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Chemicals of Life. Chemistry chemicals give cells properties of life –must know principles of chemistry to understand biology –organisms-bags of chemicals.

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Presentation on theme: "Chemicals of Life. Chemistry chemicals give cells properties of life –must know principles of chemistry to understand biology –organisms-bags of chemicals."— Presentation transcript:

1 Chemicals of Life

2 Chemistry chemicals give cells properties of life –must know principles of chemistry to understand biology –organisms-bags of chemicals –structure determines function Hierarchy chemicals organelles cells tissues organs organisms

3 Matter living things are made of matter –anything that occupies space & has mass composed of elements

4 Elements substances which cannot be decomposed into simpler substances by chemical means 92 naturally occurring ones 25 found in living things 96%-H, O, C & N 4%-Ca, P, K & S trace elements-Fe, Mg, Mn (manganese) & I –called essential –cannot live without them

5 Periodic Table

6 Atoms elements are composed of atoms only one kind of atom for each element –smallest units of matter that retain the properties of an element

7 Sub-atomic Particles Protons Electrons Neutrons –different elements have different numbers of sub-atomic particles –chemical & physical differences of elements are due to these differences

8 Sub-Atomic Particles Protons –o–one positive charge –f–found in nucleus of atom Neutrons –n–no charge –f–found in nucleus of atom Electrons –o–one negative charge –o–orbit nucleus

9 Periodic Table atoms structure determines how element it comprises forms compounds & molecules key to this can be found by knowing number of sub-atomic particles an element possess found in Periodic Table of the Elements

10 atomic number-number in upper left corner atomic number-number in upper left corner atomic weight or mass number-number located on bottom atomic weight or mass number-number located on bottom

11 Atomic Number gives number of protons in an atom Helium Atomic Number = 2 –has 2 protons

12 Mass Number found by adding number of neutrons & number of protons He = 4 some atoms of an element may have different mass numbers these are isotopes –same number of protons & electrons but different number of neutrons

13 Number of Electrons net charge of an atom is zero each proton has one positive charge each electron has one negative charge neutrons have no charge to be neural atom must have the same number of electrons and protons atom of helium with 2 protons has 2 electrons

14 Atomic Number How many protons does Sulfur have? How many electrons? Why?


16 Chemical Properties arrangement of electrons determines chemical properties of an atom electrons orbit around nucleus found at different energy levels- shells each shell accommodates a specific number of electrons

17 Electron Shells innermost shell-2 2 nd & 3 rd- 8 number of electrons in outermost shell determines chemical properties of atom those with shells that are not full will interact with other atoms & participate in chemical reactions those with full shells do not interact-inert

18 Electron Shells H-only one electron in outer most shell –very reactive C, N, & O also highly reactive since outer shells are incomplete He-inert or nonreactive because outer shell is full

19 Reactivity of Chlorine Is Chlorine reactive or not reactive? How can you tell?

20 Atom Interactions-Chemical Bonds when an atom with an incomplete outer shell reacts with another atom with an incomplete outer shell they can interact or form a bond Share Donate Receive electrons in this way both atoms can have a completed outer shell

21 Types of Chemical Bonds Covalent Bonds –share electrons Ionic –give or receive electrons

22 Sodium & Chloride

23 Ionic Bonding


25 Covalent Bonds 2 atoms with incomplete shells each share a couple electrons so at any one time one atom has a completed outer shell forms molecules


27 In Class Exercise Pretend you are an atom Take the number of your birth month as your atomic number Determine the configuration of electrons in your valence shell Find another atom that you might interact with to form ions or new molecules Demonstrate-draw on the board

28 Chemical Reactions elements combine to make molecules & compounds 2 H 2 + O 2 2H 2 O 2 molecules of H react with one molecule of O (reactants) to form 2 molecules of water (product) arrow indicates direction of reaction two sides of equation on either side of arrow must balance

29 Water single most important constituent of body life on Earth depends on unusual structure & nature of water

30 Importance of Water Organisms consist mostly of water –2/3rds total body weight of humans Biochemistry is a wet chemistry –biological molecules do not react chemically unless in solution Water is an important reactant –nearly all chemical reactions in the body occur in water Foods are digested to their building blocks by decomposition reactions called hydrolysis –involves addition of water When large molecules form from smaller ones, water is removed in dehydration synthesis or condensation reactions

31 Water Structure 2 H atoms attached covalently to one O 2 molecule sharing of electrons is not equal oxygen pulls more on electrons than does hydrogen electrons spend more time near oxygen than hydrogen unequal sharing produces- polar bond Nonpolar bond –bonds in which two atoms involved have an equal pull on electrons

32 Water Structure O 2 attracts electrons more strongly than H- giving water an asymmetrical distribution of charge result-V-shape H end has positive charge Oxygen end has negative charge water has 2 poles-polar polarity results in weak electrical attractions between neighboring water molecules

33 Polarity of Water Polarity results in weak electrical attraction between neighboring water molecules slightly positive Hs in one water molecule attract slightly negatively charged O 2 in another water molecule opposite electrical charges attract water molecules attract each other making water kind of sticky these weak attractions- hydrogen bonds –much weaker than covalent or ionic bonds

34 Polarity, H Bonding & Waters Properties cohesive nature ability to moderate temperature ice floating universal solvent properties

35 Dissociation compounds formed by ionic bonds will ionize or dissociate in water dissociation produces cations (+) & anions (-) aqueous solution containing anions & cations will conduct electrical currents cations move to negative side having a + change & anions move to positive side having a – charge soluble inorganic molecules whose ions will conduct an electrical current in solution are called electrolytes NaCl is an electrolyte NaCl + H 2 O Na + + Cl -

36 Acids H + & OH - are in solutions at all times H 2 O < > H + + OH - -reversible reaction some compounds add more hydrogen ions others remove them compound that donates hydrogen ion- acid HCl H + + Cl - acidic solution is one that has more H + than OH -

37 Bases compound that accepts or removes hydrogen ions is a base NaOH Na + +OH - basic solution- has more OH - than H +

38 pH scale pH = potential hydrogen scale developed in 1909 by Dane Soren Sorensen –beer brewer looking for a way to check acidity of beer describes how acidic or basic a solution is scale ranges from = most acidic 14 = most basic 7=neutral

39 pH at neutral pH H + = OH - pH < 7 is acidic pH > than 7 is more basic or alkaline

40 Buffers pH of blood ranges between value must be maintained in narrow range even small change can lead to severe metabolic consequences biological fluids contain buffers –substances that resist changes in pH by accepting H + when in excess & donating H + when depleted

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