Download GLYCOGEN – energy storage in ANIMALS • Stored as cytoplasmic

CHAPTER 5- The Structure and Function of Large Biological Molecules
CARBOHYDRATES = sugars and their polymers
FUNCTIONS:
*Energetic fuel source/storage
*Structural building blocks
MONOSACCHARIDES:
• C, H, O in 1:2:1 ratio (CH2O)n
• 3-7 carbons
• Pentoses (5C) & hexoses (6C) most common;
but glycerol (3C) also important
• OH attached to each carbon except one
• Major nutrient for cells
• names often end with -ose.
• Aldehydes (=O at end) form OR ketones (=O in middle)
*Glucose & fructose = structural isomers
*Glucose & galactose = stereoisomers
*All = (C6H12O6)
DISACCHARIDES:
*2 monosaccharides joined together by a condensation (dehydration synthesis) reaction
*bond is a GLYCOSIDIC linkage (covalent)
• Sucrose = glucose + fructose
• Maltose = glucose + glucose
• Lactose = glucose + galactose
POLYSACCHARIDES
• long polymers of monosaccharides (few 100-few 1000)
• formed by condensation (dehydration synthesis) reaction
• Numbers identify the linked carbons and form of glucose
STARCH - energy storage in plants (EX: potatoes)
GLYCOGEN – energy storage in ANIMALS
• Stored as cytoplasmic granules in liver and muscle
• Liver controls blood sugar level
Ex) low blood sugar between meals (glycogen→ glucose)
(GLUCAGON)
Ex) high blood sugar after eating (glucose →glycogen)
(INSULIN)
Muscle tissue- source of ATP for muscle contraction
CELLULOSE
• major component in plant cell walls (EX: wood, cotton)
• straight unbranched chains
• Form MICROFIBRILS that give cellulose its structural rigidity
• Dietary fiber in human diet
• Can’t be digested by animals without the help of symbiotic microorganisms
• Don’t have enzymes to break
linkages
CHITIN:
• Support and protection
EX: Cell walls in fungi; exoskeletons in arthropods
LIPIDS = diverse group of hydrophobic molecules
Many nonpolar C—H bonds/long hydrocarbon skeleton
Hydrophobic - insoluble in water (dissolve in nonpolar solvents)
FATS = TRIACYLGLYCEROL = TRIGLYCERIDE
• store large amounts of energy
• NOT polymers but assembled from smaller molecules
by dehydration synthesis reactions
• Adipose tissue is made primarily of triacylglycerols (fat)
• FAT = 1 glycerol + 3 fatty acids
FATTY ACID:
Hydrocarbon chain of 10-50 carbons in length
Fatty acids vary in length (number of carbons)
and in the number and locations of double bonds
Three fatty acids can be the same or different
SATURATED - no double bonds in carbon chains
Form straight chains
Most animal fats are saturated (butter, lard)
Solid at room temperature
UNSATURATED –one/more double bonds in tails
have kinks wherever there is a double bond
prevents tight packing of molecules so not solid
Plant and fish fats = liquid at room temperature
= oils (olive oil, cod liver oil)
POLYUNSATURATED = many double bonds
FUNCTION - (fats, oils) - ENERGY STORAGE
• Compact energy storage; energy stored in C-H bonds; about 3X the energy of carbohydrates
• Humans and other mammals store fats as long-term energy reserves in adipose cells
• Adipose tissue also functions to cushion vital organs, such as the kidneys
• A layer of fat can also function as insulation
(especially in whales, seals, and most other marine mammals)
PHOSPHOLIPIDS
FAT with one fatty acid replaced by a phosphate group
• The phosphate group carries a negative charge
• Additional sugars, amines, or other groups may be attached to
the phosphate group to form a variety of phospholipids
• Heads are often zwitterions: they have both + and -charge.
AMPHIPATHIC –
• Both phobic AND philic parts
• polar head
• non-polar tails
ADDING PHOSPHOLIPIDS TO WATER
• self-assemble into MICELLES
• sphere with hydrophobic tails toward interior
• polar/philic heads toward outside
FUNCTION OF PHOSPHOLIPIDS
• Major component in cell membranes
• Arranged as a bilayer
• Hydrophilic heads toward the outside of the bilayer
in contact with the aqueous solution
• Hydrophobic tails point toward the interior of the bilayer away
from aqueous solution
environment.
