User:RyanPF/Bio Ch5

1. Explain how enzymes can be used to produce "stonewashed" jeans.
Washing denim in cellulase breaks down the polysaccharide ceullulose, the main component of cotton and other natural fibers. This softens the denim and releases the indigo dye, making it lighter.

energy
The capacity to perform work.

kinetic energy
Energy of motion

potential energy
Energy that an object has because of its position (i.e. an object on a shelf. If it falls, its energy is converted to kinetic energy)

conservation of energy
A principle that states that energy cannot be created or destroyed, only changed from one form to another.

3. Explain the relationship between heat and entropy.
All energy conversions generate some heat. Heat is less useful because it is difficult to use for useful work. Entropy is a measure of disorder, and it increases every time energy is converted.

Car
A car mixes gasoline with oxygen to create an explosive chemical reaction (combustion) that pushes the pistons to provide kinetic energy. The exhaust is mostly carbon dioxide and water.

Human
Cells also use oxygen to harvest chemical energy. Cellular respiration acts as combustion, and also produces heat. The result is ATP, energy for cellular work. The waste is also mostly carbon dioxide and water.

Efficiency
Cars only retain about 25% of the energy created in combustion. The rest is released as heat. The human process is more efficient because it operates more slowly and uses about 40% of the energy created for movement, and the heat energy released is used to keep the body warm.

5. Compare the amount of energy in a Calorie to that found in a kilocalorie. Which is most commonly used on food labels?
A calorie (small c) is a tiny unit of energy, not practical to use to describe the fuel content of food. A kilocalorie is 1,000 calories, and is actually what is called a "Calorie" (captial C) on the nutrition facts of food packaging.

6. Explain how ATP powers cellular work.
ATP has three phosphate groups, like the backbone of DNA or RNA. The triphosphate tail is the part that provides energy for cellular work. Each phosphate group is negatively charged, and repels each other. It's analogous to storing energy by compressing a spring. It releases the phosphate at the tip of the triphosphate tail and makes energy available to the working cells, leaving behind ADP. (two phosphate groups instead of three)

7. Describe the process of energy coupling in cells
Cellular work uses ATP, leaving behind ADP. The ADP can be restored to ATP (reloaded, compressed like a spring) by adding a phosphate group back to the ADP. The phosphate group comes from processes that yield energy, like the breakdown of food.

8. Explain why enzymes are needed in living organisms.
Metabolism is the sum of all chemical reactions in an organism. Almost no chemical metabolic reactions occur without help. Enzymes speed up chemical reactions.

9. Explain how enzymes are able to speed up specific chemical reactions.
An enzyme binds itself to reactant molecules and puts them under physical or chemical stress, making it easier to break their bonds and start a reaction.

10. Explain how inhibitors and poisons can affect enzyme activity.
They plug up the place where the substrates normally go (the active site) or they change the shape of the enzyme to where it can no longer fit the substrate.

diffusion vs. osmosis
Diffusion is the tendency of molecules to spread out. Osmosis is specifically water being transported.

passive transport vs. active transport
Passive requires no energy to move the molecules across the membrane. Active requires energy.

hypertonic vs. hypotonic
hypertonic has a high concentration of solute. Hypotonic has a low concentration of solute.

endocytosis vs. exocytosis
Exocytosis: proteins exit the cell. Endocytosis: proteins enter the cell.

phagocytosis vs. pinocytosis
In phagocytosis, the cell eats particles and packages it in a food vacuole. In Pinocytosis, the cell drinks droplets of fluid by forming tiny vesicles.

12. Explain how signal transduction pathways permit environmental stimuli to impact the activities inside of a cell.
It begins with the reception of a hormone into a specific receptor protein in the plasma membrane. The proteins and other molecules relay the signal and convert it to chemical forms that can function within the cell. This leads to chemical responses, like the activation of certain metabolic functions, and structural responses like the rearrangement of the cytoskeleton.

13. Explain how new enzymes can be produced by directed evolution.
Most enzymes are proteins, and proteins are encoded by genes. One ancestral gene randomly duplicates, and the two copies of that gene diverge over time via genetic mutation, eventually becoming two distinct genes which produce two distinct enzymes.

14. Explain how directed evolution and natural selection are similar and different.
They both result in the production of new enzymes and new functions. There is much less time in directed evolution. Directed evolution is controlled to achieve the researchers' purpose, while natural selection simply favors those best fit to survive.