Macromolecules! By Andrew Kozlevcar
Carbohydrates are sugars!
Structure of Monosaccharides:
A monosaccharide is comprised solely of three elements: carbon, hydrogen, and oxygen.
Most of the time, monosaccharides possess a carbon-hydrogen-oxygen ratio of 1:2:1.
Monosaccharides are generally three to seven carbons, one carbonyl group, and multiple hydroxyl groups.
If the carbonyl is located within the carbon skeleton, a monosaccharide is considered to be a ketone. If the carbonyl is located on the end of the carbon skeleton, a monosaccharide is considered to be an aldehyde.
For stability reasons, monosaccharides (particularly five and six-carbon sugars) form rings in aqueous solutions.
Function/Role of Monosaccharides:
Monosaccharides are nutrients for cells In cellular respiration, glucose is broken down, releasing large amounts of energy. This energy is stored in the third phosphate bond of ATP.
Decomposed monosaccharides provide raw materials for the synthesis of other small organic molecules (amino acids)
Most importantly, monosaccharides are the building blocks of polysaccharides!
Disaccharides are two monosaccharides bonded together through a glycosidic linkage. A glycosidic linkage is a dehydration synthesis reaction in which hydrogen is removed from one monosaccharide and a hydroxyl group is removed from another → The result is a covalent bond between the two sugars (disaccharide).
Examples of disaccharides are table sugar, maltose (beer making), and lactose (a carbohydrate found in milk).
Notably, sucrose (disaccharide) is the form that carbohydrates take on when they are transferred from the leaves to the roots of a plant.
Polysaccharides are many monosaccharides bonded together through glycosidic linkages.
Cellulose is the major component of the rigid walls that encloses plant cells.
Although cellulose is formed with 1-4 glycosidic bonds just like starch, cellulose uses beta glucose, meaning that the hydroxyl group on the first carbon of each glucose is above the ring. As a result, every other glucose monomer is flipped, leading to an entirely different structure.
While starch can be helical or branched, cellulose is straight, unbranched, and hydrogen bonds with other parts of the cellulose that lay parallel to it. This forms incredibly strong, tight-knit microfibrils. Cotton is also made from cellulose.
While certain beings, such as cows, termites, and fungi, possess enzymes needed to hydrolyze and break apart cellulose, humans do not.
Chitin is a major component of insect exoskeletons and fungi walls. Chitin is similarly structured to cellulose other than the nitrogen group attachment to each glucose monomer.
Starch is a polymer of glucose molecules that are stored as granules in the plant cell.
Amylopectin is an unbranched starch formed when each glycosidic bond has the first carbon of alpha glucose linking with the fourth carbon of the successive alpha glucose (alpha glucose means that the first carbon of the glucose has a hydroxyl group below the ring).
Amylopectin is a complex, branched starch formed when each glycosidic bond has the first carbon of alpha glucose linking with the sixth carbon of the successive alpha glucose (alpha glucose means that the first carbon of the glucose has a hydroxyl group below the ring).
When glucose is needed for cellular respiration, plants can break down either starch into its monomers by adding water (hydrolysis).
Humans (and most animals) have enzymes that allow them to break down starch into glucose (and energy).
Glycogen is similar in structure to amylopectin starch, but it is even more branched.
Glycogen serves short-term energy storage for vertebrates like humans, which keeps the polysaccharide in the liver and muscle cells.
Lipids are predominantly hydrophobic molecules because they are dominated by non-polar hydrocarbon structures (though they contain oxygen and sometimes nitrogen, phosphorus, and sulfur). Lipids do not possess true monomers, nor are they large enough to be classified as macromolecules.
Structure of Fat:
A fat (triglyceride) is generally constructed from three fatty acids and a glycerol head. Glycerol is alcohol comprised of hydrocarbons (non-polar) and three hydroxyl groups. Fatty acids are 16-18 carbons atoms in length and contain one carboxyl group.
In a form of dehydration synthesis, hydrogen from a hydroxide group of glycerol and a hydroxide from the carboxyl group of the fatty acid is removed, resulting in a covalent bond between the two compounds.
Three total fatty acids will bond to glycerol in this manner, forming a triglyceride. While triglycerides may contain polar functional groups, the immense amount of hydrocarbons make the substance hydrophobic.
