WEEK 1 Flashcards
Define the term “chemical element”, specify the name and symbol for the four most common chemical elements in the body, and describe the importance of each.
An element is a pure substance that is distinguished from all other matter by the fact that it cannot be created or broken down by ordinary chemical means. While your body can assemble many of the chemical compounds needed for life from their constituent elements, it cannot make elements. They must come from the environment.
The elements in the human body are shown in Figure 1, beginning with the four most abundant: oxygen (O), carbon (C), hydrogen (H), and nitrogen (N). Each element’s name can be replaced by a one- or two-letter symbol;
you will become familiar with some of these during this course. All the elements in your body are derived from the foods you eat and the air you breathe.
Define the term “atom” and describe the structure of an atom.
An atom is the smallest quantity of an element that retains the unique properties of that element. In other words, an atom of hydrogen is a unit of hydrogen—the smallest amount of hydrogen that can possibly exist. As you might guess, atoms are almost unfathomably small. The period at the end of this sentence is millions of atoms wide.
Atoms are made up of even smaller subatomic particles, three types of which are important: the proton, neutron, and electron. The number of positively-charged protons and non-charged (“neutral”) neutrons, gives mass to the atom, and the number of protons in the nucleus of the atom determine the element. The number of negatively-charged electrons equals the number of protons.
Define the terms “molecule” and “compound”.
A compound is a substance containing at least two different elements joined by chemical bonds.
A molecule is atoms linked together through chemical bonds
Describe the formation of an ion and of an ionic bond.
an atom typically has the same number of positively charged protons and negatively charged electrons. As long as this situation remains, the atom is electrically neutral. But when an atom participates in a chemical reaction that results in the donation or acceptance of one or more electrons, the atom will then become positively or negatively charged. This happens frequently for most atoms in order to have a full valence shell, as described previously. This can happen either by gaining electrons to fill a shell that is more than half-full, or by giving away electrons to empty a shell than is less than half-full, thereby leaving the next smaller electron shell as the new, full, valence shell. An atom that has an electrical charge—whether positive or negative—is an ion.
The opposite charges of cations and anions exert a moderately strong mutual attraction that keeps the atoms in close proximity forming an ionic bond. An ionic bond is an ongoing, close association between ions of opposite charge.
Describe the formation of a covalent bond.
Unlike ionic bonds formed by the attraction between a cation’s positive charge and an anion’s negative charge, molecules formed by a covalent bond share electrons in a mutually stabilizing relationship. Like next-door neighbors whose kids hang out first at one home and then at the other, the atoms do not lose or gain electrons permanently. Instead, the electrons move back and forth between the elements. Because of the close sharing of pairs of electrons (one electron from each of two atoms), most covalent bonds are not broken apart in water.
Distinguish between organic and inorganic molecules.
An inorganic compound is a substance that does not contain both carbon and hydrogen. A great many inorganic compounds do contain hydrogen atoms, such as water (H2O) and the hydrochloric acid (HCl) produced by your stomach. In contrast, only a handful of inorganic compounds contain carbon atoms. Carbon dioxide (CO2) is one of the few examples.
An organic compound, then, is a substance that contains carbon-hydrogen bonds. Many organic compounds can be synthesized via covalent bonds within living organisms, including the human body. Recall that carbon and hydrogen are the second and third most abundant elements in your body. You will soon discover how these two elements combine in the foods you eat, in the compounds that make up your body structure, and in the chemicals that fuel your functioning.
Describe the composition of organic molecules, specify two characteristics of organic molecules
that make them useful to living organisms, and give examples of organic molecules.
Carbon atoms can bind to other carbon atoms as well as atoms of other elements in multiple ways, so organic molecules come in many different shapes with different properties depending on their exact chemical composition. The fact that organic molecules can be assembled into very large molecules with complex structures makes them useful to living cells in several ways. Examples can include structural components of cells or functional components that allow chemical reactions to proceed.
Specify the chemical properties of water.
water is 2 hydrogen atoms covalently bonded to 1 oxygen atom. water is a polar covalent bond because oxygen is highly electronegative in comparison to hydrogen.
Hydrogen is a weak bond so water molecules can interact with one another(up to 4 bonds)
Explain the biological importance of water.
- Acts as a universal solvent, meaning that the things we need to survive are dissolved in water
- Used in various essential chemical reactions in the cell
- Used to maintain body temperature
- Acts as a lubricant and cushion
More than half our body is water!!
Specify the percentage of body weight that is composed of water and estimate the amount of body water you contain in liters.
60%
0.60 x 84 kg = 50.4 kg = 50.4 L
Describe the distribution of body water.
- All the water in our body is compartmentalized:
- Cytoplasm of each cell contains fluid (intracellular fluid) = 66% (2/3) of our total body fluid
- Remaining 33% (1/3) is extracellular fluid
- 80% of this extracellular fluid is found between our cells (interstitial fluid)
- 20% of this extracellular fluid is found in our blood (plasma)
Describe the chemistry of carbon.
The Chemistry of Carbon: What makes organic compounds ubiquitous is the chemistry of their carbon core. Recall that carbon atoms have four electrons in their valence shell, and that the octet rule dictates that atoms tend to react in such a way as to complete their valence shell with eight electrons. Carbon atoms do not complete their valence shells by donating or accepting four electrons. Instead, they readily share electrons via covalent bonds.
Commonly, carbon atoms share with other carbon atoms, often forming a long carbon chain referred to as a carbon skeleton. It is also possible for carbon atoms to form more than one covalent bond with one another, and can form double bonds and triple bonds.
Describe the structure and function of carbohydrates.
