Origin and chemistry of life ch 2

Question 1

2.1 Describe the properties of water that are essential for life.

Answer 1

Properties of Water:
1) Water has a high specific heat capacity.
* Once heated, does not cool rapidly.
* Moderates the environment; protects from temperature
fluctuations
2) High heat of Vaporization
* Evaporation of water is important cooling mechanism
3) Unique Density
* Less dense in solid state; ice floats on water
other properties of water:
4) Water has a high surface tension.
* Provides ecological niche on surface of water
5) Excellent solvent – binds ions; regulates acids & bases
6) Performs chemical reactions (hydrolysis and condensation)
* Enzymes have evolved to speed up these reactions

Question 2

2.2. What are carbohydrates? Name the three classes of carbohydrates.

Answer 2

• they are sugar molecules
  Composed of C, H, and O usual ratio of 1C : 2H : 1O
  Function = energy (sugars) and structural elements (cellulose & chitin)

monosaccharides-
or simple sugars;glucose, fructose, galactose

disaccharides- Two simple sugars bonded together
Examples:
Maltose = glucose + glucose.
Sucrose = glucose + fructose.

polysaccharides- Many simple sugars joined together; form long chains (polymers) Empirical formula: (C6H12O5)n
* Starch = storage form of glucose in plants.
* Glycogen = storage form of glucose in animals
* Cellulose = structural carbohydrate in plants.
* Chitin = structural element in exoskeleton of
animals (also fungi cell walls)

Question 3

Four classes of organic molecules:

Answer 3

• Carbohydrates.
• Lipids.
• Proteins.
• Nucleic acids

Question 4

2.3 Describe the three main groups of lipids.

Answer 4

Triglycerides:
The “True” Fats
Major source of fuel for animals.
Composed of Glycerol + three fatty acid molecules
Saturated fatty acids:
* Every carbon in the chain holds two hydrogen atoms.
Unsaturated fatty acids:
* Have two or more carbon atoms joined by double bonds.

Phospholipids & Steroids:
Phospholipids and Steroids are components of cell membranes
* Phospholipids: resemble triglycerides; have a phosphate group which is charged and polar
* Steroids: ring-shaped biologically active molecules; serve signaling functions e.g. sex hormones
* Both are are amphiphilic – water soluble on one end &
insoluble at the other

Question 5

What are the three main groups of lipids?

Answer 5

• Triglycerides.
• Phospholipids.
• Steroids.

Question 6

What are the properties of water?

Answer 6

1) Water has a high specific heat capacity.
2) High heat of Vaporization
3) Unique Density
4) Water has a high surface tension.
5) Excellent solvent
6) Performs chemical reactions (hydrolysis and condensation)

Question 7

structure of protein
Spiral or pleat the primary structure;
stabilized by hydrogen bonds (e.g. alpha helix)

Answer 7

Secondary structure of a protein

Question 8

structure of protein
Linear sequence of amino acids
(polypeptide chain)

Answer 8

Primary structure of a protein

Question 9

structure of protein
Bend and fold secondary structure;
bonds between side groups produce complex, stable
structure.

Answer 9

Tertiary structure of a protein

Question 10

structure of protein
Proteins that contain more than one
polypeptide chain (e.g. hemoglobin).

Answer 10

Quaternary structure of a protein

Question 11

Protein Functions:

Answer 11

Structural components of cells (e.g., collagen).
- helps repair and build your body’s tissues, allows metabolic reactions to take place and coordinates bodily functions.
* Enzymes - Catalyze chemical reactions

Question 12

_________ _________ are complex polymeric molecules whose sequence of nitrogenous bases encodes the genetic information necessary for biological inheritance
-naturally occurring chemical compounds that serve as the primary information-carrying molecules in cells.

Answer 12

Nucleic acids

Question 13

How old is the earth?

Answer 13

4 billion years old

Question 14

Features of early earth:

Answer 14

Early earth; no oxygen; reducing environment
Atmosphere = simple compounds:
– Water vapor.
– Carbon dioxide (CO2).
– Hydrogen gas (H2).
– Methane (CH4).
– Ammonia (NH3).
– No free oxygen
Energy sources for chemical reactions.
– Lightening
– UV light.
– Heat from volcanoes.

