PS 1

Question 1

Why does firewood stacked beside the fireplace not undergo spontaneous combustion to its much more stable products?

Answer 1

The thermal energy in the wood is not sufficient to overcome the activation energy.

Question 2

A bacterial spore is metabolically inert, and may remain so for years. Spores contain no measurable ATP, exclude water, and consume no oxygen. However, when the spore is transferred into an appropriate liquid medium, it germinates, makes ATP, and begins cell division within an hour. Is the spore dead or alive? Why?

Answer 2

Spores are alive because they can transition from a state of being metabolically inert under harsh environmental conditions to an actively growing state when conditions improve.

Question 3

What does the second law of thermodynamics state about energy?

a) The movement of energy can only occur in systems with a low level of randomness.
b) When a hot object contacts a cold object, coldness moves from the cold object into the hot object.
c) Given the opportunity, energy disperses from areas of high energy to areas of low energy.
d) Energy destruction releases heat, whereas energy production results in heat absorption.

Answer 3

c) Given the opportunity, energy disperses from areas of high energy to areas of low energy.

Question 4

Suppose that a rare DNA replication error results in the duplication of a single gene, giving the daughter cell two copies of the same gene. How does this change favor the acquisition of a new function by the daughter cell?
Select all that apply:
A) The cell can make additional proteins, which then undergo alterations and can give rise to new functions.
B) The copy has already‑formed domains with biological activity, so new functions do not need to evolve de novo.
C) The two genes can combine to form a new gene that encodes a protein with a new, additional function.
D) The duplicated gene increases the rate at which the cell can perform the function encoded by the original gene.
E) The copy can undergo a gain‑of‑function or loss‑of‑function mutation without altering the original gene’s function.

Answer 4

B & E are correct
B) The copy has already‑formed domains with biological activity, so new functions do not need to evolve de novo.

E) The copy can undergo a gain‑of‑function or loss‑of‑function mutation without altering the original gene’s function.

Question 5

Arabidopsis thaliana, a plant, has twice as many genes as humans. Is Arabidopsis more biochemically sophisticated than humans?
A) Yes, a larger number of genes indicates a more diverse set of proteins.
B) Yes, Arabidopsis has added genes that synchronize nuclear, mitochondrial, and chloroplast functions.
C) No, since Arabidopsis is a plant, chloroplast genes are part of the total number.
D) No, the number of genes does not necessarily indicate the number of unique proteins.

Answer 5

D) No, the number of genes does not necessarily indicate the number of unique proteins.

Question 6

Distinguish between a phototroph and chemotroph; an autotroph and heterotroph

Answer 6

phototroph: utilize/harvest the free energy from sunlight (photosynthesis)
chemotroph: cannot capture free solar energy, must rely on oxidation of glucose organic compounds obtained by other organisms
autotroph: carbon source comes from CO2
heterotroph: carbon source comes from organic compounds