The student is expected to: 4B investigate and explain cellular processes, including homeostasis, energy conversions, transport of molecules, and synthesis of new molecules and 9A compare the structures and functions of different types of biomolecules, including carbohydrates, lipids, proteins, and nucleic acids

KEY CONCEPT Living things consist of atoms of different elements

Living things consist of atoms of different elements. An atom is the smallest basic unit of matter. An element is one type of atom. Hydrogen atom (H) H O Oxygen atom (O)

An atom has a nucleus and electrons. The nucleus has protons and neutrons. Electrons are in energy levels outside nucleus. Oxygen atom (O) Nucleus: 8 protons (+) 8 neutrons outermost energy level: 6 electrons (-) inner energy level: 2 electrons (-)

Protons with a positive charge Electrons with a negative charge Neutrons with a neutral charge/ no charge

Elements Elements are pure substances made up of one kind of atom. All atoms of that element look just the same, with the same number of protons, neutrons (average), and electrons. The number of protons indicates the type of atom.

O A compound is made of atoms of different elements bonded together. water (H2O) O H _ +

A compound is made of atoms of different elements bonded together. water (H2O) carbon dioxide (CO2)

A compound is made of atoms of different elements bonded together. water (H2O) carbon dioxide (CO2) many other carbon-based compounds in living things

Ions form when atoms gain or lose electrons. An ion is an atom that has gained or lost one or more electrons. positive ions form when atoms lose electrons negative ions form when atoms gain electrons Ionic bonds form between oppositely charged ions. Sodium atom (Na) Chlorine atom (CI) Sodium ion (Na+) Chloride ion (CI-) Na loses an electron to CI ionic bond gained electron

Atoms share pairs of electrons in covalent bonds. A covalent bond forms when atoms share a pair of electrons. multiple covalent bonds diatomic molecules covalent bonds Oxygen atom (O) Carbon atom (C) Carbon dioxide (CO2 )

Isotopes are uncharged atoms with a different atomic mass than the common element. Count the number of neutrons in each isotope of carbon above

Isotopes Carbon-12 Carbon-14 P = 6 P = 6 N = 6 N = 8 e = 6 e = 6 Carbon-14 has two more neutrons than Carbon-12. it’s nucleus has a greater mass.

Some isotopes are radioactive and break down at a constant rate over time. We can use these to help date rocks and fossils, use them to treat cancers, and use them as biological markers within an organism

The student is expected to: 4B investigate and explain cellular processes, including homeostasis, energy conversions, transport of molecules, and synthesis of new molecules and 9A compare the structures and functions of different types of biomolecules, including carbohydrates, lipids, proteins, and nucleic acids

Life depends on hydrogen bonds in water. Water is a polar molecule. Polar molecules have slightly charged regions. O H _ + Nonpolar molecules do not have charged regions. Hydrogen bonds form between slightly positive    hydrogen atoms and slightly negative atoms.

Polarity refers to the unequal sharing of electrons. Although water is an electrically neutral molecule it is does exhibit polarity. Polarity refers to the unequal sharing of electrons. Polarity creates partial positive charges and partial negative charges on each water molecule. The electrons spend more time around oxygen than they do around Hydrogen. Hydrogen is NAKED!

POLARITY The shared electrons between oxygen and hydrogen tend to spend more time orbiting the oxygen atom giving it a unequal charge distribution e In a water molecule, are the electrons more likely to be near the oxygen nucleus or the hydrogen nucleus? _______________ Oxygen nucleus

The oxygen end gets a partial negative charge Hydrogen end gets a partial positive charge

Negative charges are attracted to positive charges. In a water molecule the negative oxygen end is attracted to the positive hydrogen end of another molecule This creates a weak Hydrogen Bond between water molecules

Water can form multiple hydrogen bonds between molecules Hydrogen bonding the charges in parentheses are partial charges H O (-) (+) Water can form multiple hydrogen bonds between molecules

Hydrogen bonds are responsible for some important properties of water. high specific heat Cohesion a)Surface tension Adhesion b)meniscus

Cohesion Cohesion is an attraction between molecules of the same substance. Water is very cohesive because of hydrogen bonding.

Cohesion creates surface tension A measure of how difficult it is to stretch or break the surface of a liquid. The weight of the paper clip isn’t enough to break the weak hydrogen bonds between the water molecules

Water striders rely on cohesion between water molecules

Adhesion Adhesion is an attraction between molecules of different substances. Water also sticks to, or adheres, to other surfaces well. This is why a meniscus forms when you are measuring liquid.

Capillary action Cohesion and adhesion combined allows water to move up certain materials. This is how plants get water from the ground up through their stems

Polarity also affects Solubility Solubility refers to the ability of one substance (solute) to dissolve in another (solvent)

Many compounds dissolve in water. A solution is formed when one substance dissolves in another. A solution is a homogeneous mixture. Solvents dissolve other substances. Solutes dissolve in a solvent. solution

Solubility Polar substances can dissolve other polar substances. Non-polar substances dissolve other non-polar substances. Polar substances and non-polar substances do not mix.

“Like dissolves like.” Polar solvents dissolve polar solutes. Nonpolar solvents dissolve nonpolar solutes. Polar substances and nonpolar substances generally remain separate.

Water is a polar molecule Oil is a non-polar molecule Oil and water do not mix for this reason

Some compounds form acids or bases. An acid releases a hydrogen ion when it dissolves in water. high H+ concentration pH less than 7 more acidic stomach acid pH between 1 and 3

A base removes hydrogen ions from a solution. low H+ concentration pH greater than 7 bile pH between 8 and 9 more basic

A neutral solution has a pH of 7. pure water pH 7

Myth: All acids are harmful and will burn your skin. Busted: Not all acids cause burns…some examples are lemon juice and vinegar

Myth: Bases are safe to handle Busted: Lye or Sodium Hydroxide is very dangerous