Download Chemistry of Cells Chapter 3

Pre-AP Biology
Ms. Haut
 Organic Compounds
 Contain Carbon
 Derived from living
things
 Carbon atom has four
outer electrons, which
can covalently bond
with an electron from
another atom
http://www.hk-phy.org/articles/laser/c-atom_e.gif
 A carbon atom forms four covalent bonds
 It can join with other carbon atoms to make chains or
rings
Structural
formula
Ball-and-stick
model
Space-filling
model
Methane
The 4 single bonds of carbon point to the corners of a tetrahedron.
Figure 3.1, top part
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Figure 3.2
 The simplest organic compounds are hydrocarbons.


These are organic molecules containing only carbon and
hydrogen atoms.
The simplest hydrocarbon is methane.
 Larger hydrocarbons

Are the main molecules in the gasoline we burn in our cars.
 The hydrocarbons of fat molecules provide energy for
our bodies.
http://www.notesandsketches.co.uk/pics/Plastic-Formula.jpg
 Most of the large molecules
in living things are
macromolecules called
polymers
 Polymers are long
chains of smaller
molecular units called
monomers
 A huge number of
different polymers can
be made from a small
number of monomers
 Cells link monomers to form polymers by
dehydration synthesis
Figure 3.6a
 Polymers are broken down to monomers by the
reverse process, hydrolysis
Figure 3.6b




Carbohydrates
Lipids
Proteins
Nucleic Acids
 Living things use carbohydrates as their many
source of energy.
 Compounds made up of carbon, hydrogen, and
oxygen
 1C:2H:1O
(C6H12O6)
 Monomer units are monosaccharides
(simple sugars)
 Disaccharides are made up of 2 simple sugars
Glucose ➞
← Fructose
Sucrose – (common table sugar)
Glucose
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Benjamin Cummings
Glucose
Maltose
 Polysaccharides —long chains of simple sugars
 Function as storehouse of energy
 Starches —storage form of glucose in plants
 Glycogen —storage form of glucose in animals (in the liver)
 Cellulose —tough fibers give plant strength and rigidity
(found in wood and paper)
 Large nonpolar
molecules, made
mostly of carbon and
hydrogen
 Fats
 Phospholipids (cell membranes)
 Steroids
 Can be used to store energy
 Carbon-hydrogen bond store a lot of energy
 Lipids do not mix with water (hydrophobic)
• Fats are lipids whose main function is
energy storage
• They are also called triglycerides
– One glycerol molecule linked to three fatty acids
Figure 3.15a
 The fatty acids of unsaturated fats (plant oils)
contain double bonds
 These prevent them from solidifying at room temperature
 Saturated fats (lard, animal fats) lack double bonds
 They are solid at room temperature
Figure 3.8C
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
• Fats perform essential functions in the human body:



Long term energy storage
Cushioning
Insulation
 Steroids are very different
from fats in structure and
function.
 The carbon skeleton is
bent to form four fused
rings.
 Cholesterol helps keep
cell membrane fluid
 Cholesterol is the “base
steroid” from which your
body produces other
steroids.
 Example: sex hormones
 Make up the lipid
bilayer of cell
membranes
 Keeps inside of cell
separate from the
external environment
http://www.biology.arizona.edu/cell_BIO/problem_
sets/membranes/graphics/bilayer.jpg
Proteins
 A protein is a polymer constructed from amino acid
monomers.
 Proteins perform most of the tasks the body needs
to function






cellular structure
movement
Defense (immunity)
transport
communication
Enzymes regulate chemical reactions
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
 Proteins are the most structurally and functionally
diverse of life’s molecules
 Their diversity is based on different arrangements of
amino acids
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
 Each amino acid contains:
– an amino group
– a carboxyl group
– an R group, which distinguishes each of the 20
different amino acids
Figure 3.12A
Amino
group
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Carboxyl (acid)
group
 Each amino acid has specific properties
Leucine (Leu)
Serine (Ser)
HYDROPHOBIC
Figure 3.12B
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Cysteine (Cys)
HYDROPHILIC
 Cells link amino acids together by dehydration
synthesis
 The bonds between amino acid monomers are
called peptide bonds
 A protein, such as lysozyme, consists of
polypeptide chains folded into a unique shape
 The shape determines the protein’s function
 A protein loses its specific function when its polypeptides
unravel
Figure 3.14A
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Figure 3.14B
• Primary structure

The specific sequence
of amino acids in a
protein
• A slight change in the
primary structure of a
protein affects its
ability to function.
 The substitution of one
amino acid for another
in hemoglobin causes
sickle-cell disease.
Figure 3.23
 Secondary structure is polypeptide coiling or
folding produced by hydrogen bonding
Primary
structure
Amino acid
Secondary
structure
Hydrogen
bond
Pleated sheet
Alpha helix
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Figure 3.15, 16
 Tertiary structure is the overall shape of a
polypeptide
 Quaternary structure is the relationship among
multiple polypeptides of a protein
Tertiary
structure
Polypeptide
(single subunit
of transthyretin)
Quaternary
structure
Transthyretin, with four
identical polypeptide subunits
Figure 3.17, 18
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
 A protein’s shape is sensitive to the surrounding
environment.


Unfavorable temperature and pH changes can cause a
protein to unravel and lose its shape thus making the protein
unable to function and do its job.
This is called denaturation.
Nucleic Acids
 Nucleic acids are information-rich polymers of
nucleotides
 Nucleic acids such and DNA and RNA serve as
the blueprints for proteins
 They ultimately control the life of a cell
 The monomers of nucleic acids are nucleotides
– Each nucleotide is composed of a sugar,
phosphate, and nitrogenous base
Nitrogenous
base (A)
Phosphate
group
Figure 3.20A
Copyright © 2003 Pearson Education, Inc. publishing Benjamin Cummings
Sugar
 The sugar and phosphate form the backbone
for the nucleic acid
Copyright © 2001 Pearson Education, Inc. publishing Benjamin Cummings
 DNA consists of two
polynucleotides
twisted around each
other in a double helix
 The sequence of the
four kinds of
nitrogenous bases in
DNA carries genetic
information
Fig. 3.28
Fig. 3.27
 Stretches of a DNA molecule called genes program
the amino acid sequences of proteins
 DNA information is transcribed into Ribonucleic acid
(RNA), a single-stranded nucleic acid
 RNA is then translated into the primary structure of
proteins
Fig. 3.25
DNA
Sugar = Deoxyribose
Double helix
RNA
Sugar = Ribose
Single strand
Adenine
Adenine
Cytosine
Cytosine
Guanine
Guanine
Thymine
Uracil
A—T
C—G
A—U
C—G
 ESSENTIALS IN BIOLOGY WITH PHYSIOLOGY 2nd edition, by
Campbell and Reece, 2007. These images have been produced
from the originals by permission of the publisher. These illustrations
may not be reproduced in any format for any purpose without
express written permission from the publisher.
 BIOLOGY: CONCEPTS AND CONNECTIONS 4th Edition, by
Campbell, Reece, Mitchell, and Taylor, ©2003. These images have
been produced from the originals by permission of the publisher.
These illustrations may not be reproduced in any format for any
purpose without express written permission from the publisher.
 BIOLOGY: CONCEPTS AND CONNECTIONS 4th Edition, by
Campbell, Reece, Mitchell, and Taylor, ©2001. These images have
been produced from the originals by permission of the publisher.
These illustrations may not be reproduced in any format for any
purpose without express written permission from the publisher.
 Background on slides is a painting, by Jon Lomberg,
http://ieti.org/hello/index.html.