Final Review Answers
BIOCHEMISTRY
Chapter 3 Water and the Fitness of the Environment
- The slightly negative regions of one molecule are attracted to the slightly positive regions of nearby molecules, forming a hydrogen bond.
- Expansion upon freezing causes water to be less dense than liquid water.
- Transport of water and dissolved nutrients in a plant.
- Hydrogen bonds repel air molecules creating a skin between the water and the air.
- By absorbing heat from air that is warmer and releasing the stored heat to air that is cooler.
6. Heat depends in part on the matter’s volume, while temperature is the average kinetic energy of molecules, regardless of volume.
7. Water has a high specific heat because of the hydrogen bonds acting on the molecules. These hydrogen bonds can "store" thermal energy, and this allows water to absorb or release a lot of heat without a large change in temperature.
8. Water's cohesive behavior, its ability to moderate temperature, its expansion upon freezing, and its versatility as a solvent
9. Hydrogen bonds form, break and reform. Liquid water is denser than the solid
10. Clinging to walls of the cell
11. Can absorb or release a large amount of heat with only slight change in own temp
12. Heat passes from warmer to the cooler until the two are the same temperature
13. Large body of water can absorb and store a huge amount of heat from the sun in the daytime and during summer while warming up only a few degrees - at night and during winter, the gradually cooling water can warm the air
14. Presence of sulfur oxides and nitrogen oxides in the atmosphere that react with water to form strong acids
15. Accepting hydrogen ions from the solution when they are in excess and donating hydrogen ions to the solution when they have been depleted
16. Can damage life in lakes and streams, washes away calcium and magnesium ions
- Water’s high heat of vaporization moderates climate. Much of the sun’s heat absorbed by tropical oceans is used for the evaporation of surface water. As moist tropical air moves to the poles, water vapor condenses to form rain, releasing heat.
- Water is an effective solvent because it readily forms hydrogen bonds with charged and polar covalent molecules
- They form hydrogen bonds with water.
- Their molecules are too large.
- Vaporization occurs when a molecule moves fast enough to overcome the attraction of other molecules in the liquid
22. Much of the energy is used to disrupt hydrogen bonds, not speed up the movement of water molecules.
23. Heat must be absorbed to break hydrogen bonds and heat must be released to form hydrogen bonds.
- The heat of vaporization is high because hydrogen bonds must be broken before a water molecule can evaporate from the liquid.
- Living things are made of primarily water, so they resist changes in temperature better than they would if composed of a liquid with a lower specific heat.
Chapter 5 Macromolecules
1) Structure: composed of atoms of carbon, hydrogen and oxygen in a ratio of 1:2:1.
Function: Short-term energy storage and structural support in cells (such as cellulose in cell wall).
2) Structure: structures vary but they all possess large number ofC - H bondswhich make them non-polar.
Function: energy storage, also function as structural components in the cell (phospholipid bi-layer of cell membranes).
3) Structure: amino acids joined by dehydration synthesis that make up chains which are hundreds of amino acids long.
4) Structure: made of nucleotides (nitrogenous base: pyrimidine or purine, 5 carbon ribose sugar, phosphate group). Double helix.
Function: Serve as information-carrying molecules or, in the case of some RNA molecules, catalysts.
5) Caused by the breaking of hydrogen bonds within enzyme structure.High/low temperatures, strong acidity or alkalinity, and salinity.
6) Carbon, hydrogen, oxygen, nitrogen, phosphorus.
7) Carbon, hydrogen, oxygen
8) The double bond gives unsaturated fatty acids a bend in the methylene chain. Have as many hydrogen bonded to their carbons as possible allowing no space for fluidity.
9) Monomers make up polymers and polymers make up macromolecules.
10) Molecule is broken down into two parts by the addition of H2O. One part of the parent molecule gains a hydrogen ion (H + ) from the H2O. The other halve takes the remaining hydroxyl group (OH − ).
11) 2monomers joined by H2O. One monomer has ahydroxyl groupon one end (OH) and the other has hydrogen (H) on the end facing the other monomer. When OH and H are adjacent to each other, H2O forms, and comes out as a product.
12) Hydrophilic heads are polar (bond shared unequally) so they are attracted to H2O which is also polar. Hydrophobic tails are non-polar so they are repelled from water (no difference in electronegativity).
