Transcript video slide - yayscienceclass

CHAPTER 3
The Molecules of Life
Did you know?
Organic Molecules
• A cell is mostly water.
– The rest of the cell consists mostly of carbonbased molecules.
– Organic chemistry is the study of carbon
compounds.
– An organic compound must contain Carbon!
Note that there are some inorganic compounds
that also contain carbon, but these lack hydrogen.
An example is CO2. Another way to determine if
a carbon containing compound is organic is to
decide if it is found in living tissue.
Carbon Chemistry
• Carbon is a versatile atom.
• Carbon has the atomic number of 6.
• How many valence electrons available for covalent
bonding does it have______?
– Carbon can share its electrons with other atoms to
form up to ________ covalent bonds.
• ___ single bond(s)
• ____ double bond(s)
• ___ triple bond(s)
Carbon Chemistry
• Carbon can use its bonds to
– Attach to other carbons.
– Form an endless diversity of carbon skeletons in
many shapes as shown below.
Carbon Chemistry
• The simplest organic compounds are hydrocarbons.
– These are organic molecules containing only carbon
and hydrogen atoms.
– The simplest hydrocarbon is methane (shown below)
Carbon Chemistry
• Larger hydrocarbons are used in our bodies and
elsewhere.
– Are the main molecules in the gasoline we burn in
our cars.
– The hydrocarbons of fat molecules provide
energy for our bodies.
Carbon Chemistry
• Each type of organic molecule has a unique threedimensional shape that defines its function in an
organism.
– The molecules of your body recognize one
another based on their shapes.
Carbon Chemistry
• The unique properties of an organic compound
depend not only on its carbon skeleton but also on
the atoms attached to the skeleton.
– These atoms are called functional groups.
Hydroxyl: -OH alcohols
Carbonyl: -CO aldehydes & ketones
Carboxyl: -COOH aka carboxylic acids
Amino: -NH2 amines
Phosphate: -PO4 phosphates
Memorize the names, chemical formula, where
they are found and the structure of the parts.
-CO
-OH
Phosphate Group
-PO4
-NH2
Found in amino acids
and used in energy
storage in ATP!
-COOH
Giant Molecules from Smaller Building Blocks
• On a molecular scale, many of life’s molecules are
gigantic.
– Biologists call them macromolecules.
• macro = large
– Examples: carbohydrates, proteins, lipids, the
nucleic acids - & RNA DNA
Giant Molecules from Smaller Building Blocks
• Most macromolecules are polymers.
– Polymers are made by stringing together many
smaller molecules called monomers.
– Cells link monomers to build polymers by
dehydration reactions.
Note that water
has been lost
when the
polymer is
formed this is
what makes it a
“dehydration
reaction”
Breaking down large molecules
• Organisms also have to break down macromolecules.
– Cells do this by a process called hydrolysis.
• Hydro = water, lysis = split/destroy
Note that water
has been split to
create break
apart the
polymer into
smaller subunits
such as
monomers.
Biological Molecules
• There are four categories of large molecules in
cells:
1. Carbohydrates
2. Lipids
3. Proteins
4. Nucleic acids
Carbohydrates
• Carbohydrates include:
– Small sugar molecules in soft drinks
– Long starch molecules in pasta and potatoes
Monosaccharides
• Monosaccharides are simple sugars.
– Examples:
• Glucose is found in sports drinks.
• Fructose is found in fruit.
• Honey contains both glucose and fructose.
Monosaccharides
• The monosaccharides glucose, fructose and
galactose are isomers.
– They have the same formula, but their atoms are
arranged differently.
Isomers
(watch and take notes!)
L-Dopa
(watch and take notes!)
Monosaccharides
• In aqueous solutions, monosaccharides form rings.
• Monosaccharides are the main fuel that cells use
for cellular work.
Disaccharides
• A disaccharide is a double sugar.
– It is constructed from two monosaccharides.
• Disaccharides are joined through a dehydration
reaction.
Disaccharides
Disaccharides
• Lactose is another type of disaccharide.
– Some people have trouble digesting lactose, a
condition called lactose intolerance.
Disaccharides
• The most common disaccharide is sucrose,
common table sugar.
– It consists of a glucose linked to a fructose.
– Sucrose is extracted from sugar cane and the roots
of sugar beets.
• The United States is one of
the world’s leading markets
for sweeteners.
– The average American
consumes about 64 kg
of sugar per year.
Polysaccharides
• Complex carbohydrates are called polysaccharides.
– They are long chains of sugar units.
– They are polymers of monosaccharides.
Polysaccharides
Polysaccharides
• One familiar example of a polysaccharide is starch.
– Plant cells store starch for energy.
– Potatoes and grains are major sources of starch in
the human diet.
Polysaccharides
• Animals store excess sugar in the form of a
polysaccharide called glycogen.
– Glycogen is similar in structure to starch.
• Cellulose is a structural component of plant cells
and is the most abundant organic compound on
Earth.
