Chapters 4 and 5

Mrs. Svencer

CP Biology

4.1 Life Requires About 25 Chemical Elements

Matter– anything that occupies space and mass – “stuff” of the universe (ex: desk,

pencil, you…) Element

– pure substance - can’t be broken down by chemical reactions. Ex: Gold, mercury, oxygen.

– C, H, O, N – make 96% of living matter Trace Elements

– < .01% of body mass– critical for life

Compound– 2+ elements chemically combined in a fixed ratio– Ex: water- H2O, sodium chloride - NaCl

                                                        

                                                       

Figure 4-1This chart compares percentages of various elements in your body. All of the elements represented are essential to life.

4.2 Chemical Properties are based on the structure of atoms

Atom vs. Element

Atom:

-no observable traits (like Element)

-no melting or boiling points, density, color

An atom has an atomic number.

Atoms

“atomos” – “indivisible” Smallest possible particle of an element Ex: oxygen atom, gold atom Made of subatomic particles

– Proton: positive electrical charge (+)– Electron: negative electrical charge (-). e-, least

mass– Neutron: electrically neutral – no charge

                                                 

                                  Figure 4-4This model of a helium atom indicates the number of each kind of subatomic particle it contains. Though no visual model can accurately show an atom's structure, models can help you in understanding certain aspects of an element's chemical behavior.

An element’s physical and chemical properties depend on the number and arrangement of subatomic particles.

Nucleus: core of an atom– protons and neutrons– e- found in cloud around nucleus

travel at great speeds attracted to (+)

– Number of protons = atomic number

Isotopes

Same # of protons, different # of neutrons– 12C has 6 neutrons, 13C has 7 neutrons

6 + 6 6 + 7

– Radioactive isotopes – nucleus decays, gives off radiation

Useful as “biological spies” in organisms

                                                                                                                   

                                                        Figure 4-5Atoms of three isotopes of carbon differ only in their numbers of neutrons. The isotopes are named for the total number of particles in their nuclei (protons plus neutrons). Carbon-13, for example, has 6 protons and 7 neutrons, for a total of 13.

Electrons and Reactivity

e- belong to different energy levels e- fill the 1st levels 1st

– 1st level = 2 e- – 2nd level = 8 e-– Partially filled levels make atoms more reactive;

they want to fill their highest occupied energy levels

                                                                                                                      

                                                     Figure 4-7An atom's lowest (first) energy level can hold up to 2 electrons. The second level can hold up to 8. Notice that the second energy levels of carbon, nitrogen, and oxygen atoms are unfilled with 4, 5, and 6 electrons, respectively. (Remember that atomic models are limited in what they can represent. Energy levels are not actual physical locations.)

5.1 Carbon is KEY!

Carbon can connect to 4 other atoms.– It has 4e- in its outer cloud, but wants 8e-

Organic : carbon Inorganic : no carbon Hydrocarbons – consist of C and H, fuels

– Ex: methane CH4

                                                                                                                       

                                                    Figure 5-1The carbon backbones of organic molecules can take many shapes. These molecules may include single, double, and rarely, triple bonds. The only rule is that each carbon forms a total of four bonds.

Functional Groups

Group of atoms - acts in predictable ways

                                                                                                                           

                                                Figure 5-2These four common functional groups give specific properties to the organic molecules that contain them.

Hydroxyl groups - hydrophilic– Hydrophilic =“water-loving”– Hydrophobic = “water-fearing”

Monomers– Single molecular units

Polymers– Long chains of monomers

Four groups of large Biomolecules

Carbohydrates Lipids Proteins Nucleic Acids

Building and Breaking Polymers

Dehydration reaction: BUILDING– Water released– Monomer added

Hydrolysis reaction: BREAKING– Water added– Polymer broken down

Dehydration

                                                                      

                                              

Figure 5-4In the dehydration reaction, two monomers bond to each other, making a polymer chain longer. The hydroxyl group of one monomer reacts with a hydrogen atom from the other monomer. The reactions involved ultimately release a water molecule.

