chp 2 (cont.) organic molecules - cabrillo collegedbard/bio11a/lectures/pdfs1/3...amino acid...
TRANSCRIPT
Molecular Diversity is Based on Carbon
An organic molecule contains both carbon and hydrogen. Ex: Methane - a simple organic molecule
C atoms can bond to 4 other atoms – chains, rings, branches
A chain of C atoms is called a carbon skeleton
Methane
Double bonds.
2-Butene Skeletons may have double bonds, which can vary in location.
Cyclohexane
1-Butene
Benzene Skeletons may be arranged in rings. Rings.
3!
What is the chemical formula for Butane and Isobutane?
Carbon skeletons vary in length.
Branching. Skeletons may be unbranched or branched. Butane Isobutane
Propane Ethane Length.
Carbohydrate polymer
Protein polymer
Nucleic acid polymer Monomer
Monomer Monomer
4!
Large organic molecules are called macromolecules
– Aka. polymers b/c they are made from same units linked together (draw train cars linked)
– The repeating units are called monomers
Cells Make Lots of Large Molecules From a Limited Set of Small Molecules
5!
During dehydration synthesis, an enzyme binds two monomers, releasing a water molecule
Building a polymer chain
H
OH H
OH
H OH
Unlinked monomer
Dehydration reaction
Longer polymer
Short polymer
OH H
H OH
Unlinked monomer
Dehydration reaction
Short polymer
H2O
6!
Hydrolysis is the reverse reaction, it breaks polymers into monomers
Breaking a polymer chain
H
H2O
OH
H OH OH H
Hydrolysis
7!
Carbohydrates include small simple sugars and large polysaccharides
– Monosaccharides are the monomers of carbs
– Exs: Glucose and Fructose
Bees with honey, a mixture of 2 different monosaccharides
Organic Molecules: Carbohydrates
What do you think a chemical formula would be for “carbo” “hydrate”?
8!
Molecular formula of a monosaccharide is a multiple of CH2O – Glucose is C6H12O6
Monosaccharide structures
Monosaccharides are the main fuel for cellular work
9!
Two monosaccharides can join to form one disaccharide (a dehydration synthesis reaction)
– Glucose bonding to fructose forms sucrose, table sugar
– Glucose linked to galactose = lactose, sugar found in milk
What problem is associated with this disaccharide in some people?
10!
Starch and glycogen = polysaccharides in plant and animal respectively, storage of ___________
Cellulose = polysaccharide in plant cell walls, structural support
Polysaccharides are long chains of carbohydrates
11!
Lipids = hydrophobic (water _________ )
– Long-term energy storage
– Not large
– Not built of monomers
Fats = lipids made from glycerol and fatty acids
– Long hydrocarbon chains
– Saturated fatty acid vs. unsaturated fatty acid
Organic Molecules: Lipids
Formation of a fat molecule
13!
Phospholipids & Sterols are Also Lipids
Phospholipids = main component of cell membranes
Similar to fats, but imp. differences
— Two fatty acids
— Hydrophilic head and hydrophobic tails
✶ Form stable bilayer in water
Steroids = lipids with 4 fused rings
Cholesterol = common component of animal cell membranes
– Starting material for sex hormones
– Too much in the blood can lead to atherosclerosis
Fig. 3.9C Cholesterol, a type of steroid
14!
16!
The monomers of proteins are amino acids
– Protiens; hair, cartilage, muscle, antibodies, enzymes, hemoglobin
– 3-D structure directly related to function
– Made from genetic info (DNA) found in the _______ of the cell
Organic Molecules: Proteins
17!
Amino acids structure: amino group, carboxyl group, central carbon atom, and an R group
Linked together by dehydration reactions Links called peptide bonds
– Carboxyl group bonded to amino group (C-N bond)
Fig 3.11C Peptide bond formation
H
H
N C C O
OH H
H N + C
H
R
C O
OH H2O
H
H
N C C N C C
R H R OH
O
Peptide bond
Dipeptide Amino acid
Dehydration reaction
Amino group
H
R
Amino acid
Carboxyl group
H O H
18!
A polypeptide chain has hundreds or thousands of aa’s linked by peptide bonds
– Amino acid sequence of polypeptide determines shape
– Shape determines its specific function
Polypeptides must fold into a protein to work
Groove Groove
Space-filling model of lysozyme Ribbon model of lysozyme
Four Levels of Protein Structure
Amino acids
Primary structure
Alpha helix
Hydrogen bond
Secondary structure Pleated sheet
Polypeptide (single subunit of transthyretin)
Tertiary structure
Transthyretin, with four identical polypeptide subunits Quaternary structure
19!
If protein’s shape is altered, it may no longer function
– Denaturation = polypeptide chains unravel, lose their shape, and lose their function
– Can happen w/ changes in salt concentration, heating, changes in pH
– Ex. Frying an egg (egg white is protein)
20!
21!
Organic Molecules: Nucleic Acids
DNA and RNA are nucleic acids
Monomers of nucleic acids are nucleotides
✶ Nucleotides have 3 parts
– A 5-C sugar called ribose in RNA and deoxyribose in DNA
– A phosphate group
– A nitrogenous base A nucleotide
DNA - 2 polynucleotide strands wrap around each other, double helix – 2 strands are held together
by __________ bonds
– A pairs with T, and C pairs with G, producing base pairs
RNA is a single strand
Figure 15C DNA double helix 23!
Clicker Question #5
Which monomer is incorrectly paired?
A. protein: monopeptide B. carbohydrate: monosaccharide C. nucleic acid: nucleotide D. lipid: no monomer