Unit 1 (Chapter 4, Part 1) Flashcards
What is the study of individual cells and their interactions with each other?
Cell biology
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?
Cell theory
What are the four stages to understand the origin of cells?
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.
What gave rise to organic molecules and eventually living cells?
Primordial soup
What does prebiotic and abiotic mean?
Before Life and Without Life
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?
Prebiotic soup
What are the three widely debated ideas about the origin of life for Stage 1?
- Reducing Atmosphere Hypothesis
- Extraterrestrial Hypothesis
- Deep-sea Vent Hypothesis
How many monomers are needed in polymers to store enough information to make a viable genetic system?
30-60
What is the argument for organic polymers forming on the surface of clay?
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.
(Stage 3 - Membrane forming) What is the term used to describe the first nonliving structure that could have evolved into a living cell?
Protobiont
What are the four key features scientists envisioned about protobionts?
- A boundary, such as a membrane, separated the internal contents of the protobiont from the external environment.
- Polymers inside the protobiont contained information.
- Polymers inside the protobiont had catalytic functions.
- The protobionts eventually developed the capability of self-replication.
What are the droplets that form spontaneously from the association of charged polymers such as proteins, carbohydrates, or nucleic acids surrounded by water?
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.
Which protobiont seems most similar to today’s cells?
A liposome is more similar to today’s cells, which are surrounded by a membrane that is composed of a phospholipid bilayer.
What is the physical/chemical reason why phospholipids tend to form a bilayer?
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.
(Stage 4) What are the three key functions of RNA?
- RNA has the ability to store information in its nucleotide base sequence.
- Due to base pairing, its nucleotide sequence has the capacity for self-replication.
- 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.
What is a ribozyme?
A biological catalyst that is an RNA molecule.
Why is RNA so versatile?
Well, DNA has really no catalytic functions and proteins cannot replicate themselves. RNA can do both.
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.
Chemical selection
What is the process by which a population of molecules changes over time to become a new population with a different chemical composition?
Chemical evolution. Chemical selection results in this. (Much like natural selection in a population of animals)
What is meant by the term chemical selection?
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)
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?
RNA world
What was RNA world superseded by?
The RNA/DNA/Protein world
What supports RNA/DNA/Protein world over just a RNA world based off of DNA?
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.
How do scientists believe DNA came to be?
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.
How would proteins come into being in a RNA world? (4)
- 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.
What is a magnification tool that enables researchers to visualize the structures and inner workings of cells?
Microscope
What is an image taken with the aid of a microscope?
Micrograph
What are the three important parameters in microscopy?
Resolution
Contrast
Magnification
What is resolution?
In microscopy, the ability to observe two adjacent objects as distinct from one another; a measure of the clarity of an image.
What is contrast?
In microscopy, relative differences in the lightness, darkness, or color between adjacent regions in a sample.
What is magnification?
The ratio between the size of an image produced by a microscope and the object’s actual size.
What is the difference between a light microscope and a electron microscope?
A light microscope uses light for illumination while an electron microscope uses a beam of electrons for illumination.
Why does a electron microscope better than a light microscope?
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.
Which type of microscope would you use to observe a virus?
Electron microscope
What two types of electron microscopy have advanced our ability to understanding cell structure?
Transmission electron microscopy and scanning electron microscopy.
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?
Transmission electron microscopy (TEM)
What is a type of microscopy that utilizes an electron beam to produce an image of the three-dimensional surface of a biological sample?
Scanning electron microscopy (SEM)
What is the primary advantage of SEM?
The primary advantage is that it gives an image of the 3-D surface of an object.