Changes to Fats:
Saturated fatty acids are triglycerides that contain three fatty acids with hydrocarbon chains that lack double bonds. Saturated fatty acids are straight in shape and have the capacity to consolidate at room temperature, forming solids.
Unsaturated (cis) fatty acids are triglycerides that contain three fatty acids with hydrocarbon chains that contain double-bonded carbons; the carbons involved in the double bonds have hydrogens bonded to them on the same side.
Unsaturated fatty acids are kinky and do not have the capacity to consolidate at room temperature.
Hydrogenation is the process of adding hydrogens to unsaturated fat, breaking the double bond in the process. By doing so, the unsaturated fat is now saturated and can solidify at room temperature.
Oftentimes, hydrogenation fails to break the double bond, moving one of the hydrogens to the other side of the bond; this formation is known as a trans fat and cannot be easily digested by the body
Function/Role of Fat:
The major function of fats is long-term energy storage. The hydrocarbons of fat are rich in energy, allowing them to store twice as much energy as a gram of starch. So, for animals and organisms that must carry their energy storage with them, fat serves as efficient and mobile storage.
Structure of Phospholipid:
Phospholipids contain two fatty acids, with one containing a cis double bond (kink forms). In addition, glycerol is attached to the two fatty acids. The final hydroxyl group in the glycerol is bound to a phosphate group, which may also have additional polar/charged attachments.
Function/Role of Phospholipid:
While the fatty acid tails of phospholipids are hydrophobic, the phosphate/polar head is hydrophilic. As a result, phospholipids are amphipathic.
In water, phospholipids will orient themselves into two layers. While the hydrophilic heads will point towards the water, the hydrophobic tails will point inward. In cells, this bilayer forms a membrane boundary between the cell and the external environment.
Structure of Steroids:
Steroids consist of a carbon skeleton with four fused rings. Different steroids are distinguished by the chemical groups attached to the rings.
Function/Role of Steroids:
Cholesterol is a part of the animal cell membrane, maintaining the integrity of the structure. Equally important, cholesterol is the precursor for other steroids, which are necessary signal molecules that coordinate/regulate the body.
Proteins are biologically functional molecules made up of one or more polypeptides folded into a specific three-dimensional structure.
Proteins vary in their structure and function:
Enzymatic Proteins (selective acceleration of chemical reactions)
Storage Proteins (storage of amino acids)
Hormonal Proteins (coordinate organism’s activities)
Contractile and Motor Proteins (movement)
Defensive Proteins (protection against disease)
Transport Proteins (transport of substances)
Receptor Proteins (response of the cell to chemical stimuli)
Structural Proteins (support)
Structure of Amino Acids:
Amino Acids are the building blocks of proteins (monomers). Amino acids contain an alpha carbon, hydrogen atom, amino group, carboxyl group, and an R side chain.
The R side chain makes each of the 20 amino acids unique.
Non-Polar Side Chains: Glycine, Alanine, Valine, Leucine, Isoleucine, Methionine, Phenylalanine, Tryptophan, Proline.
Polar Side Chains: Serine, Threonine, Cysteine, Tyrosine, Asparagine, Glutamine.
Charged (ionized form): Aspartic Acid (negative - acidic), Glutamic Acid (negative - acidic), Lysine (positive - basic), Arginine (positive - basic), Histidine (positive - basic).
Structure of Polypeptides:
Polypeptides are two or more amino acids bonded together through a peptide bond.
A peptide bond is a dehydration synthesis reaction in which hydrogen is removed from an amino group of one amino acid and a hydroxyl group is removed from the carboxyl group of another amino acid → The result is a covalent bond between the two amino acids.
When the process is repeated, a polypeptide chain is formed, with the free amino end being the N-terminus and the free carboxyl end being the C-terminus.
The shape of a protein informs its function. For most proteins, its function completely depends on its ability to recognize and bind to some other molecule, which must fit its own shape properly.
In order to achieve their proper function, proteins are formed through a three to four-step process
The primary structure in this period in which the amino acid chain or chains are formed.
Semi-charged oxygen and semi-charged hydrogen in different parts of the polypeptide backbone begin to hydrogen bond. Because there are so many hydrogen bonds, the interactions help to stabilize a rudimentary shape for the to-be protein.
The alpha helix shape is formed when every fourth amino acid hydrogen bonds. This generates a sort of coiled, curl-like structure.
