes, chemical reactions in cells would occur too slowly to support life

53. Enzymes and Activation Energy

54. Enzyme-Substrate Complex

55. Energy & Chemical Reactions
Energy can be stored and can move or change matter: Potential energy is stored energy, while kinetic energy is energy having to do with motion.
The first law of thermodynamics states energy can be harnessed and transformed but not created or destroyed.
The second law of thermodynamics states that every transfer of energy increases the entropy (disorder) of matter in the universe.

56. LEARNING OBJECTIVE
State the first and second laws of thermodynamics, and describe how each applies to plants and other organisms

57. KEY TERMS FIRST LAW OF THERMODYNAMICS SECOND LAW OF THERMODYNAMICS
Energy cannot be created or destroyed, although it can be transformed from one form to another
SECOND LAW OF THERMODYNAMICS
When energy is converted from one form to another, some of it is degraded into a lower-quality, less useful form

58. Energy The ability to do work
Plants and other organisms cannot create the energy they require to live, but must capture energy from the environment and use it to do biological work

59. Potential and Kinetic Energy

60. Entropy
Continuously increases in the universe as usable energy is converted to lower-quality, less usable form (heat)
As each energy transformation occurs in organisms, some energy changes to heat
Given off into the surroundings
Can never be used again for biological work

61. Animation: Activation Energy
Click To Start

62. Secondary Metabolites
Secondary metabolites such as phenolics, alkaloids, and terpenoids often protect or strengthen plants