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Ch. 5: Structure and Function of Large Biological Molecules - Coggle…
Ch. 5: Structure and Function of Large Biological Molecules
Carbohydrates
Includes sugars + polymers of sugars
Sugars
Disaccharides ("two sugar")
2 monosaccharides
joined by glycosidic linkage (monosaccharides joined covalently via dehydration)
must be broken down to monosaccharides for energy
Examples
sucrose
lactose
Monosaccharides ("one sugar")
Major nutrients for cells
Cellular respiration
Energy extracted from glucose by breaking it down
have asymmetric carbon (carbon attacked to 4 different atoms/groups)
Have C skeleton 3-7 carbons long
e.g. triose, hectose, hexose
Have C, H, O in 1:2:1 ratio
Polysaccharides
Macromolecules made of monosaccharides
Storage Polysaccharides
Plants store starch
Starch = glucose polymer, stored as plastids in plants
Starch hydrolyzed for energy
Sources: potatoes, grains, etc.
Animals store glycogen
Glycogen = glucose polymer
Mainly in liver + muscle cells
Breakdown releases glucose for energy
Structural Polysaccharides
Used to build strong materials
Cellulose
Chitin
Carb used by arthropods to build exoskeletons
Arthropods include insects, spiders, crustaceans, etc.
Also used by fungi
Used to build cell walls
Macromolecules
Macromolecules = huge molecules
Monomers = smaller molecules (the building blocks of polymers)
Covalently bonded in polymers
Polymer = large molecules made up of building blocks
Synthesis and Breakdown
Enzymes = catalysts (speed up chemical reactions)
Condensation reactions
Join molecules/monomers covalently by removing a smaller molecule
Dehydration reaction
Joins monomers by removing a water molecule
Example: carb and protein polymers built this way
Hydrolysis
Breaks up monomers by adding water back
H attaches to one, Hydroxyl attaches to other
Example: digestion
Diversity of Polymers
Cells have 1,000s of macromolecules
Polymers built w/ 40-50 common monomers
Arrangement accounts for diversity
Four main classes: Carbs, Lipids, Proteins, Nucleic Acids
Proteins
Amino Acids (Monomers)
Organic molecules with amino group and carboxyl group
Structure
Asymmetric Carbon
Called alpha carbon
4 partners
Carboxyl group
Hydrogen atom
Amino group
Variable group (R)
Side chains
Acidic Amino Acids
Side chains generally negatively charged
Due to carboxyl group
Hydrophilic
Basic Amino Acids
Side chains generally positively charged
Hydrophilic
Polypeptides (Amino Acid Polymers)
Bonding
Dehydration reaction links amino acids (peptide bond)
Polypeptide backbone = repeating pattern of atoms when joined
Amino group on one end (N-Terminus)
Carboxyl group on other (C-Terminus)
Side chains attached to polypeptide backbone
Determine chemical nature of molecule
Intro
Proteins more than 50% of dry mass of most cells
Diverse functions
Defense
Example: Antibodies
Storage and Transport
Examples: Transport proteins, Casein
Speed up reactions
Example: Enzymatic Proteins
Most enzymes are proteins
Act as catalysts (agents that selectively speed up chemical reactions)
Cellular Communication
Example: Receptor Proteins
Movement
Example: Motor proteins, Actin and Myosin Proteins
Structural Support
Example: Keratin
Made from 20 amino acids
Bond between amino acids = peptide bond
Polymer of amino acids = polypeptide
Protein = biologically functional, made of 1+ polypeptides
Has specific 3D structure
Protein Structure and Function
Sickle-Cell Disease
Slight primary structure changes affect function/shape
Example: sickle-cell disease
An inherited blood disorder
Caused by substitution of single amino acid (valine for glutamic acide)
Cells become sickle-shaped
Can clog arteries
What Determines Structure?
Key factors
Salt concentration
Temperature
pH
Other environmental aspects
Crowded environment
Denaturing
Denaturing = protein losing its structure
Caused by environmental changes (e.g. high heat exposure)
Protein becomes biologically inactive
Four levels
Secondary
Segments of coiled + folded amino acid chain
Result of H bonds between backbone components
Shapes
Helix
Created by H bonds every 4th amino acid
Pleated sheet
2+ segments laying side by side
1 more item...
Tertiary
Overall shape of polypeptides
Interactions
Hydrophobic interactions
Nonpolar substances become excluded by water (closer to each other)
Van der Waals
help hold nonpolar substances together
Disulfide bridges
Formed by cysteine monomers coming close together
May reinforce protein shape
Primary
Linear amino acid sequence
Dictates secondary + tertiary structures
Quaternary
Protein Folding in Cell
Difficult to determine how proteins fold
Misfolding
Diseases associated: Alzheimer's, mad cow disease, etc.
X-Ray Crystallography
Used to determine protein's 3D structure
Method
Diffraction of X-Ray beam by crystallized molecule
Other approaches: NMR, spectroscopy, etc.
