Origin of life, cell metabolism, cellular processes, thermodynamics, organelle structure and function, mitosis/meiosis, cell structure Flashcards
What is the Primordial soup?
Origin of life theory.
- Early Earth had a chemically reducing atmosphere.
- This atmosphere, exposed to energy in various forms, produced simple organic compounds (“monomers”).
- These compounds accumulated in a “soup”, which may have been concentrated at various locations (shorelines, oceanic vents etc.).
- By further transformation, more complex organic polymers – and ultimately life – developed in the soup.
What is the Primordial soup?
Origin of life theory.
- Early Earth had a chemically reducing atmosphere.
- This atmosphere, exposed to energy in various forms, produced simple organic compounds (“monomers”).
- These compounds accumulated in a “soup”, which may have been concentrated at various locations (shorelines, oceanic vents etc.).
- By further transformation, more complex organic polymers – and ultimately life – developed in the soup.
What type of monomers were produced in the Miller-Urey experiment?
Formation of organic molecules spontaneously from inorganic precursors: methane, amonia, and hydrogen gasses were used to form amino acid monomers.
What is the most crucial challenge unanswered by the primordial soup theory?
how the relatively simple organic building blocks polymerise and form more complex structures, interacting in consistent ways to form a protocell.
What is the Electric Spark Theory?
Origin of Life Theory.
Miller demonstrated how an electric spark (simulating lightening) passed through simple inorganic gasses said to resemble the conditions of the early earth, resulted in the formation of amino acids, the basic building blocks of most living tissues
Community Clay
The first molecules of life might have met on clay, an idea by Cairns-Smith. These surfaces might not only have concentrated these organic compounds together, but also helped organize them into patterns much like our genes do now. Cairns-Smith suggests that mineral crystals in clay could have arranged organic molecules into organized patterns. After a while, organic molecules took over this job and organized themselves.
Community Clay
The first molecules of life might have met on clay, an idea by Cairns-Smith. These surfaces might not only have concentrated these organic compounds together, but also helped organize them into patterns much like our genes do now. Cairns-Smith suggests that mineral crystals in clay could have arranged organic molecules into organized patterns. After a while, organic molecules took over this job and organized themselves.
Chilly Start
Ice might have covered the oceans 3 billion years ago, as the sun was about a third less luminous than it is now. This layer of ice, possibly hundreds of feet thick, might have protected fragile organic compounds in the water below from ultraviolet light and destruction from cosmic impacts. The cold might have also helped these molecules to survive longer, allowing key reactions to happen.
RNA World
Origin of life Theory.
The self-replicating ribonucleic acid (RNA) molecules were precursors to all current life on Earth. Later DNA and proteins succeeded this “RNA world,” because they are more efficient. It is generally accepted that current life on Earth descends from an RNA world, although RNA-based life may not have been the first life to exist.The question still remains how RNA got here in the first place. And while some scientists think the molecule could have spontaneously arisen on Earth, others say that was very unlikely to have happened.
Other nucleic acids other than RNA have been suggested as well, such as the more esoteric PNA or TNA.
Panspermia
Origin of life Theory.
Perhaps life did not begin on Earth at all, but was brought here from elsewhere in space, a notion known as panspermia. For instance, rocks regularly get blasted off Mars by cosmic impacts, and a number of Martian meteorites have been found on Earth that some researchers have controversially suggested brought microbes over here, potentially making us all Martians originally. Other scientists have even suggested that life might have hitchhiked on comets from other star systems. However, even if this concept were true, the question of how life began on Earth would then only change to how life began elsewhere in space
Community Clay
Origin of life Theory.
The first molecules of life might have met on clay, an idea by Cairns-Smith. These surfaces might not only have concentrated these organic compounds together, but also helped organize them into patterns much like our genes do now. Cairns-Smith suggests that mineral crystals in clay could have arranged organic molecules into organized patterns. After a while, organic molecules took over this job and organized themselves.
Deep-Sea Vents/Hot Thermal Vents
Origin of life Theory.
The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents, spewing key hydrogen-rich molecules.
