Quiz #2 Flashcards
Name the different kinds of bonds.
Ionic, non-polar covalent, polar covalent, and hydrogen bonds.
How do bonds occur?
Stability (if there is an unpaired electron in the outer shell, it is not stable, atoms want to be stable)
What are ionic bonds and how do they form?
This chemical bond involves a transfer of an electron, so one atom gains an electron while one atom loses an electron. One of the resulting ions carries a negative charge (anion), and the other ion carries a positive charge (cation). Because opposite charges attract, the atoms bond together to form a molecule, occurs in very rigid and strong solids - metals and salts, “taken, not shared”.
What are covalent bonds and how do they form?
The most common bond in organic molecules, a covalent bond involves the sharing of electrons between two atoms. The pair of shared electrons forms a new orbit that extends around the nuclei of both atoms, producing a molecule. Covalent bonds often form between similar atoms, nonmetal to nonmetal or metal to metal. Covalent bonding signals a complete sharing of electrons. There is usually a direct correlation between positive and negative ions, meaning that because they share electrons, the atoms balance. Covalent bonds are usually strong because of this direct bonding.
What are polar covalent bonds and how do they form?
Two atoms connected by a covalent bond may exert different attractions for the electrons in the bond, producing an unevenly distributed charge, one end of the molecule slightly negatively charged and the other end slightly positively charged. Polar covalent bonds often indicate polar molecules, which are likely to bond with other polar molecules but are unlikely to bond with non-polar molecules. (UNEQUAL SHARING OF ELECTRONS)
What are hydrogen bonds and how do they form?
Hydrogen bonds only form between hydrogen and oxygen (O), nitrogen (N) or fluorine (F). Hydrogen bonds are very specific and lead to certain molecules having special properties due to these types of bonds. Hydrogen bonding sometimes results in the element that is not hydrogen (oxygen, for example) having a lone pair of electrons on the atom, making it polar. Lone pairs of electrons are non-bonding electrons that sit in twos (pairs) on the central atom of the compound. Water, for example, exhibits hydrogen bonding and polarity as a result of the bonding.
What are non-polar covalent bonds and how do they form?
(EQUAL SHARING OF ELECTRONS) Completely neutral, similar electronegativities so there is an equal pull on electrons, resulting in no partial charges like there are in polar covalent bonds.
What are condensation reactions?
“Dehydration synthesis”, water coming out to pull two molecules together. Used to build biological polymers, need an H and an OH group on monomers, water forms.
What are polymers?
Long chains of individual units (monomers), proteins, nucleic acids, polysaccharides.
What are hydrolysis reactions?
Using water to split apart molecules, used to break polymers, water necessary.
What is an isomer?
Something with the same molecular formula but a different molecular structure.
Why are fats that can be easily stacked more stable?
They’re more solid because less entropy.
Why do trans fats stack easier than cis fats do?
In cis unsaturated fats, the hydrogen is bound in the same orientation as the hydrogen on the other end of the carbon-carbon double bond. Trans fats, due to relatively linear shape when compared to other unsaturated fats, are able to bundle together and stack. Stacked trans fats are extremely stable and have much higher melting point than the corresponding cis unsaturated fat.
What is steric?
The shape of something.
What is the main importance of chemical interactions?
Holds molecules together.
WHAT IS THE REASON FOR LIFE ITSELF?
HYDROGEN BONDS.
What is hydrogen bonding?
Attraction between partial positive and partial negative atoms involved in a polar covalent bond. Not a permanent physical bond, like covalent, but a weak electrical attraction. Weakest after London Forces.
What is cohesion?
Water bonding to each other.
What is adhesion?
Water bonding to something else (ex: holding your finger on one end of a straw).
What are London Forces?
Interactions between hydrophobic compounds, due to short-lived electrical imbalances, weak, shape important, (single electron jumping from one fat to another, this creates this intermolecular force). WEAKEST!
What is charge repulsion?
It forces molecules to be away from each other, keeps them from making contact. Charges can be neutralized, which stops repulsion. Ion bridges = Putting a negative in between two positive things, forming an ionic bridge.
