CHEMICAL BONDING IONIC BONDS COVALENT BONDS HYDROGEN BONDS METALLIC BONDS.
Chapter 2 - Chemical Bonds and Macromolecules
description
Transcript of Chapter 2 - Chemical Bonds and Macromolecules
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INTRODUCTORY BIOLOGY
By
HOANG ANH HOANG, Ph.D.
Department of Biotechnology,
Faculty of Chemical Engineering, HCMUT
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Chapter 2 Chemical bonds and Macromolecules
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Monomers - Macromolecules
• A cell Is mainly formed from Carbon compounds
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I. Chemical bonds
• Covalent bonds
• Non-covalent bonds
- Hydrogen bonds
- Ionic bonds
- Van de waal interaction
- Hydrophobic effect
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1. Covalent bonds
- Principle force to hold atoms together
- Sharing electrons
- Typical length: 0.15-0.2 nm
- strong bond
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• Single-double-triple bonds
C – C
C = C
C C---
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• Chirality (optical isomers)
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• Polar-nonpolar bonds
C – C, C – H : nonpolar
H-O-H: polar
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2. Noncovalent bonds
- Hydrogen bonds
- Ionic bonds
- Van der Waals bonds
- Hydrophobic effect
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• Hydrogen bonds
- A hydrogen bond is the interaction of a partially positively charged hydrogen atom with O or N (negative charged)
- Strength: ~1/20 covalent bonds
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• Example:
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• Ionic bond (Electrostatic)
Ionic interactions result from the attraction of a positively charged ion—a cation—for a negatively charged ion—an anion.
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• Van der Waals Interactions
When any two atoms approach each other closely, they create a weak, nonspecific attractive force called a van der Waals interaction.
• Weak: 1/3-1/4 hydrogen bonds
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• Hydrophobic Effect
- Molecules that contain nonpolar bonds are usually insoluble in water and are termed hydrophobic
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• Strength of the bonds
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II. Macromolecules
• Carbohydrates
• Proteins
• Nucleic acids
• (Lipid)
Monomers Polymers
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1. Carbohydrates
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Monosaccharides
• The general formula (CH2O)n, n can be 3, 5, 6,… and have two or more hydroxyl groups.
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• Ring formation
In aqueous solution, the aldehyde or ketone group of a sugar molecule tends to react with a hydroxyl group of the same molecule
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• Isomers
- Many monosaccharides differ only in the spatial arrangement of atoms
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Disaccharides
• The carbon that carries the aldehyde or the ketone can react with any hydroxyl group on a second sugar molecule to form a disaccharide.
• The linkage is called a glycosidic bond.
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Oligosaccharides and Polysaccharides
• Short chains are called oligosaccharides
• Long chains are called polysaccharides
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2. Nucleic acid
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• Monomer: nucleotides
Two types of chemically similar nucleic acids, DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are the principal information-carrying molecules of the cell.
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Five Different Bases to Build Nucleic Acids
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• A DNA molecule is composed of two antiparallel DNA strands held together by hydrogen bonds between the paired bases.
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The Structure of DNA Provides a Mechanism for Heredity
• How could the information to specify an organism be carried in a chemical form?
• How could this information be duplicated and copied from generation to generation?
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3. Protein
• The amino acid
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• Amino acid families:
- acidic
- basic
- uncharged polar
- nonpolar
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• Basic side chains
- example:
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• Acidic side chains
- example:
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• Uncharged polar side chains
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• Nonpolar side chains
- example:
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• There are 20 different of amino acids in proteins
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• Peptide bonds
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• N-terminus; C-terminus
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• Protein folding
- noncovalent bonds
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The α Helix and the β Sheet Are Common Folding Patterns
• α Helix
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• β Sheet
(A) An antiparallel β sheet; (B) A parallel β sheet.
Example: antiparallel β sheet
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Covalent Cross-Linkages Stabilize Extracellular Proteins
• the most common cross-linkages in proteins are covalent sulfur–sulfur bonds.
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• Protein structure
- Primary (sequence of aa)
- Secondary (local)
- Tertiary
The α Helix and the β Sheet
- Quaternary
> 1 polypeptide chain
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4. Lipids• R-COOH (R: tail)
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• Triacylglycerols (triglycerides)
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• Phospholipids
- the major constituents of cell membranes.