The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents, spewing key hydrogen-rich molecules. Their rocky nooks could then have concentrated these molecules together and provided mineral catalysts for critical reactions. Even now, these vents, rich in chemical and thermal energy, sustain vibrant ecosystems.
The mineral Pyrite, (Fe-Sulfide) which occurs in great abundance around deep-sea hydrothermal vents, have crystal surfaces that could attract phosphate complexes contained in many organic molecules, particularly nucleic acids. These organo-phosphate compounds could line up in close order on the pyrite surface. The crowding together of these molecules may eventually cause polymerization via organic bonds. Once polymerized, these new organic complexes could detach from their pyrite template and become free organic molecules. In this way, nucleic acids and even cell membranes may have evolved.
Deep-sea hydrothermal vents are known to be the home of primitive Archaebacteria which live on H2S, on CH4 or in hot salty springs. The primitive Archaebacteria may represent the earliest life forms on earth.
The origin of life time line
- Life on earth probably didn’t begin until 3.8 - 3.5 billion years ago when the planet had cooled enough such that water was able to condense from the primitive atmosphere.
- The oldest known life forms were cyanobacteria (blue-green algae) whose fossils are preserved as tiny filaments in rocks about 3.5 b.y. old. Thus, the earth was already 1 billion years old before the first signs of life appeared.
- Once established, the early life forms continued as simple, unicellular bacteria and cyanobacteria over the next 1.5 b.y.
- The first multicellular animals did not appear in the fossil record until 600-700 m.y. ago, almost 3 b.y. after the first evidence of life.
What was the early life’s atmosphere like?
The earth’s present atmosphere is too oxidizing and corrosive to allow simple organic compounds to combine into more complex molecules. A reducing, oxygen poor environment is required.
What was the early life’s earth atmosphere like?
The earth’s present atmosphere is too oxidizing and corrosive to allow simple organic compounds to combine into more complex molecules. A reducing, oxygen poor environment is required.
When did the earth’s atmosphere become oxidizing?
The earth’s atmosphere 3.5 b.y. ago was rich in CO2, methane, ammonia and N2, but not free O2. There also was no ozone layer back then, so the earth was constantly bombarded by ultraviolet radiation that helped catalize the breaking of bonds in simple organic compounds to form more complex molecules.
What did Darwin suggest about early life’s atmosphere?
He suggested that organic compounds that were the precursors of life must have formed in a warm pond containing ammonia and phosphoric salts that were exposed to light, heat and electricity.
What is required to form C-H compounds? (Origin of life)
A reducing (anarobic) environment is required to form C-H compounds. Any free O2 would prevent this by immediately oxidizing carbon to CO2 or CO32+
What organic compounds were formed in the Urey-Miller experiment?
The organic compounds produced included cyanide (HCN), formaldehyde (H2CO) and small quantities of four amino acids. Later experiments produced the 12 most common amino acids of the 20 known to occur in life.
From fossil evidence, what are the two groups of early life on earth?
The oldest fossils show that life had already split into two groups by 3.5 b.y. ago. One group, the Eubacteria, include true bacteria plus cyanobacteria. The other group comprised the Archaebacteria which can live in extremely hot, anoxic water and include microbes that feed off sulfur compounds or methane.
When did Eukaryotes appear on earth? And what might have caused their appearance?
By 1.8 b.y. ago, atmospheric oxygen released from photosynthesis of cyanobacteria reached 1% of the present level.
Aeraobic bacteria developed while anaerobic bacteria sought niches within reduced environments. This was cyst stage of early eukaryotic algae.Eukaryotes may have evolved from earlier colonies of prokaryotes formed through symbiosis of both archae- and eubacteria beginning around 1.75 billion years ago.
Anabolism
These reactions occur by dehydration synthesis, removing a molecule of water to join two smaller molecules. e.g. polysaccharides, lipids, and proteins are constructed via dehydration synthesis. The bond between two amino acids is a peptide bond; two bound amino acids form a dipeptide, while many joined form a polypeptide.
Catabolism
Catabolism breaks apart larger molecules into their building blocks. These reactions occur by hydrolysis, wherein a molecule of water is inserted into
a polymer and split into two smaller molecules. The reactions of metabolism are often reversible.
