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Chem 115 Post-Exam 3
| Question | Answer |
|---|---|
| What are the basic components of the DNA nucleotide | Phosphate; sugar; base (in that order) |
| What are the complimentary base pairs in DNA? | A-T / C-G |
| DNA exists as a double helix shape with two helices held together through what? | Hydrogen bonding |
| Which is stronger? A-T or C-G | C-G has 3 H bonds! while A-T has 2 |
| What is different between DNA and RNA? | RNA's sugar is ribose & Has U instead of T |
| Why can DNA replicate itself by separating its strands during cell division? | Complementary pairing |
| Describe the 3 main components of the DNA structure | 1. Helix 2. Sugar-phosphate backbone 3. Rungs of very specific base pairs held together by h-bonds |
| What is the complementary sequence of RNA to this DNA sequence? ACGTTC | UGCAAG |
| What is translation | Converting information from nucleotide sequence to amino acid sequence in a protein |
| A 3-base sequence is called what? What does it indicate? | Codon - indicated specific amino acids |
| Steps of translation: | 1. portion of DNA unwinds 2. mRNA reads and codes (transcribes)... then goes out 3. tRNA (transfer) links amino acids in correct order ... comes in |
| What drives function | SHAPE |
| DNA and RNA a are polymers of what | nucleotides |
| What's the difference between and addition reaction and a condensation reaction | Addition has no products; Condensation produces polymer and H2O |
| Characterized by repetition of a group of atoms that are bonded to each other | Polymer |
| What is the repeat unit in protein? In DNA? | amino acid; nucleotide |
| Is the cell membrane a polymer? Why/Why not? | NO; Not covalently bonded |
| What are the three shapes of polymers | Linear; Branched; Cross linked |
| What kind of materials are linear polymers | strong |
| Difference between thermoset and thermoplastic polymers | Thermoset: HAS crosslinks; very rigid; can't move of degrades in heat Thermoplastic: NO crosslinks; Heat melts and then reshapes |
| What is required for an addition reaction | A double or triple bond |
| How does addition stop | 2 free radicals run into each other and bond |
| Two monomers react and form a chain and a small second molecule | Condensation polymerization |
| Is a protein an addition or a condensation polymer? | Condensation |
| What are three biopolymers? | DNA, protein, and cellulose |
| How many unit cells share an atom located at a corner of a unit cell | 8 |
| How many unit cells share an atom located on an edge of a unit cell | 4 |
| How many unit cells share an atom located on a face of a unit cell | 2 |
| How many atoms are in a simple cubic unit cell | 1 |
| How many atoms are in a body centered cubic unit cell | 2 |
| How many atoms are in a face-centered cubic unit cell | 4 |
| What are the five major types of crytalline solids | 1. covalent/ network 2. ionic 3. molecular 4. atomic (noble gasses; dispersion only) 5. metallic |
| Density = | Mass/ volume |
| What type of solids lack an ordered internal structure | amorphous solids |
| Solids in which atoms, ions, or molecules are arranged in a repeating pattern | crystalline solids |
| The collection of all the points within a crystal that have identical environments is called what | space lattice |
| What is the unit cell arrangement of NaCl | Face centered cubic lattice of anions; cations in octahedral holes |
| What two factors determine ionic structures? | 1. Size of the ions 2. Ratio of positive to negative ions |
| Which type of packing is each? 1. ababababab... 2. abcabcabcabc... | 1. Hexagonal closest packing 2. cubic closest packing |
| What type of holes do small cations occupy? Large cations? | Small - tetrahedral Large - octahedral |
| The color of gold nanoparticles in solution depends on what | size and shape |
| What is an n-type semiconductor | extra negative; more valence electrons |
| What is a p-type semiconductor | less valence electrons; empty orbitals act as positive holes |
| As the number of atoms in a solid increase, the amount of valence energy levels ________-. | increases |
| The filled band at the bottom | valence band |
| an empty band at the top | conduction band |
| What is the gap in energy between the conduction band and valence band in band theory | Band gap |
| What does the band gap determine | electrical properties/ conductivity |
| It is useful for solar cells to be responsive to light in the visible portion of the spectrum. Which would be most useful? a. bandgap = 5.5E-19 J b. bandgap = 1.5E-19 J c. bandgap = 1.2E-18 J | A... E=hc/wavelenth |
| What are nanomaterials | Materials where the particle dimensions are on the 10E-9 (nm) scale |
| What is adding small amounts of other elements to increase or decrease the number of valence electrons in the bands | doping |
| What are some applications of nanomaterials | cancer/biomedical, electronic devices, drug delivery, clothing |
| Adding a certain organic group to a nanoparticle | funcitonalizing |
| _____________result when large number of atoms combine to form crystal | Energy bands |
| Power(w) = ?? | energy(j)/Time (S) |
| What does it mean to use solar energy in a passive way? | allowing solar radiation to be captured as heat which is then released as needed |
| What does it mean to use solar energy in an active way? | allowing solar radiation to strike a solar cell which converts it to an electric current |
| What are intrinsic semiconductors? | The PURE crystalline material has semiconducting properties |
| What are extrinsic semiconductors? | The material is DOPED with a small amount of impurity of a similar material so that it may conduct |
| What does doping do to the band gap | Decrease |
| What is a p-type doped semiconductor | Doped with an element with fewer electrons; provides positive charge |
| What is an n-type doped semiconductor | Doped with an element with more electrons; provides negative charge |
| What is the Fermi level | average energy of unpaired electrons |
| Put n-type and p-type material together to get a __________ | diode |
| What is an LED and what does it stand for? | Light Emitting Diode; p-n jjunction |
| For an LED: ___________in, ____________out | Electricity in, light out |
| For a solar cell: ______________ in, _________out | Light in, electricity out |
| There is more/less than enough solar energy striking the planet to meet our planet's energy demands | MORE |
Created by:
jkmccord11
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