Transcript PowerPoint lecture

Chapter 3
Molecules of Life
Albia Dugger • Miami Dade College
3.1 Fear of Frying
• Trans fats in
hydrogenated
vegetable oil raise
levels of cholesterol in
our blood more than
any other fat, and
directly alter blood
vessel function
Trans Fats
• Trans fats
• Partially hydrogenated vegetable oils formed by a
chemical hydrogenation process
• Double bond straightens the molecule
• Pack tightly; solid at room temperature
• Bonds are cis or trans, depending on the way the hydrogens
are arranged around them
Cis and Trans Fatty Acids
A Oleic acid, a cis fatty acid.
B Elaidic acid, a trans fatty acid.
3.2 Organic Molecules
• All molecules of life are built with carbon atoms
• We can use different models to highlight different aspects of
the same molecule
Carbon – The Stuff of Life
• Organic molecules are complex molecules of life, built on a
framework of carbon atoms
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids
Carbon – The Stuff of Life
• Carbon atoms can be assembled and remodeled into many
organic compounds
• Can bond with one, two, three, or four atoms
• Can form polar or nonpolar bonds
• Can form chains or rings
Carbon Rings
A Carbon’s versatile bonding
behavior allows it to form a variety
of structures, including rings.
B Carbon rings form the
framework of many sugars,
starches, and fats, such as
those found in doughnuts.
Representing Structures
of Organic Molecules
• Structural model of an
organic molecule
• Each line is a covalent
bond; two lines are
double bonds; three
lines are triple bonds
glucose
Representing Structures
of Organic Molecules
• Carbon ring structures are represented as polygons; carbon
atoms are implied
glucose
glucose
Representing Structures
of Organic Molecules
• Ball-and-stick models show
positions of atoms in three
dimensions; elements are
coded by color
glucose
Representing Structures
of Organic Molecules
• Space-filling models show
how atoms sharing
electrons overlap
glucose
Hemoglobin Molecule: Space-Filling Model
A A space-filling model of hemoglobin.
Hemoglobin Molecule: Surface Model
B A surface model of the same molecule reveals crevices and folds that are
important for its function. Heme groups, in red, are cradled in pockets of the
molecule.
Hemoglobin Molecule: Ribbon Model
C A ribbon model of hemoglobin shows all four heme groups, also in red, held in
place by the molecule’s coils.
Take-Home Message:
How are all molecules of life alike?
• The molecules of life (carbohydrates, lipids, proteins, and
nucleic acids) are organic, which means they consist mainly
of carbon and hydrogen atoms
• The structure of an organic molecule starts with its carbon
backbone, a chain of carbon atoms that may form a ring
• We use different models to represent different characteristics
of a molecule’s structure; considering a molecule’s structural
features gives us insight into how it functions
3.3 From Structure to Function
• The function of organic molecules in biological systems
begins with their structure
• The building blocks of carbohydrates, lipids, proteins, and
nucleic acids bond together in different arrangements to form
different kinds of complex molecules
• Any process in which a molecule changes is called a reaction
Assembling Complex Molecules
• Monomers
• Molecules used as subunits to build larger molecules
(polymers)
• Polymers
• Larger molecules that are chains of monomers
• May be split and used for energy
What Cells Do to Organic Compounds
• Metabolism
• Activities by which cells acquire and use energy to
construct, rearrange, and split organic molecules
• Allows cells to live, grow, and reproduce
• Requires enzymes (proteins that increase the speed of
reactions)
Metabolism
ANIMATED FIGURE: Condensation and
hydrolysis
To play movie you must be in Slide Show Mode
PC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
What Cells Do to Organic Compounds
• Condensation
• Covalent bonding of two molecules to form a larger
molecule
• Water forms as a product
• Hydrolysis
• The reverse of condensation
• Cleavage reactions split larger molecules into smaller
ones
• Water is split
Condensation
B Condensation. Cells build a large
molecule from smaller ones by this
reaction.
An enzyme removes a hydroxyl group
from one molecule and a hydrogen
atom from another. A covalent bond
forms between the two molecules, and
water also forms.
