Chapter 2

The atom

What is an Atom? Atom: Smallest unit of all matter 3 Main Parts: Proton (+) Neutron (0) Electron (-) Protons & Electrons usually equal in number Elements (substance made of only 1 type of atom) are identified on the Periodic Table

Reading the Periodic Table Atomic Number: Number of protons the atom contains Usually # of electrons also Atomic Mass: Combined # of protons and neutrons inside the nucleus Electrons too small to affect mass

Reading the Periodic Table How many protons, electrons, and neutrons does Carbon contain? Protons = ______ Electrons = ______ Neutrons = ______ 6 Atomic Number: Number of protons the atom contains Usually # of electrons also Atomic Mass: Combined # of protons and neutrons inside the nucleus Electrons too small to affect mass

Reading the Periodic Table How many protons, electrons, and neutrons does Carbon contain? Protons = ______ Electrons = ______ Neutrons = ______ 6 6 Atomic Number: Number of protons the atom contains Usually # of electrons also Atomic Mass: Combined # of protons and neutrons inside the nucleus

Reading the Periodic Table 6 + Neutrons = 12 How many protons, electrons, and neutrons does Carbon contain? Protons = ______ Electrons = ______ Neutrons = ______ 6 Protons + Neutrons = 12 6 6 Atomic Number: Number of protons the atom contains Usually # of electrons also Atomic Mass: Combined # of protons and neutrons inside the nucleus Electrons too small to affect mass

What’s the: Atomic number = amount of protons Atomic number = amount of protons Atomic number = protons usually same as electrons Atomic mass = amount of protons + neutrons Atomic mass = amount of protons + neutrons 4 A) Atomic number of Beryllium? B) Atomic mass of Beryllium? C) How many protons? D) How many electrons? E) How many neutrons? 9 4 4 5

Electron Cloud Electrons orbit the nucleus in “energy levels” 1st level: closest to nucleus stable w/ 2 electrons

Electron Cloud Electrons orbit the nucleus in “energy levels” 7 Electrons orbit the nucleus in “energy levels” 1st level: closest to nucleus stable w/ 2 electrons 2nd level: stable w/ 8 electrons 1 6 8 5 1 4 2 2 3

Electron Cloud Electrons orbit the nucleus in “energy levels” 1st level: closest to nucleus stable w/ 2 electrons 2nd level: stable w/ 8 electrons Examine Carbon. It has 2 electrons in the first level and 4 electrons in the 2nd level. Is Carbon stable?

Electron Cloud Electrons orbit the nucleus in “energy levels” 7 Electrons orbit the nucleus in “energy levels” 1st level: closest to nucleus stable w/ 2 electrons 2nd level: stable w/ 8 electrons 3rd level: Atoms are stable when the outermost level is “full” 7 6 8 1 8 6 1 5 1 5 2 2 4 4 2 3 3

Molecules Molecule: 2 or more atoms held together by a covalent bond 8 protons 8 electrons Molecule: 2 or more atoms held together by a covalent bond Form when atoms are unstable Covalent Bond: Chemical bond where atoms share electrons Ex: Oxygen (O2) Why unstable? Only 6 electrons in outer energy level 6 1 1 5 2 4 2 3

Molecules Molecule: 2 or more atoms held together by a covalent bond Form when atoms are unstable Covalent Bond: Chemical bond where atoms share electrons Ex: Oxygen (O2) Why unstable? Only 6 electrons in outer energy level What happens? Oxygen atom will share two electrons with neighboring oxygen atom End result? Both end up with 8 electrons in outer level (stable)

Ionic Bonds e e e e e e e e e e e e e e e e e e e e e e e e e e e e + - Ionic bond: chemical bond where electrons are gained/lost Held together by magnetic attraction Cause: 1 atom may steal an electron from another Ion: + or – charged atom Ex: Sodium + Chlorine = Sodium Chloride

Na Cl Na Cl 11+ 17+ 11+ 17+ 11- 17- 10- 18- +1 -1 Protons (+) Na atomic number = 11 Before the bonding Cl atomic number = 17 After the bond Na Cl Protons (+) Electrons (-) Net charge Na Cl Protons (+) Electrons (-) Net charge 11+ 17+ 11+ 17+ 11- 17- 10- 18- +1 -1

