NS1: CPF Flashcards

Question

what is power and its related equations

Answer 1

Power is measured in watts and can be solved through one of three power equations (derived from Ohm’s law). P = IV P = I2R P = V2/R Ohm’s Law: The three quantities of current, voltage, and resistance are linked together: V = IR

Answer 2

Reduction is defined as a decrease in the oxidation state of an atom → eg. (1) gain of an electron, (2) decreased oxidation state, (3) formation of a C–H bond (e.g. alkene → alkane), and (4) loss of a C–O or C–N bond (or any bond between carbon and an electronegative atom) Oxidation is defined as an increase in the oxidation state of an atom → eg. (1) loss of an electron, (2) increased oxidation state, (3) loss of a C–H bond (e.g. alkane → alkene), and (4) gain of a C–O or C–N bond (or any bond between carbon and a highly electronegative atom) LEO goes GER lose electrons = oxidation gain electrons = reduction

Answer 3

alcohols (most reduced / least oxidized) to aldehydes and ketones (intermediate reduction / oxidation) to carboxylic acids (least reduced / most oxidized) A primary alcohol can be oxidized to an aldehyde by a mild oxidizing agent or to a carboxylic acid by a strong oxidizing agent. -- A strong oxidizing agent will likewise oxidize an aldehyde to a carboxylic acid. A secondary alcohol will be oxidized to a ketone by either a mild or a strong oxidizing agent. A strong reducing agent can reduce a carboxylic acid directly to an alcohol, while weak reducing agents will not reduce carboxylic acids at all. Both mild and strong reducing agents can reduce aldehydes and ketones to primary and secondary alcohols, respectively.

Answer 4

derived from cholesterol, which means they share a four-ring lipid structure and are permeable to the cell membrane - - hydrophobic, therefore transported using plasma proteins in the blood - - lipophilic, therefore cannot be stored in vesicles (bc they would diffuse out easily) and only synthesized when needed synthesized by the adrenal cortex and the gonads, in the mitochondria and smooth endoplasmic reticulum

Answer 5

three “S’s”: sex, salt, and sugar -- aldosterone, testosterone / estradiol, and cortisol respectively Since steroid hormones diffuse freely through the plasma membrane due to their hydrophobicity, steroid hormone receptors are found on the inside of the cell, and these receptors form a complex with the hormone before entering the nucleus. Once inside the nucleus, the hormone-receptor complex binds to promoter regions of target genes and can stimulate or inhibit transcription of those genes. Thus, steroid hormones directly regulate gene expression in target cells. Direct gene effects take time to manifest, so steroid hormone responses are generally slower than peptide hormone responses. However, since these changes are at the genetic level, they are much longer-lasting and sometimes permanent.

Answer 6

Lyases break molecules into two smaller molecules without using water or redox reactions. → eg. decarboxylases Isomerases convert a molecule from one isomer to another (including stereoisomers and constitutional isomers). Ligases are used in catalysis where two substrates are stitched together (i.e., ligated) via the formation of C-C, C-S, C-N or C-O bonds while giving off a water (condensation) molecule. Hydrolases catalyze reactions that involve cleavage of a molecule using water (hydrolysis). This cases usually involves the transfer of functional groups to water. → eg. amylases, proteases/peptidases, lipases, and phosphatases. Oxidoreductases catalyze oxidation-reduction reactions where electrons are transferred. In metabolism, these electrons are usually in the form of hydride ions or hydrogen atoms. When a substrate is being oxidized, it is the hydrogen donor. Examples include reductases, oxidases, and dehydrogenases. Transferases move functional groups from one molecule to another (such as kinases that move phosphate groups onto their substrates)

Answer 7

Disulfide linkages only form between the side chains of cysteine (C) residues. When not part of such a linkage, cysteine side chains contain a thiol group (S-H). Through the process of oxidative folding, two thiol groups can connect and form an S-S bond. These linkages are an important part of protein tertiary and quaternary structure. Note: Methionine does contain sulfur, but it cannot form disulfide bonds. This apparent contradiction can be explained by looking at the structure of methionine. The side chain of this amino acid includes a sulfur atom bound to carbon instead of hydrogen. As such, it cannot easily lose its proton and form a disulfide linkage through oxidation.