The beta-pleated sheet is formed when amino acids laying parallel to each other hydrogen bond. This generates a flat, sturdy, and sheet-like structure.
Some proteins can have regions with differing secondary structures; some proteins have neither.
Interactions between side-chains help to fold, bend, and mold the structure, adding additional unique 3D shape.
Polar side chains will be attracted to the semi-charged regions of each other and subsequently form hydrogen bonds.
Hydrophobic side chains, which will be repelled by the aqueous solution, will try to orient themselves away from the water. In so doing, they fold inside and congregate together. From there, van der Waals interactions between the side chains reinforce the alignment.
Oppositely charged ions between side chains are also attracted to each other, so they will form ionic bonds.
If two sulfhydryl groups (from the side chain of the amino acid cysteine) come in close proximity, the sulfurs in each group will covalently bond, riveting parts of the protein together
If a protein is made up of more than one subunit (meaning that multiple amino acid chains were originally synthesized), then the quaternary structure serves as the period in which the two subunits aggregate together
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If the pH, salt concentration, temperature, or other aspects of the protein’s environment are altered, the weak hydrogen bonds and interactions within a protein may be destroyed. The protein will lose its shape: Denaturation.
Denature agents may also include non-polar solvents or any chemical that may disrupt the hydrogen bonds, ionic bonds, and disulfide bridges that establish a protein’s shape. When a protein has denatured, it can sometimes return to its original shape if the original conditions are reinforced.
When a protein is denatured, it can no longer function like it is supposed to → Structure/Shape = Function
Nucleic acids are molecules that handle gene expression, which is the process of converting genetic instructions into functional products.
Structure of Nucleotides:
Nucleotides are the building blocks of nucleic acids.
Structure of RNA nucleotides:
Ribose (deoxyribose with one more oxygen) + Nitrogenous Base + One Phosphate Group
Nitrogenous Bases = Adenine and Uracil, Guanine and Cytosine
Structure of DNA nucleotides:
Deoxyribose (ribose with one less oxygen) + Nitrogenous Base + One Phosphate Group
Nitrogenous Bases = Adenine and Thymine, Guanine and Cytosine
Pyrimidines vs. Purines:
Pyrimidines are nitrogenous bases comprised of one six-membered ring of carbon and nitrogen atoms: Cytosine, Thymine,
Purines are nitrogenous bases comprised of a six-membered ring of carbon fused to a five-membered ring: Adenine and Guanine
Structure of Polynucleotides:
Polynucleotides are two or more nucleotides bonded together by a phosphodiester linkage.
A phosphodiester linkage is a dehydration synthesis reaction in which hydroxyl is removed from a phosphate group of one nucleotide and a hydrogen group is removed from the sugar of another nucleotide → The result is a covalent bond between the two nucleotides.
These bonds help to form the sugar-phosphate backbone, which does not include nitrogenous bases. The sugar-phosphate backbone is denoted in direction by its 5’ end (where a 5th carbon is a terminal) to its 3’ end (where a 3rd carbon is a terminal).
Polynucleotides form a sequence of nitrogenous bases, which code for a different sequence of amino acids and ultimately a different protein
Function of DNA and RNA:
In simple terms, DNA in the nucleus directs the creation of mRNA, which replicates a portion of the DNA strand. This mRNA travels out of the nucleus and into the cytoplasm. Here, it interacts with ribosomes, which translate the mRNA into amino acids by signaling for specific tRNA. Once the amino acid chain is complete, a protein can begin to form.
Structure of DNA polynucleotides:
DNA molecules have two polynucleotides or strands that wind around an imaginary axis, forming a double helix.
These strands run antiparallel, meaning that their 5’ and 3’ ends are opposite each other. While the sugar-phosphate backbone is on the outside, the nitrogenous bases pair and hydrogen bond on the inside.
These DNA strands that match pairs are considered complementary. Base Pairs = Adenine and Thymine, Guanine and Cytosine.
Structure of RNA polynucleotides:
RNA molecules generally exist as single strands, but complementary base pairing can occur. Regions of the same RNA strand or different RNA strands can form hydrogen bonds (due to complementary pairing), which gives the molecule a unique 3D shape.
This is important because RNA works as a sort of utility molecule that must fulfill versatile objectives in gene expression. Base Pairs = Adenine and Uracil, Guanine and Cytosine