Life on earth is based on carbon. A carbon atom forms four covalent bonds It can join with other carbon atoms to make chains or rings

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2 Some atoms share outer shell electrons with other atoms, forming covalent bonds Atoms joined together by covalent bonds form molecules Molecules can be represented in many ways Table 2.8

3 Life on earth is based on carbon A carbon atom forms four covalent bonds It can join with other carbon atoms to make chains or rings

4 Carbon skeletons vary in many ways Ethane Propane Carbon skeletons vary in length. Butane Isobutane Skeletons may be unbranched or branched. 1-Butene 2-Butene Skeletons may have double bonds, which can vary in location. Cyclohexane Benzene Skeletons may be arranged in rings.

5 3.6 Forming Macromolecules Fig An organic molecule consists of a carbon-based core with functional groups attached Functional groups are the groups of atoms that participate in chemical reactions A relatively small number of structural patterns underlies life s structural and functional diversity

6 Ethane Ethanol Flammable gas Makes you drunk

7 3.6 Forming Macromolecules Cells make a huge number of large molecules from a small set of small molecules Most of the large molecules in living things are macromolecules called polymers Polymers are long chains of smaller molecular units called monomers Organisms are primarily made of four kinds of macromolecules Proteins Nucleic acids Carbohydrates Lipids

8 Macromolecules are made by a process termed dehydration synthesis Fig. 3.18a H 2 O Macromolecules are broken down by a process termed hydrolysis Fig. 3.18b H 2 O HO H HO H Energy HO H Energy HO H HO H HO H Both types of processes require enzymes

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11 3.7 Proteins Made up of subunits called amino acids Fig Six amino acids There are 20 common amino acids, and they fall into one of four general groups Five amino acids Six amino acids Three amino acids

12 Each amino acid contains: an amino group a carboxyl group an R group, which distinguishes each of the 20 different amino acids Amino group Carboxyl (acid) group

13 Amino acids monomers can be linked by peptide bonds Carboxyl group Amino group PEPTIDE BOND Dehydration synthesis Amino acid Amino acid Dipeptide

14 Protein Structure Determined by the sequence of its amino acids There are four general levels Primary Secondary Tertiary Quaternary

15 Fig Levels of protein structure

16 Atoms are shown as balls in this space-filing model. The protein s shape (yellow) fits into the grooves of DNA. The protein is a repressor that inhibits transcription of a gene.

17 Protein Structure Primary structure The specific amino acid sequence of a protein Secondary structure The initial folding of the amino acid chain by hydrogen bonding Tertiary structure The final three-dimensional shape of the protein Quaternary structure The spatial arrangement of polypeptides in a multi-component protein

18 More info (not on exam) A typical protein contains amino acids - some are much smaller (smallest are peptides) -some much larger (titin a protein in skeletal and cardiac muscle contains 26,926 amino acids in a single chain!)

19 Protein Structure Changes in a protein s environment can cause a protein to denature It loses its threedimensional structure And becomes inactive Fig. 3.22

20 Chaperone Proteins Help newly-produced proteins to fold properly Fig Chaperone protein deficiencies may play a role in certain diseases like Alzheimer s

21 Proteins are the most structurally and functionally diverse of life s molecules Proteins are involved in cellular structure movement defense transport Communication Enzymes are proteins, but not all proteins are enzymes

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25 3.8 Nucleic Acids Long polymers of repeating subunits termed nucleotides Nucleic acids such and DNA and RNA serve as the blueprints for proteins They ultimately control the life of a cell A nucleotide is composed of three parts Five-carbon sugar Nitrogen-containing base Phosphate

26 Fig The structure of a nucleotide Nitrogenous bases

27 Fig The DNA double helix Space-filling model

28 DNA (Deoxyribonucleic acid) Sugar = Deoxyribose Bases = A, G, C, T Double-stranded RNA (Ribonucleic acid) Sugar = Ribose Bases = A, G, C, U Single-stranded

29 Stretches of a DNA molecule called genes program the amino acid sequences of proteins DNA information is transcribed into RNA, a single-stranded nucleic acid RNA is then translated into the primary structure of proteins more later