Answer 8

The first level, referred to as the primary structure, is the amino acid sequence that codes the protein. Each amino acid is coded for by a three-nucleotide sequence known as a codon. The second level of protein structure refers to its two-dimensional arrangement (secondary structure). This folding is due to hydrogen bonds between groups along the peptide backbone that link different segments of the polypeptide chain to each other. - - In the alpha-helix, there are 3.6 residues per turn, which means that there is one residue every 100 degrees of rotation of the molecule. - - In beta-sheets, the protein is arranged into several β-strands, which are stretched segments of the polypeptide chain that are also kept together by hydrogen bonds. Beta-sheets may be parallel (the strands point in the same direction) or anti-parallel (the strands point in opposite directions). The third level of protein structure, known as tertiary structure, refers to the actual three-dimensional shape of the native protein. These folds are caused and maintained primarily by hydrophobic/hydrophilic interactions and hydrogen bonds between the side chains of amino acids and between the amino acids and the protein’s environment. The fourth level of protein structure, which is not present in all proteins, is quaternary structure. Quaternary structure exists when a single protein consists of two or more polypeptide chains (called subunits). The number of subunits will be reflected in the name given to its structure (dimer, trimer, pentamer). If the subunits are identical, the prefix “homo” is used, and if they differ, the term “hetero” is used. Thus, a protein with two identical subunits would be a homodimer, while a heterotetramer would be a protein with four subunits, at least some of which are different. These subunits can interact with each other, contribute to an active site or to the dynamics of the complex, or interact with some target molecules.

Answer 9

enzymes decrease the activation energy note: enzymes are not changed or consumed in their associated reactions, do not affect the equilibrium constant (Keq) of these reactions, and do not affect any thermodynamic parameters of the reaction (ΔG, ΔH, and ΔS). For this reason, enzymes cannot make an energetically unfavorable reaction into a favorable one.

Answer 10

Enzymes and substrates interact at the active site of an enzyme, which can be divided into a binding site and a catalytic site. The catalytic site is the very specific place where a reaction is catalyzed, while the binding site is a larger area where the substrate interacts with the enzyme through intermolecular interactions in a way that positions the substrate properly relative to the catalytic site. When the substrate interacts with the active site of an enzyme, it forms what is known as the enzyme-substrate complex. The lock-and-key theory proposes that the active site of an enzyme and the substrate fit together like puzzle pieces, with no change in tertiary or quaternary structure. However, it eventually became clear that the lock-and-key theory was not sufficient to adequately explain enzyme-substrate interactions, leading to the development of the induced fit model. In the induced fit model, the enzyme and substrate are seen as affecting each other; the initial stages of binding induce conformational shifts that allow closer attachment and more efficient catalysis.

Answer 11

The most basic definition of spontaneity is ∆G < 0, meaning that the reaction has a negative change in Gibbs free energy. Spontaneity is associated with exothermic (∆H < 0) reactions and those that increase entropy (∆S > 0) through the equation ∆G = ∆H – T∆S. Note that a reaction can still be spontaneous even if it fulfills only one of these requirements. it is important to automatically recognize that spontaneity is equivalent to ∆G < 0, Keq > 1, and E° > 0 where ∆G°rxn = −RTlnK eq

