1 km (kilometer) = 10 3 m height of Mount Everest: 8.85 km. 1 m (meter) = 10 2 cm = 10 3 mm average adult height: 1.7 m = 5 7

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1 Cell Chemistry metric units elements, atoms, orbitals, the periodic table compounds, molecules, molecular bonds Metric units of length commonly used in biology 1 m = 3.28 feet; 1 km = 0.62 miles; 1 mile = 5,280 feet (lab manual, appendix II) LENGTH EXAMPLE 1 km (kilometer) = 10 3 m height of Mount Everest: 8.85 km 1 m (meter) = 10 2 cm = 10 3 mm average adult height: 1.7 m = cm (centimeter) = 10-2 m = 10 2 mm 1 inch = 2.54 cm structure and properties of water ph and buffers 1 mm (millimeter) = 10-3 m = 10 3 µm length of a red ant: 5 mm 1 µm (micrometer) = 10-6 m = 10 3 nm diameter of a red blood cell: 7 µm 1 nm (nanometer) = 10-9 m = 10 Å diameter of DNA helix: 2 nm 1 Å (angstrom) = m intracellular dimensions Metric units of mass commonly used in biology 1 kg = 2.20 lbs Metric units of volume commonly used in biology 1 liter = 2.11 pints = 1.06 quart MASS EXAMPLE 1 kg (kilogram) = 10 3 g newborn baby: 2-6 kg (4-13 lbs) 1 g (gram) = 10 3 mg 1 ml water 1 mg (milligram) = 10 3 µg = 10-3 g typical mosquito: 1-2 mg VOLUME 1 kl (kiloliter) = 10 3 L 1 L (liter) = 10 3 ml EXAMPLE 1 µg (microgram) = 10 3 ng = 10-6 g 1 ng (nanogram) = 10 3 pg = 10-9 g 1 pg (picogram) = 10 3 fg = g E. coli bacterium: 0.67 pg 1 fg (femtogram) = 10 3 pg = g 1 ag (attogram) = 10 3 fg = g a small virus: 10 ag 1 ml (milliliter) = 10-3 L = 10 3 µl 1 gm of water = 1 cm 3 water 1 µl (microliter) = 10-6 L = 10 3 nl 1 nl (nanoliter) = 10-9 L = 10 3 pl 1 pl (picoliter) = L DEFINITION There are 94 naturally occurring elements Most organisms are composed of 25 elements Hydrogen, Carbon, Nitrogen and Oxygen make up 96% of the human body A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus

2 There are 94 naturally-occurring elements Most organisms are composed of 25 elements Hydrogen, Carbon, Nitrogen and Oxygen make up 96% of the human body The air we breathe is mostly Nitrogen (N!N) ~ 78% Oxygen (O=O) ~ 21% Argon (Ar) 0.93% carbon dioxide (O=C=O) 0.33% transition metals halogens transition metals halogens alkaline metals alkaline metals Each element consists of one kind of atom (e.g., helium) DEFINITION An atom is the smallest unit of matter that still retains the properties of an element Atoms are composed of subatomic particles nucleus protons (2) cloud of negative charge (2 electrons) neutrons (2) electrons (2) Atoms are composed of subatomic particles Electron Atomic number is the sum of protons in an atom The atomic number determines the element atomic number of hydrogen = 1 atomic number of helium = 2 Proton Positive charge Determines element Neutron No charge Determines isotope Negative charge Participates in chemical reactions Outer-shell electrons determine chemical behavior Consists of neutrons and protons atomic number of carbon = 6 2 Protons 2 Neutrons 2 - Electrons 2e Electron cloud Electron cloud 6e 6 Protons 6 Neutrons 6 - Electrons

3 Atomic mass is the sum of protons plus neutrons atomic mass of hydrogen = 1 atomic mass of helium = 4 Electrons have negligible atomic mass atomic number atomic mass atomic mass of carbon = 12 2e Electron cloud Electron cloud 6e 2 Protons 2 Neutrons atomic mass = Electrons atomic mass = 12 6 Protons 6 Neutrons 6 - Electrons Isotopes are different mass forms of the same element DEFINITION An isotope is one of several atomic forms of an element, each containing a different number of neutrons and thus differing in atomic mass They have the same number of protons and electrons but a different number of neutrons Radioactive isotopes (or radioisotopes or radionuclides) are isotopes with unstable nuclei Radioactive isotopes (or radioisotopes or radionuclides) are isotopes with unstable nuclei Radioactive decay is the process by which an unstable atomic nucleus loses energy by emitting ionizing radiation or particles Ionizing radiation is composed of energized, subatomic particles (e.g., neutrons) or short wavelength electromagnetic waves (e.g., gamma rays, X-rays, UV rays) that can remove electrons from atoms or molecules

