Transcript video slide - Delran High School

CHAPTER 3
The 4 Macromolecules of
Life
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.
Carbon Chemistry
• Carbon is a versatile atom.
– It has four electrons in an outer shell that holds eight.
• Carbon can share its electrons with other atoms to form
up to four covalent bonds. Carbon can use its bonds to
– Attach to other carbons.
– Form an endless diversity of carbon skeletons.
• Each type of organic molecule has a unique 3D shape
that defines its function in an organism.
– The molecules of your body recognize one another
based on their shapes.
• A compound’s properties depend on both the shape and
the atoms attached to the skeleton.
– These atoms are called functional groups.
Figure 3.5
Giant Molecules from Smaller Building Blocks
• On a molecular scale, many of life’s molecules are
gigantic.
– Biologists call them macromolecules.
– Examples: DNA, carbohydrates
• Most macromolecules are polymers.
– Polymers are made by stringing together many
smaller molecules called monomers.
• Cells link monomers by dehydration (or
condensation) reactions.
• Organisms also have to break down
macromolecules.
– Cells do this by a process called hydrolysis.
Figure 3.6a
Figure 3.6b
• There are four categories of large molecules in
cells:
– Carbohydrates
– Lipids
– Proteins
– Nucleic acids
Carbohydrates
• Carbohydrates include:
– Small sugar molecules in soft drinks
– Long starch molecules in pasta and potatoes
Monosaccharides
• Monosaccharides are simple sugars.
– Glucose is found in sports drinks.
– Fructose is found in fruit.
• Honey contains both glucose and fructose.
The monosaccharides
glucose and fructose
are isomers.
– They have the
same formula, but
their atoms are
arranged
differently.
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. (Condensation)
Disaccharides
• Lactose is another type of disaccharide.
– Some people have trouble digesting lactose, a
condition called lactose intolerance.
• 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.
• Simple sugars and double sugars dissolve readily in
water.
– They are hydrophilic, or “water-loving.”
Polysaccharides
• Complex carbohydrates are called polysaccharides.
– They are long chains of sugar units.
– They are polymers of monosaccharides.
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.
• Animals store excess sugar in the form of a
polysaccharide called glycogen.
– Glycogen is similar in structure to starch.
• Cellulose 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.
• 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.
• There are four categories of large molecules in
cells:
– Carbohydrates
– Lipids
– Proteins
– Nucleic acids
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 perform essential functions in the human
body:
– Energy storage
– Cushioning
– Insulation
• Unsaturated fatty acids = double bond
–
Have less than the maximum number of hydrogens bonded to the carbons.
• Saturated fatty acids = single bond
–
Have the maximum number of hydrogens bonded to the carbons.
Figure 3.15b
• 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 (or high
in unsaturated) fatty acids.
– Example: corn oil
• Not all fats are unhealthy. MUST have some fat.
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
Figure 3.17
• Some athletes use anabolic steroids to build up
their muscles quickly.
– However, these substances can pose serious
health risks.
• There are four categories of large molecules in
cells:
– Carbohydrates
– Lipids
– Proteins
– Nucleic acids
Proteins
• A protein is a polymer constructed from amino acid
monomers.
• Proteins perform most of the tasks the body needs
to function.
Structural Proteins
Receptor Proteins
Storage Proteins
Enzymes
Contractile Proteins
Hormonal Proteins
Transport Proteins
Sensory Proteins
Defensive Proteins
Gene Regulatory
Proteins
Figure 3.19
The Monomers: Amino Acids
• All proteins are constructed from a common set of
20 kinds of amino acids.
• Each amino acid consists of
– A central carbon atom bonded to four covalent
partners.
– A side group that is variable among all 20.
Figure 3.20
Proteins as Polymers
• Cells link amino acids together by dehydration
reactions.
– The resulting bond between them is called a
peptide bond.
Figure 3.21
• Your body has tens of thousands of different kinds
of protein.
– The arrangement of amino acids makes each one
different.
• 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.
Protein Shape
• Proteins have four levels of structure.
– Transformers
• Plastic, paint, metal, rubber = primary
• Wheels, door, engine = secondary
• Car = tertiary
• Megadude = quartinary
• DEVASTATOR!
Figure 3.24
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.
• There are four categories of large molecules in
cells:
– Carbohydrates
– Lipids
– Proteins
– Nucleic acids
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
• The genetic instructions in DNA
– Must be translated from “nucleic acid language”
to “protein language.”
Figure 3.25
Figure 3.26
• Each DNA nucleotide has one of the following
bases:
– Adenine (A)
– Guanine (G)
– Thymine (T)
– Cytosine (C)
Figure 3.27
• Nucleotide monomers are linked into long chains.
– These chains are called polynucleotides, or DNA
strands.
– A sugar-phosphate backbone joins them together.
• Nucleic acids are polymers of nucleotides.
• Two strands of DNA join together to form a double
helix.
Figure 3.28a
Figure 3.28b
• RNA, ribonucleic acid, is different from DNA.
– Its sugar has an extra OH group.
– It has the base uracil (U) instead of thymine (T)
– Generally single stranded
Figure 3.29
Evolution Connection:
DNA and Proteins as Evolutionary Tape Measures
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
Structures in cells are made of macromolecules
Cell Membrane = PhosphoLIPID bilayer
Also called the plasma membrane
Phospholipid bilayer
-Hydrophilic head
-Hydrophobic tails
-Proteins
All can rotate and move in the membrane
-Fluid Mosaic Model
-Extracellular Matrix (ECM)
holds cells together, protection, support
Figure 5.11 Primary functions of membrane proteins.
•
Attachment to the cytoskeleton and extracellular matrix. Elements of the cytoskeleton
may be bonded to membrane proteins, a function that helps maintain cell shape and
fixes the location of certain membrane proteins. Proteins that adhere to the fibers of
the extracellular matrix can coordinate extracellular and intracellular changes.
•
Cell signaling. A membrane protein may have a binding site with a specific shape
that fits the shape of a chemical messenger, such as a hormone. The external
messenger (signal) may cause a change in the protein that relays the message to
the inside of the cell.
•
Enzymatic activity. A protein built into the membrane may be an enzyme with its
active site exposed to substances in the adjacent solution. In some cases, several
enzymes in a membrane are organized as a team that carries out the sequential
steps of a metabolic pathway.
•
Transport. A protein that spans the membrane may provide a channel across the
membrane that is selective for a particular solute.
•
Intercellular joining. Membrane proteins of adjacent cells may be hooked together to
form various kinds of junctions. Cell-cell recognition. Some proteins with short chains
of sugars serve as identification tags that are specifically recognized by other cells.