13) Enzymes are catalysts. Catalyst is asubstance that has the ability to increase the rate of a chemical reaction, andis not changed or destroyed by the chemical reaction that it accelerates.
14) Primary, secondary, tertiary, quaternary.
15) Composed of an amino group, R (variable group), and an OH – hydroxyl group.
16) Composed of nitrogenous base: pyrimidine or purine, 5 carbon ribose sugar, phosphate group.
17) 20 types of amino acids differ by the composition of the R-group.
18) Purines: A,G Pyrimidines: C,T,U
19) Adenine, Guanine, Cytosine, Thymine, Uracil
20) Structure: Composed of 3 fatty acids bonded to a glycerol.
Function: Store energy (fatty acids contain most of the energy).
21) Isomers are molecules with identical formulas but different structures.
22) Monosaccharides. Glucose, fructose, galactose.
23) Amino acids. (Any of the 20 main amino acids)
24) Nucleotides. DNA and RNA.
25) Capable of forming 4 bonds.
Chapter 6 Metabolism
1. Substrate.
2. Energy coupling, ATP.
3. Mechanical work: beating of cilia, contraction of muscle cells, and movement of chromosomes during cellular reproduction. Transport work: the pumping of substances across cell membranes against the direction of spontaneous movement. Chemical work: pushing of endergonic reactions that would not occur spontaneously, such as the synthesis of polymers from monomers.
4. Energy can be transferred and transformed, but it cannot be destroyed. Thermodynamics is the study of the energy transformations that occur in a collection of matter.
5. Every energy transfer or transformation increases entropy of the universe. Entropy is a measure of disorder or randomness.
6. Anabolic, consume, catabolic, release.
7. The totality of an organism’s chemical reactions.
8. Free energy is the portion of a system’s energy that can perform work when temperature is uniform throughout the system (e.g. In a living cell).
9. A competitive inhibitor mimics the substance and competes for the active site, a noncompetitive inhibitor binds to the enzyme at a location away from the active site, but alters the conformation of the enzyme so that the active site is no longer fully functional.
10. Cofactor.
11. Temperature, pH.
12. Feedback Inhibition.
13. Induced fit is the slight change in shape of the active site of an enzyme as it embraces its substrate.
14. Allosteric enzyme, allosteric.
15. Catalyst, enzyme.
16. Free energy of Activation, Activation energy (or vice versa)
17. Active site.
18. Kinetic energy, potential energy.
19. The study of how organisms manage their energy resources.
20. The system is the matter under study. The surroundings are everything outside the system, the rest of the universe.
21. More, less, greater, less, more, less.
22. Release, gain.
23. The system’s total energy, its entropy.
24. A cell can maintain disequilibrium because it is an open system. Constant flow of materials in and out of the cell keeps the metabolic pathways from ever reaching equilibrium and the cell continues to do work throughout its life.
25. Sunlight
CELLS
Chapter 7 Cells
1. A—Cell walls exist in plant cells and prokaryotic cells, but not animal cells. They function to shape and protect cells.
2. D—The lysosome acts like the stomach of the cell. It contains enzymes that break down proteins, lipids, nucleic acids, and carbohydrates. Absence of these enzymes can lead to storage disorders such as Tay-Sachs disease.
3. B—The mitochondrion is the power plant of the cell. This organelle specializes in the production of ATP and hosts the Krebs cycle and oxidative phosphorylation.
4. C—The ribosome is an organelle made in the nucleolus that serves as the host for protein synthesis in the cell. It is found in both prokaryotes and eukaryotes.
5. D—The fluid mosaic model says that proteins can extend all the way through the phospholipid bi-layer of the membrane, and that these proteins are of various sizes and lengths.
6. B—Answer choice B is the definition of active transport, which requires the input of energy. Facilitated diffusion (answer choice E), simple diffusion (answer choices A and D), and osmosis (answer choice C) are all passive processes that do not require energy input.
7. C—Prokaryotes do not contain many organelles, but they do contain cell walls.
8. D—This is the description of the smooth endoplasmic reticulum. I know that this is a tricky question, but I wanted you to review the distinction between the two types of endoplasmic reticulum.
9. C—Microtubules play an enormous role in cell division. They make up the spindle apparatus that works to pull apart the cells during mitosis (Chapter 5). A loss of microtubules would cripple the cell division process. Actin fibers (answer choice D) are the building blocks of microfilaments (answer choice A), which are involved in muscular contraction. Keratin fibers (answer choice E) are the building blocks of intermediate filaments (answer choice B), which function as reinforcement for the shape and position of organelles in the cell.
