Download Lecture 4 - Linn-Benton Community College

9/27/2015
Biomolecules
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Biology 102
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Lecture 4: Biomolecules
Molecules that make up living things
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Based on carboncarbon-carbon bonds
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Contain other elements (H, O, N, P, S)
Simplest organic molecules are the hydrocarbons
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Contain only C and H
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Non--polar
Non
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Soluble in water??
Biomolecules
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Biomolecules are
modified hydrocarbons
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Biomolecules
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4 broad categories of biomolecules
Contain functional
groups that change
the chemical
properties of the
molecule
Biomolecules
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All biomolecules are built in the same
fundamental way, regardless of complexity
Carbohydrates
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Make up less than 3% of human body weight
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Much more prevalent in plants
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Made of exclusively C, H, O
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Ratio of 1:2:1 or CH2O (= carbo
carbo--hydrate)
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Carbohydrates
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Monosaccharides
Simple carbohydrates = sugars
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Monosaccharides
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In categories based on number of carbons
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Number of carbons determines beginning of
category name
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Most sugar names end in ““-ose”
ose”
Number of carbon atoms Monosaccharide Category
What is the chemical formula for a hexose
sugar?
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Dozens of hexose sugars exist
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All have the same chemical formula
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Differ in the arrangement of atoms
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Termed structural isomers
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Therefore also shape, enzymes, absorbability
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tetrose
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pentose
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hexose
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heptose
Ex: glyceraldehyde
Important in cellular respiration
Used in some self-tanners
Reacts w ith aa in skin and turns brow n
Ex: ribose
Building block for RNA
Ex: glucose
Main source of cellular fuel
Ex: sedoheptulose
Intermediate in lipid A biosynthesis
Hexose Sugars
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Dozens of hexose sugars exist
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All have the same chemical formula
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Differ in the arrangement of atoms
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Termed structural isomers
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Hexose Sugars
triose
Ex: D-erythrulose
Question
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Biologically Relevant
Therefore also shape, enzymes, absorbability
Hexose Sugars
Enzymes
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Hexose Sugars
Disaccharides
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Can also exist in ring form
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Atoms are reorganized, but formula stays the same
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Reversible
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Two monosaccharides bound together
Disaccharides
Disaccharides
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More efficient way to store energy
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Commonly encountered in our diets
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Require enzymatic digestion to be absorbed
Sucrose
Lactose
Disaccharide
Monosaccharide Units
Type
of Bond by Enzyme
Digested into
Monomers
Sucrose
glucose and fructose
1-2sucrase
glycosidic
Lactose
galactose and glucose
1-4 lactase
glycosidic
Maltose
glucose and glucose
1-4maltase
glycosidic
Maltose
Polysaccharides
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Dehydration synthesis can be repeated
indefinitely
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Builds polysaccharides
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Can be very large!
Example: glycogen
Polysaccharides
Polysaccharide
Starch
Glycogen
Cellulose
Chitin
Organism
plants
animals and fungi
plants
arthropods and fungi
Function
Energy source for plant
(and us when we eat it)
Very efficient glucose storage in liver
and muscle
Structural component of cell walls
Indigestible to humans (fiber)
Structure
Digested into Monomers
by Enzyme
glucose monomers
1-4α linkage with some
Amylase
1-6α for branching
glucose monomers
1-4α linkage with more
Glycogen phosphorylase
1-6α for more branching
glucose monomers
1-4 β linkage with no
N/A
branching
Structural component of cell walls and
exoskeleton - analagous to keratin
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Carbohydrates
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Lipids
Primary functions of carbohydrates
1.
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Storage/source of energy
2. Structural support
3. Component of coco-enzymes
Glycocalyx
4. Part of RNA/DNA
5. Biological recognition
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Artificial grouping of biomolecules
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Not based on common structure
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Based on common insolubility in water
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Polarity?
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Need special transport mechanism
Made up of C and H with very little oxygen
Lipids
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Fatty Acids
Includes:
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Long, unbranched hydrocarbon chains
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Fats
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Carboxyl group at one end
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Waxes
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Polarity??
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Sterols
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Fat--soluble vitamins
Fat
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Saturated or unsaturated – with what?