Carbohydrates: A carbohydrate is a molecule composed of carbon, hydrogen, and oxygen; in most carbohydrates, hydrogen and oxygen are found in the same two-to-one relative proportions they have in water. In fact, the chemical formula for a “generic” molecule of carbohydrate is (CH2O)n. The structure also contains several hydroxyl groups, which makes carbohydrates polar in terms of chemical nature.
Carbohydrates are also referred to as saccharides, a word meaning “sugars.”. Three forms are important in the body. Monosaccharides are the monomers of carbohydrates. Disaccharides (di- = “two”) are made up of two monomers. Polysaccharides are the polymers, and can consist of hundreds to thousands of monomers.
Describe the structure and function of lipids.
Lipids: A lipid is one of a highly diverse group of compounds made up mostly of hydrocarbons. The few oxygen atoms they contain are often at the periphery of the molecule. Their nonpolar hydrocarbons make all lipids hydrophobic. In water, lipids do not form a true solution, but they may form an emulsion, which is the term for a mixture of solutions that do not mix well.
Describe the structure and function of proteins.
Proteins: You might associate proteins with muscle tissue, but in fact, proteins are critical components of all tissues and organs. A protein is an organic molecule composed of amino acids linked by peptide bonds. Proteins include the keratin in the epidermis of skin that protects underlying tissues, the collagen found in the dermis of skin, in bones, and in the meninges that cover the brain and spinal cord. Proteins are also components of many of the body’s functional chemicals, including digestive enzymes in the digestive tract, antibodies, the neurotransmitters that neurons use to communicate with other cells, and the peptide-based hormones that regulate certain body functions (for instance, growth hormone). While carbohydrates and lipids are composed of hydrocarbons and oxygen, all proteins also contain nitrogen (N), and many contain sulfur (S), in addition to carbon, hydrogen, and oxygen, in varying ratios depending on the structure.
Describe the structure and function of nucleic acids.
Nucleotides and Nucleic Acids: The fourth type of organic compound important to human structure and function are the nucleotides (Figure 12). A nucleotide is one of a class of organic compounds composed of three subunits:
* one or more phosphate groups
* a pentose sugar: either deoxyribose or ribose
* a nitrogen-containing base: adenine, cytosine, guanine, thymine, or uracil
Nucleotides can be assembled into nucleic acids (DNA or RNA) or the energy compound adenosine triphosphate.
Identify the number of covalent bonds carbon can form.
4
Define the term “hydrocarbon chain”.
Organic molecule containing only Hydrogen(H) and Carbon(C)
Define the term “functional group”, and identify five examples that are important in human physiology.
A functional group is a group of atoms linked by strong covalent bonds and tending to function in chemical reactions as a single unit. You can think of functional groups as tightly knit “cliques” whose members are unlikely to be parted. Five functional groups are important in human physiology; these are the hydroxyl, carboxyl, amino, methyl and phosphate groups
Specify the three chemical elements of which carbohydrate molecules consist, and their relative (approximate) proportions in a typical carbohydrate molecule.
Carbon(C), Hydrogen(H), Oxygen(O). They arranged themselves in a 1:2:1 ratio. Ex. Glucose is C6 H12 O6
Refer to the chemical structure of carbohydrates and the chemical properties of water to explain why carbohydrates are generally hydrophilic (soluble in water).
Carbohydrates are usually hydrophilic because in most carbohydrates, hydrogen and oxygen are found in the same two-to-one relative proportions they have in water. In fact, the chemical formula for a “generic” molecule of carbohydrate is (CH2O)n. The structure also contains several hydroxyl groups, which makes carbohydrates polar in terms of chemical nature.
Carbohydrate molecules can be grouped based on how many monomers they contain. For each of the three main size groups of carbohydrate:
◦ Name and define the group (based on the number of monomers it contains)
◦ Name at least three specific examples of each group
◦ Briefly describe at least one major function in the human body of each group
- Monosaccharides: A monosaccharide is a monomer of carbohydrates. Five monosaccharides are important in the body. Three of these are the hexose sugars, so called because they each contain six atoms of carbon. These are glucose, fructose, and galactose (Figure 1a). The remaining monosaccharides are the two pentose sugars, each of which contains five atoms of carbon: ribose and deoxyribose (Figure 1b).
- Disaccharides: A disaccharide is a pair of monosaccharides. Disaccharides are formed via dehydration synthesis, and the bond linking them is referred to as a glycosidic bond (glyco- = “sugar”). Three disaccharides are important to humans. These are sucrose, commonly referred to as table sugar; lactose, or milk sugar; and maltose, or malt sugar (Figure 2). As you can tell from their common names, you consume these in your diet; however, your body cannot use them directly. Instead, in the digestive tract, they are split into their component monosaccharides via hydrolysis.
Polysaccharides: Polysaccharides can contain a few to a thousand or more monosaccharides. Three are important to the body (Figure 3):
* Starches are polymers of glucose. They occur in long chains called amylose or branched chains called amylopectin, both of which are stored in plant-based foods and are relatively easy to digest.
* Glycogen is also a polymer of glucose, but it is stored in the tissues of animals, especially in the muscles and liver. It is not considered a dietary carbohydrate because very little glycogen remains in animal tissues after slaughter; however, the human body stores excess glucose as glycogen, again, in the muscles and liver.
* Cellulose, a polysaccharide made of glucose that is the primary component of the cell wall of green plants, is the component of plant food referred to as “fiber”. In humans, cellulose/fiber is not digestible; however, dietary fiber has many health benefits. It helps you feel full so you eat less, it promotes a healthy digestive tract, and a diet high in fiber is thought to reduce the risk of heart disease and possibly some forms of cancer.
Specify the major elements of lipid molecules.
Specify the chemical elements of which lipid molecules typically consist, and their relative (approximate) proportions in a typical lipid molecule.