Question 15

Early atmosphere and current atmosphere

Answer 15

Early atmosphere → strongly reducing; conditions conducive to prebiotic synthesis of life.

Current atmosphere → strongly oxidizing Strongly oxidizing; molecules for life cannot be
synthesized outside of cells.

Question 16

2.6 What is the significance of the Miller-Urey experiments?

Answer 16

-stimulated experimental work to test the hypothesis that organic compounds characteristic of life could be formed from the simpler molecules present in the prebiotic environment.
-successfully simulated the conditions thought to prevail on the primitive earth.
-Miller’s work stimulated many other investigators to repeat and to extend his experiment
-and it suggests that prebiotic synthesis on the primitive earth may have occurred under conditions not greatly different from those that Miller simulated
What it included:
-Circulated a mixture of:
* H2.
* H2O.
* CH4.
* NH3.
- Energy source: Electrical spark (lightening)
- In a week, 15% of the carbon in the mixture was converted to organic compounds such as: amino acids, urea, simple fatty acids

Question 17

_________ ______ ________ proposed the chemical evolution of life, prebiotic synthesis of small organic molecules.
-life arose gradually from inorganic molecules, with “building blocks” like amino acids forming first and then combining to make complex polymers

Answer 17

Oparin–Haldane hypothesis (1920s)

Question 18

2.7. Describe how chemical evolution could have formed polymers

Answer 18

In the second stage of chemical evolution, the simple organic molecules (such as amino acids) that formed and accumulated joined together into larger structures (such as proteins). The units linked to each other by the process of dehydration synthesis to form polymers.

Question 19

the simple organic molecules (such as amino acids) that formed and accumulated joined together into larger structures (such as proteins). The units linked to each other by the process of __________ ____________ to form polymers. hydrothermal vents(on slides)- help for polymers too

Answer 19

dehydration synthesis

Question 20

First enzymes could have been what?

Answer 20

RNA

Question 21

First cells would have been ____________, membrane-bound units capable of self-replication requiring nucleic acids

Answer 21

autonomous

Question 22

RNA has catalytic activity also known as ____________

Answer 22

ribozymes

Question 23

Earliest self-replicating molecules could have been_______.

Answer 23

RNA

Question 24

Prokaryotic oxygen-producing _____________
arose ~ 3 billion years ago; oxygen increases

Answer 24

cyanobacteria

Question 25

Explain the current hypothesis of the origin of a self-
replicating molecule

Answer 25

Self-Copying RNA. The RNA world hypothesis suggests that life on Earth began with a simple RNA molecule that could copy itself. The RNA world hypothesis suggests that life on Earth began with a simple RNA molecule that could copy itself without help from other molecules.

Question 26

2.9a What is endosymbiosis and how is this important in the evolution of eukaryotes?

Answer 26

1. A symbiotic relationship where one organism lives inside the other
2. The endosymbiotic theory explains how eukaryotic cells evolved
   *Mitochondria and plastids (e.g., chloroplasts) have own DNA.
   *Nuclear, plastid, and mitochondrial rRNAs different evolutionary lineages.
   *Plastid and mitochondrial ribosomal DNA closely related to bacterial DNA.
   *Plastids closest to cyanobacteria in structure and function.

Question 27

Symbiotic Origin of Eukaryotes
- symbiotic relationship where one organism lives inside the other

Answer 27

(Endosymbiosis):

Question 28

2.9b What is the Cambrian explosion?

Answer 28

-All Major Body Plans Evolve
- The Cambrian Period marks an important point in the history of life on Earth; it is the time when most of the major groups of animals first appear in the fossil record. This event is sometimes called the “Cambrian Explosion,” because of the relatively short time over which this diversity of forms appears.

Question 29

Eukaryote cells:

Answer 29

• Membrane-bound nucleus—“true nucleus”
• More DNA with chromatin that contains histones.
• Membrane-bound organelles in cytoplasm.