4 Ionizing radiation is composed of energized, subatomic particles (e.g., neutrons) or short wavelength electromagnetic waves (e.g., gamma rays, X-rays, UV rays) that can remove electrons from atoms or molecules ionizing non-ionizing Non-ionizing radiation is electromagnetic radiation (e.g., visible light, radio waves) that can shift electrons to higher energy states but not remove electrons from atoms or molecules DEFINITIONS Radiation is a process in which energetic particles or waves travel through space Non-ionizing radiation can only change the rotation, vibration, or electron valence of atoms and molecules (e.g., light, heat) Biological uses for ionizing radiation (e.g., "-rays, X-rays) Food preservation and sterilization - low dose inhibits sprouting (potatoes, onions) kills parasites (fresh fruit, dried foods) delays ripening (fresh fruit, vegetables) - medium dose extends shelf life (fish, strawberries) Ionizing radiation are subatomic particles or electromagnetic waves strong enough to remove electrons (e.g., "-rays, X-rays) kills parasites (seafood, poultry, meat) - high dose sterilization (seafood, poultry, meat, prepared foods) decontamination (spices) Biological uses for radioactive isotopes Food preservation and sterilization Archaeology (study of human cultures) and paleontology (study of life on earth) - Living tissues incorporate radioactive CO 2 from the air - Once the tissues die, no further uptake occurs - The decline in C-14 levels is proportional to the radioisotope half-life (5,730 years) Research applications Biological uses for radioactive isotopes Research applications Radioisotopes are chemically very similar to non-radioactive isotopes EXAMPLE: label a plant with radioactive [ 14 C]CO 2 ; then examine parts of the plant (e.g., proteins or sugars) that incorporate radioisotope Medical diagnosis and therapy

5 Computer Assisted Tomography (CAT) Scan 3D images constructed from 2D X-ray pictures taken at different angles Magnetic Resonance Imaging (MRI) Patient is exposed to pulses of electromagnetic energy from 3 magnets (X, Y, Z planes) High energy nuclei generated within the tissues provide information about the environment Biomedical Research Foundation of Northwest Louisiana Positron Emission Tomography (PET) Scan 3D image from positron-emitting, radioactive, biologically-active tracers Positron Emission Tomography (PET) Scan positron-emitting, radioactive tracers collide with electrons in adjacent tissue molecules causing release of "-rays Patient with metastatic breast cancer is injected with a radio-labeled sugar A positron is the anti-particle counterpart of the electron. It has the same mass as an electron and an electrical charge of 1e. When a positron collides with an electron, "-rays are emitted; the Tumor masses were detected in the left breast and associated lymph node "-rays are detected and used to form a computer image. Single Photon Emission Computed Tomography (SPECT) Scan 3D images generated from "-ray emitting radiopharmaceuticals MRI showing damaged area of the brain (seizures) MRI A patient with cutaneous T cell lymphoma was injected with a radioisotope-labeled monoclonal antibody that specifically binds tumor cells High uptake (red) of radio-labeled antibody is detected in the pelvis, the axilla, and skin of the thigh and right shoulder (green)

6 PET showing decreased uptake of radio-labeled glucose in seizure-damaged brain SPECT showing increased blood flow through the brain during a seizure MRI MRI SPECT PET PET Radioisotope-labeled antibodies for treating cancer Zevalin (Biogen Idec) and Bexxar (Corixa [Glaxo-SK]) are FDA-approved, radio-labeled monoclonal antibodies for treatment of Non-Hodgkins Lymphoma Yttrium-90 anti-cd20 (Zevalin ) mab - Y-90 half-life (T 1/2 ) = 64 hrs Electron The 4 most abundant elements in life First electron shell (can hold 2 electrons) Outermost electron shell (can hold 8 electrons) Iodine-131 anti-cd20 (Bexxar ) mab - I-131 T 1/2 = 8 days Hydrogen atomic number = 1 atomic mass = 1 Carbon atomic number = 6 atomic mass = 12 Nitrogen atomic number = 7 atomic mass = 14 Oxygen atomic number = 8 atomic mass = 16 H C N O Electron configurations of the first 18 elements Electrons determine how an atom behaves when it encounters other atoms Electrons orbit the nucleus of an atom in specific electron shells (or orbits) electrons in the outermost shell determine the chemical properties of an atom (valence electrons)

7 Ionic Bonds Chemical reactivities are based on energy levels and valence electrons When an atom loses or gains electrons, it becomes electrically charged Sodium atom (Na) Chlorine atom (Cl) Charged atoms are called ions Ionic bonds are formed between oppositely charged ions Complete outer shells NaCl MgCl 2 Sodium ion (Na ) Chloride ion (Cl#) CaCl 2 Sodium chloride (NaCl) Ionic bonds form between electron donors and acceptors Electron donors typically have only 1 or 2 electrons in their outer shell (e.g., sodium) Electron acceptors typically are 1 or 2 electrons short of a filled outer shell (e.g., chlorine) DEFINITION Compound: two or more elements combined and bonded in a fixed ratio Metals (e.g., Na, K, Mg 2, Mn 2 ) usually participate in ionic bonds Charged electron donors (Na ) and acceptors (Cl - ) are held together by electrostatic attraction Sodium Chlorine Sodium Chloride Na Cl Covalent bonding A covalent bond forms when two atoms share one or more pairs of outer-shell electrons Electron configurations of the first 18 elements

8 Covalent bonding A covalent bond forms when two atoms share one or more pairs of outer-shell electrons Chemical reactivities are based on energy levels and valence electrons CH 4 NH 3 H 2 O DEFINITIONS compound: when two or more different elements are combined and bonded in a fixed ratio (e.g., NaCl and H 2 O but not H 2 or O 2 ) The air we breathe is mostly Nitrogen (N!N) ~ 78% Oxygen (O=O) ~ 21% Argon (Ar) 0.93% carbon dioxide (O=C=O) 0.33% molecule: an electrically neutral cluster of two or more atoms joined by covalent bonds (e.g., H 2 O, H 2 and O 2 but not NaCl) Cell Chemistry metric units elements, atoms, orbitals, the periodic table compounds, molecules, molecular bonds structure and properties of water ph and buffers