What are steric effects?
Shape effects, shape affects how much two molecules can make contact and therefore associate with one another.
What are stereoisomers?
Same shape but mirror images.
What are summation effects?
All molecules have a myriad of forces acting within (and between) them. Behavior of a molecule is determined by the sum of these effects.
What is macromolecule behavior?
Behavior of the food in the kitchen largely due to the behavior of macromolecules. Techniques can be manipulated to get to desired end products (ex: changing the shape of albumin by heat, shape then changes the composition of the egg) ((denaturing protein)).
Why is using oil to cook meat beneficial?
High temperature, less time, cooks thoroughly, easier to get a better outcome this way.
What is happening when making ceviche molecularly?
Denaturing with an acid, H+ ions breaking apart bonds, attacking them and changing the shape of it, making it okay for us to eat; H+ ions are bonding and affecting the protein structure.
What is happening in jellies molecularly?
Protein molecules are meshing together and forming bonds, while this is occurring, water and other particles are getting trapped in the matrix and become immobile.
What is happening in brining?
Pulling water out (osmosis) and then salt breaks apart cell membranes, and then the liquid seeps back in and diffuses.
What does the reaction rate depend on?
The concentration of the “limiting reactant”, temperature and pH dependent ex: having one pound of cheese, five pounds of ham and ten pounds of bread, the limiting reactant is the one pound of cheese. Most reactions have enzymes to speed up their reactions rate.
What is equilibrium determined by?
The relative energies of the reactants and products.
What is activation energy?
Energy needed to form the activated complex.
Temperature effects on chemical reactions?
High temperatures speed reactions, low temperatures will slow them down.
pH effects on chemical reactions?
Some reactions require an addition or removal of a proton (H+), such as ceviche.
What are catalysts?
Speed reactions without being consumed by lowering the activation energy requirement. Meaning more collisions have the necessary energy.
What are enzymes?
Protein catalysts, reduces the amount of energy to get a reaction started.
What is a substrate?
A reactant that an enzyme works upon.
All enzymes are catalysts -
but not all catalysts are enzymes.
What is stoichiometry?
“Balancing equations”, relative proportions of reactants and products.
What is the composition of water?
One mole of oxygen to two moles of hydrogen, bent shape, only two covalent bonds and they are both polar (a mickey head, the middle is a negative oxygen, and the ears are two positive hydrogens).
What does molecular motion mean?
Atoms and molecules are constantly moving around, never stay in one spot, rotation and vibration as well also occur.
What is ionization?
One H breaks apart and becomes either an H+ or an H-. Oxygen pulls on one of them, then the other can dissociate and it’s free floating now.
Explain a liquid water structure vs an ice structure.
A liquid structure is going to be denser and more organized than the ice’s structure will be, this is why ice floats in water because it is less dense.
What is surface tension?
Hydrogen bonds taking the weight of something (fly on water example) and they disperse it. The fly is standing on the water because of surface tension.
What is heat capacity?
How much heat energy something can hold before going to another phase, water is not a good conductor but it has a high heat capacity, whereas copper conducts really well but it has a low heat capacity.
Why can’t we use certain fruits to make gelatin? (proteases)
The proteases found in these fruits cut the gelatin’s proteins into such small pieces that they are no longer able to tangle together and create a semisolid structure.
What does temperature do and how does it affect polyphenol oxidases?
If you raise the temperature of the environment in which a banana is, polyphenol oxidase (decompose) will occur even faster as the heat and increased moisture in the air encourages bacteria and mold growth and increases the rate of natural food enzyme reactions. If you put it in the freezer, you’re stopping the movement of water, therefore it will slow this process down.
Why do certain fruits brown after you cut them?
The cells of apples and other produce (e.g., pears, bananas, peaches, potatoes) contain an enzyme (called polyphenol oxidase or tyrosinase) that, when in contact with oxygen, catalyzes one step of the biochemical conversion of plant phenolic compounds to brown pigments known as melanins. You see the browning when the fruit is cut or bruised because these actions damage the cells in the fruit, allowing oxygen in the air to react with the enzyme and other chemicals.
