The Chemical Composition of Cells Chapter 2. Learning Objectives- 1 Understand the Structure of the Molecular Components of Living Organisms Carbohydrates,

The Chemical Composition of Cells

Chapter 2

Learning Objectives- 1 Understand the Structure of the Molecular

Components of Living Organisms Carbohydrates, which supply and store energy and

serve as structural building blocks, include sugars and polymers of sugars.

Proteins, which catalyze reactions and are structural building blocks, are polymers of amino acids.

The nucleic acids DNA and RNA, which code and express genetic information, are polymers of nucleotides.

Lipids are membrane components consisting mainly of carbon and hydrogen atoms derived from acetates and other molecules.

Secondary metabolites such as phenolics, alkaloids, and terpenoids often protect or strengthen plants.

Learning Objectives -2 To Understand Energy and Chemical Reactions

Energy can be stored and can move or change matter . Chemical reactions involve either a net input or a net

output of free energy. The movement of electrons is the basis of energy transfer

through oxidation and reduction reactions. The terminal phosphate bond in ATP releases energy

when broken. NADH, NADPH, and FADH2 are universal carriers of

energy-rich electrons in living organisms.

Learning Objectives -3 To Understand the Nature of Chemical Reactions

and Enzymes Enzymes position reactants, allowing reactions to occur

with minimal activation energy or increase in temperature.

Cofactors such as coenzymes interact with enzymes to assist reactions and indirectly provide energy in the form of electrons for biochemical reactions.

Competitive and noncompetitive inhibition can slow or stop enzymatic reactions and pathways.

Enzymatic reactions are linked together into metabolic pathways.

Learning Objective

Know the basic structure of atom, and know the role of ionic, covalent and hydrogen bonds.

Key Terms: Atoms

Proton positive electric charge, small mass

Neutron uncharged, about same mass as proton

Electron negative charge, extremely small mass

A Carbon Atom

Electrons

Move around the nucleus at different energy levels

Allow elements to combine chemically to form chemical compounds

Ions are atoms which tend to gain or lose electrons

Electron Configurations

Acids and Bases

Acids dissociate in water to form hydrogen ions (protons, H+)

Bases dissociate in water to yield negatively charged hydroxide ions (OH-)

pH Scale

A measure of the relative concentrations of H+ and OH- in a solution

A solution’s acidity or alkalinity is expressed in terms of the pH scale

KEY TERMS

IONIC BOND An electrostatic attraction between

oppositely charged ions

Ionic Bonding

KEY TERMS

COVALENT BOND A chemical bond involving one or

more shared pairs of electrons

Covalent Bonding in Hydrogen

Covalent Bonding in Methane

KEY TERMS

HYDROGEN BOND An attraction between a slightly

positive hydrogen atom in one molecule and a slightly negative atom (usually oxygen) in another molecule

Animation: How Atoms Bond

CLICKTO PLAY

LEARNING OBJECTIVE

Discuss the properties of water, and explain the importance of water to life

Water Has a strong dissolving ability

Molecules form hydrogen bonds with one another (cohesion)

Molecules form hydrogen bonds to substances with ionic or polar regions (adhesion)

Adhesion & Cohesion are particularly important for transport

All living things require water to survive Almost all chemical reactions that sustain life occur

in aqueous solution High Melting & Freezing Points Insulation Property after freezing (e.g., lakes)

Water Structure

Animation: Structure of Water

CLICKTO PLAY

water_polarity.html

LEARNING OBJECTIVE

Describe the chemical compositions and functions of carbohydrates, lipids, proteins, and nucleic acids

KEY TERMS

CARBOHYDRATE An organic compound containing

carbon, hydrogen, and oxygen in the approximate ratio of 1C:2H:1O

Carbohydrates 1

Include sugars, starches, cellulose Important fuel molecules,

components of molecules (nucleic acids) and cell walls

Carbohydrates 2

Monosaccharides simple sugars

Disaccharides two monosaccharide units

Polysaccharides many monosaccharide units

Common Monosaccharides

Sucrose Synthesis

Starch: A Storage Polysaccharide

Cellulose: A Structural Polysaccharide

KEY TERMS

LIPID Any of a group of organic

compounds that are insoluble in water but soluble in fat solvents

Lipids 1

Have a greasy consistency, do not readily dissolve in water

Important fuel molecules, components of cell membranes, waterproof coverings over plant surfaces, light-gathering molecules for photosynthesis