Theory
Most likely go through intermediate steps
Intro
3D shape makes polypeptides proteins
Determines function
Folding
May fold spontaneously
Shapes
globular
fibrous
Binding
Many proteins fit with molecules like puzzle pieces
E.g. receptor proteins binding with endorphins
Lipids
Types
Phospholipids
Structure
glycerol + 2 fatty acids
Phosphate group attached
Typically has another small charged/polar molecule linked to phosphate group
Properties
Hydrocarbon tails = hydrophobic
Phosphate group + its attachments = hydrophilic
Create bilayer when added to water ("phospholipid bilayer")
Tails face inward (phosphate group outward)
Function
phospholipid bilayer forms cell membrane
Steroids
Structure
C skeleton, 4 fused rings
distinguished by chemical groups attached
Example: cholesterol
Synthesized in liver in vertebrates
Precursor for other steroids
Common in animal cell membranes
May lead to atherosclerosis in high amounts
Fats
Structure
glycerol + 3 fatty acids
Glycerol = an alcohol; each C has hydroxyl group
Fatty acid = large C skeleton' carboxyl group + hydrocarbon chain
Properties
Hydrophobic
Types
Unsaturated
Has double bonds; not fully saturated
"unsaturated fatty acid"
Nearly every double bond is a cis bond
Saturated
N0 double bonds; fully saturated with H
Fatty acid called "saturated fatty acid"
Trans
Created via hydrogenation
hydrogenation = added H atoms to fully hydrate
Produces trans bonds instead of cis
Function
Energy storage
Fat stored in adipose cells (used for long-term food reserves)
Protection
adipose tissue cushions vital organs
Properties
Not true polymers
Not usually macromolecules
Examples
Most important biologically
Fats, phospholipids, steroids
Misc
Waxes, certain pigments
Hydrophobic
Due to structure
Mostly nonpolar C-H bonds
Genomics
DNA Sequencing
determining the sequence of nucleotides along DNA strand
History
1st techniques developed in 1970s
The Human Genome Project
To sequence entire human genome
Led to faster/less expensive methods
Bioinformatics = use of computer software/other tools to analyze large sets of biological data (e.g. DNA sequences)
Started in 1990, finished 2000s
Genomics
Studying large sets of genes/comparing genomes
Proteomics
Analyzing large sets of proteins + sequences
DNA/Proteins and evolution
Nucleotide sequences are passed to offspring
Family more similar than unrelated species members
Nucleic Acids
Components
Nucleic acids = macromolecules, exist as polynucleotides
Made of monomers (nucleotides)
Nucleotide components
Nitrogenous base
Each has 1-2 nitrogen-containing rings
2 Families
Pyrimidines
1 more item...
Purines
1 more item...
1-3 phosphate groups
Nucleoside = part of nucleotide without phosphate groups
1st monomer used to build nucleotide has 3 phosphate groups
2 lost during polymerization
With only one phosphate = nucleoside monophosphate (aka nucleotide)
5-carbon sugar (pentose)
In DNA: Deoxyribose
lacks an O atom in second C in ring
In RNA: ribose
Polymers
Linking nucleotides involves condensation reaction
joined by phosphodiester linkage
Phosphate covalently links sugars of 2 nucleotides
Sugar-phosphate backbone
Repeating pattern of sugar-phosphate units created by bond
Directionality
Ends of polymer differ
5' end
Phosphate attached to 5' carbon
3' end
Hydroxyl group attached to 3' carbon
Direction = from 5' end to 3' end
Order of bases determines amino acid sequence (primary structure of protein)
Roles
DNA + RNA enable reproduction of complex components
DNA = Deoxyribonucleic acid
genetic material inherited from parents
1 chromosome contains 1 DNA strand
several hundred + genes
RNA = Ribonucleic acid
Gene expression = Process of synthesizing RNA and (subsequently) proteins
Steps
mRNA goes to ribosome, directs production of polypeptide (translation)
Polypeptide folds into protein/part of one
Genes in DNA direct mRNA synthetization (transcription)
mRNA = Messenger RNA
Structures of DNA and RNA
DNA
2-stranded, double helix
Antiparallel (backbones run opposite 5' -> 3' directions)
backbones on outside of helix
strands held together by H bonds between paired bases
Base pairing
Adenine always pairs with Thymine
Guanine always with Cytosine
RNA
Single-stranded, shape more variable
Base pairing
Substitution
Adenine with Uracil
Thymine not present in RNA
Method
Occurs within single RNA strand
Allows necessary 3D shape
Example: tRNA (brings amino acids to ribosome during synthesis)
Background
What determines primary structure?
Amino acid sequence programmed by a gene
Genes
Consist of DNA
DNA belongs to class called "nucleic acids"
Nucleic Acids
Polymers made of monomers called nucleotides