Human Biology Concepts and Current Issues - Valenciafd.valenciacollege.edu/file/nwilliams46/Human...

© 2014 Pearson Education, Inc.

Human Biology Concepts and Current Issues Seventh Edition

Michael D. Johnson

Lecture Presentations by Robert J. Sullivan

Marist College

2 The Chemistry of

Living Things


All Matter Consists of Elements

  Chemistry: the study of matter   Matter

– Anything that has mass and occupies space – Composed of elements

  Elements – Cannot be broken down to a simpler form – Periodic table of elements—lists all known elements


Figure 2.2

Element symbol Atomic mass

Nonmetals

Metals

Nonmetals

Lanthanides

Transition elements

Metals

Actinides

Group number Atomic number 1

2

2

3

3

4

4

5

5 6

6

7

7

8 1


Atoms—Smallest Functional Units of an Element

  Atoms consist of – Nucleus (central core)

– Protons – positive charge – have mass

– Neutrons – no charge – have mass

– Shells (surrounding nucleus) – Electrons

– negative charge – no discernable mass


Figure 2.3 Electron

a) Hydrogen 1 proton

Proton

Shell

Neutron

Nucleus

b)  Oxygen 8 protons 8 neutrons 8 electrons in 2 shells

c)  Sodium 11 protons 11 neutrons 11 electrons in 3 shells


More About Atoms

  Atomic symbol: one or two letters – Na: sodium – O: oxygen

  Atomic number – Number of protons, always the same number for any

atom of a particular element   Atomic mass

– Roughly equal to number of protons plus neutrons   In an electrically neutral atom

– Number of protons = number of electrons


Isotopes Have a Different Number of Neutrons

  All atoms of an element have the same number of protons

  Isotopes are atoms of the same element that have a different number of neutrons – They will have a different atomic mass

  Unstable isotopes are called radioisotopes


Isotopes Have a Different Number of Neutrons

  Radioisotopes are unstable and give off: – Energy in the form of radiation – Particles

  Some radioisotopes have scientific and medical uses – Carbon-14: used for dating fossils – Diagnostic imaging – Cancer treatment – Power supply for implants such as cardiac

pacemakers


Energy Fuels Life’s Activities

  Energy: the capacity to do work   Potential energy: stored energy   Kinetic energy: energy in motion, doing work   Potential energy can be transformed into kinetic

energy


Figure 2.4

Potential energy is locked up in the chemical bonds of energy-storage molecules in Greg Louganis’ tissues.

Kinetic energy is energy in motion.


Energy Fuels Life’s Activities

  Electrons have potential energy – Each shell corresponds to a specific level of potential

energy – Shells that are farther from the nucleus contain

electrons with more potential energy   Atoms are most stable when their outermost shell is

full   Atoms will interact with other atoms to fill their

outermost shells


Chemical Bonds Link Atoms to Form Molecules

  Chemical bonds: attractive forces holding atoms together

  Kinds of chemical bonds – Covalent bonds –  Ionic bonds – Hydrogen bonds


Covalent Bonds Involve Sharing Electrons

  Covalent bonds form when atoms share electrons   Very strong bonds   Examples

– Hydrogen molecule: H2

– Oxygen molecule: O2

– Water: H2O


Covalent Bonds Involve Sharing Electrons

  Nonpolar covalent bonds: electrons are shared equally – H2

– O2

– CH4

  Polar covalent bonds: electrons are NOT shared equally – H2O: The oxygen has a stronger pull on the shared

electrons than the hydrogen does


Figure 2.5

Hydrogen (H2)

Oxygen (O2)

Water (H2O)

Single covalent bond

Double covalent bond

Two single covalent bonds

Structural representation Structural formula with covalent bond

Written formula

H H

H

H

O O

O


Ionic Bonds Occur Between Oppositely Charged Ions

  Ion: an electrically charged atom or molecule   Positively charged ion: forms if an atom or molecule

loses electrons   Negatively charged ion: forms if an atom or molecule

gains electrons   Ionic bond: attractive force between oppositely

charged ions   Example: NaCl


Figure 2.6

Loss of electron: positive charge

Sodium atom (Na)

