Unit 1 (Chapter 4, Part 1)

Question 1

What is the study of individual cells and their interactions with each other?

Answer 1

Cell biology

Question 2

What is a theory that states that all organisms are made of cells, cells are the smallest units of living organisms, and new cells come from pre-existing cells by cell division?

Answer 2

Cell theory

Question 3

What are the four stages to understand the origin of cells?

Answer 3

Stage 1 - Nucleotides and amino acids were produced prior to the existence of cells.

Stage 2 - Nucleotides become polymerized to form RNA and/or DNA, and amino acids become polymerized to form proteins.

Stage 3 - Polymers became enclosed in membranes.

Stage 4 - Polymers enclosed in membranes acquired properties that are associated with living cells.

Question 4

What gave rise to organic molecules and eventually living cells?

Answer 4

Primordial soup

Question 5

What does prebiotic and abiotic mean?

Answer 5

Before Life and Without Life

Question 6

What is the medium formed by the slow accumulation of organic molecules in the early oceans over a long period of time prior to the existence of life?

Answer 6

Prebiotic soup

Question 7

What are the three widely debated ideas about the origin of life for Stage 1?

Answer 7

• Reducing Atmosphere Hypothesis
• Extraterrestrial Hypothesis
• Deep-sea Vent Hypothesis

Question 8

How many monomers are needed in polymers to store enough information to make a viable genetic system?

Answer 8

30-60

Question 9

What is the argument for organic polymers forming on the surface of clay?

Answer 9

Since hydrolysis competes with polymerization, many scientists believe polymers to form RNA, DNA, and proteins happened on land.

Additionally, it was previously shown in 2004, that polymers can also form in aqueous solutions with carbonyl sulfide (amino acids to peptides) under mild conditions in water.

Question 10

(Stage 3 - Membrane forming) What is the term used to describe the first nonliving structure that could have evolved into a living cell?

Answer 10

Protobiont

Question 11

What are the four key features scientists envisioned about protobionts?

Answer 11

1. A boundary, such as a membrane, separated the internal contents of the protobiont from the external environment.
2. Polymers inside the protobiont contained information.
3. Polymers inside the protobiont had catalytic functions.
4. The protobionts eventually developed the capability of self-replication.

Question 12

What are the droplets that form spontaneously from the association of charged polymers such as proteins, carbohydrates, or nucleic acids surrounded by water?

Answer 12

Coacervates (possible option where living cells evolved from) Theses are molecules surrounded by a skin of water with charges proteins and carbohydrates inside.

(Bonus) This term is related to a more similar cell today.

Liposomes - A hollow sphere of phospholipid filled with water. The membrane is a phospholipid bilayer.

Question 13

Which protobiont seems most similar to today’s cells?

Answer 13

A liposome is more similar to today’s cells, which are surrounded by a membrane that is composed of a phospholipid bilayer.

Question 14

What is the physical/chemical reason why phospholipids tend to form a bilayer?

Answer 14

Phospholipids are amphipathic molecules; they have a polar end (the head) and a nonpolar end (the two fatty acid tails). Phospholipids form a bilayer such that the heads interact with water, whereas the tails are shielded from the water. This is an energetically favorable structure.

Question 15

(Stage 4) What are the three key functions of RNA?

Answer 15

1. RNA has the ability to store information in its nucleotide base sequence.
2. Due to base pairing, its nucleotide sequence has the capacity for self-replication.
3. RNA can perform a variety of catalytic functions. The results of many experiments have shown that some RNA molecules can function as ribozymes–RNA molecules that catalyze chemical reactions.

Question 16

What is a ribozyme?

Answer 16

A biological catalyst that is an RNA molecule.

Question 17

Why is RNA so versatile?

Answer 17

Well, DNA has really no catalytic functions and proteins cannot replicate themselves. RNA can do both.

Question 18

What is the process that occurs when a chemical within a mixture has special properties or advantages that cause it to increase in amount? May have played a key role in the formation of an RNA world.

