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Practice Short Answer Exam for Biology 191
Made just for you by Erika  - (Answer Guide to be posted Monday)
Short Answer Questions:
1.
Write the chemical formula for aerobic cellular respiration. Is this reaction endergonic
or exergonic?
C6H12O6 + 6 O2 -> 6 H2O + 6 CO2 + Energy
The reaction is exergonic because energy is released.
2. Write the chemical formula for photosynthesis. Is this reaction spontaneous or nonspontaneous?
6 H2O + 6 CO2 + Light -> 6 O2 + C6H12O6
The reaction is non-spontaneous since it needs an input of energy from light.
3. Define all of the variable in the following formula for ∆G = ∆H -T∆S
Change in free energy equals the change in enthalpy which is a measure of heat,
minus the change in the temperature multiplied by the enthalpy which is a measure of
disorder.
How do you know when a reaction is spontaneous or non-spontaneous based upon the
formula above?
Based upon the sign of ∆G: a positive ∆G is non-spontaneous, a -∆G is spontaneous.
4. What is the first law of thermodynamics? How about the second law?
1. Energy can neither be create nor destroyed, only transformed from one
form to another. (Conservation of energy)
2. Everything tends towards chaos.
5. What is an enzyme? What are the characteristics of enzymes?
Enzymes are proteins that are biological catalysts. They help to control rate of chemical
reactions. Enzymes lowers the activation energy barrier for a reaction by acting as a
catalyst. They promote favorable reactions. Enzymes participate in the reaction but they
are not consumed (they are recycled). They are very specific and highly regulated.
Enzymes names end in –ase for example, sucrase, which breaks down glucose and
fructose.
6. Referring to the diagram below, label ∆G and Ea activation energy of the catalyzed
pathway. Does this represent an endergonic or an exergonic reaction and why?
ΔG is labeled as ΔE in this diagram. Ea activation energy is the distance
between the dotted line and the top of the products reaches. This is an
endergonic reaction because an energy input was needed to go from lower
to higher energy.
7. What are the steps of cellular respiration and where do they occur in the cell? In which
step is the majority of ATP made?
1. Glycolysis – cytosol
2. Formation of Acetal Co-A – matrix of mitochonidria
Citric Acid Cycle – matrix of mitochonidria
3. Electron Transport Chain and Chemiosmosis – inner-membrane of
mitochondria, crystae
8. What are the two types of aerobic ATP formation?
Substrate-level and oxidative phosphorylation.
Substrate level phosphorylation occurs in glycolysis, and citric acid cycle.
Oxidative phosphorylation occurs with the electron transport chain.
9. What type of diffusion is osmosis? Passive or Active
It is a passive process, moving from a high to low concentration, but really it is it’s
very own kind of diffusion specific to water.
Draw an example of osmosis through a cell membrane: See worksheet on blog.
10. In what type of solution is an animal cell ‘happiest’? In what type of solution in a plant
cell ‘happiest’? (Hypotonic / Isotonic / Hypertonic) Why?
Happiest isn’t a good scientific word I should have said: what are the ideal
conditions for the animal and plant cells.
An animal cell is ‘happiest’ in an isotonic solution, while a plant cell is ‘happiest’
in a hypotonic solution.