Hydrolysis
C Hydrolysis. Cells split a large
molecule into smaller ones by
this water-requiring reaction.
An enzyme attaches a hydroxyl
group and a hydrogen atom (both
from water) at the cleavage site.
Functional Groups
• Hydrocarbon
• An organic molecule that consists only of hydrogen and
carbon atoms
• Most biological molecules have at least one functional group
• A cluster of atoms that imparts specific chemical
properties to a molecule (polarity, acidity)
Table 3-1 p41
Table 3-1 p41
Table 3-1 p41
ANIMATION: Functional groups
To play movie you must be in Slide Show Mode
PC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
Glucose: Conversion of
Straight Chain to Ring Form
Take-Home Message: How do organic
molecules work in living systems?
• All life is based on the same organic compounds: complex
carbohydrates, lipids, proteins, and nucleic acids
• By processes of metabolism, cells assemble these molecules
of life form monomers. They also break apart polymers into
component monomers.
• Functional groups impart chemical characteristics to organic
molecules; such groups contribute to the function of biological
molecules
• An organic molecule’s structure dictates its function in
biological systems
3.4 Carbohydrates
• Carbohydrates are the most plentiful biological molecules in
the biosphere
• Cells use some carbohydrates as structural materials; they
use others for fuel, or to store or transport energy
Carbohydrates
• Carbohydrates
• Organic molecules that consist of carbon, hydrogen, and
oxygen in a 1:2:1 ratio
• Three types of carbohydrates in living systems
• Monosaccharides (simple sugars)
• Oligosaccharides (short-chain carbohydrates)
• Polysaccharides (complex carbohydrates)
Simple Sugars
• Monosaccharides (one sugar unit) are the simplest
carbohydrates
• Used as an energy source or structural material
• Backbones of 5 or 6 carbons
• Very soluble in water
• Example: glucose
Short-Chain Carbohydrates
• Oligosaccharides
• Short chains of monosaccharides
• Example: sucrose, a disaccharide
glucose
+
fructose
sucrose
+
water
Stepped Art
Complex Carbohydrates
• Polysaccharides
• Straight or branched chains of many sugar monomers
• The most common polysaccharides are cellulose, starch, and
glycogen
• All consist of glucose monomers
• Each has a different pattern of covalent bonding, and
different chemical properties
Cellulose
• Cellulose
• Polysaccharide
• Major structural material in plants
• Consists of long, straight chains of glucose monomers
• Does not dissolve in water; not easily broken down
• Dietary fiber or “roughage” in our vegetable foods
Cellulose
Starch
• Starch
• Polysaccharide
• Energy reservoir in plants
• Covalent bonding pattern between monomers makes a
chain that coils up into a spiral
• Does not dissolve easily in water, but less stable than
cellulose
• An important component of human food
Starch
Glycogen
• Glycogen
• Polysaccharide
• Covalent bonding pattern forms highly branched chains of
glucose monomers
• Energy reservoir in animal cells; stored in muscle and liver
cells
Glycogen
Chitin
• Chitin
• A nitrogen-containing polysaccharide that strengthens
hard parts of animals such as crabs, and cell walls of fungi
Take-Home Message:
What are carbohydrates?