+ –

Chlorine atom (Cl) Sodium ion (Na+) Chlorine ion (Cl–)

Sodium chloride molecule (NaCl)

Gain of electron: negative charge

-

Na Na Cl Cl


Weak Hydrogen Bonds Form between Polar Molecules

  Form between polar molecules   Polar molecules

– Contain polar covalent bonds in which there is unequal sharing of electrons

– Electrically neutral overall, but uneven charge distribution

  Hydrogen bond – Weak attraction between oppositely charged regions

of polar molecules – Example: weak forces between water molecules


Figure 2.8

Molecule

Oxygen (O)

Hydrogen (H)

Water Ice


Table 2.1


Living Organisms Contain Only Certain Elements

  Over 100 different elements   99% of body weight consists of 6 elements

– Oxygen – Carbon – Hydrogen – Nitrogen – Calcium – Phosphorus


Table 2.2


Life Depends on Water

Key properties of water: – Water is an excellent solvent – Water is liquid at body temperature – Water can absorb and hold heat energy – Evaporation of water uses up heat energy – Water participates in essential chemical reactions


Water Is the Biological Solvent

  Solvent: liquid in which other substances dissolve   Solute: any dissolved substance   Hydrophilic: polar molecules that are attracted to

water and interact easily with water   Hydrophobic: nonpolar neutral molecules that do

not interact with or dissolve in water


Water Is a Liquid at Body Temperature

  Water serves an important transport function in the blood, which is 90% water

  Water is the main constituent of: –  Intracellular spaces – Extracellular spaces

  60% of body weight is water


Water Helps Regulate Body Temperature

  Water absorbs and holds a large amount of heat energy with only a modest increase in temperature – Prevents rapid changes in body temperature

  Evaporative cooling enables body to lose excess heat quickly


Water Participates In Chemical Reactions

  Synthesis of carbohydrates, proteins, and lipids produces water molecules

  Breakdown of carbohydrates, proteins and lipids consumes water molecules


The Importance of Hydrogen Ions

  Acids – Donate hydrogen ions (H+) –  Increase hydrogen ion concentration in solutions

  Bases – Accept hydrogen ions – Decrease hydrogen ion concentration in solutions

  pH Scale –  A measure of hydrogen ion concentration


The pH Scale Expresses Hydrogen Ion Concentration

  Measure of hydrogen ion concentration in solution   Ranges from 0 to 14

– Acids: pH < 7 – Neutral: pH = 7 – Basic: pH > 7


Figure 2.10

Drain opener Bleach

Ammonia cleanser Soapy water Baking soda

Human blood, tears Saliva, urine Black coffee

Tomatoes Vinegar, cola Lemon juice Hydrochloric acid

Concentrated nitric acid

Mor

e al

kalin

e M

ore

acid

ic

Neutral pH


Buffers Minimize Changes in pH

  Minimize pH change   Help maintain stable pH in body fluids   Carbonic acid and bicarbonate act as one of the

body’s most important buffer pairs   HCO3

- + H+ H2CO3

(reversible reaction)

If blood is too acidic: HCO3- + H+ H2CO3

If blood is too alkaline: H2CO3 HCO3- + H+


Carbon Is the Common Building Block of Organic Molecules

•  Carbon, the building block of living things – Comprises 18% of the body by weight – Forms four covalent bonds – Can form single or double bonds – Often bonds with hydrogen, nitrogen, oxygen, or other

carbons – Can form linear, branched, or ring-shaped molecules – Can build micro- or macromolecules


Figure 2.12

In carbon dioxide, a carbon atom forms two covalent bonds with each oxygen atom.

Lipid molecules (a portion of one is shown here) contain long chains of carbon atoms covalently bound to hydrogen.

Carbon is the backbone of amino acids, the building blocks of protein. This amino acid is phenylalanine.


