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Biomolecules:
Life's most organic compounds,
carry out major…
Biomolecules:
Life's most organic compounds,
carry out major functions in
the cell.
Carbohydrates
Primarily sugars and sugar polymers. Made up of carbon, oxygen, and hydrogen.
Made up of 3 different types of
sugars: Monosaccharides,
disaccharides, and polysaccharides
Monosaccharides are single units of sugar, and are molecular formulas of repeating units of CH2O (1:2:1) (i.e. Glucose, C6H12O6)
A disaccharide is two monosaccharides joined together by a glycosidic linkage, a covalent bond formed in a dehydration reaction.
Polysaccharides are polymers with hundreds
to thousands of monosaccharides joined by glycosidic linkages.
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Cellulose is a carbohydrate used in plants, and is a polymer of glucose. It is used to give plants strong structure in parts such as the stem. Chitin is used by bugs and crustaceans to build an exoskeleton and by fungi for their cell walls.
Lipids
Lipids are the only biomolecule that does not include polymers. Lipids are generally non-polar, and as such, hydrophobic. Made of oxygen, hydrogen, and most significantly, carbon. A carboxyl group is the head, hydrocarbon chains are the tails.
3 main types of Lipids: fats, phospholipids, and steroids
Fats (aka triglycerides, for having 3 hydrogen/carbon tails) are very large molecules, and are made of glycerol (an alcohol) and fatty acids (long carbon skeleton, 16-18 C atoms) Fats store significant amounts of energy in their hydrogen - carbon bonds, and are mainly used for energy storage in living things.
Saturated fat: made from fatty acid that has all available carbon bonds on the hydrocarbon chain tail taken by hydrogen. Common in animal fats (lard and butter) and are solid at room temperature.
Unsaturated fats are like saturated fats but one hydrogen on the tail is replaced with a cis double bond in carbon, giving the tail a bent shape. Liquid at room temp, found in plant and fish fat.
Trans fats are unsaturated fats artificially converted to saturated fats by adding hydrogen, giving it a trans double bond. Is found in baked goods and linked to negative health effects.
Phospholipids replace one of their two fatty acid chains with a polar phosphate group, making the head hydrophilic and the tail hydrophobic. When placed in water, they make a bilayer in opposite directions, with the heads facing out and tails facing in (this is what makes up the cell membrane).
Steroids have a carbon skeleton with 4 fuzed rings. Cholesterol is an important steroid that is not only used in the cell membrane, but is used to make other hormones and steroids in animals.
Proteins
Carry out nearly all cellular functions. Comes from Greek word proteios, which means "first".
Makes up about 50% of cell dry mass and carries out many functions ranging from cellular transport, defense, and construction. Proteins called enzymes act as catalysts in vital biological chemical reactions.
Proteins are 3D shapes built out of many combinations of polymers called amino acids (made primarily out of carbon, hydrogen, oxygen, and nitrogen), of which there are 20 main types.
Long strands of amino acids bond together to form polymers in what is known as a peptide bond. Peptide bonds are formed when the amino group of one polypeptide meets the carboxyl group of another, and bond in a dehydration reaction. This long chain of peptide bonds gives it the name "polypeptide". Polypeptides have an amino end (N terminus) and a carboxyl end (C terminus).
Amino acids contain an amino group and a carboxyl group linked together by a central carbon atom known as the "Alpha" (A) carbon. One of the carbon's four bonds goes to a "R" group, or a side chain. This is the part that varies between amino acids, and is what gives each one its unique properties. There are 20 different amino acids in cells.
Polypeptide composition gives proteins their properties, but a polypeptide is NOT a protein. Proteins must be folded into a three dimensional structure before they are functional. Many different proteins have different 3D shapes, and their shape also is part of what defines their function. There are four levels of protein structure.
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Secondary: Hydrogen atoms in amino acids form hydrogen bonds with oxygen atoms, polypeptide coils into a helix shape, polypeptide backbone forms
Tertiary: Weak bonds such as hydrogen bonds and van der walls interactions cause polypeptide to form into a 3D form. Covalent bonds may form disulfide bridges to help further stabilize the structure. This is now a protein.
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Even a slight error in protein composition may have serious effects on its function in the cell (i.e. sickle cell disease).
A protein will unfold and denature if the pH, salt level, or temperature is incorrect, and it will become biologically inactive. Some proteins may or may not be able to re-fold.
Nucleic Acids
Polypeptide instructions are laid out by genes, which are made of DNA, which consist of a biomolecule called a nucleic acid.
Two types of nucleic acids: DNA and RNA. DNA provides instructions for its own replication, uses RNA to control protein synthesis, called gene expression
DNA is passed from parent to child. Chromosomes are long DNA molecules holding hundreds of genes. DNA does not actually create proteins, but holds instructions to do so, and sends instructions via RNA.
RNA interacts with cell machinery (ribosome) to create proteins. Messenger RNA transfers data from DNA in nucleus to ribosome, where proteins are built.
Polynucleotides are polymers of nucleotides, they contain a nitrogen base, a five carbon sugar (a pentose), and three phosphate groups. Each nitrogen base has two rings.
Pyrimidine has a six member ring of carbon and a nitrogen atom. Pyrimidines include Cytosine, Thymine (DNA only), and Uracil (RNA only)
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DNA has a deoxyribose sugar (no oxygen), while RNA has a ribose sugar (has oxygen).
Nucleotides form polynucleotides through dehydration reactions. A phosphate group covalently bonds to two nucleotides (phosphodiester linkage). This creates the sugar phosphate backbone of DNA and RNA. One end has a 5' carbon and the other has a 3' carbon. (5' to 3')
Adenine always goes with Thymine or Uracil, Guanine always goes with Cytosine. Two double helix strands are complimentary.
DNA consists of two chains in a double helix shape running antiparallel. Paired bases form hydrogen bonds with each other, holding the two strands together. RNA is only a single strand.