• Simple carbohydrates (sugars), bonded together in different
ways, form various types of complex carbohydrates
• Cells use carbohydrates for energy or as structural materials
ANIMATION: Structure of starch and
cellulose
3.5 Greasy, Oily – Must Be Lipids
• Lipids function as the body’s major energy reservoir, and as
the structural foundation of cell membranes
• Lipids
• Fatty, oily, or waxy organic compounds that are insoluble
in water
• Triglycerides, phospholipids, waxes, and steroids are lipids
common in biological systems
Fatty Acids
• Many lipids incorporate fatty acids
• Simple organic compounds with a carboxyl group joined to
a backbone of 4 to 36 carbon atoms
• Saturated fatty acids (animal fats)
• Fatty acids with only single covalent bonds
• Molecules are packed tightly; solid at room temperature
• Unsaturated fatty acids (vegetable oils)
• Fatty acids with one or more double bonds
• Molecules are kinked; liquid at room temperature
Saturated and Unsaturated Fatty Acids
Fats
• Fats
• Lipids with one, two, or three fatty acids “tails” attached to
glycerol
• Triglycerides
• Neutral fats with three fatty acids attached to glycerol
• The most abundant energy source in vertebrates
• Concentrated in adipose tissues (for insulation and
cushioning)
Triglycerides
ANIMATED FIGURE: Triglyceride formation
To play movie you must be in Slide Show Mode
PC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
Phospholipids
• Phospholipids
• Molecules with a polar head containing a phosphate and
two nonpolar fatty acid tails
• Heads are hydrophilic, tails are hydrophobic
• The most abundant lipid in cell membranes
• Form lipid bilayers with hydrophobic tails sandwiched
between the hydrophilic heads
Phospholipids
Phospholipids in a Lipid Bilayer
hydrophilic head
two hydrophobic tails
Phospholipids in a Lipid Bilayer
one layer of lipids
one layer of lipids
Waxes
• Waxes
• Complex mixtures with long fatty-acid tails bonded to longchain alcohols or carbon rings
• Protective, water-repellant covering
Steroids
• Steroids
• Lipids with a rigid backbone of four carbon rings and no
fatty-acid tails
• Cholesterol
• Component of eukaryotic cell membranes
• Remodeled into bile salts, vitamin D, and steroid
hormones such as the female sex hormone estrogen, and
the male sex hormone testosterone
Estrogen and Testosterone
an estrogen
testosterone
Effects of Estrogen and Testosterone
female
wood duck
male
wood duck
Take-Home Message:
What are lipids?
• Lipids are fatty, waxy, or oily organic compounds. Common
types include fats, phospholipids, waxes, and steroids
• Triglycerides are lipids that serve as energy reservoirs in
vertebrate animals
• Phospholipids are the main lipid component of cell
membranes
• Waxes are lipid components of water-repelling and lubricating
secretions
• Steroids are lipids that occur in cell membranes; some are
remodeled into other molecules
3.6 Proteins – Diversity
in Structure and Function
• All cellular processes involve proteins, the most diverse
biological molecule (structural, nutritious, enzyme, transport,
communication, and defense proteins)
• Cells build thousands of different proteins by stringing
together amino acids in different orders
From Structure to Function
• Protein
• An organic compound composed of one or more chains of
amino acids
• Amino acid
• A small organic compound with an amine group (—NH3+),
a carboxyl group (—COO-, the acid), and one or more
variable groups (R group)
Amino Acid Structure
Stepped Art
Polypeptides
• Protein synthesis involves the formation of amino acid chains
called polypeptides
• Polypeptide
• A chain of amino acids bonded together by peptide
bonds in a condensation reaction between the amine
group of one amino acid and the carboxyl group of another
amino acid
Polypeptide Formation
methionineserine
arginineglutamine
serine
methionine
methionine
serine
Stepped Art
ANIMATED FIGURE: Peptide bond
formation
To play movie you must be in Slide Show Mode
PC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
Levels of Protein Structure
• Primary structure
• The unique amino acid sequence of a protein
• Secondary structure
• The polypeptide chain folds and forms hydrogen bonds
between amino acids
• Tertiary structure
• A secondary structure is compacted into structurally stable
units called domains
• Forms a functional protein
Levels of Protein Structure
• Quaternary structure
• Some proteins consist of two or more folded polypeptide
chains in close association
• Example: hemoglobin
• Some proteins aggregate by thousands into larger structures,
with polypeptide chains organized into strands or sheets
• Example: hair
lysine
glycine
A protein’s primary
structure consists of a
linear sequence of
amino acids (a
polypeptide chain).
Each type of protein
has a unique primary
structure.
1
arginine
glycine
2 Secondary structure
arises as a polypeptide
chain twists into a coil
(helix) or sheet held in
place by hydrogen
bonds between different
parts of the molecule.
The same patterns of
secondary structure
occur in many different
proteins.
3 Tertiary structure
occurs when a chain’s
coils and sheets fold
up into a functional
domain such as a
barrel or pocket. In
this example, the coils
of a globin chain form
a pocket.
