Transcript Protein
Chemistry Comes Alive
Part B
Human Anatomy & Physiology, Sixth Edition
Elaine N. Marieb
2
Categories of Molecules
Organic molecules
Contain carbon
Covalent bonds
Produced by living or once living organisms
Inorganic molecules
Typically do not contain carbon
Include:
Water, ammonia, salts, and some acids and bases
Salts
Electrolytes
conduct electrical currents
Examples: NaCl, KCl, CaCl2, Ca3(PO4)2
Acids and Bases
Acids release H+
HCl H+ + Cl –
Bases release OH–
NaOH Na+ + OH–
Acid-Base Concentration (pH)
pH describes the concentration of H+ in a solution
pH = -log[H+]
A scale based on [H+] found in H2O is used
H2O H+ + OHˉ
[H+] =1x10-7M and [OHˉ] = 1x10-7M
Therefore H2O has a pH = 7
Acidic solutions have [H+] higher than 1x10-7M and
therefore a pH < 7
Alkaline solutions have lower [H+] concentrations
and therefore a pH > 7
Acid-Base Concentration (pH)
Acidic: pH 0–6.99
Neutral: pH 7.00
Basic: pH 7.01–14
Figure 2.12
Buffers
Solutions of molecules that resist changes in pH
pH of blood is maintained by carbonic acidbicarbonate buffering system
Carbonic acid dissociates, reversibly releasing
bicarbonate ions and protons
The chemical equilibrium between carbonic acid
and bicarbonate resists pH changes in the blood
H2O + CO2
H2CO3
H+ + HCO3ˉ
Organic Molecules
Unique to living systems - hence organic
Small molecules & macromolecules (biomolecules)
Macromolecules are polymers of smaller organic
molecules
Major biomolecule groups
Carbohydrates
Lipids
Proteins
Nucleic Acids
Carbohydrates
Major functions are
energy source
support (plants, fungi & bacteria)
parts of other macromolecules
Monosaccharides or simple sugars
Carbohydrates
Disaccharides
Carbohydrates
Polysaccharides - polymers of simple sugars
Each monosaccharide is a residue
Glycogen - energy storage in animals
Starch – energy storage in plants
Cellulose – support structures in plants
Figure 2.13c
Carbohydrates in other Biomolecules
Glycoproteins
Proteins containing sugar residues
Glycolipids
Phospholipids with sugar residues
Ribose and Deoxyribose sugars as part of
nucleotides and nucleic acids
Lipids
Representatives
Neutral fats – triglycerides - adipose tissue
Phospholipids – chief component of cell membranes
Steroids – cholesterol, bile salts, vitamin D, hormones
Vitamins A, E & K
Eicosanoids – prostaglandins
Fatty Acids & Triglycerides
Phospholipids
Figure 2.14b
Phospholipids in membranes
Phospholipids make up cellular membranes (lipid bilayers)
Steroid Lipids
Prostaglandins
Eicosanoids –
Used to make
prostaglandins
Protein
Polymers of amino acids
Figure 2.16
Amino Acids
Building blocks of protein, containing an amine
group, a carboxyl group, & a variable side chain
Structural Levels of Proteins
Structural Levels of Proteins
Structural Levels of Proteins
Figure 2.17d, e
Fibrous and Globular Proteins
Fibrous proteins
Extended and thread-like proteins
Examples: keratin, elastin, collagen, myosin, actin
Globular proteins
Compact, spherical proteins with tertiary and
quaternary structures
Examples: antibodies, peptide-hormones, and
enzymes
Characteristics of Enzymes
Proteins that are biological catalysts
Chemically specific
Usually named for the reaction they catalyze
Names often end in suffix -ase
Protein Function - Enzymes
Protein and substrate fit together in a specific way due to Hbonds, ionic bonds and non-polar interactions
Figure 2.18a
Mechanism of Enzyme Action
Active site
Substrates
1
Enzyme (E)
Substrates (s)
H20
Enzymesubstrate
complex (E–S)
2
Free enzyme (E)
3
Covalent bond
Internal rearrangements
leading to catalysis
Product (P)
Nucleic Acids
Polymers of nucleotides
Nucleotide is
N-containing base
pentose sugar
phosphate group
DNA and RNA
Nucleotides – The Bases
Nucleotides – The Sugars
for RNA
for DNA
Nucleosides – Sugar + Base
Deoxyadenosine
Nucleotide – Nucleoside + Phosphates
Nucleic Acids – Polymers of Nucleotides
Structure of DNA
Complementary base-pairing
A-T
G-C
Figure 2.21a
Deoxyribonucleic Acid (DNA)
Double-stranded helical molecule
Constitutes chromosomes in nucleus
Replicates ensuring genetic continuity
Provides instructions for protein synthesis
Ribonucleic Acid (RNA)
Contains the base uracil in place of thymine
Made from a DNA template
Three major varieties of RNA:
mRNA – encodes a protein
tRNA – conveys amino acid to ribosome as directed
by mRNA
rRNA – joins amino acids together to form protein
as directed by mRNA
Adenosine Triphosphate (ATP)
Source of immediately usable energy
for the cell
Figure 2.22
How ATP Drives Cellular Work
Figure 2.23