Answer 18

Chemical selection

Question 19

What is the process by which a population of molecules changes over time to become a new population with a different chemical composition?

Answer 19

Chemical evolution. Chemical selection results in this. (Much like natural selection in a population of animals)

Question 20

What is meant by the term chemical selection?

Answer 20

Chemical selection occurs when certain molecules, such as RNAs, have properties that provide advantages and therefore cause them to increase in number relative to other molecules in the same environment. (In the case of self-replication and the ability to form ribonucleotides)

Question 21

What is a hypothetical period on primitive Earth when both the information needed for life and the catalytic activity of living cells were contained solely in RNA molecules?

Answer 21

RNA world

Question 22

What was RNA world superseded by?

Answer 22

The RNA/DNA/Protein world

Question 23

What supports RNA/DNA/Protein world over just a RNA world based off of DNA?

Answer 23

DNA is much more stable and less likely to spontaneously break.

DNA would have relieved RNA of its storing role and would have had RNA the opportunity to do more functions like binding cofactors, modify bases, and bind peptides that might enhance catalytic function.

Question 24

How do scientists believe DNA came to be?

Answer 24

A process called reverse transcription where DNA is created by RNA using RNA as a template.

Ex. RNA sequence in the enzyme telomerase is used as a template to copy the ends of chromosomes, thus preventing progressive shortening of the chromosomes.

Question 25

How would proteins come into being in a RNA world? (4)

Answer 25

• RNA has a central role for synthesis of polypeptides
• mRNA provides information for a polypeptide sequence.
• tRNA (transfer RNA) molecules act as adaptors for the formation of polypeptides
• Ribosomes containing rRNA (ribosomal RNA) provide a site for polypeptide synthesis. rRNA within ribosomes acts as a ribozyme to catalyze peptide bond formation.

Question 26

What is a magnification tool that enables researchers to visualize the structures and inner workings of cells?

Answer 26

Microscope

Question 27

What is an image taken with the aid of a microscope?

Answer 27

Micrograph

Question 28

What are the three important parameters in microscopy?

Answer 28

Resolution

Contrast

Magnification

Question 29

What is resolution?

Answer 29

In microscopy, the ability to observe two adjacent objects as distinct from one another; a measure of the clarity of an image.

Question 30

What is contrast?

Answer 30

In microscopy, relative differences in the lightness, darkness, or color between adjacent regions in a sample.

Question 31

What is magnification?

Answer 31

The ratio between the size of an image produced by a microscope and the object’s actual size.

Question 32

What is the difference between a light microscope and a electron microscope?

Answer 32

A light microscope uses light for illumination while an electron microscope uses a beam of electrons for illumination.

Question 33

Why does a electron microscope better than a light microscope?

Answer 33

Because the wavelength of an electron beam is much shorter than the wavelength of visible light. This helps increase the resolution.

The limit of an electron microscope if typically around 2 nm, which is about 100 times better than a light microscope. A very good light microscope can resolve structures that are as close as 0.2 um, or micrometers

For comparison, for visibility, a fish egg is 1 mm. Mitochondria is 1 um, and atoms are 0.1 nm.

Question 34

Which type of microscope would you use to observe a virus?

Answer 34

Electron microscope

Question 35

What two types of electron microscopy have advanced our ability to understanding cell structure?

Answer 35

Transmission electron microscopy and scanning electron microscopy.

Question 36

What is a type of microscopy in which a beam of electrons is transmitted through a biological sample to form an image on a photographic plate or screen?

Answer 36

Transmission electron microscopy (TEM)

Question 37

What is a type of microscopy that utilizes an electron beam to produce an image of the three-dimensional surface of a biological sample?

Answer 37

Scanning electron microscopy (SEM)

Question 38

What is the primary advantage of SEM?

Answer 38

The primary advantage is that it gives an image of the 3-D surface of an object.