Macromolecules Are Synthesized and Broken Down Within the Cell

  Dehydration synthesis – Removes equivalent of a water molecule to link

molecular units – Requires energy – Builds macromolecules from smaller subunits

  Hydrolysis – Adds the equivalent of a water molecule to break

apart macromolecules – Releases energy

  Dehydration synthesis is the reverse of hydrolysis


Figure 2.13 Sugars

Energy Energy

Hyd

roly

sis

Deh

ydra

tion

synt

hesi

s

Carbohydrate


Carbohydrates: Used for Energy and Structural Support

  General formula: Cn(H20)n

  Monosaccharides: simple sugars – Glucose – Fructose – Galactose – Ribose – Deoxyribose


Oligosaccharides: More than One Monosaccharide Linked Together

  Monosaccharides can be linked together via dehydration synthesis

  Disaccharides: two monosaccharides linked together – Sucrose: glucose + fructose – Maltose: glucose + glucose –  Lactose: glucose + galactose


Figure 2.14

Ribose Deoxyribose

Glucose (a monosaccharide)

Sucrose (a disaccharide)

Fructose (a monosaccharide)

The five-carbon monosaccharides ribose and deoxyribose.

Two 6-carbon monosaccharides (glucose and fructose) are joined together by dehydration synthesis, forming sucrose.


Polysaccharides Store Energy

  Polysaccharides: thousands of monosaccharides joined in linear and/or branched chains – Starch: made in plants; stores energy – Glycogen: made in animals; stores energy – Cellulose: indigestible polysaccharide made in plants

for structural support


Figure 2.15 Glucose Glucose

Glycogen granules

Dehydration synthesis

Glycogen is formed by dehydration synthesis from glucose subunits.

A representation of the highly branched nature of glycogen.

A portion of an animal cell showing granules of stored glycogen (blue). The large pink structures are mitochondria.


Lipids: Insoluble in Water

  Three important classes of lipids – Triglycerides: energy storage molecules – Phospholipids: cell membrane structure – Steroids: carbon-based ring structures


Triglycerides Are Energy-Storage Molecules

  Also known as fats and oils   Composed of glycerol and three fatty acids

– Fatty acids – Saturated (in fats)—all single bonds between carbons – Unsaturated (in oils)—include some double bonds

between carbons   Stored in adipose tissue   Energy-storage molecules


Figure 2.16

Glycerol

Saturated fatty acid

Triglycerides (neutral fats) are synthesized from glycerol and three fatty acids by dehydration synthesis.

Triglycerides with saturated fatty acids have straight tails, allowing them to pack closely together.

Triglycerides with unsaturated fatty acids have kinked tails, preventing them from packing closely together.


Phospholipids Are the Primary Component of Cell Membranes

  Structure – Glycerol + two fatty acids and phosphate group – One end of molecule (phosphate and glycerol) is

water soluble (hydrophilic) – Other end of molecule (2 fatty acid tails) is water

insoluble (hydrophobic)   Function

– Primary component of cell membranes


Figure 2.17

Phosphate

Glycerol

Fatty acid

Nonpolar tail

Polar head

+

Membrane structure


Steroids Are Composed of Four Rings

  Structure – Composed of four carbon rings

  Examples: – Cholesterol – Hormones

– Estrogen – Testosterone


Figure 2.18

Cholesterol: A normal component of the cell membrane.

Estrogen (estradiol): Female sex hormone synthesized from cholesterol.

Testosterone: Male sex hormone synthesized from cholesterol.


