Basic Unit of Life: The Cell. All living organisms are composed of one or more cells. Performs two type of functions: Generate energy: chemical reactions necessary to maintain our life. Passes the information for maintaining life to the next generation. Unicellular vs Multicellular Prokaryotes vs Eukaryotes What about virus (and phage)? Basic Unit of Life: The Cell. Prokaryotes and Eukaryotes. a) A membrane-bound nucleus is in eukaryotic cells and not in prokaryotes. b) Eukaryotic cells contain membrane-bound organelles, while prokaryotes do not. c) Prokaryotes have circular DNA molecules, while eukaryotes have linear chromosomes condensed with many proteins. 1
Basic Unit of Life: The Cell. Organelles 1. Nucleus : location of DNA and chromosomes. 2. Endoplasmic reticulum : makes and modifies newly synthesized polypeptides; synthesizes lipids. 3. Golgi body (Dictyosome in plants) : modifies polypeptides, and sorts and ships proteins and lipids for either secretion or for use inside the cell. 4. Mitochondria : produces ATP (chemical form of energy cells use). 5. Chloroplasts : site of photosynthesis in plants and algae. 6. Vesicles : functions such as transport or storage, and digestion. 7. Ribosomes : helps assemble polypeptides during protein synthesis. 8. Cytoskeleton : confers shape to cells and aids in the internal organization of the cell, allows cells and parts of cells to move, and aids in the movement of internal structures. Organelles and other structures of cells are made of polymers called macromolecules. Lipids and Polysaccharides for structure / function of membranes and energy storage. Proteins primary functional molecules of the cell: enzymatic, regulatory & structural. Nucleic Acids (DNA & RNA) involved in storage and transmission of information within the cell. 2
Lipids a) A broad group of hydrophobic (insoluble in water) organic compounds. b) Make up cellular membranes and define cells boundaries and organelles. Phospholipids 3
Proteins: a) Large organic compounds that determine many organismal characteristics. b) Proteins have different roles: (1) Enzymes (2) Hormones (3) Antibodies (4) Transcription factors (5) Structure (6) Movement (7) Regulation of cellular processes c) Made of monomers called amino acids, of which there are twenty. Average protein contains around 350 amino acids. Proteins: Amino Acids (1) An amino (-NH2) group at one end. (2) A carboxyl (COOH) group at one end. (3) A carbon atom in the middle, called the α (alpha) carbon. (4) A side group (called an R group) that determines its characteristics. 4
Proteins: Amino Acids Peptide bonds link amino acids together by linking the carboxyl group of one amino acid to the amino group on the next amino acid. Proteins Amino acids can form three-dimensional conformations that will ultimately determine how the protein will fold and function. Proteins are folded and interact with substrates by: Hydrogen bond Ionic bond Hydrophobic interaction van der Waals association Covalent bond Some molecules have the capacity to form several different types of weak bonds simultaneously or reversibly. This is the advantage of weak bonds: They are reversible. Because molecules are always in motion, weak bonds are constantly breaking and reforming. 5
Proteins Amino acids can form threedimensional conformations that will ultimately determine how the protein will fold and function. Hydrogen bond between amino acid backbone. α (alpha) helix β (beta) pleated sheet Proteins: Three dimensional structures 6
Proteins: Amino Acids (1) An amino (-NH2) group at one end. (2) A carboxyl (COOH) group at one end. (3) A carbon atom in the middle, called the α (alpha) carbon. (4) A side group (called an R group) that determines its characteristics. Proteins: Amino Acids Involved in chemical reaction. Can form ionic bonds : Association between positively & negatively charged groups. Dependent upon ph, and salt concentration (salt ions can shield charged groups by forming their own ionic bonds). They can also form hydrogen bonds. 7