– It forms cable-like fibrils in the tough walls that
enclose plants.
– It is a major component of wood.
– It is also known as dietary fiber.
Polysaccharides
• Most animals cannot derive nutrition from fiber.
– Grazing animals survive on a diet of cellulose
because they have prokaryotes in their digestive
tracts that can break down cellulose.
Polysaccharides
• Simple sugars and double sugars dissolve readily in
water.
– They are hydrophilic, or “water-loving.”
Low-Carb Diets
• In recent years, “low-carb diets” and “no carb
diets” have become popular.
– Are these diets healthy?
– But consumers need to be wary of products
boasting that
they are
“low-carb”
because they
can be
unhealthy.
Lipids
• Lipids are hydrophobic.
– They do not mix with water.
– Examples: fats and steroids
Fats
Fats
• Dietary fat consists largely of the molecule
triglyceride.
– Triglyceride is a combination of glycerol and
three fatty acids.
Fats
• Fats perform essential functions in the human
body:
1. Energy storage
2. Cushioning
3. Insulation
Fats
• Unsaturated fatty acids
– Have less than the maximum number of
hydrogens bonded to the carbons.
• Saturated fatty acids
– Have the maximum number of hydrogens bonded
to the carbons.
Fats
• Most animal fats have a high proportion of
saturated fatty acids, which can be unhealthy.
– Example: butter
• Most plant oils tend to be low in saturated fatty
acids.
– Example: corn oil
Fats
• Not all fats are unhealthy.
– Fats perform important functions in the body and
are essential to a healthy diet.
– Are no fat diets healthy?
Steroids
• Steroids are very different from fats in structure
and function.
– The carbon skeleton is bent to form four fused
rings.
• Cholesterol is the “base steroid” from which your
body produces other steroids.
– Example: sex hormones
Steroids
Figure 3.17
Steroids
• Synthetic anabolic steroids are controversial.
– They are variants of testosterone.
• Some athletes use anabolic steroids to build up
their muscles quickly.
– However, these
substances can pose
serious health risks.
– Testicle shrinkage, Addiction, Growth of Breasts (in men),
Facial Hair (in women) Reduced Sexual Function,
Baldness & Skin Conditions, Infertility, Halted Growth
(in teens) High Blood Pressure, Liver Damage, Pain,
Psycosis, Heart Attack, Death and more!
Proteins
• A protein is a polymer constructed from amino acid
monomers.
• Proteins perform most of the tasks the body needs to
function.
Protein Videos
• Information on many important proteins below.
• I encourage you to watch those we do not get to in
class online for more information!
Structural Proteins
Receptor Proteins
Storage Proteins
Enzymes
Contractile Proteins
Hormonal Proteins
Transport Proteins
Sensory Proteins
Defensive Proteins
Gene Regulatory
Proteins
The Monomers: Amino Acids
• All proteins are constructed from a common set of
20 kinds of amino acids.
• Each amino acid consists of
1. A central carbon atom bonded to four covalent
partners.
2. A side group that is variable among all 20.
Proteins as Polymers
• Cells link amino acids together by dehydration
reactions.
– The resulting bond
between them is
called a peptide
bond.
Proteins as Polymers
• Your body has tens of thousands of different kinds
of protein.
– The arrangement of amino acids makes each one
different.
Proteins
• Primary structure
– The specific
sequence of
amino acids in
a protein
Proteins
• 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.
Protein Shape
• Proteins have four levels of structure.
Protein Structure Introduction
Primary Protein Structure
Secondary Protein Structure
Tertiary Protein Structure
Quaternary Protein Structure
What Determines Protein Structure?
• 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.
– This is called denaturation.
Nucleic Acids
• Nucleic acids are information storage molecules.
– They provide the directions for building proteins.
• There are two types of nucleic acids:
– DNA, deoxyribonucleic acid
– RNA, ribonucleic acid
DNA
Nucleic Acids
• The genetic instructions in DNA
– Must be translated from “nucleic acid language”
to “protein language.”
Nucleic Acids
• Nucleic acids are polymers of nucleotides.
Nucleic Acids
• Each DNA nucleotide has one of the following
bases:
– Adenine (A)
– Guanine (G)
– Thymine (T)
– Cytosine (C)
Nucleic Acids
• Nucleotide monomers are
linked into long chains.
– These chains are called
polynucleotides, or DNA
strands.
– A sugar-phosphate
backbone joins them
together.
DNA and RNA Structure
Nucleic Acids
• Two strands of DNA join together to form a double
helix.
Nucleic Acids
• RNA, ribonucleic acid, is different from DNA.
– Its sugar ribose
has an extra
OH group.
– It has the base
uracil (U) instead
of thymine (T).
Evolution Connection:
DNA and Proteins as Evolutionary Tape Measures
• Evolutionary relationships between organisms can
be assessed.
– Molecular genealogy extends to relationships
between species.
– Biologists use molecular analysis of DNA and
protein sequences for testing evolutionary
hypotheses.
Figure 3.30