Download Carbon Compounds In Cells

Carbon Compounds in Cells
Chapter 3
Importance of Carbon
Carbon permeates the world of life—
from the energy-requiring activities and
structural organization of cells, to
physical and chemical conditions that
span the globe and influence
ecosystems everywhere.
Humans and Global Warming
• Fossil fuels are rich in carbon
• Use of fossil fuels releases CO2 into
atmosphere
• Increased CO2 may contribute to global
warming
Organic Compounds
Hydrogen and other elements
covalently bonded to carbon
Carbohydrates
Lipids
Proteins
Nucleic Acids
Carbon’s Bonding Behavior
• Outer shell of
carbon has 4
electrons; can
hold 8
• Each carbon atom
can form covalent
bonds with up to 4
atoms
Methane: Simplest Organic
Compound
H
H
C
H
Ball-and-stick
model
H
Structural formula
Space-filling
model
Figure 3.2
Page 36
Bonding Arrangements
• Carbon atoms can
form chains or rings
• Other atoms project
from the carbon
backbone
Glucose
(ball-and-stick model)
In-text figure
Page 36
Hemoglobin Molecular Models
Ball-and-stick model
Space-filling model
Ribbon model
Figure 3.3
Page 37
Functional Groups
• Atoms or clusters of atoms that are
covalently bonded to carbon backbone
• Give organic compounds their different
properties
Examples of Functional
Groups
Methyl group
- CH3
Hydroxyl group
- OH
Amino group
- NH3+
Carboxyl group
- COOH
Phosphate group
- PO3-
Sulfhydryl group
- SH
Carbohydrates
Monosaccharides
(simple sugars)
Oligosaccharides
(short-chain carbohydrates)
Polysaccharides
(complex carbohydrates)
Lipids
• Most include fatty acids
– Fats
– Phospholipids
– Waxes
• Sterols and their derivatives have no
fatty acids
• Tend to be insoluble in water
Phospholipids
• Main component of
cell membranes
• Hydrophobic head
• Hydrophilic tails
Fig. 3.14a,b
Page 43
Sterols and Derivatives
• No fatty acids
• Rigid backbone of
four fused-together
carbon rings
Cholesterol
• Cholesterol - most
common type in
animals
Figure 3.15a
In-text p43
Waxes
• Long-chain fatty acids linked to
long-chain alcohols or carbon
rings
• Firm consistency, repel water
• Important in water-proofing
Protein Synthesis
• Peptide bond
– Condensation reaction links amino group of
one amino acid with carboxyl group of next
Water forms as a by-product
Fig. 3.18a
Page 45
Primary Structure
• Sequence of amino acids
• Unique for each protein
• Two linked amino acids = dipeptide
• Three or more = polypeptide
• Backbone of polypeptide has N atoms:
-N-C-C-N-C-C-N-C-C-N-
Second and Third Levels
• Hydrogen bonding
produces helix or
sheet
• Domain formation
Tertiary structure
Secondary
structure
Figure 3.19a
Page 46
Fourth Level Structure
Some proteins
are made up of
more than one
polypeptide
chain
Figure 3.20
Page 47
HLA-A2 quaternary structure
Hemoglobin
alpha chain
beta chain
beta chain
alpha chain
Nucleotide Structure
• Sugar
• At least one
ATP
phosphate group
• Nitrogen-
containing base
Figure 3.23a
Page 50
Nucleotide Functions
• Energy carriers
• Coenzymes
• Chemical messengers
• Building blocks for
nucleic acids
DNA
• Double-stranded
• Sugar-phosphate
backbone
• Covalent bonds in
backbone
• H bonds between
bases
Figure 3.25
Page 51
RNA
• Usually single strands
• Four types of nucleotides
• Unlike DNA, contains the base uracil in
place of thymine
• Three types are key players in protein
synthesis