Unit 1 Flashcards
When did the Sun form, and how was the Earth formed afterward?
The Sun formed around 4.5 billion years ago, and Earth formed soon after from dust and gaseous particles.
How do we know about the pre-biotic atmosphere of early Earth?
We know about the pre-biotic atmosphere from rock samples.
What indicates the presence of oxygen in early Earth’s atmosphere?
Traces of oxygen were indicated by the production of metal-oxides, like iron oxide.
What gases were produced by volcanic activity on early Earth?
Methane and carbon dioxide were produced by volcanic activity.
How were temperatures on early Earth compared to today, and why was this significant?
Temperatures were higher than today, even though the Sun was cooler, affecting early chemical processes.
What was the range of ocean pH on early Earth?
Ocean pH ranged from 5-11.
How might lightning have affected early Earth’s chemistry?
Increased lightning might have resulted in other chemical processes.
Why didn’t the stratospheric ozone layer exist on early Earth?
The stratospheric ozone layer did not exist due to the lack of oxygen.
Where might organic carbon compounds have originated on early Earth?
Deep Sea Hydrothermal Vents or Hot Springs,
inital carbon compounds may have been brought to earth through meteorites
What caused the organic aerosol haze in early Earth’s atmosphere?
Water droplets and environmental factors caused the organic aerosol haze.
How did organic life affect oxygen and carbon concentrations in the atmosphere?
Organic life increased oxygen concentrations and decreased carbon concentrations, making conditions for re-establishing life impossible.
What are the factors deciding whether a cell is living?
Living cells use energy to maintain a highly ordered state, can divide to produce more cells, and can be taken from a body and cultured.
What does the theory of spontaneous generation state, and who proved it false?
It states living cells can be produced from non-living matter; this was proven false by Louis Pasteur and other biologists.
What did Robert Remark observe that supported the cell theory?
He observed that every new cell came from the division of a pre-existing cell.
What does cell theory state about modern cells and their origins?
All modern cells can be traced back to ancestral cells if evolution is accepted.
What are the requirements for the origins of cells over a long period of time?
Catalysis, self-assembly, compartmentalization, and self-replication of molecules.
What did J.B.S Haldane claim about the pre-biotic ocean in his 1929 article?
He claimed it was made of water vapor, carbon dioxide, and ammonia that when exposed to ultraviolet light, created organic compounds.
What was the Stanley Miller and Harold Urey experiment, and what did it demonstrate?
It tested the formation of organic compounds under pre-biotic conditions and demonstrated that such substances could have been formed on pre-biotic Earth.
Define “vesicles.”
Vesicles are small droplets of fluid enclosed in a membrane.
What are the main parts of phospholipids, and how do they behave in water?
They have a polar, hydrophilic head and a non-polar, hydrophobic tail, forming stable circular bilayers in water.
What is a significant fault of DNA compared to RNA?
DNA needs enzymes for replication, while RNA is self-replicating and can store the same information.
Why is RNA considered to have come before DNA?
RNA is self-replicating and can store the same information as DNA without needing enzymes.
How does the accuracy of RNA polymerase compare to DNA polymerase?
RNA polymerase is much less accurate, leading to a higher mutation rate
Why is a higher mutation rate beneficial for viruses but harmful for multicellular organisms?
It allows viruses to invade the host’s immune system faster but disrupts the gene stability needed by multicellular organisms.
What role does RNA play in living cells?
RNA catalyzes certain reactions, including the synthesis of polypeptides in ribosomes.
What evidence supports the universal use of RNA in all species?
All species use 64 codons with minimal variation, and key cellular structures like ribosomes and enzymes are effectively the same in all organisms.
What is the oldest undisputed evidence of life?
Structures resembling fossilized stromatolites from Western Australia, dating back 3.2 billion years.
Why are there no rocks older than 4 billion years?
Rocks undergo subduction over long periods, preventing older rocks from remaining intact.
What are hydrothermal vents, and why are they significant for life?
Cracks in the Earth’s surface that carry unoxidized inorganic materials, they provided energy and conditions suitable for the formation of early life.
What did Robert Hooke and other biologists conclude about living organisms?
Living organisms consist of cells.
What advancements did the electron microscope bring?
It allowed for magnifications up to 1,000,000x with higher resolution, providing detailed views of cellular structures.
What is freeze-fracture electron microscopy?
A process that produces images of surfaces within cells by rapidly freezing and fracturing the sample, then etching and coating it for electron microscopy.
What is cryogenic electron microscopy (cryo-EM)?
A method for researching protein structure by flash-freezing a pure protein solution and examining it under an electron microscope.
What is the plasma membrane, and what does it do?
The outer boundary of the cell that encloses its contents and can pump substances into the cell through active transport.
Where is DNA located in prokaryotic and eukaryotic cells?
