General Biology/Getting Started/Matter
General Biology | Getting Started | Cells | Genetics | Classification | Evolution | Tissues & Systems | Additional Material
Matter is defined as anything that has mass (an amount of matter in an object) and occupies space (which is measured as volume).
- Particles, from smallest to largest and amal is the greatest
- Origin of matter
- All matter consists of atoms, which are composed of : electrons, protons, neutrons
- Example: Hydrogen
- The simplest element
- One proton (+)
- One electron in orbit (-)
- Built by adding one proton (and one electron) at a time
- Number of protons determines atomic number and number of electrons
- Neutrons
- Neutral charge
- Contribute mass
- May decay
- Oxygen
- 8 protons (mass)
- 8 electrons
- 8 neutrons (mass)
Mass and isotopes
edit- Atomic mass
- Sum of masses of protons and neutrons
- Measured in daltons or AMU (Atomic Mass Unit)
- An AMU is 1/12 the mass of Carbon-12
- proton ~1 AMU or dalton
- 6.024 x 1023 daltons/gram
- Atoms with same atomic number belong to same element
- Isotopes
- Same atomic number but different atomic mass
- Some are radioactive
- Uses of isotopes
- Radioactive: 3H, 14C, 32P, 35S
- Tracers in biochemical reactions
- Detection of molecules in recombinant DNA technology (genetic engineering)
- Half-life: dating of rocks, fossils
- Non-radioactive (N, C, O)
- Diet of organisms (including fossils)
- Biochemical tracers
- Radioactive: 3H, 14C, 32P, 35S
Electrons
edit- Negative charge
- Held in orbit about nucleus by attraction to positively charged nucleus
- Atom may gain or lose electron, altering charge
- Cation: loses electron, positive charge
- Na+
- Anion: gains electron, negative charge
- Cl-
- Cation: loses electron, positive charge
- Determine chemical properties of atoms
- Number
- Energy level
Chemical bonds
edit- Form molecules
- Enzymes: make, break, rearrange chemical bonds in living systems
- Ionic
- Covalent
- Sharing of one or more pairs of electrons
- Called single, double, or triple
- No net charge (as in ionic bonds)
- No free electrons
- Give rise to discrete molecules
- Hydrogen
- Sharing of one or more pairs of electrons
Chemical reactions
edit- Formation and breaking of chemical bonds
- Shifting arrangement of atoms
- Reactants -> products
- Reactions are influenced by:
- Temperature
- Concentration of reactants, products
- Presence of catalysts (enzymes)
- Oxidation:reduction
- Essential for life
- ~75% earth's surface is water
- Life evolved in water
- Solvent for many types of solutes
- High specific heat
- High polarity
- Creates a slightly negative Oxygen and a Slightly positive hydrogen
- allows formation of Hydrogen Bonds
Hydrogen bonding
edit- A type of polar interaction
- Critical for:
- Protein structure
- Enzymatic reactions
- Movement of water in plant stems
- Weak and transient
- Powerful cumulative effect
- Solubility of many compounds
- Cohesion (capillary action)
- Lower density of ice
- Formed between molecules other than water
Water organizes nonpolar molecules
- Nonpolar molecules: no polarity (+/-) charges
- Hydrophobic: exclude water because they don't form hydrogen bonds with it
- Consequences:
- Membranes
- Protein structure
- Hydrophilic: polar substances associate with water
Ionization of water: H2O -> H+ + OH-
- Forms a Hydrogen ion (H+), hydroxide ion (OH-)
- Due to spontaneous breakage of covalent bond
- At 25 °C, 1 liter of water contains 10-7 moles of H+ ions: 10-7 moles/liter
pH
- A convenient way of indicating H+ concentration
- pH = -log[H+]
- For water, pH = -log[10-7] = 7
- Since for each H+ in pure water, there is one OH-, pH of 7 indicates neutrality
- Logarithmic scale
Buffer
- Reservoir for H+
- Maintains relatively constant pH over buffering range
References
editThis text is based on notes very generously donated by Dr. Paul Doerder, Ph.D., of the Cleveland State University.