Proteins: Amino Acids Polar amino acids are overall uncharged,but they have uneven charge distribution. They can form hydrogen bonds so they are called hydrophilic amino acids. Ser, Tyr and The - can be phosphorylated. Proteins: Amino Acids Hydrophobic interactions : Association of regions that are generally uncharged & carbon-rich. Association of hydrophobic regions results in exclusion of water. 8
Proteins: Amino Acids Cysteine can form disulfide covalent linkage 9
a) Involved in storage and transmission of information within the cell. a) Involved in storage and transmission of information within the cell. b) Composed of units called nucleotides: 10
Adenine and guanine are double-ring structures called purines Cytosine and thymine are single-ring structures called pyrimidines. a) Involved in storage and transmission of information within the cell. b) Made of units called nucleotides: c) Nucleotides are linked by phosphodiester bond. (5 and 3 of the sugar). 11
5 -TACG-3 12
1. Complementary Base Pairing. Nucleotides always pair by hydrogen bonding. A purine will always attach to a pyrimidine: a) Adenine pairs with thymine with two hydrogen bonds. b) Cytosine pairs with guanine with three hydrogen bonds. 2. The strands run opposite to each other, like opposite directions on a street (called antiparallel). 3. Hydrogen bonds help to hold the DNA double helix together so it does not separate spontaneously. However, the two strands can break apart (or denature) under several possible conditions: a) High temperatures (near boiling) can break hydrogen bonds, but the strands can reform (reanneal) at lower temperatures. b) ph extremes (< 3 or > 10) can break hydrogen bonds. c) Proteins can also break the double helix. DNA strands also held together by base stacking between pairs of neighboring bases. 13
1. Negative charge (will move toward a + electrode!) 2. Denatured and renatured (nucleic acid hybridization). 3. Soluble in water. 4. Insoluble in ethanol. 5. Absorbs UV light. 6. Double-stranded DNA can be stained and amounts of DNA can be measured using ethidium bromide. Ethidium bromide intercalates into the DNA double helix EthBR fluoresces under UV light, enabling us to see DNA no fluorescent color fluorescent 14
Ribonucleic Acid: RNA (1) The pentose sugars of the backbone are ribose instead of deoxyribose. (2) The base uracil (U) substitutes for thymine (T), and pairs with adenine (A). (3) RNA is a single strand, but can adopt different structure: RNA 5 HOCH2 O 4 H H H 3 2 OH OH RIBOSE O H 1 OH DNA 5 HOCH2 O H 4 H H H 1 OH 3 2 OH H 2-DEOXY-RIBOSE O Short nucleotide sequences can base pair to form short doublestranded regions. It may be needed to maintain the RNA s integrity. H N N H URACIL O H N O CH3 N H THYMINE RNA can undergo folding with secondary and tertiary structures. Ribonucleic Acid: RNA (1) The pentose sugars of the backbone are ribose instead of deoxyribose. (2) The base uracil (U) substitutes for thymine (T), and pairs with adenine (A). (3) RNA is a single strand, but can adopt different structure: Short nucleotide sequences can base pair to form short doublestranded regions. It may be needed to maintain the RNA s integrity. RNA can undergo folding with secondary and tertiary structures. 15
Ribonucleic Acid: RNA (1) The pentose sugars of the backbone are ribose instead of deoxyribose. (2) The base uracil (U) substitutes for thymine (T), and pairs with adenine (A). (3) RNA is a single strand, but can adopt different structure: Short nucleotide sequences can base pair to form short doublestranded regions. It may be needed to maintain the RNA s integrity. RNA can undergo folding with secondary and tertiary structures. Ribonucleic Acid: RNA (1) The pentose sugars of the backbone are ribose instead of deoxyribose. (2) The base uracil (U) substitutes for thymine (T), and pairs with adenine (A). (3) RNA is a single strand, but can adopt different structure: Short nucleotide sequences can base pair to form short doublestranded regions. It may be needed to maintain the RNA s integrity. RNA can undergo folding with secondary and tertiary structures. 16