Unit 1: Biochemistry

Activation Energy

the minimum amount of energy required to initiate a biochemical reaction, acting as an energy barrier that reactants must overcome to form products

Active Site

a specific region on an enzyme where substrate molecules bind and chemical reactions occur, forming the product(s)

Amino Acid

an organic molecule that serves as the building block of proteins

Atom

the basic, fundamental building block of all matter, including the molecules that make up living organisms and cells. It is the smallest unit of an element that still retains the properties of that element

Carbohydrate

organic compounds composed of carbon, hydrogen, and oxygen atoms. They are essential nutrients for living organisms, providing energy and structural support. 

Catalyst

a substance that speeds up a chemical reaction without being consumed by it, primarily by lowering the activation energy required for the reaction to occur. These biological catalysts are known as enzymes (mostly proteins, but some RNA molecules called ribozymes also exist)

Cellulose

the most abundant organic polymer on Earth, a polysaccharide forming the primary structural component of plant and algae cell walls. Composed of linear chains of glucose units linked by β(1→4) glycosidic bonds, its rigid structure provides plants with tensile strength, structural support, and protection. While humans cannot digest it, some microorganisms and animals can break it down using cellulase enzymes, utilizing it as an energy source

Denaturation

the process by which a macromolecule (like a protein or nucleic acid) unfolds and loses its unique, functional three-dimensional structure due to external factors such as heat, extreme pH levels, or certain chemicals

Disaccharide

a type of carbohydrate formed when two monosaccharide units (simple sugars) are linked together by a glycosidic bond. These molecules serve as vital energy sources, as they can be broken down into their simple sugar components through hydrolysis to provide immediate metabolic fuel or be stored as glycogen. Key examples include sucrose (table sugar), formed from glucose and fructose, and lactose (milk sugar), a glucose-galactose combination vital for infant nourishment. 

Electron

primarily refers to the subatomic particle that moves between molecules in processes like the electron transport chain (ETC) during cellular respiration to produce ATP, or in photosynthesis

Element

a fundamental, pure substance that cannot be broken down by chemical means and is composed of only one type of atom

Enzyme

a biological catalyst, almost always a protein, that speeds up specific chemical reactions without being consumed or permanently changed in the process. Enzymes reduce the activation energy needed for a reaction, allowing it to occur at a biologically significant rate, which is essential for nearly all metabolic processes and functions within a cell, from nutrient breakdown to energy transformation

Glycogen

a multi-branched polysaccharide of glucose that serves as a primary storage form of energy in animal cells, fungi, and bacteria. Stored mainly in the liver and muscles, glycogen is a reserve that can be rapidly broken down into glucose to provide energy for essential biological processes and physical activity when blood glucose levels are low. 

Lipid

a diverse group of organic compounds that are insoluble in water but soluble in organic solvents, including fatty, oily, or waxy substances. Lipids perform vital functions in the body, such as building cell membranes (e.g., phospholipids), storing energy (e.g., fats), absorbing certain vitamins, and acting as signaling molecules (e.g., steroids). 

Molecule

the smallest unit of a pure substance, made of two or more atoms held together by chemical bonds, that retains the chemical properties of that substance. This definition extends to complex biological molecules (biomolecules) such as DNA, proteins, and carbohydrates, which are essential for life and are made of thousands of atoms

Monomer

a small molecule that serves as a building block for a larger molecule, called a polymer. Monomers link together through chemical bonds in a process called polymerization to form essential biological macromolecules such as carbohydrates (like starch), proteins, and nucleic acids (like DNA and RNA). Examples of biological monomers include amino acids, nucleotides, and monosaccharides like glucose. 

Monosaccharide

a single, simple sugar molecule that cannot be broken down into simpler sugars by hydrolysis and serves as the basic building block for complex carbohydrates. They are fundamental units for energy production and cellular processes, with common examples including glucose, fructose, and galactose. Monosaccharides can exist as straight chains or rings and are classified by their number of carbon atoms

Neutron

a subatomic particle located in the nucleus of an atom that has no electric charge and contributes to the atom's mass. Neutrons are crucial for stabilizing atomic nuclei by balancing the repulsive forces between positively charged protons. The number of neutrons determines an element's isotope, influencing properties like nuclear stability and radioactivity.  