Carbon Saturation
Carbon Saturation
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Saturated or unsaturated with hydrogens
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Carbon needs 4 bonds to be stable
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Has 3 options to get them
C
C
C
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In a fatty acid, almost all carbons are bound to 2
other carbons
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This builds the backbone of the fatty acid chain
C C C
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Carbon Saturation
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If all bonds between carbons are single, a
greater number of hydrogens can bind
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This is said to be a saturated fatty acid – one
with the maximum number of hydrogens
H
H
Saturated Fatty Acids
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Every carbon has 4 single bonds
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2 with carbons
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2 with hydrogens (except at the ends)
H
C C C
H
H
H
Saturated Fatty Acids
Unsaturated Fatty Acids
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Very stable – not prone to rancidity
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Carbons can also form double bonds
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Straight chains stack tightly
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Leaves less room for hydrogen
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Solid at room temperature
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Said to be unsaturated
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Found in butter, animal fats, eggs, coconut oil,
palm oil – and in your body!
Unsaturated Fatty Acids
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Double bonds prone to rancidity
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Bent chains do not stack as tightly
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Liquid at room temperature
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Found in plant oils
Unsaturated Fatty Acids
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One double bond = monounsaturated
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Olive, avocado
> 1 double bond = polyunsaturated
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Corn, soy, peanut, Canola
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An Unfortunate Discovery
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In the early 1900s, Proctor & Gamble cornered
the market on cottonseed oil
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Electricity meant people weren’t using candles
much anymore – what to do with the oil?
An Unfortunate Discovery
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An Unintended Consequence
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Don’t want to completely saturate oil
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Oil hydrogenation turns double bonds into single
bonds
An Unintended Consequence
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Changes shape to something not found in nature
Turns waxy and gross
Instead only partially hydrogenate, which
changes some of the double bonds from cis to
trans
An Unintended Consequence
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Changes the shape
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Fat behaves more like it’s saturated
Shortening
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Trans Fatty Acids
Trans Fatty Acids
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Cheap
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Shape doesn’t occur in nature
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Lend “buttery” quality to processed foods
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Used in crackers, cookies, pie crusts, French
fries, fried chicken, even coffee creamer
No enzymes that break it down – in us, or in
bacteria!
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Less prone to rancidity than vegetable oil, lard,
or butter
Solid at room temperature – and at body
temperature!
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Body doesn’t know how to deal with it
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You’re probably eating more than you think
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Extend shelf life of products
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Highly inflammatory = immune response
Trans Fat Free?? Don’t Buy It!!
Cis Fatty Acids
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Shape does occur in nature
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Prone to oxidation
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But at least your body knows what to do with it!
So Which Fat Is Healthiest?
Cis fat
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Glycerides
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Form when fatty acids bind to glycerol
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Most common dietarily = triglycerides
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Triglycerides in the Body
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3 fatty acids
+ 3H2O
Very efficient longlong-term energy storage
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Large molecules = high potential energy
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Gram for gram more than twice the energy of
carbohydrates
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Fat deposits under skin and throughout body cut
heat loss by 2/3
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Protects and cushions organs
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Virtually nonnon-polar – allows for more efficient
storage
Problem: We have too much of it!
Phospholipids
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Modified triglycerides
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One fatty acid replaced
with a phosphorus and
nitrogen--containing
nitrogen
functional group
Phospholipids
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Phosphorus group is polar = hydrophilic
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Fatty acids are nonnon-polar = hydrophobic
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Allows nonnon-polar molecules to associate with
water
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Extremely important in cell membrane structure
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More about them later
Cholesterol
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Synthesized by all living organisms
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Humans make in liver
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Dietary cholesterol esterified and poorly
absorbed
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High cholesterol usually due to metabolic
disregulation rather than dietary sources
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Exception: oxidized cholesterol
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Cholesterol
Steroid Hormones
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Important molecule!
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Made in adrenals
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Component of cell membranes
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Functions
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50% dry weight
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Chemical communication
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Adds rigidity
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Calcium homeostasis (calcitrol
(calcitrol))
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Regulate sperm/egg development and sexual
function
Needed for growth and development
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Breastmilk is extremely high in cholesterol
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Critical for myelin production
Needed to make sterols
Steroid Hormones
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Male hormones, including testosterone, are also
called anabolic steroids
Vitamin D
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Critical for calcium absorption
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Ongoing research implicates it in multiple
biological processes
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We lack the enzyme to make it from cholesterol!
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Require sunlight
Functions of Lipids
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Most varied of the biomolecules
2. Energy reserves
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Make up more than half the dry weight of cells
3. Insulation and protection
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Categorized by function
1.