Enzyme Action
- Enzymes are complex proteins that function to lower the activation energy of a reaction so it may proceed more rapidly.
- Enzymes work in small quantities and are recycled by the cell.
- Each enzyme is specific, acting on only one kind of substrate.
- Active sites on the enzyme combine with the substrate and a reaction occurs.
- The speed of enzymatic reactions depends on the number of enzyme and substrate molecules available.
Factors That Alter Enzymes
Enzymes (proteins) can be denatured by heat, pH extremes, chemicals, electricity, radiation, and by other causes.
Release of Chemical Energy
- Release of chemical energy in the cell often occurs through the oxidation of glucose.
- Burning glucose requires energy to begin the process.
- The end-products of these reactions are heat as well as stored energy.
Anaerobic Respiration
- The first part of cellular respiration is the splitting of 6-C glucose that occurs through a series enzyme-catalyzed steps.
- The result is two 3-C molecules of pyruvate.
- Glycolysis occurs in the cytosol and does not require oxygen (is anaerobic).
- Energy from ATP is used to start the process but there is a net gain of energy as result.
Aerobic Respiration
- Oxygen is needed for aerobic respiration, which occurs within the mitochondria.
- There is a much greater gain of ATP molecules from aerobic respiration.
- The final products of glucose oxidation are carbon dioxide, water, and energy.
ATP Molecules from cellular repiration
- Up to 38 molecules of ATP are produced for each molecule of glucose oxidized.
- ATP molecules contain three phosphates in a chain.
- Energy is stored in the last phosphate bond.
- Energy is stored while converting ADP to ATP; when energy is released, ATP becomes ADP, ready to be regenerated into ATP.
What is a a metabolic pathway?
A sequence of enzyme-controlled reactions.
Where does the first phase of cellular respiration occur?
In the cytosol and is anaerobic. Glucose is split into two molecules of pyruvic acid.
What is the second phase of carbohydrate breakdown?
pyruvic acid is oxidized to an acetyl group, combines with coenzyme A, and is carried into the mitochondrion.
What are the general steps in lipid metabolism?
- Lipolysis is carried out by lipases.
- Once freed from glycerol, free fatty acids can enter blood and muscle fiber by diffusion.
- Beta oxidation splits long carbon chains of the fatty acid into acetyl CoA, which can eventually enter the TCA cycle.
Briefly, what are the steps in β-oxidation (lipolysis of free fatty acids)? Hint: 4 steps.
- Dehydrogenation by acyl-CoA dehydrogenase in the mitochondria of a cell, yielding 1 FADH2.
- Hydration by enoyl-CoA hydratase
- Dehydrogenation by 3-hydroxyacyl-CoA dehydrogenase, yielding 1 NADH
- Cleavage by thiolase, yielding 1 acetyl-CoA and a fatty acid that has now been shortened by 2 carbons (acyl-CoA)
Where do micro tubules originate from?
They originate from basal bodies or centrioles (MYOC)
What the features of a plasma membrane?
- Has a double phospholipid membrane (phospholipid bilayer)
- selective permeability: only small, uncharged, polar molecules (such as H2O) and hydrophobic molecules (non polar like O2, CO2, and hydrocarbons) can pass freely across the membrane. Large polar molecules (e.g. glucose) and ions are impermeable.
- contains proteins (peripheral and integral)
- contains cholesterol.
What is a Channel protein?
Provide open passageways through the membrane for certain hydrophilic e.g. large charged molecules. Aquaporins are channel proteins which increases the passage rate of water.
What is an Ion channel?
Allow the passage of ions across the membrane. In nerve and muscle cells, ion channels called “gated channels” open and close in response to specific chemical or electrical stimuli to allow the passage of specific ions, such as Na and K.
What is a Carrier protein?
bind to specific molecules, which are then transferred across the membrane after the carrier protein undergoes a change of shape. The passage of glucose in a cell is by a carrier protein.
What is a Transport protein?
Use energy (ATP) to transport materials across the membrane. When energy is used for this purpose, the materials are said to be actively transported, and the process is called “active transport”. The “sodium-potassium pump” for e.g. uses ATP to maintain higher concentrations of sodium and potassium on opposite sides of the plasma membrane.
