From Atoms to Cells: Fundamental Building Blocks. Models of atoms. A chemical connection

Transcription

1 From Atoms to Cells: A chemical connection Fundamental Building Blocks Matter - all materials that occupy space & have mass Matter is composed of atoms Atom simplest form of matter not divisible into simpler substances composed of protons, neutrons, & electrons Element atoms that differ in numbers of protons, neutron & electrons Models of atoms

2 Atomic number number of protons Mass number number of protons & neutrons Isotopes variant forms of an element that differ in mass number Atomic weight average of the mass numbers of all of the element s isotopic forms Molecules & Bonds Molecule distinct chemical substance that results from the combination of two or more atoms Chemical bonds when 2 or more atoms share, donate or accept electrons. 3 types: covalent, ionic, & hydrogen

3 3 Types of Chemical Bonds 1. Covalent bonds electrons are shared among atoms polar covalent bonds unequal sharing nonpolar covalent bonds equal sharing 2. Ionic bonds electrons are transferred to one atom forming positively charged cations & negatively charged anions 3. Hydrogen bonds weak bonds between hydrogen & other atoms 3 Types of Chemical Bonds Covalent bonds

4 H 2 O a polar molecule Ionization H-bonding in H 2 O

5 Solution a mixture of one or more substances called solutes, dispersed in a dissolving medium called a solvent Solutes Na+ & Cl - Solvent H 2 O Most biological activities occur in aqueous (water-based) solutions. hydrophilic molecules dissolve in water hydrophobic molecules repel water amphipathic molecules -have both hydrophilic and hydrophobic properties

6 Ionization of H 2 O releases hydrogen ions [H + ] & hydroxyl ions [OH - ] ph scale ranges from 0 to 14, expresses the concentration of H + ions ph is the negative logarithm of the concentration of H+ ions. ph 6 = moles H + / l ph 9 = moles H + / l ph scale Carbon Atom Carbon atoms contain a total of 6 electrons, with only four in the outer shell. Very diverse as it can bond with up to four different elements. Often shares with other carbon atoms, producing long carbon chains. Hydrocarbons are chains of carbon bonded only to hydrogen atoms.

7 Functional Groups and Isomers Functional groups are specific combinations of bonded atoms that always react in the same manner, regardless of the particular carbon skeleton. Determine polarity of organic molecule. Biologically Important Functional Groups Group Structure Compound Significance Hydroxyl R OH Alcohols Polar, forms H-bonds; R C O some Aldehydes sugars Polar; some sugars Example: Formaldehyde and amino acids; Carbonyl H Example: Ethanol Polar; O some Polar; some sugars Ketones sugars Example: Acetone Example: R C R Formaldehyde Carboxyl Polar; R C O some Carboxylic sugars Example: Acetic acid Example: OH Acids Acetone Amino Polar, acidic; R fats N H and amino Polar, basic; amino acids Amines acids Example: Tryptophan Example: Polar, acidic; Acetic some H acid amino acids Sulfhydryl Example: Polar, Adenosine R SH basic; triphosphate amino Thiols acids Example: Ethanethiol Disulfide Bonds; Example: O some Tryptophan amino acids Organic Phosphate Example: Ethanethiol 21 R C R Phosphates OH Polar, forms H-bonds; some sugars and amino acids Example: Ethanol Polar, acidic; fats and amino acids Disulfide Bonds; some amino acids Polar, acidic; some amino acids Example: Adenosine triphosphate

8 Isomers Isomers -organic molecules that have identical molecular formulas but a different arrangement of atoms. Macromolecules Carbohydrates, lipids, proteins, and nucleic acids are referred to as macromolecules because of their large size. Polymers are made up of monomers. Dehydration - Removal of water molecule. Hydrolysis - Addition of water molecule. Enzymes speed up reactions. Macromolecules Some molecules called macromolecules because of their large size Usually consist of many repeating units Resulting molecule is a polymer (many parts) Repeating units are called monomers Some examples: Category Lipids Carbohydrates Proteins Nucleic Acids Example Fat Polysaccharide Polypeptide DNA, RNA Subunit(s) Glycerol & fatty acids Monosaccharide Amino acid Nucleotide 24

9 Synthesis and Degradation of Polymers 25 Carbohydrates Used as immediate energy sources. Monosaccharides - Single sugar molecule. Glucose, ribose, deoxyribose Disaccharides - Contain two monosaccharides joined during dehydration reaction. Sucrose Polysaccharides - Polymers of monosaccharides. Starch, cellulose, chitin Carbohydrates

10 Lipids Insoluble in water due to hydrocarbon chains. Fats Glycerol - Contains three OH - groups. Triglycerides - Three fatty acids attached to each glycerol molecule. Fatty acid consists of long hydrocarbon chain.» Saturated - No double bonds.» Unsaturated - Double bonds. Fat and Fatty Acids

11 Lipids Phospholipids Instead of third fatty acid attached to glycerol as in fat, there is a polar phosphate group. Hydrophilic heads and hydrophobic tails. Arrange themselves so polar heads are adjacent to water.» Bulk of cell plasma membrane consists of phospholipid bilayer. Phospholipids Lipids Steroid Have skeletons of four fused carbon rings. Cholesterol, testosterone, estrogen Waxes Long-chain fatty acid bonds with a long-chain alcohol. High melting point Waterproof Resistant to degradation

12 Proteins Functions Support Enzymes Transport Defense Hormones Motion Proteins Amino acids are subunits of proteins. Bond to a hydrogen atom, an amino group - NH 2, an acidic group -COOH, and an R (remainder) group. Peptide Bond - Covalent bond between two amino acids. Peptide - Two or more amino acids bonded together. Polypeptide - Chain of many amino acids joined by peptide bonds.

13 37 Proteins Protein Structure Primary - Sequence of amino acids. Secondary - Polypeptide coils or folds in a particular fashion. Tertiary - Folding and twisting that results in final three-dimensional shape of a polypeptide. Quaternary - Consists of more than one polypeptide.

14 Protein Folding Disorders As proteins are being synthesized, chaperones bind and prevent incorrect interactions. Mad cow is an example of a category of fatal brain disorder TSEs, that could be due to misfolded proteins. Nucleic Acids Polymers of nucleotides with very specific cell functions. DNA (deoxyribonucleic acid) Double stranded RNA (ribonucleic acid) Single stranded Every nucleotide is made up of phosphate, pentose sugar, and a nitrogenous base. Complementary base pairing Nucleotides 42

15 DNA RNA Nucleic Acids ATP (adenosine triphosphate) is composed of adenine and ribose. In cells, the terminal phosphate bond is hydrolyzed to give the molecule ADP (adenosine diphosphate) and a phosphate molecule. Releases energy

16 ATP 46 Prokaryotes vs Eukaryotes Size smaller Larger Nucleus - + Organelles - + Chromosomes 1 circular Multiple, linear Ribosomes smaller 70s Larger 80s r Define life Organized Require Energy Respond to stimuli Reproduce Adapt growth