Proteins: Complex Structures Constructed of Amino Acids

  Long chains (polymers) of subunits called amino acids

  Amino acids –  20 different types – Amino end, carboxyl end, R group

  Amino acids are joined by peptide bonds, which are produced by dehydration synthesis reactions


Figure 2.19

Alanine (Ala)

Isoleucine (Ile)

Leucine (Leu)

Methionine (Met)

Phenylalanine (Phe)

Proline (Pro)

Tryptophan (Trp)

Valine (Val)

Aspartic acid (Asp)

Glutamic acid (Glu) Lysine (Lys)

Histidine (His)

Arginine (Arg)

Tyrosine (Tyr)

Threonine (Thr)

Serine (Ser)

Glycine (Gly)

Glutamine (Gln)

Cysteine (Cys)

Asparagine (Asn)

Amino acids with nonpolar R groups Amino acids with uncharged polar R groups

Amino acids with positively charged R groups

Amino acids with negatively charged R groups


Figure 2.20

Isoleucine (Ile) Alanine (Ala) Valine (Val)

Polypeptide

Amino acids

Ile Ala Val


Proteins: Complex Structures Constructed of Amino Acids

  Peptide bond: forms between carboxyl end of one amino acid and amino end of the next amino acid

  Polypeptide: a polymer of 3–100 amino acids   Protein: a polypeptide longer than 100 amino acids

that has a complex structure and function


Protein Function Depends on Structure

  Denaturation – Permanent disruption of protein structure

– Can be damaged by temperature or changes in pH –  Leads to loss of biological function


Enzymes Facilitate Biochemical Reactions

  Enzymes – Are proteins – Function as biological catalysts

– Speed up chemical reactions – Are not altered or consumed by the reaction

– Without enzymes, many biochemical reactions would not proceed quickly enough to sustain life

– Maintenance of homeostasis is critical, in order to maintain the shape and biologic activity of enzymes


Figure 2.22

Enzyme changes shape

Reactants Product

Products are released

Reactants approach enzyme

Reactants bind to enzyme

Enzyme


Enzymes Facilitate Biochemical Reactions

  The functional shape of an enzyme is dependent on – Temperature –  pH –  Ion concentration – Presence of inhibitors


Nucleic Acids Store Genetic Information

  Nucleic acids are long chains containing subunits known as nucleotides

  Two types of nucleic acids – DNA: deoxyribonucleic acid – RNA: ribonucleic acid

  DNA contains the instructions for producing RNA   RNA contains the instructions for producing proteins   Proteins direct most of life processes   DNA → RNA → Proteins



  Nucleotides: building blocks (monomers) of nucleic acids

  Each nucleotide contains –  5 carbon sugar

– DNA nucleotides: deoxyribose – RNA nucleotides: ribose

– Nitrogenous base – Phosphate group


Figure 2.23

Phosphate

Deoxyribose

Adenine (A) Thymine (T)

Cytosine (C) Guanine (G)



  Structure of DNA (deoxyribonucleic acid) – Double–stranded – Nucleotides contain

– Deoxyribose (sugar) – Nitrogenous bases

– Adenine – Guanine – Cytosine – Thymine

– Pairing – Adenine - Thymine – Guanine - Cytosine


Figure 2.24

Base pair Phosphate Sugar Nucleotide

C

C

G

G

A

A

A C

G

G

G C

A

T T

T

T

P

P

P

P

P

P

P

P

P

T

A



  Structure of RNA (ribonucleic acid) – Single–stranded – Nucleotides contain

– Ribose – Nitrogenous bases

– Adenine – Guanine – Cytosine – Uracil


ATP Carries Energy

  Structure and function of adenosine triphosphate (ATP) – Nucleotide – adenosine triphosphate – Universal energy source – Bonds between phosphate groups contain potential

energy – Breaking the bonds releases energy

– ATP → ADP + P + energy


Figure 2.26

Adenosine

Adenosine Adenosine

Adenine (A)

Triphosphate

Ribose

H2O

(ATP) (ADP)

Hydrolysis of ATP produces useful energy for the cell

P P P P P P

H2O

Energy for ATP synthesis comes from food or body stores of glycogen or fat

The breakdown and synthesis of ATP. The breakdown (hydrolysis) of ATP yields energy for the cell. The reaction is reversible, meaning that ATP may be resynthesized using energy from other sources.

The structure of ATP.

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