Carbon Compounds in Cells

1. Carbon Compounds in Cells Chapter 3

2. Importance of Carbon Carbon permeates the world of life—from the energy-requiring activities and structural organization of cells, to physical and chemical conditions that span the globe and influence ecosystems everywhere.

3. Humans and Global Warming • Fossil fuels are rich in carbon • Use of fossil fuels releases CO2 into atmosphere • Increased CO2 may contribute to global warming

4. Organic Compounds Hydrogen and other elements covalently bonded to carbon Carbohydrates Lipids Proteins Nucleic Acids

5. Carbon’s Bonding Behavior • Outer shell of carbon has 4 electrons; can hold 8 • Each carbon atom can form covalent bonds with up to 4 atoms

6. H Ball-and-stick model C H H H Structural formula Space-filling model Methane: Simplest Organic Compound Figure 3.2Page 36

7. Bonding Arrangements • Carbon atoms can form chains or rings • Other atoms project from the carbon backbone Glucose (ball-and-stick model) In-text figurePage 36

8. Hemoglobin Molecular Models Ball-and-stick model Space-filling model Figure 3.3Page 37 Ribbon model

9. Functional Groups • Atoms or clusters of atoms that are covalently bonded to carbon backbone • Give organic compounds their different properties

10. Examples of Functional Groups Methyl group - CH3 Hydroxyl group - OH Amino group - NH3+ Carboxyl group - COOH Phosphate group - PO3- Sulfhydryl group - SH

11. Carbohydrates Monosaccharides (simple sugars) Oligosaccharides (short-chain carbohydrates) Polysaccharides (complex carbohydrates)

12. Lipids • Most include fatty acids • Fats • Phospholipids • Waxes • Sterols and their derivatives have no fatty acids • Tend to be insoluble in water

13. Phospholipids • Main component of cell membranes • Hydrophobic head • Hydrophilic tails Fig. 3.14a,bPage 43

14. Sterols and Derivatives • No fatty acids • Rigid backbone of four fused-together carbon rings • Cholesterol - most common type in animals Cholesterol Figure 3.15aIn-text p43

15. Waxes • Long-chain fatty acids linked to long-chain alcohols or carbon rings • Firm consistency, repel water • Important in water-proofing

16. Protein Synthesis • Peptide bond • Condensation reaction links amino group of one amino acid with carboxyl group of next Water forms as a by-product Fig. 3.18aPage 45

17. Primary Structure • Sequence of amino acids • Unique for each protein • Two linked amino acids = dipeptide • Three or more = polypeptide • Backbone of polypeptide has N atoms: -N-C-C-N-C-C-N-C-C-N-

18. Second and Third Levels • Hydrogen bonding produces helix or sheet • Domain formation Tertiary structure Figure 3.19aPage 46 Secondary structure

19. Fourth Level Structure Some proteins are made up of more than one polypeptide chain Figure 3.20Page 47 HLA-A2 quaternary structure

20. alpha chain Hemoglobin beta chain beta chain alpha chain

21. Nucleotide Structure • Sugar • At least one phosphate group • Nitrogen-containing base ATP Figure 3.23aPage 50

22. Nucleotide Functions • Energy carriers • Coenzymes • Chemical messengers • Building blocks for nucleic acids

23. DNA • Double-stranded • Sugar-phosphate backbone • Covalent bonds in backbone • H bonds between bases Figure 3.25Page 51

24. RNA • Usually single strands • Four types of nucleotides • Unlike DNA, contains the base uracil in place of thymine • Three types are key players in protein synthesis