Recap Name the 3 subatomic particles. Which subatomic particles are found inside the nucleus? The atomic number usually allows us to determine the amount of which two subatomic particles? If an atom has the atomic mass of 14 and the atomic number of 6, how many protons, neutrons, and electrons does the atom contain? After an ionic bond is formed, what is the charge of the atom that gained an electron? Which type of chemical bond shares electrons?

water H H O

+ + Water Basics 1 1 1 1 Polar: part of a molecule is slightly positive, while another part is slightly negative Creates hydrogen bonds where one water sticks to another 1 2 6 1 5 2 3 4 -

Red = Oxygen (negative) White = Hydrogen (positive) - - - - - - - - - + + + + + + + + + + + + + + + + + + - - - - - - - - + + + + + + + + + + + + + + + + + + - - - - - - - - - + + + + + + + + + + + + + + + + + +

Water Properties High specific heat: Resists temperature changes A lot of energy is needed to break bonds between water molecules Helps to maintain a constant body temp (Homeostasis) Cohesion: polar water molecules attracted to other polar water molecules Adhesion: polar water sticks to other molecules 7ml 6.8ml Why can this insect walk on water? It is not heavy enough to break the bonds that hold the water molecules together.

Solutions Solution: mixture where 1 substance dissolves in another 2 parts to a solution 1) Solute: substance that dissolves Atoms, ions, molecules 2) Solvent: substance in which the solute is dissolved in Usually water S U G A R K O O L A I D

Solutions Ex: Human blood Solvent: Plasma (watery part of blood) Solutes: Carbs, proteins, sugars, etc…

pH Scale Acid Base Few H+ More H+ neutral Few OH- More OH- Lemons Soft drink Milk Blood Baking soda Ammonia pH scale measures the amount of H+ ions in a solution pH scale measures how acidic or basic a substance is and ranges from 0 to 14 1 minute: Discuss with your neighbor: Which base has the most H+ ions? Which substance has the fewest H+ ions? Which is the strongest acid? blood Ammonia Lemons

pH Scale Some molecules release H+ ion when dissolved H+ ions accumulate (acids) Acidic solution Substance A H+ H+ H+ H+ H+ H+ H+ H+ H+

pH Scale Some molecules release OH- ions when dissolved Basic (alkaline) solution Some molecules release OH- ions when dissolved OH- ions accumulate (bases) OH- OH- OH- Substance B OH- OH- OH- OH- OH- OH-

Recap 1) Name 4 basic features of water. 2) Which water property explains that one atom is positively charged, while another is negatively charged? 3) How does cohesion and adhesion differ? 4) Which is a stronger acid? Substance A with a pH of 5 or substance B with a pH of 3? 5) Which has more H+ ions? Substance A with a pH of 5 or substance B with a pH of 3? 6) How does a solute differ from a solvent?

Organic molecules

Organic Molecules Carbon = building block of organic molecules 6 protons 6 electrons Carbon = building block of organic molecules Carbon is unique Unstable: 2nd level not full Will bond up to four times 1 1 4 2 2 3

Organic Molecules Monomer: Small carbon molecules Ex: Amino acid Polymer: chain of linked monomers Ex: Protein monomer monomer Polymer monomer monomer monomer monomer monomer

Carbohydrates

Carbohydrates Readily available food source C1: H2: O1 ratio Ex: Glucose = C6 H12 O6 Monomer: Monosaccharides Simple sugars Bond to form larger sugars Polymer: Polysaccharide Complex sugars Fructose (monosaccharide) Glucose (monosaccharide) Sucrose (disaccharide)

Carbohydrate Polymers: Polysaccharide Polysaccharides: Long chain of monosaccharides Ex: Starch: excess plant sugar converted & stored Ex: Glycogen: animal starch stored in liver & muscles Ex: Cellulose: used in plants to make cell walls glucose glucose glucose glucose glucose

Recap How many electrons does Carbon have in the 1st energy level? 2nd energy level? Which type of organic molecule is most commonly used as energy for cells? What are the monomers of carbohydrates called? What are the polymers of carbohydrates called? Which polymer is stored by animals? Which polymer is stored by plants?