4 Some proteins have
quaternary structure, in
which two or more
polypeptide chains
associate as one
molecule. Hemoglobin,
shown here, consists of
four globin chains (green
and blue). Each globin
pocket now holds a heme
group (red).
5
Many proteins aggregate
by the thousands into much
larger structures, such as the
keratin filaments that make
up hair.
Stepped Art
Figure 3-16 p47
ANIMATED FIGURE: Secondary and
tertiary structure
To play movie you must be in Slide Show Mode
PC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
Some Functional Proteins
• Some fibrous proteins contribute to the structure and
organization of cells and tissues; others help cells, cell parts,
and bodies move
• Sugars bond to proteins to make glycoproteins that allow a
tissue or a body to recognize its own cells
• Lipids bond to proteins to make lipoproteins such as HDL and
LDL, which transport cholesterol to and from the liver
HDL: A Lipoprotein
lipid
protein
an HDL particle
Take-Home Message:
What are proteins?
• Proteins are chains of amino acids. The order of amino acids
in a polypeptide chain dictates the type of protein.
• Polypeptide chains twist and fold into coils, sheets, and loops,
which fold and pack further into functional domains
• A protein’s shape is the source of its function
3.7 Why Is Protein Structure
So Important?
• Proteins function only as long as they maintain their correct
three-dimensional shape
• Changes in a protein’s shape may have drastic health
consequences
Denaturation
• Heat, changes in pH, salts, and detergents can disrupt the
hydrogen bonds that maintain a protein’s shape
• When a protein loses its shape and no longer functions, it is
denatured
• Once a protein’s shape unravels, so does its function
Prions
• Prion diseases are caused by misfolded proteins
• Mad cow disease (bovine spongiform encephalitis)
• Creutzfeldt–Jakob disease in humans
• Scrapie in sheep
• All are infectious diseases characterized by deterioration of
mental and physical abilities that eventually causes death
Variant Creutzfeldt–Jakob Disease (vCJD)
Take-Home Message:
Why is protein structure important?
• A protein’s function depends on its structure.
• Conditions that alter a protein’s structure may also alter its
function
• Protein shape unravels if hydrogen bonds are disrupted
3.8 Nucleic Acids
• Nucleotides are subunits of nucleic acids such as DNA and
RNA
• Some nucleotides have roles in metabolism
Nucleotides
• Nucleotide
• A small organic molecule consisting of a sugar with a fivecarbon ring, a nitrogen-containing base, and one or more
phosphate groups
• ATP
• A nucleotide with three phosphate groups
• Important in phosphate-group (energy) transfer
base: adenine (A)
3 phosphate
groups
sugar: ribose
A ATP, a nucleotide monomer of RNA, and also an essential
participant in many metabolic reactions.
Figure 3-18a p49
ANIMATED FIGURE: DNA close up
To play movie you must be in Slide Show Mode
PC Users: Please wait for content to load, then click to play
Mac Users: CLICK HERE
A Chain of Nucleotides
B A chain of nucleotides is a nucleic
acid. The sugar of one nucleotide is
covalently bonded to the phosphate
group of the next, forming a sugar–
phosphate backbone.
Nucleic Acids
• Nucleic acids
• Polymers of nucleotides in which the sugar of one
nucleotide is attached to the phosphate group of the next
• RNA and DNA are nucleic acids
RNA
• RNA (ribonucleic acid)
• Contains four kinds of nucleotide monomers, including
ATP
• Important in protein synthesis
DNA
• DNA (deoxyribonucleic acid)
• Two chains of nucleotides twisted together into a double
helix and held by hydrogen bonds
• Contains all inherited information necessary to build an
organism, coded in the order of nucleotide bases
The DNA Molecule
• The cell uses the
order of nucleotide
bases in DNA (the
DNA sequence)
guide production of
RNA and proteins
Take-Home Message: What are
nucleotides and nucleic acids?
• Nucleotides are monomers of the nucleic acids DNA and
RNA; some have additional roles
• DNA’s nucleotide sequence encodes heritable information
• RNA plays several important roles in the process by which a
cell uses the instructions written in its DNA to build proteins