Biology Unit 4. Chemistry of Life

Transcription

1 Biology Unit 4 Chemistry of Life

2 Elements Everything in our universe that has a mass and a volume is made of matter. Matter in its purest form is an element. There are 118 elements on the periodic table, each of which is distinguished by its atomic number (number of protons)

3 Elements in Living Things There are 5 elements that make up about 96% of living things. They are: Carbon Hydrogen Nitrogen Oxygen Phosphorus Sulfur Remember them with CHNOPS

4 Atoms Elements are all made of the same type of atoms. Atoms have protons and neutrons in the nucleus. Orbited by negative electrons Electrons exist in energy levels around an atom.

5 Electron Energy Levels The first energy level can hold 2 electrons. The second can hold 8 The third can hold 18 In order to be stable, atoms want to have 8 electrons in their outer shells.

6 Isotopes Although every element has a specific number of protons, they can have different numbers of neutrons. Atoms of the same element with differing numbers of neutrons are called isotopes. Atomic mass from the periodic table is a decimal because it is an average.

7 How to Find Subatomic Particles Protons=Atomic number on periodic table Neutrons= Rounded atomic mass- protons Electrons= Protons if atom is neutrally charged How many protons, neutrons, electrons in a neutral Helium atom?

8 Compounds and Bonding Multiple atoms of similar and different elements can bond together to form compounds. Examples: H2O, CO2, NaCl Chemical bonds are formed and broken through chemical reactions.

9 Ionic vs. Covalent Bonds Covalent compounds are formed when atoms share electrons. Most compounds in the body are formed this way Ionic compounds are formed when charged atoms transfer electrons. Charged atoms are called ions. Positive ions are called cations. Cat Ion Negative ions are called anions. An Ion

10 Charges on Ions Ions have specific charges based on their groups (columns) on the periodic table.

11 Number of Valence Electrons Valence electrons are electrons on the outermost energy level of an atom. Magic # is 8. You can find out how many valence electrons an element has by looking at group number on periodic table. IA has 1, IIA has 2, IIIA, has 3, etc.

12 How Ionic Compounds Form Charges need to balance to make 0. Ex: Na+Cl, Ca+F, K+O Named by leaving the cation as is and changing the ending on the anion to ide Ex: NaCl Sodium Chloride

13 Name The Compounds KCl Li2S NaF MgBr2

14 Chemical Reactions Chemical reactions occur constantly in the body. These reactions are called metabolism.

15 Chemical Equations We can represent chemical reactions by writing chemical equations.

16 Law of Conservation of Mass The law of conservation of mass says that mass can never be lost or gained during a chemical reaction. Because of this, we have to make sure we balance our chemical equations.

17 How to Balance an Equation You can balance a chemical equation by changing the coefficients (big numbers) that come before each product or reactant. It works like the distributive property in math. Each compound gets multiplied by the coefficient in front of it. YOU CAN NEVER CHANGE THE SUBSCRIPT!!!!!!!

18 Example Balance these equations: H2 + O2 -> H2O K+Cl2 -> KCl

19 The Molecules of Life Known as organic molecules Not the organic you see at the grocery store All organic molecules contain carbon

20 Carbon Bonding Carbon is special because it is so easy to bond with. Each carbon atom can form up to 4 bonds. Carbon can even bond more than once with the same atom. These are called double and triple bonds.

21 Polymers Many carbon based molecules can form polymers. Polymers are giant molecules that are made up of smaller molecules. The smaller molecules that make up polymers are called monomers.

22 Condensation vs. Hydrolysis Polymers are formed by a chemical reaction called condensation. Condensation causes 2 monomers to come together while a water molecule is released. Hydrolysis happens when a water molecule breaks apart a polymer and uses the H and OH from the water to fill in the gaps.

23 4 Classes of Biomolecules Carbohydrates Lipids Proteins Nucleic Acids

24 Carbohydrates (sugar and starch) Used by cells to provide energy. 4 calories per gram Monomers: Monosaccharides Multiple monomers can form polysaccharides. Polysaccharides form through condensation. 1:2:1 ratio of Carbon to hydrogen to oxygen

25 Carbohydrate Examples Examples of monosaccharides: Fructose and Glucose Found in fruits, used for energy by both animals and plants Examples polysaccharides: Cellulose, glycogen Very large molecules, take a long time to break down Animals store glycogen in their livers for back up energy. Plants use cellulose to help provide structure.

26 Lipids (fats) Large biomolecules made of mostly carbon and hydrogen with a little bit of oxygen. Non-Polar: Means they will not dissolve in water Monomer: Fatty acids 9 calories per gram

27 Lipids Examples/Uses Fats, oils, waxes, steroids Used for energy storage/insulation in many animals High in energy Major component in cell membranes

28 Proteins Made up of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Essential for all life Monomer: Amino Acids Come together to form proteins. Held together by peptide bonds. 4 calories per gram

29 Proteins Uses/Examples Come in a huge variety of shapes and sizes. Shape determines function. Building blocks of many structural components in living things. Muscle tissue, assist with immunity, transport oxygen, carry out chemical reactions. Used as enzymes!

30 Enzymes Life as we know it would not be possible without enzymes. Enzymes speed up reactions exponentially but do not get used up in the reaction. The activity of enzymes depends on ph and temperature. Every enzyme has an active site where a substrate must bind in order to speed up the reaction.

31 Active Site and Substrate

32 Nucleic Acids Made up of carbon, hydrogen, oxygen, nitrogen, and phosphorus atoms. These atoms are arranged into a nitrogenous base, a simple sugar, and a phosphate group. Monomer: Nucleotides

33 Nucleic Acids: Examples and Uses DNA and RNA DNA contains the instructions to form all of an organism s enzymes for structural proteins. DNA determines how an organism looks and acts. RNA is used by the body to make a copy of DNA for use in making proteins.

34 Water, Solutions, and ph

35 Water is Polar Water is a covalently bonded molecule. Sometimes, covalently bonded molecules do not share electrons equally. This makes them polar. Polar molecules have both positive and negative parts. This allows them to make solutions very easily.

36 Hydrogen Bonds Water is attracted to itself through hydrogen bonds. This means that the negative oxygen is attracted to the positive hydrogen. Causes surface tension and capillary action.

37 High Specific Heat of Water Water is very resistant to temperature change. It takes more energy to change the temperature of water than it does to change most other liquids. Allows cells to maintain homeostasis. Why do you think coastal cities usually have milder temperatures than those inland?

38 Water Expands when it Freezes Water is one of the few substances that becomes less dense when it becomes a solid. It also expands when it becomes solid. This is helpful for breaking up rock and returning nutrients to the soil. What animals might benefit from this property of water?

39 Diffusion in Water Particles are in constant random motion. Diffusion is the net movement of particles from high concentration to low concentration. High temp can increase rate of diffusion. Eventually, concentration will be even. This is called dynamic equilibrium. Cells use diffusion to move substances in and out.

40 Water and Solutions The polarity of water makes it perfect for dissolving other compounds. Because it has both negative and positive charges, it can bond to both parts of other polar molecules, creating weak bonds that allow solutions to be made. See example on board:

41 Water and ph Acids are substances that release H + ions in water. These substances have a ph below 7. More H + = more acidic= lower ph Bases are solutions that release OH - above 7. More OH- = more basic= higher ph ions in water. They have a ph Atoms that release fewer H+ ions that pure water would be classified as:

42 Example ph Scale