Hydrolysis

                                                                      

                                              Figure 5-5In the hydrolysis reaction, the addition of a water molecule breaks the polymer chain.

5.2 Carbohydrates - fuel , building material

Carbohydrate– Organic compound - sugar molecules– Any sugar is a multiple of CH2O

Monosaccharide– Simple sugar, 1 sugar unit– Ex: glucose, fructose, galactose– All end in -ose

                                                                 

                                         Figure 5-6The complete structural diagram of the monosaccharide glucose (left) shows all its atoms. The simplified representation (right) shows just the core ring formed by some of the carbon and oxygen atoms. Ring shapes are common in sugar molecules found in nature.

Complex Sugars

Disaccharide– “double sugar” – 2 monosaccharides– Ex: sucrose, plant sap, table sugar

Polysaccharide– Many simple sugars together– All glucose monomers – store sugar

Plants – starch Animals – glycogen

– Cellulose: in plants, protects/stiffens plant Fiber –can’t be digested by humans

                                    

                           Figure 5-7Sucrose is a disaccharide (double sugar) consisting of two monosaccharides linked together.

                                                                                          

                                                               Figure 5-8Glycogen, cellulose, and starch are three types of polysaccharides found in food. Though all three polymers are composed of the same monomer, glucose, the way the glucose monomers link together is different for each.

5.3 Lipids - fats and steroids

Lipid: Hydrophobic– boundary for cells

Fat: – 3 carbon backbone = glycerol + 3 fatty acids (long

hydrocarbon chains)

                                                                                                                 

                                                          Figure 5-9Certain vegetable oils contain unsaturated fat molecules, which have at least one double bond in at least one of the fatty acid chains. In this case, the double bond is located about halfway along the bottom chain.

Saturated Fat vs. Unsaturated Fat

Saturated fat: – max possible # of H atoms in chain – all single bonds– animal fats - lard , butter

Unsaturated fat: – < max # of H atoms in one or more or its fatty acid chains– some double bonds– fruits, vegetables, and fish – corn oil, olive oil

Steroids and Cholesterol

Steroids– Lipids - four fused rings of carbon for base– All steroids - core set of four rings– Functional groups on rings differ

Cholesterol– Essential in cell membranes– Where other steroids are produced

                                                                                 

                                                Figure 5-10The only difference in these two steroid hormones is the location of their functional groups. Yet, these two molecules contribute to major differences in the appearance and behavior of male and female mammals.

5.4 Proteins – cellular functions

Protein: polymer of amino acids– 20 kinds of amino acids

Amino acid: central carbon atom bonded to four partners

Polypeptide: chain of amino acids Denaturation: protein loses its normal shape

– change in temperature, pH

                                                                                                                     

                                                      Figure 5-12All amino acids consist of a central carbon bonded to an amino group, a carboxyl group, and a hydrogen atom. The fourth bond is with a unique side group. The differences in side groups convey different properties to each amino acid.

                                                              

                                                    Figure 5-13The order of amino acids makes each polypeptide unique. There are 129 amino acids in this protein, called lysozyme. The three-letter symbols are abbreviations for the amino acid names.

5.5 Enzymes = proteins that speed up specific reactions in cells

Activation energy:– “start up” energy - triggers a chemical reaction

Catalyst: speed up chemical reactions Enzyme: special protein – catalyst in organisms

– Ex: sucrase, amylase– -ase = enzyme

Substrate: binds to the enzyme; must fit into active site– Ex: sucrose

Active site: place (on enzyme) where the substrate fits– Lock and key

                                                                                   

                                               Figure 5-15The activation energy barrier is like a wall between two parts of a pond. If an enzyme lowers the wall, more frogs have enough energy to reach the other side.

                                                                         

                                                 Figure 5-16A substrate binds to an enzyme at an active site. The enzyme-substrate interaction lowers the activation energy required for the reaction to proceed. In this example, water is added to the weakened bond in sucrose, breaking sucrose into glucose and fructose.

The End