Unit 3: Biochemistry Intro Review QUESTIONS!!

The Basics Atom: smallest unit of matter that maintains ALL of the properties of an element Proton, Neutron, Electron: (+), (0), (-) Element: substance that cannot chemically be broken down any further. Consisting entirely of one type of atom (ex. Carbon, hydrogen, oxygen) Compound: two or more elements combined Matter: has mass and takes up space

The Specifics Protons and Neutrons are located in the atomic nucleus together. Electrons are found in the outer valence shells of the atom. Atomic mass: the sum of the protons and neutrons in an atom. Electrons are not counted as part of the atomic mass b/c they are 1/2000 of 1 amu.

In the HUMAN BODY 96% of the body is made up of 4 elements: Oxygen, Carbon, Hydrogen, & Nitrogen (Outerspace Cowboys Hide in Narnia) The remaining 4 percent is composed of several important elements: P, Ca, K, S, Na, Cl, Mg Several trace elements Can use the regular symbols on periodic table….see? This is why you make sure to review EVERY homework assignment!!

Elements in the Human Body Oxygen – 65% Carbon – 18.5% Hydrogen – 9.5% Nitrogen – 3.3% All of these equal 96.3%. The other 4% are trace elements: Calcium (1.5), Phosphorous (1.0), Potassium (0.4), & others. Water Most abundant element in our body Click for animation Most abundant compound in our body

Reading the Periodic Table Atomic number 25 Tells number of protons in the nucleus Mn 54.9380 Atomic Weight Mass in the nucleus

Subscript A subscript is a small lowered number after a symbol for an element. H2O– the 2 is lowered and considered a subscript. The 2 indicates how many atoms of the element are present in that compound.

Chemical Compounds Compound: A substance formed by the chemical combination of 2 or more elements in definite proportions. Examples: H2O (water) NaCl (Salt) C6 H12 O6 (Sugar)

Chemical Formula States how many atoms are in each molecule. How many carbon atoms are in C6 H12 O6? How many hydrogen atoms? How many oxygen atoms? Click for answers 6 12 6

Chemical Equations CO2 + H2O -------- C6 H12 O6 + O2 REACTANTS Let’s say I give you a chemical equation like— CO2 + H2O -------- C6 H12 O6 + O2 What are the names of these compounds? Could you tell me which side are the reactants and which side are the products? REACTANTS PRODUCTS Carbon dioxide Water Sugar/glucose Oxygen Click for answers Click for answers

Which of the following is an element? ReviewQuestion #1 Which of the following is an element? Carbon dioxide Methane Oxygen Water

How many atoms are in: NH3 ReviewQuestion #2 How many atoms are in: NH3 1 2 3 4

Which of the following are the reactants? ReviewQuestion #3 Which of the following are the reactants? CH4 + 2 O2 CO2 + 2 H2O CH4 + 2 O2 CO2 + 2 H2O CH4 + 2 H2O None of the above

Isotopes All atoms of the same element contain the same number of protons **Some atoms have a greater number of neutrons and therefore have a greater atomic weight– these are isotopes** Most common isotope = carbon Carbon 12, Carbon 13, and Carbon 14 All have 6 protons, but different number of neutrons

Covalent Bonds Occurs when electrons are shared between two or more elements When 1 electron is shared, a single covalent bond is formed When 2 electrons are shared between elements, a double covalent bond is formed. Make up abbreviations or use well-known ones such as “e-” for electrons, or “p+” for protons, etc

Compounds and Molecules Molecules are formed between 2 atoms of the same element O2 or H2 Compounds are formed between two or more elements H2O

Electronegativity Defined as the attraction for a covalent bond Non-polar covalent bonds are formed between elements that have the same electronegativity Polar covalent bonds are formed when one atom in the bond has a higher electronegativity. In other words when they have different electronegativities.

Ionic bonds Typically form when an electron is pulled away from an element by another element Cation- positive charged atom Anion- negative charged atom Ionic bonds are very dependent on the environment to form and stay together Temperature, humidity, exposure to other elements

Weaker Interactions Other bonds exist in chemical interactions H bonds All very influential in biological chemistry Influences shape, structure, and formation of specific molecules (proteins) All very influential not necessary to write down!!

Special Properties of H2O

Special Properties of Water 1) Cohesion: The H’s in water create H bonds Creating relatively strong bonds between H2O molecules 2) High Specific Heat: takes a lot of energy to heat 1 gram of water 1 degree Celsius. 3) Expands when frozen 4) Excellent solvent (it is often referred to as the “Solvent of life.”) Notice the title on notes and handout….what is different? Water is abbrev as h2o!! Notice the same for item 2!

Acids, Bases and the pH scale The pH scale measures the concentration of H+ ions (how acidic something is) Ranges from 0-14 At 7: H+ ions and OH- ions are equal so it is neutral 0-7: acidic, has more H+ ions 7-14: basic, has more OH- ions

ACIDS: release H+ when mixed with water Sour, corrosive Ex: HCl, H2SO4 Always have H at front of formula BASES: release OH- when mixed with water Bitter, slippery, usually in cleaners NaOH, CaOH Always have OH at end of formula

What is a buffer? Buffers are weak acids or bases that react with strong acids and bases to prevent sharp changes in pH Helps to neutralize Help to control pH in blood, digestive tract, etc. to maintain homeostasis