Lipids 2

A neutral fat or oil molecule is composed of a molecule of glycerol plus one, two or three fatty acids

Formation of a Neutral Fat or Oil

KEY TERMS

PROTEIN A large, complex organic

compound composed of amino acid subunits

Protein

A macromolecule composed of amino acids joined by peptide bonds

Order of amino acids determines structure and function of a protein molecule

Enzymes: Proteins that increase the rate of chemical reactions

Amino Acids

Peptide Bonds

Protein Synthesis Animation http://www.wisc-online.com/

objects/index_tj.asp?objid=AP1302

Organization of Protein Molecules

KEY TERMS

NUCLEIC ACID Deoxyribonucleic acid (DNA) and

ribonucleic acid (RNA) Large, complex organic molecules

composed of nucleotides

Nucleic Acids

Control the cell’s life processes Deoxyribonucleic acid (DNA)

Transmits information from one generation to the next

Ribonucleic acid (RNA) Involved in protein synthesis

Nucleotides Repeating units that form nucleic acids

Order of nucleotides in a nucleic acid chain determines the specific information encoded

Adenosine triphosphate (ATP) A modified nucleotide compound important in

energy transfers in biological systems

Nucleic Acids

Nucleic Acids

Nucleic Acids

DNA Replication Animation http://www.visionlearning.com/

library/module_viewer.php?mid=63&l=&c3=

KEY TERMS

ADENOSINE TRIPHOSPHATE (ATP) An organic compound of prime

importance for energy transfers in biological systems

ATP

ATP is a nucleotide that performs many essential roles in the cell.

It is the major energy currency of the cell, providing the energy for most of the energy-consuming activities of the cell.

It is one of the monomers used in the synthesis of RNA and, after conversion to deoxyATP (dATP), DNA.

It regulates many biochemical pathways.

LEARNING OBJECTIVE

Discuss the role of enzymes in cells

KEY TERMS

ENZYME An organic catalyst, produced

within an organism, that accelerates specific chemical reactions

ACTIVATION ENERGY The energy required to initiate a

chemical reaction

Enzymes Speed up a chemical reaction by

lowering its activation energy (energy needed to initiate the reaction)

Most enzymes are highly specific and catalyze only a single chemical reaction

Without enzymes, chemical reactions in cells would occur too slowly to support life

Enzymes and Activation Energy

Enzyme-Substrate Complex

Energy & Chemical Reactions Energy can be stored and can move

or change matter: Potential energy is stored energy, while kinetic energy is energy having to do with motion.

The first law of thermodynamics states energy can be harnessed and transformed but not created or destroyed.

The second law of thermodynamics states that every transfer of energy increases the entropy (disorder) of matter in the universe.

LEARNING OBJECTIVE

State the first and second laws of thermodynamics, and describe how each applies to plants and other organisms

KEY TERMS

FIRST LAW OF THERMODYNAMICS Energy cannot be created or destroyed, although

it can be transformed from one form to another SECOND LAW OF THERMODYNAMICS

When energy is converted from one form to another, some of it is degraded into a lower-quality, less useful form

Energy

The ability to do work Plants and other organisms cannot

create the energy they require to live, but must capture energy from the environment and use it to do biological work

Potential and Kinetic Energy

Entropy Continuously increases in the

universe as usable energy is converted to lower-quality, less usable form (heat)

As each energy transformation occurs in organisms, some energy changes to heat Given off into the surroundings Can never be used again for

biological work

Animation: Activation Energy

Click To Start

water_polarity.html

Secondary Metabolites

Secondary metabolites such as phenolics, alkaloids, and terpenoids often protect or strengthen plants