Midterm 2 Study Guide

Question 1

When did Earth start to form?

Answer 1

4.6 billion years ago

Question 2

When was the first evidence of photosynthetic cells?

Answer 2

3.2-2.5 billion years ago

Question 3

During what period was there a reducing atmosphere?

Answer 3

Precambrian Period

Question 4

What is a reducing atmosphere?

Answer 4

An atmosphere that contains compounds that remove oxygen from metals and other materials leaving little to no free oxygen

Question 5

What produced the oxygen in a reducing atmosphere?

Answer 5

Photosynthetic bacteria

Question 6

What are the two characteristics of the Precambrian Period?

Answer 6

1.) Life is mostly unicellular

2.) Reducing atmosphere where photosynthetic bacteria produced oxygen

Question 7

What is the Heterotroph Hypothesis?

Answer 7

Life on earth developed through gradual chemical evolution of carbon-based molecules in a “primordial soup”

In this hypothesis, earth’s atmosphere was reducing, which allowed biochemically important compounds to be produced abiotically and to be concentrated. Early cells could then feed on these compounds

(The first cells were heterotrophic and fed on organic molecules that were not produced by cells)

Question 8

Who proposed the Heterotroph HYpothesis?

Answer 8

Oparin

Question 9

When was the atmosphere reducing?

Answer 9

4.2 billion years ago to 2.5 billion years ago

Question 10

What did the rise of photosynthetic organisms do?

Answer 10

Change the atmosphere to oxidizing

This also ends the reducing atmosphere hypothesized to be suitable for the origin of life in the Heterotroph Hypothesis

Question 11

What molecules tend to be mainly present in a reducing atmosphere?

Answer 11

H2, NH3, H2S, H2O, CH4

Question 12

What molecules tend to be mainly present in an oxidizing atmosphere?

Answer 12

N2, O2, H2, CO2, NOx

Question 13

In order to support the Heterotroph Hypothesis, who tested whether or not small organic molecules could be formed abiotically under specified conditions?

Answer 13

Miller and Urey (1935) and Joan Oro (1954)

Question 14

What molecules were used in Miller and Urey’s experiment and what did they produce?

Answer 14

CH4 + NH3 + H2O + Energy

15% of the carbon in the system was used to produce organic materials and 5% of the materials produced are biochemically important

Question 15

What molecules were produced in Oro’s experiment and what did they produce?

Answer 15

HCN + NH3 + Energy

Produced adenine

Question 16

What are protocells?

Answer 16

Vesicles

Question 17

What are liposomes?

Answer 17

Small, fatty globules

Question 18

What are coacervate droplets?

Answer 18

Protein-based spheres that are common in solutions

Question 19

When can some properties associated with living organisms can emerge from nonliving organisms

Answer 19

When molecules interact and are organized into higher levels of order

Question 20

What are membranes made of?

Answer 20

Amphiphiles

Question 21

What are amphiphiles?

Answer 21

Molecules with parts that are hydrophilic and parts that are lipophilic (fat loving)

The hydrophilic head interacts with water solutes on the inside and outside of the cell

Hydrophobic/liphophilic tails are double layered