Answer 12

One quick way to determine the orbital hybridization around the central atom is to simply count up the number of bonds and lone pairs. For example, ammonia has three bonds and one lone pair around its central nitrogen atom, for a total of four regions of electron density. This orbital hybrid therefore needs four orbitals to hybridize: s, p, p, and p. Thus, ammonia is an sp3 hybrid. Next, XeF4 has two lone pairs and four bonds around the central xenon atom. We know this because the central Xe atom has eight valence electrons. It gets four of these eight electrons from the two lone pairs and four from the bonds — one electron from each bond. Alternatively, we could try drawing the Lewis structure of XeF4, knowing that 8 electrons must come from the Xe atom and 7 from each of the F atoms, for a total of 8 + 7(4) = 36 electrons. Drawing XeF4 with Xe as the central atom and single bonds between the Xe atom and each F atom produces a structure with only 32 electrons, so we must add two lone pairs to the central Xe atom. Two lone pairs and four bonds gives us six total regions of electron density. So we need six hybrid orbitals to hold those electrons: s, p, p, p, d, and d. That’s an sp3d2 hybrid.

Answer 13

Leucine is hydrophobic, since its side chain contains only carbon and hydrogen. If the solvent were also hydrophobic, the face of a leucine zipper could interact just as favorably with the solvent as with the opposite alpha helix. Some leucine residues would likely interact only with the solvent, preventing formation of the dimer entirely.

Answer 14

based on whether the residues are hydrophobic or hydrophilic If hydrophilic (meaning you are polar), residues favor facing into the aqueous solution, thus promoting hydrogen bonding → yields high entropy, which is energetically favorable If hydrophobic, residues favor facing away from the soln, thus limiting hydrogen bonding with nonpolar residues → yields low entropy, which is energetically unfavorable

Answer 15

Electron-rich molecules tend to act as nucleophiles when a covalent bond is being made; they also tend to act as Bronsted-Lowry bases when making a bond to an H+ or as Lewis bases when a coordinate bond is formed. Vs. Electron-poor molecules tend to act as electrophiles; BL-acids, or as Lewis acids.

Answer 16

A resistor is a device that impedes the flow of charge in a circuit. A galvanic cell (battery) is a device that uses a spontaneous redox reaction to produce an electrical potential. An electrolytic cell is a device that uses an electrical potential to drive a nonspontaneous redox reaction. Capacitors have several medical applications (e.g. defibrillators) and are used to store charge and electrical potential energy, precluding the need for large batteries in electrical components. A basic capacitor consists of two metal plates separated by a layer of insulating material called a dielectric. Capacitance is the ability to store charge and is calculated as C = ɛ0A/d, where A is the area of the plates and d is the distance between them.

Answer 17

thermoregulation via the anterior hypothalamus serves as the body’s “thermostat” to maintain body core temperature Heat exchange is determined by convection, conduction, evaporation, and radiation. The body can lose heat by increasing cutaneous blood flow and sweating, or by decreasing the basal metabolic rate through thyroid signaling. Vs. It can gain heat by decreasing cutaneous blood flow, increasing muscular activity (through movement and shivering), increasing the basal metabolic rate through thyroid signaling, metabolizing brown adipose (in infants only), or triggering piloerection of the hair on the body (goosebumps).

Answer 18

Forced change (in body temp): occurs when an environmental stress is sufficient to overcome the thermoregulatory systems of the body Regulated change: when the hypothalamic “temperature setting” is shifted, as when a fever results from infection by a pathogen

Answer 19

Structural proteins: fibrous proteins that have an elongated shape and provide structural support for cells and organ tissues Keratins: classified as soft or hard according to their sulfur content → low content becomes skin bc it is much more flexible than high content (eg nails); hair is a intermediate content example Actin and Myosin proteins (of muscle tissue): interaction btwn the two form cross-linkages that allow the sliding of filaments over each other during muscle contraction via the sarcomere (the fundamental unit of all muscle fibers) Collagen: found in tendons; forms connective ligaments within the body and provides the skin with extra support → forms by three proteins wrapped around each other in a triple helix; molecules of collagen are cross-linked together in the extracellular space to form collagen fibrils that provide structural support to the cell → flexible, elastic, and stretchy, thus allowing for spontaneous recoil