Nucleic Acid

a large biomolecule, or macromolecule, composed of repeating units called nucleotides that serve to store, transmit, and express genetic information, ultimately dictating cellular activities and traits

Nucleotide

the basic structural unit of nucleic acids such as DNA and RNA, composed of a nitrogenous base, a five-carbon sugar (ribose or deoxyribose), and one or more phosphate groups. Nucleotides are essential for storing and transmitting genetic information and also serve as energy carriers in the form of ATP

Organic

compounds and molecules that are primarily made of carbon atoms, often bonded to hydrogen, and are essential for the structure and function of living organisms. These carbon-based molecules, such as carbohydrates, lipids, proteins, and nucleic acids, serve as the fundamental building blocks of all known life forms. 

Peptide Bond

a chemical bond formed between two amino acids by a dehydration synthesis (or condensation) reaction, where the carboxyl group of one amino acid links to the amino group of another, forming a polypeptide chain. This covalent bond is essential for constructing proteins, as it links amino acids in a specific sequence (primary structure) that determines the protein's overall three-dimensional structure and, consequently, its biological function.  

polymer

a macromolecule (a very large molecule) composed of many repeating smaller units, or monomers, linked together by chemical bonds. Examples of essential biological polymers include proteins (made of amino acid monomers), nucleic acids like DNA (made of nucleotide monomers), and polysaccharides such as starch (made of sugar monomers). These polymers are crucial for building cellular structures and carrying out vital biological functions

Polysaccharide

a complex carbohydrate made of many simple sugar units (monosaccharides) linked together by glycosidic bonds. These long chains function primarily as energy storage molecules, like starch in plants and glycogen in animals, or as structural components providing support, such as cellulose in plant cell walls and chitin in the exoskeletons of insects and crustaceans. They are high-molecular-weight, insoluble, and not sweet to the taste. 

Protein

large, complex molecules composed of amino acids that play essential roles in living organisms. Proteins consist of one or more polypeptide chains, which are linear sequences of amino acids. 

• The amino acids are linked together by peptide bonds. 

• The sequence and arrangement of amino acids determine the protein's unique structure and function. 

Proton

a positively charged subatomic particle found in the nucleus of every atom. Protons are essential to the structure and chemical properties of elements, as the number of protons determines an element's atomic number. Their role in chemical bonding and biological processes, such as the movement of protons across cell membranes or within proteins, makes them fundamental to life

R Group

the variable group of atoms attached to the central carbon of an amino acid. It is unique for each of the 20 common amino acids and determines the amino acid's chemical properties, such as whether it is polar, nonpolar, acidic, or basic. These properties are crucial because they influence the amino acid's behavior in protein structure and function, including protein folding, interactions with water, and the ability to catalyze reactions.  

Saturated

the complete filling of bonding sites, most notably in fatty acids where a saturated hydrocarbon chain has the maximum possible number of hydrogen atoms bonded to its carbon atoms, with no double bonds, leading to tightly packed molecules that are solid at room temperature. The term also applies to enzyme saturation, where all active sites are filled with substrates, and to "saturated solutions" in chemistry, meaning the maximum amount of solute has dissolved into a solvent. 

Starch

the main energy storage polysaccharide in plants, composed of linked glucose units forming both linear (amylose) and branched (amylopectin) chains that create insoluble granules. It is a vital source of energy for organisms, particularly in the human diet, and plays a crucial role in plant growth and development. Its structure provides physical properties used in the food industry as a thickener and texturizer

Substrate

the surface an organism lives on, providing structural or nutrient support, or it can refer to the specific molecule that an enzyme binds to and acts upon, transforming it into a product.

Triglyceride

a molecule composed of a glycerol backbone and three fatty acid chains. It serves as the primary form of fat in the diet and the body's main way to store energy. Triglycerides provide energy, insulate the body, and help absorb certain vitamins. They are formed from dietary fats and excess calories, and they circulate in the bloodstream as well as being stored in adipose tissue.  

Unsaturated

refers to the chemical structure of fatty acids and lipids that contain one or more double or triple bonds between carbon atoms, resulting in fewer hydrogen atoms than a saturated counterpart. These double bonds create "kinks" in the molecular chain, which prevents them from packing tightly, making unsaturated fats liquid at room temperature and increasing cell membrane fluidity. These characteristics are vital for processes like membrane transport and cellular signaling and are essential for life in varying environments, with unsaturated fats a key component in diets and also playing roles in stress tolerance and metabolic regulation.