chapter 3 biology sixth edition raven/johnson (c) the mcgraw-hill companies, inc
TRANSCRIPT
Chapter 3
BiologySixth Edition
Raven/Johnson
(c) The McGraw-Hill Companies, Inc.
www.nicholls.edu/biol-qcf
The Chemistry of Carbon
Because carbon only has 4 electrons in its outer shell, it can attach to four separate molecules
Organic molecules consisting of only C and H are called hydrocarbons.
Organic molecules contain C and H
Hydrocarbon chains can have functional groups that cause the macromolecule to behave in a certain way.
Carboxyl Group: -COOH -COO¯ + H+
Making and Breaking Macromolecules
• Macromolecules (polymers) are formed from smaller building blocks called monomers.
• Macromolecules are formed by dehydration synthesis (requires energy)
• Macromolecule bonds are broken by hydrolysis (releases energy in bonds)
Energy must be used to build macromolecules.
Energy is released when macromolecules are split.
Four Types of Organic Macromolecules
• Proteins• Nucleic Acids• Lipids• Carbohydrates
Protein Types and Function
• Enzyme Catalyst– Facilitate chemical
reactions• Defense
– Body’s hormone and immune system
• Transport– Specific small
molecules and ions
• Support– Structural roles
• Motion– Aid in muscle
movement• Regulation
– Intercellular messengers
Protein Building Blocks
• Proteins are made of linked amino acids
• Only 20 amino acids available
• Sequence of amino acids are unique for each protein
C
NH2
COOH
H R
Structure of Amino Acids
(AcidicGroup)
(R or FunctionalGroup)
(AminoGroup)
(HydrogenGroup)
Five Groups of Amino Acids
• Nonpolar • Polar• Aromatic• Ionizable• Special Structural Property
Contains –CH2 or –CH3
Contains –O or only H
Contains carbon ring that has alternating single and double bonds
Contains acids or bases
Special function
Amino acids are linked by peptide bonds:
Dehydration synthesis
Primary Structure - Amino Acid Sequence
Secondary Structure - Folding due to hydrogen bond
Motifs – Characteristic secondary structure ( creates a fold or crease)
Driven into its tertiary structure by hydrophobic reactions with water, disulfide bonds, and other ionic and covalent bonds
-remember: some amino acids are nonpolar.
Two or more polypeptide chains associate to form a functional protein
Domain – structurally independent functional unit
subunits
Protein Structure Viewed at Six Levels
• Amino acid sequence (primary structure)
• Coils and sheets (secondary structure)
• Folds or creases (motifs)
• Three-dimensional shape (tertiary structure)
• Functional units (domains)
• Individual polypeptide subunits associated in quaternary structure
Chaperonins – proteins that help other proteins fold correctly
Primary structure determines tertiary structure!
Nucleic Acids
Nucleic acids are polymers of nucleotides.
Examples include Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA).
All nucleotides have:1.) nitrogenous base2.) pentose sugar
-deoxyribose-ribose
3.) phosphate group
Fig. 3.14
Fig. 3.15
A chemical difference between DNA and RNA
Nucleotides (monomer) connected by phosphodiester bonds to form nucleic acid (polymer).
Hydrogen bonds between base pairs gives DNA its characteristic double-helix shape.
Purines always bond with a pyrimidine, and with DNA it is always:
A-T; G-C
Adenine
Guanine
Cytosine
Thymine
UracilDNA vs RNA: RNA has Uracil instead of Thymine
H instead of CH3
DNA – double stranded, contains thymine, #2 C attached to H
RNA – single stranded, contains uracil, #2 C attached to OH
Nucleotide bases also play an important part in other molecules crucial to life: ATP, NAD, and FAD.
Adenosine triphosphate
Lipids- triglycerides, phospholipids, steroids
Lipids serve as long-term energy stores in cells, form membranes, and serve as hormones and insulation.
Lipids contain more energy per gram than any other biological molecule.
Lipids are nonpolar, thus they do not dissolve in water (hydrophobic).
All lipids are insoluble in water!!
Structure of Triglycerides
unsaturated
saturated
functional group –COOH
Fatty Acids: long chains of hydrocarbons with an acidic functional group –COOH
Saturated: no double bonds between carbons, “saturated
with hydrogen”, higher melting point than unsaturated
Unsaturated: has one or more double bonds between carbons
Dehydration or
Solids (butter) at room temperature; fatty acids can align close to each other
Liquids (corn oil) at room temperature; double bonds prevent fatty acids from aligning close to each other
Phosphate
Phospholipids consist of:
Glycerol
2 Fatty acids
Phosphate group
Polar end
Non- Polar end
Contains a phosphate group
Cellular membranes
Terpenes – long chain lipids; components of many biologically important pigments
All steroids characteristically have four carbon rings.
Carbohydrates
Carbohydrates contain C, H, and O and serve as quick energy and short-term energy storage.
Monomers of carbohydrates are the monosaccharides (simple sugars)
6-Carbon sugars – primary energy storage
Empirical formula for a 6-C sugar:
C6H12O6
Glucose is metabolized by cellular respiration
Dehydration synthesis – consumes energy
Hydrolysis splits the disaccharides and releases energy
‘double sugars’ – important in sugar transport
Your taste buds can taste the difference!
Same empirical formula (C6H1206)– different arrangement.
Energy storage for plants
Energy storage for animals
Structural polysaccharide – chief component of plant cell walls
Modified form of cellulose with a nitrogen group added to the glucose units. Structural building material in insects, many fungi, and certain other organisms.
The End.