10. E—Lipids are the only substances listed that are able to freely diffuse across selectively permeable membranes.
11. A
12. C
13. B
14. A
15. D
16. E
17. A
18. B
19. Ea
20. A
21. C
22. D
23. C
24. A
25. E
26. B
Chapter 8 Cell Transport
1. The solution with a lower solute concentration is hypotonic. The solution with the higher solute concentration is hypertonic. Solutions of equal solute concentration are said to be isotonic.
2. Facilitated diffusion is still passive transport because although it increases the rate of diffusion, the solute is still moving down a concentration gradient and energy is not used.
3. Proton pumps actively transports hydrogen ions (protons) out of the cell. It is the main electrogenic pump of plants, bacteria, and fungi.
4. It is a mechanism in which a single ATP-powered pump transports a specific solute can indirectly drive the active transport of several other solutes. Example: An ATP driven pump pumps H+ on one side of the membrane, creating a concentration gradient. As H+ leaks back across the membrane through specific transport proteins, it escorts other substances (such as sucrose) into the cell.
5. Osmosis is the movement of water through the membrane. It is passive transport. When extra water accumulates on one side, the osmotic pressure increases.
6. Water will move into the cell. The cell will swell up and become either turgid (plants) or lysed (animals).
7. Transport proteins are specific for the substances they transport. Thus, the numbers and kinds of different transport proteins embedded in the membrane affect its permeability to various substances.
8. It is selectively permeable meaning that some substances can pass through but others cannot. It also maintains homeostasis. The cell survives by preventing its interior from mixing with a watery environment outside.
9. It is arranged in a lipid bilayer. The phospholipid structure consists of a hydrophilic head (polar) that attracts water and a hydrophobic tail (non polar fatty acid chain) that repels water.
10. Endocytosis is when larger molecules enter as the membrane surrounds the substance. Exocytosis is the removal of cell waste vacuoles and gland secretions through the cell membrane.
11. Pinocytosis is the intake of liquids. Phagocytosis is the intake of solids. Receptor mediated endocytosis enables cells to acquire large quantities of specific substances.
12. Transport, enzymatic activity, signal transduction, intercellular joining, cell-cell recognition, and attachment to the cytoskeleton and extracellular matrix.
13. Particle size/pore size, molecular weight, solubility of H2O, concentration of solvent/solute, temperature, pressure, organic solvents/lipid solubility, and surface area/volume.
14. Membrane proteins are dispersed and individually inserted into the phospholipid bilayer, with only their hydrophilic regions protruding far enough form the bilayer to be exposed to water. This molecular arrangement would maximize contact of hydrophilic regions of proteins and phospholipids with water. According to this model, the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids.
15. Peripheral proteins are under the phospholipid bilayer, while integral proteins are inscribed in the bilayer. Integral proteins pass entirely through the lipid bilayer of the plasma membrane and have domains that go from the outside of the cell to the cytoplasm inside the cell. While peripheral proteins are only on the one side of the lipid bilayer, either the outside of the cell or the cytoplasmic side inside the cell, but not both.
16. The sodium-potassium pump pumps ions against steep concentration gradients. The pump oscillates between two conformation states in a pumping cycle that translocates three Na + ions out of the cell for every two K+ ions pumped into the cell. ATP powers the changes in conformation by phosphorylating the transport protein (transferring a phosphate group to the protein).
17. Some transport proteins function by having a hydrophilic channel that certain molecules use as a tunnel through the membrane. Other transport proteins hold onto their passengers and physically move them across the membrane. In both cases the transport protein is specific for the substances it moves.
18. The lipid bilayer forms non-polar interior zone. Therefore, polar molecules (glucose, amino acids, ions, cell wastes) cannot pass through because they are repelled by the non-polar tails. *Passage of these molecules requires certain membrane proteins.
19. They distinguish one cell from another and are involved in cell-cell recognition.
20. They are water channel proteins that facilitate massive amounts of diffusion of water.
21. Gated channels are proteins that open or close upon a stimulus, which can be electrical or chemical. If chemical, it is a substance other than the one to be transported. For example, stimulus of a nerve cell by neurotransmitter molecules opens gated channels allowing sodium ions into the cell.