Lipids

1 2 Lipid Structure Monomer: Fatty Acid Polymer: Lipid Examples: Fats, Oils, Waxes Phospholipid Structure (3 parts): “Head” of glycerol & phosphate(polar) “Tail” of 2 fatty acids (non-polar) Make up the cell membrane Phospholipid 1 2

Lipid Structure Triglyceride: Structure (2 parts) “head” = glycerol Glycerol molecule Triglyceride: Structure (2 parts) “head” = glycerol “Tail” = 3 fatty acids Function Provide Energy for cells Insulation Cholesterol: Gives cell membrane flexibility

Saturated Fats Fats and oils have different types of fatty acids. Long chain of carbon bonds (all single bonds) Each C is “saturated” with H atoms Single bonds are easier to compact = solid at room temps Very common in animal fats think

Unsaturated Fats Long chain of carbon bonds (some double bonds) Prevent H from attaching make “kinks”, which are not easily compacted = Liquid at room temps Common in Plant fats think

Normally, blood flows freely through a vein Blood vein RBC RBC RBC RBC RBC RBC

Too much saturated fats… Blood vein RBC RBC RBC RBC RBC RBC RBC RBC RBC RBC RBC RBC RBC RBC RBC RBC RBC RBC RBC Reduced circulation… Blood clots… High blood pressure Cholesterol & saturated fats

Cholesterol levels

Recap What are the three parts of a phospholipid? Which part(s) is/are the “head”? Which part are the “tails”? What are the two parts of a triglyceride? How do saturated and unsaturated fatty acids differ? Why are saturated fats less healthy?

Nucleic Acids

Nucleic Acid Basics Contain instructions to build protein 2 types DNA RNA Made up of smaller units called nucleotides monomer = nucleotide Polymer = nucleic acid

Nucleotides are made of three parts: a sugar phosphate group nitrogen base. - Adenine (A) - Thymine (T) - Guanine (G) - Cytosine (C) A phosphate group nitrogen-containing molecule, called a base deoxyribose (sugar)

Monomers link to make polymers Monomers link to make polymers! Nucleotides combine to make nucleic acid! These are the instructions for the cell to make protein.

Nucleotides? How many

DNA Double Helix: 2 chains of nucleotides DNA stores the information required to make a protein Gene: section of DNA that codes for a protein

RNA 1 chain of nucleotides Copy the DNA code… deliver code to ribosome to create a protein

Recap Name the monomer of nucleic acids. What are the four nitrogen bases of DNA? Name the three parts to a nucleotide. How are DNA and RNA different? Same?

Protein

Protein Basics Used in variety of cellular functions Made of smaller amino acids Monomer: Amino acid Polymer: Polypeptide (Protein) Only 20 amino acids… but thousands of proteins Exact arrangement of amino acids determines the protein leucine valine glycine alanine leucine leucine histi- dine aspara- gine serine proline = Protein A valine leucine glycine alanine leucine leucine histi- dine aspara- gine serine proline = Protein B Amino acids (monomer)

Amino acids are linked by peptide bonds.

Enzymes Types of proteins Enzyme: Lowers the energy needed to start chemical reactions ex: Break down food Sensitive to pH, temp  can cause them to denature ex: If high fever: enzymes lose ability to work Very specific in actions (lock & key) ex: Amylase: Breaks starch into simple sugars Reusable Enzyme amylase glucose glucose glucose glucose Starch

Recap What are the smaller monomers that make proteins called? How many different amino acids exist? Which group of proteins help to start chemical reactions? What can cause an enzyme to denature? Explain the lock and key analogy as it relates to enzymes.

ENZYMES

Chemical Reactions Energy stored in chemical bonds When bonds broken = Energy released (heat & light) Activation Energy: amount of energy needed to start a reaction

Enzymes Catalyst: substance that decreases the activation energy needed to start a chemical reaction Speeds up reaction Enzymes are catalysts in living organisms.

Enzyme Structure Enzyme shape allows specific reactants to bind together Reactants = substrate Ex: Amylase & starch: Starch is the substrate because it binds to amylase Substrates binds to activation sites on the enzyme (key fitting into a lock) Once binded to enzyme, substrates bonds break Substrates form new bonds (product)

Recap 1) How do enzymes speed up chemical reactions? 2) What is released when chemical bonds are broken? 3) Why is photosynthesis an example of an endothermic reaction? 4) Why is cellular respiration an example of an exothermic reaction? 5) Besides enzymes, what else is often a catalyst that speeds up reactions? 6) What are the molecules called that react with enzymes? 7) What do enzymes weaken between molecules?