Structural components of cell membranes
Proteins
4. Vitamin D synthesis (calcium absorption)
5. Steroid hormones
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Others we didn’t talk about
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Bile salts (lipid digestion)
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Eicosanoids (signaling molecules)
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Protein Functions
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Storage
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Protein Functions
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Energy for embryo, young, other organisms
Structure
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Macroscopic examples: tendons, ligaments,
hair, nails (collagen, keratin)
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Cellular level examples: actin,
actin, tubulin
Protein Functions
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Transport
Protein Functions
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Proteins that carry other molecules from one
place to another
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Examples: hemoglobin, kinesins
Catalysis
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Protein Functions
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Defense
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Antibodies, interferons produced in response
to infection
Enzymes are proteins
Protein Functions
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Coordination and growth (signaling)
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Hormones (e.g. insulin, growth hormone)
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Communication (receptors)
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Protein Functions
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Buffering
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Proteins are both acids and bases at the same
time
Proteins
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Protein building blocks= amino acids
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20 amino acids
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Can be arranged to form an astounding variety
of proteins
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Much the way only 26 letters make thousands
of words
Protein Structure
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Protein function depends on 4 up to levels of
structure
Protein Structure
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Primary structure depends on peptide bonds
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Very strong and stable
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Require a chemical change to break
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Primary – number and order of amino acids
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Secondary – local folding patterns
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Tertiary – overall 3D folding
All other levels of structure depend on
interactions
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Quaternary – interaction of 2 or more fully
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assembled proteins
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Example: Hemoglobin
Hydrogen bonds
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Relatively weak
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Can be broken by changes in temperature,
pH
Disulfide bonds
Example: Sickle Cell Anemia
Normal RBC
Sickle RBC
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Sickle Cell Anemia
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Caused by defect in 1°
1° structure
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Leads to defect in 4°
4° structure
Protein Structure
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Biological activity of a protein highly dependent
on shape
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Changes in shape = denaturation
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Protein shape is maintained by hydrogen bonds
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Anything that alters hydrogen bonds can
denature a protein
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Heat, pressure, pH, heavy metals, alcohol,
UV light
PRIMARY STRUCTURE IS UNAFFECTED BY
DENATURATION
Denaturation
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Sometimes denaturation is reversible
(sometimes not)
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Denatured protein
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Storage
2. Structure
3. Transport
Sickle cell anemia
4. Catalysis (enzymes)
5. Defense
Cystic fibrosis
6. Signaling
May disrupt other cellular functions
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Primary functions of proteins
1.
May not be functional
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May fold inappropriately
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Proteins
7. Buffering
Prions
Nucleic Acids
Nucleic Acids
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Two primary types
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Two primary types
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Deoxyribonucleic acid (DNA)
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Ribonucleic acid (RNA)
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Determines inherited characteristics
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Contains information for protein building
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Regulates all areas of cellular metabolism
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3 types work together to make proteins based
on information in DNA
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Nucleic Acids
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Nucleic Acids
Several functions in cell
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Protein synthesis
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Coordinated activity of 3 RNA types
Cellular metabolism
DNA stores all genetic,
and cell communication
protein synthesis information
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NADH/NAD+
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cAMP
Information transfer
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Several functions in cell
ATP, NADH/NAD+
Information storage
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Energy transfer
RNA gets information from DNA,
takes it to cytoplasm
Nucleotides
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Nucleotide Bases
Monomer = nucleotide
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More complex than other monomers
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DNA = A G C T
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Phosphate
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RNA = A G C U
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Pentose sugar (ribose or deoxyribose)
deoxyribose)
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Nitrogenous base (1 of 5)
Polymer = nucleic acid
Adenine
nucleotide
Structure of RNA
Structure of DNA
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Single--stranded polynucleotide
Single
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Two antianti-parallel polynucleotide strands
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Phosphate and sugar alternate in a “backbone”
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Complimentary basebase-pairing with hydrogen bonds
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Bases project out at right angle
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Twisted into a double helix
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A LOT more
on this later
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One More Use For Nucleotides
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Used to shuttle energy within the cell
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Energy stored in covalent bonds
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Most universal energy carrier is ATP
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ATP
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When bonds between the phosphates are
broken, energy is released
Adenosine triphosphate
NAD
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Not as universal
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7X more energyenergy-rich than ATP
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Carries energy as electrons
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