The Chemical Composition of Cells Chapter 2. Learning Objectives- 1 Understand the Structure of the Molecular Components of Living Organisms Carbohydrates,
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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
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
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
HYDROGEN BOND An attraction between a slightly
positive hydrogen atom in one molecule and a slightly negative atom (usually oxygen) in another molecule
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)
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
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
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
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
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.
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
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
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
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