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Chemicals of Life. Chemical Basis of Life principles of chemistry help to understand biology organisms are bags of chemicals function of organisms & parts.

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Presentation on theme: "Chemicals of Life. Chemical Basis of Life principles of chemistry help to understand biology organisms are bags of chemicals function of organisms & parts."— Presentation transcript:

1 Chemicals of Life

2 Chemical Basis of Life principles of chemistry help to understand biology organisms are bags of chemicals function of organisms & parts of organisms are determined by –w–way chemicals are arranged compounds & molecules formed by chemicals structure determines function Structure Function long handle to hold easier made of wood to be strong blunt metal end to hit nails curved, claws to pull out nails

3 Chemistry chemicals give cells properties these properties are called life Hierarchy Chemicals organelles cells tissues organs organisms

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

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

6 Periodic Table

7 Atoms elements are composed of atoms only one kind of atom for each element –smallest units of matter that retainproperties of an element

8 Sub-atomic Particles Protons Electrons Neutrons –different elements have different numbers of sub-atomic particles –put together differently in different atoms –chemical & physical differences of elements are due to these differences

9 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

10 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

11 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

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

13 Mass Number number of neutrons + number of protons He = 4 variant forms of elements can exist some atoms of an element may have different mass numbers these are isotopes –same number of protons & electrons; different number of neutrons

14 Number of Electrons net charge of atom = zero each proton has one positive charge each electron has one negative charge neutrons have no charge to be neural atom must have same number of electrons as protons atom of helium with 2 protons has 2 electrons

15 ChallengeQuestion How many protons does Sulfur have? How many electrons? Why?


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

18 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

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

20 Challenge Question Is Chlorine reactive or not reactive? How can you tell?

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

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

23 Sodium & Chloride

24 Ionic Bonding


26 Covalent Bonds 2 atoms with incomplete shells share electrons so at any one time one atom has a completed outer shell molecules are formed


28 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 board

29 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

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

31 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 body occur in water Foods are digested to 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

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

33 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

34 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 –weaker than covalent or ionic bonds

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

36 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 have + change anions move to positive side having – charge soluble inorganic molecules whose ions will conduct an electrical current in solution are electrolytes –NaCl NaCl + H 2 O Na + + Cl -

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

38 Acids & Bases compound that accepts or removes hydrogen ion is a base NaOH Na + +OH - basic solution-one that has more OH - than H +

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

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

41 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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