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The Chemical Level of Organization Chapter 2. Atoms and Molecules Atoms are the smallest units of matter, they consist of protons, neutrons, and electrons.

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Presentation on theme: "The Chemical Level of Organization Chapter 2. Atoms and Molecules Atoms are the smallest units of matter, they consist of protons, neutrons, and electrons."— Presentation transcript:

1 The Chemical Level of Organization Chapter 2

2 Atoms and Molecules Atoms are the smallest units of matter, they consist of protons, neutrons, and electrons

3 Chemical bonds and chemical compounds An ionic bond results from the attraction between ions: atoms that have gained or lost electrons. Cations are positively charged Anions are negatively charged.

4 Atoms can combine to form a molecule Combinations of atoms of different elements form a compound Some atoms share electrons to form a molecule held together by covalent bonds.

5 Sharing one pair of electron creates a single covalent bond Sharing two pairs forms a double covalent bond Unequal sharing of electrons creates a polar covalent bond.

6 A hydrogen bond is the attraction between a hydrogen atom with slight positive charge and a negatively charged atom in another molecule or within the same molecule Hydrogen bond can affect the shapes and properties of molecules


8 Chemical Reactions Metabolism refers to all the chemical reactions in the body. Our cells capture, store and use energy to maintain homeostasis and support essential functions.

9 Types of Reactions A chemical reaction may be classified as DecompositionSynthesisExchange

10 Exergonic reaction release heat Endergonic reactions absorb heat Cells gain energy to power their functions by catabolism: the breakdown of complex molecules Much of this energy supports anabolism, the synthesis of new organic molecules

11 Acids and Bases An acid releases hydrogen ions A base removes hydrogen ions from a solution

12 pH The pH of a solution indicates the concentration of hydrogen ions it contains. Solutions can be classified as neutral (pH of 7)acidic (pH 7) on the basis of pH


14 Buffers maintain pH within normal limits (7.35-7.45 in most body fluids) by releasing or absorbing hydrogen ions.

15 Water and its Properties Water is the most important inorganic component of the body Water is an excellent solvent, has a high heat capacity, and participates in the metabolic reactions of the body. Many inorganic compounds will undergo ionization, or dissociation in water to form ions.


17 Inorganic Acids and Bases Inorganic acids found in the body include hydrochloric acid carbonic acid, sulfuric acid and phosphoric acid. Sodium hydroxide is an inorganic base that may form within the body.

18 Salts A salt is an ionic compound whose cation is not H + and whose anion is not OH - Salts are electrolytes, compounds that dissociate in water and conduct an electrical current.

19 Organic Compounds Organic compounds contain carbon and hydrogen, and usually oxygen as well. Large and complex organic molecules include carbohydrates, lipids proteins and nucleic acids.

20 Carbohydrates Carbohydrates are most important as an energy source for metabolic process. The three major types are monosaccharides (simple sugars), dissacharides and polysaccharides.

21 A. the straight -chain formula for glucose B. The ring form that is most common in nature. An abbreviated diagram of the ring form.

22 Lipids Lipids are water-insoluble molecules that include fats, oils, and waxes. There are four important classes of lipids: fatty acids, fats, steroids, and phospholipids.

23 Triglycerides (fats) consists of three fatty acid molecules attached to a molecule of glycerol Cholesterol is a precursor of steroid hormones and is a component of cell membranes


25 Phospholipids are the most abundant components of cell membranes.

26 Proteins Proteins perform a great variety of functions in the body. Important types of protein include structural proteins, contractile proteins, transport proteins, enzymes, hormones and antibodies.

27 Proteins are chains of amino acids linked by peptide bonds. The sequence of amino acids and the interactions of their R groups influence the final shape of the protein molecules.


29 The shape of the protein determines its function. Each protein works best at an optimal combination of temperature and pH.

30 Activation energy is the amount of energy required to start a reaction. Proteins called enzymes control many chemical reaction within our bodies. Enzymes are catalysts--substances that accelerate chemical reaction without themselves being permanently changed.


32 The reactants in an enzymatic reaction, called substrates, interact to form a product by bonding to the enzyme at the active site.


34 Nucleic Acids Nucleic acids store and process information at the molecular level. There are two kinds of nucleic acids: DNA and RNA Nucleic acids are chains of nucleotides. Each nucleotide contains a sugar, a phosphate group and a nitrogen base.

35 The sugar is always ribose or deoxyribose. The nitrogenous bases found in DNA are adenine, guanine, cytosine, and thymine. In RNA uracil replaces thymine.


37 High-Energy Compounds Cells store energy in high-energy compounds. The most important high-energy compound is ATP When energy is available, cells make ATP by adding a phosphate group to ADP When energy is needed ATP is broken down to ADP and phosphate.


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