In the cytoplasm of prokaryotic cells and the nucleus of eukaryotic cells.
What are the main differences between prokaryotic and eukaryotic cells?
Prokaryotic cells lack a nucleus and have 70S ribosomes, while eukaryotic cells have a nucleus, double membrane layers, and 80S ribosomes.
What is cell differentiation?
The process by which different genes are activated, allowing for gene expression that determines the type of proteins and gene products a cell should produce.
What are the advantages of multicellularity?
Longer lifespans, larger size, and complexity through cell differentiation.
What is endosymbiosis?
A relationship where an endosymbiont lives inside the host, entering via endocytosis.
How did mitochondria originate?
Mitochondria were prokaryotes that developed anaerobic respiration and were ingested by larger prokaryotes, becoming endosymbionts.
What evidence supports evolution through endosymbiosis?
Mitochondria and chloroplasts have double membranes, their own genes, circular DNA, 70S ribosomes, and can only be produced by existing mitochondria/chloroplasts.
Why do red blood cells lack a nucleus?
The nucleus is removed to make the cell smaller, more maneuverable, and flexible, but it cannot repair itself and dies in 100-120 days.
What are phloem sieve tube elements?
Cells in phloem tubes that retain a cell membrane but lack a nucleus and many other cell components, connected to companion cells that support them.
What is a syncytium in skeletal muscle?
A large multinucleate structure formed by the fusion of cells.
What is aseptate fungal hyphae?
Hyphae without walls (septa), forming a large multinucleate structure called a coenocyte.
What are some vital processes that are universal or very common in living organisms?
Metabolism, response to stimuli, growth, reproduction, excretion, and maintaining a complex internal environment.
Why are viruses not considered living?
They cannot carry out vital functions independently and rely on host cells for reproduction.
What is the primary function of cell membranes?
Cell membranes form a border of protection between the cell and the environment and divide the cytoplasm into compartments within eukaryotic cells.
Describe the basic structure of cell membranes.
Cell membranes have a bilayer of phospholipids and other amphipathic molecules that form a continuous sheet to control the passage of substances.
What is the composition of phospholipid molecules in cell membranes?
Phospholipid molecules have a phosphate “head” and two hydrocarbon tails.
Why is the core of the biological membrane hydrophobic?
The hydrocarbon tails of phospholipids are hydrophobic and interact with each other to form the core, resulting in low permeability to hydrophilic particles.
What type of particles have low permeability through the membrane core?
Hydrophilic particles, including ions with positive or negative charges and polar molecules like glucose, have low permeability through the membrane core.
What influences the permeability of molecules through the membrane?
The size of the molecules influences permeability; larger molecules have lower permeability.
Define diffusion.
Diffusion is the spreading out of particles in liquids and gases due to their continuous random motion, moving from higher to lower concentration areas.
What is simple diffusion in the context of cell membranes?
Simple diffusion across membranes occurs when particles pass between phospholipids, possible only if the bilayer is permeable to those particles.
What kind of molecules can easily diffuse through the cell membrane?
Nonpolar molecules like oxygen can diffuse easily through the cell membrane.
How do ions and polar molecules pass through cell membranes?
Ions and polar molecules pass through cell membranes at low rates due to their hydrophilic nature, with small polar molecules passing more easily than large ones.
What is the role of integral proteins in cell membranes?
Integral proteins are hydrophobic, remain embedded in the membrane, and may extend across both phospholipid layers, often functioning as transmembrane proteins.
Describe peripheral proteins and their attachment.
Peripheral proteins are hydrophilic on their surface, not embedded in the membrane, and usually attached to the surface of integral proteins, sometimes via a single hydrocarbon chain.
How does the protein content of membranes vary with activity?
The more active a membrane, the higher its protein content; for example, myelin sheaths have ~18% protein, plasma membranes ~50%, and chloroplasts ~75%.
Define osmosis
Osmosis is the net movement of water molecules across a cell membrane due to differences in solute concentration on either side
What influences the movement of water in osmosis?
Water moves from areas of higher concentration of free water molecules (lower solute concentration) to areas of lower concentration of free water molecules (higher solute concentration).
How do channel proteins facilitate diffusion?
Channel proteins are integral, transmembrane proteins with pores that allow specific particles to pass through, moving from higher to lower concentration without energy expenditure.
Differentiate between facilitated diffusion and simple diffusion.
Facilitated diffusion requires channel proteins for particle movement, while simple diffusion involves movement between phospholipid molecules in the membrane.
What is active transport and how does it differ from passive diffusion?
Active transport moves substances against the concentration gradient using energy (usually ATP), involving pump proteins that transport particles in one direction only.
What are glycoproteins and their role in cell membranes?
Glycoproteins are conjugated proteins with carbohydrates, embedded in the plasma membrane, projecting into the environment, and involved in cell-to-cell recognition.
