copyright © 2009 pearson education, inc. human biology chapter 2 chemistry of living things ...

Copyright © 2009 Pearson Education, Inc.

Human Biology

Chapter 2 Chemistry of living things

Atoms/Elements

Bonds

Water

pH

Molecules of life

Carbohydrates *Proteins

Lipids *Nucleic Acids


All Matter Consists of Elements Made of Atoms

Chemistry The study of matter

Atoms, the smallest functional unit, consist of Protons: positive charge, have mass

Neutrons: no charge, have mass

Electrons: negative charge, have no discernable mass


Atoms Combine to Form Molecules

Joining atoms requires energy Energy is the capacity to do work

Stored energy: potential energy

Energy in motion, doing work: kinetic energy

Electrons have potential energy Shells: the energy levels of electrons

Orbitals describe the probable location of an electron


Three Types of Chemical Bonds

Table 2.1


Elements of Living Organisms

Table 2.2


Life Depends on Water

Water molecules are polar

Water is liquid at body temperature

Water can absorb and hold heat energy


Water Keeps Ions in Solution

Figure 2.8


The Importance of Hydrogen Ions

Acids are proton (hydrogen ion) donors

Bases accept hydrogen ions

pH Scale Hydrogen ion concentration

Buffers Minimize pH change

Carbonic acid and bicarbonate act as one of the body’s most important buffer pairs


The pH Scale

Figure 2.10


The Organic Molecules of Living Organisms

Carbon, the building block of living things Comprises 18% of the body by weight

Forms four covalent bonds

Can form single or double bonds

Can build micro- or macromolecules


Carbon Can Bond in Many Ways

Figure 2.12


Making and Breaking Biological Macromolecules: Dehydration Synthesis and Hydrolysis

Figure 2.13


Dehydration Synthesis Is the Reverse of Hydrolysis

Dehydration synthesis Removes equivalent of a water molecule to

link molecular units Requires energy

Hydrolysis Adds the equivalent of a water molecule to

break apart macromolecules Releases energy

Copyright © 2009 Pearson Education, Inc. Figure 2.14

Carbohydrates are Composed of Monosaccharides


Carbohydrates are Used for Energy and Structural Support

Oligosaccharides Short chains of monosaccharides

Disaccharides Sucrose, fructose, lactose


Carbohydrates are Used for Energy and Structural Support

Polysaccharides: thousands of monosaccharides joined in chains and branches Starch: made in plants; stores energy

Glycogen: made in animals; stores energy

Cellulose: indigestible polysaccharide made in plants for structural support


Animation—Lipid Structure and Function

Lipids: Insoluble in Water

Triglycerides: energy storage molecules Fatty acids: saturated and unsaturated

Phospholipids: cell membranes

Steroids: carbon-based ring structures Cholesterol: used in making estrogen and

testosterone

PLAY


Proteins: Complex Structures Constructed of Amino Acids

Structure Primary: amino acid sequence

Secondary: describes chain’s orientation in space (e.g., alpha helix, beta sheet)



Tertiary: describes three-dimensional shape created by disulfide and hydrogen bonds Creates polar and nonpolar areas in

molecule

Quaternary: describes proteins in which two or more tertiary protein chains are associated



Denaturation Permanent disruption of protein structure

Can be damaged by temperature or changes in pH

Leads to loss of biological function


Enzyme Function

Enzymes Are proteins

Function as catalysts

Speed up chemical reactions

Are not altered or consumed by the reaction


Enzyme Function

The functional shape of an enzyme is dependent on Temperature of reaction medium

pH

Ion concentration

Presence of inhibitors


Structure and Function of Nucleic Acids

Functions Store genetic information

Provide information used in making proteins

Structure Nucleotides consist of a phosphate group, a sugar,

and a nitrogenous base

DNA structure is a double helix: two associated strands of nucleic acids

RNA is a single-stranded molecule


Structure of DNA

DNA Deoxyribonucleic acid

Double–stranded

Sugar

Deoxyribose


Structure of DNA

DNA Nitrogenous bases

Adenine

Thymine

Cytosine

Guanine

Pairing

Adenine–thymine

Cytosine–guanine


Structure of RNA

RNA Ribonucleic acid

Single–stranded

Sugar

Ribose


Structure of RNA

RNA Nitrogenous bases

Adenine

Uracil

Cytosine

Guanine

Pairing

Adenine–uracil

Cytosine–guanine


Structure and Function of Adenosine Triphosphate (ATP)

Universal energy source

Bonds between phosphate groups contain potential energy

Breaking the bonds releases energy ATP ADP + P1 + energy


Structure and Function of Adenosine Triphosphate (ATP)

Figure 2.26

copyright © 2009 pearson education, inc. human biology chapter 2 chemistry of living things ...

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