• Forms a barrier between the cell and the external
STEROIDS
• Lipids with a carbon skeleton with four fused rings
and a small ACYL (carbon chain) tail
• Insoluble in water (nonpolar)
• Different steroids vary in the functional groups attached to the rings
CH3
CH3
OH
CHOLESTEROL
• Important precursor for all other steroids
Hormones: cortisone, cortisol, testosterone, estradiol, estrogen
• Cholesterol also found in animal cell membranes
• Synthesized in the liver
• Obtained in the diet (meat, cheese, eggs)
• Essential in animals, but high levels of cholesterol in the blood
may contribute to cardiovascular disease (atherosclerosis)
• Negative effect of saturated fats and trans-fats due to their
impact on cholesterol levels
- LDL's (low density lipoproteins)
'bad' cholesterol (deposits in coronary blood vessels)
- HDL's (high density lipoproteins)
'good' cholesterol
WAXES - protective, waterproof coatings
• fur, feathers, and skin
• leaves/fruits of plants
• insect exoskeletons
PROTEINS = “Cellular toolbox”
• Proteios = Greek “first place”
• Make up 50% or more of dray mass of most cells
• Humans have tens of thousands of different proteins
• Typical protein = 200-300 amino acids; biggest known = 34,000
• Know the amino acid sequences of > 875,000 proteins/3D shapes of about 7,000
• Scientists use X-ray cystallography to determine protein conformation
• A protein’s function = EMERGENT PROPERTY determined by its conformation
EXAMPLES OF VARIETY OF PROTEINS/FUNCTIONS:
• Structural: hair, fingernails, bird feathers (keratin); spider silk;
cellular cytoskeleton (tubulin & actin); connective tissue (collagen)
• Storage: egg white (ovalbumin); milk protein (Casein); plant seeds
• Transport: Transport iron in blood (hemoglobin);
• Hormonal: Regulate blood sugar (insulin)
• Membrane proteins (receptors, membrane transport, antigens)
• Movement: Muscle contraction (actin and myosin); Flagella (tubulin & dynein); Motor proteins move vesicles/chromosomes
• Defense: Antibodies fight germs
• Enzymatic: Enzymes act as catalysts in chemical reactions
• Toxins (botulism, diphtheria)
AMINO ACIDS
*Central (α carbon) with carboxyl, amino, H, and R groups attached
*20 common amino acids used by living things
POLYPEPTIDE = polymer of amino acid subunits connected in a specific sequence
An enzyme joins the carboxyl of one amino acid and the amino group of another via dehydration synthesis/condensation
reaction to form a PEPTIDE BOND
Peptide bonds are rigid, planar structures
The -NH bond and the -C=O bond, point away
from each other so these groups can
hydrogen bond to other parts of chain
LEVELS OF PROTEIN ORGANIZATION/3-STRUCTURE
Primary Structure: unique sequence of amino acids;
determined by DNA code; unique for each protein
Secondary Structure: Determined by amino acid sequence;
HYDROGEN BONDS (between the oxygen of C=O and the hydrogen of
N-H of peptide bonds) stabilize structure & form pattern
• α helix- polypeptide chain winds clockwise like a spiral staircase
EX: KERATIN, the main protein component of hair, nails, horns
• β pleated sheet- chains joined together like the logs in a raft
EX: SILK
Tertiary Structure: Hydrogen bonding, ionic interactions, hydrophobic
interactions, and disulfide bridges between R groups stabilize 3 D shape
IONIC INTERACTIONS
between +/ – charged amino acids
- -=glutamate, aspartate
+ = lysine, arginine, histidine
HYDROGEN BONDING
Some R groups able to form
Hydrogen bonds
Helps stabilize
3D structure
hydrop hyllic
io nic
hydrop hob ic
S
hydrog en
Quaternary Structure: protein made up of more than one amino acid chain
EX: COLLAGEN
3 polypeptides chains twisted in super coil
EX:HEMOGLOBIN
4 polypeptides
+
S
S
DISULFIDE BRIDGES
=COVALENT BOND
between amino acids w/-SH groups
(CYSTEINE but not methionine)
forms an -S-S- bridge
SIDE NOTE: Perms work by breaking
and reforming disulfide bridges in a
new hair shape
HYDROPHOBIC INTERACTIONS
Polar R groups-interact with water
and lie on the surface of the protein
Nonpolar R groups - hide in the core
of the folded protein
“ polar outside; nonpolar in.side”
disu lfid e
WHAT DO YOU CALL IT?
• two or more amino acids bonded together = PEPTIDE
• chain of many amino acids = POLYPEPTIDE
• complete folded 3D structure = PROTEIN
Final overall protein shapes
- FIBROUS. - long fiber shape EX: actin or collagen
- GLOBULAR - overall spherical structure EX: hemoglobin,
MUTATIONS CAN CHANGE PROTEIN SHAPE
Since shape is determined by amino acid sequence; changing sequence changes 3D shape
EX: Sickle cell anemia mutation changes one amino acid in the sequence (glu → ala)
Abnormal hemoglobin molecules crystallize; cause blood cells to become sickle shaped
FACTORS AFFECTING CONFORMATION
Folding occurs as protein is synthesized, but physical/chemical environment plays a role
DENATURATION: = unraveling/ loss of native confirmation
• makes proteins biologically inactive
~ Reason high fevers can be fatal
• does NOT break peptide bonds
• so primary structure remains intact
• may regain its normal structure if conditions change
• sometimes = irreversible (ie. cooking an egg)
CAUSED BY
• changes in pH (alters electrostatic interactions between charged amino acids)
• changes in salt concentration (does the same)
• changes in temperature (higher temperatures reduce the strength of hydrogen bonds)
• presence of reducing agents (break S-S bonds between cystines)
NUCLEOTIDES AND NUCLEIC ACIDS
INFORMATION FLOW IN CELLS = “Central Dogma of Molecular Biology”
DNA
RNA  PROTEINS
FUNCTION
DNA - genetic code contains info that programs cell activities
RNA - carries message from DNA to cell; protein synthesis
BASIC STRUCTURE
NUCLEOTIDE = nitrogenous base + sugar + phosphate group
PURINES = 2 rings; Adenine (A), Guanine (G)
PYRIMIDINES = 1 ring; Cytosine (C), Thymine (T), Uracil (U)
NUCLEIC ACIDS (DNA & RNA)
DEHYDRATION SYNTHESIS forms polymers of nucleotide building blocks
PHOSPHATES and SUGARS form backbone
PHOSPHATE LINKAGE between carbon 3’ of one sugar and carbon 5’ of the next