Unit 1 Flashcards
1
Q
When did the Sun form, and how was the Earth formed afterward?
A
The Sun formed around 4.5 billion years ago, and Earth formed soon after from dust and gaseous particles.
2
Q
How do we know about the pre-biotic atmosphere of early Earth?
A
We know about the pre-biotic atmosphere from rock samples.
3
Q
What indicates the presence of oxygen in early Earth’s atmosphere?
A
Traces of oxygen were indicated by the production of metal-oxides, like iron oxide.
4
Q
What gases were produced by volcanic activity on early Earth?
A
Methane and carbon dioxide were produced by volcanic activity.
5
Q
How were temperatures on early Earth compared to today, and why was this significant?
A
Temperatures were higher than today, even though the Sun was cooler, affecting early chemical processes.
6
Q
What was the range of ocean pH on early Earth?
A
Ocean pH ranged from 5-11.
7
Q
How might lightning have affected early Earth’s chemistry?
A
Increased lightning might have resulted in other chemical processes.
8
Q
Why didn’t the stratospheric ozone layer exist on early Earth?
A
The stratospheric ozone layer did not exist due to the lack of oxygen.
9
Q
Where might organic carbon compounds have originated on early Earth?
A
Deep Sea Hydrothermal Vents or Hot Springs,
inital carbon compounds may have been brought to earth through meteorites
10
Q
What caused the organic aerosol haze in early Earth’s atmosphere?
A
Water droplets and environmental factors caused the organic aerosol haze.
11
Q
How did organic life affect oxygen and carbon concentrations in the atmosphere?
A
Organic life increased oxygen concentrations and decreased carbon concentrations, making conditions for re-establishing life impossible.
12
Q
What are the factors deciding whether a cell is living?
A
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.
13
Q
What does the theory of spontaneous generation state, and who proved it false?
A
It states living cells can be produced from non-living matter; this was proven false by Louis Pasteur and other biologists.
14
Q
What did Robert Remark observe that supported the cell theory?
A
He observed that every new cell came from the division of a pre-existing cell.
15
Q
What does cell theory state about modern cells and their origins?
A
All modern cells can be traced back to ancestral cells if evolution is accepted.
16
Q
What are the requirements for the origins of cells over a long period of time?
A
Catalysis, self-assembly, compartmentalization, and self-replication of molecules.
17
Q
What did J.B.S Haldane claim about the pre-biotic ocean in his 1929 article?
A
He claimed it was made of water vapor, carbon dioxide, and ammonia that when exposed to ultraviolet light, created organic compounds.
18
Q
What was the Stanley Miller and Harold Urey experiment, and what did it demonstrate?
A
It tested the formation of organic compounds under pre-biotic conditions and demonstrated that such substances could have been formed on pre-biotic Earth.
19
Q
Define “vesicles.”
A
Vesicles are small droplets of fluid enclosed in a membrane.
20
Q
What are the main parts of phospholipids, and how do they behave in water?
A
They have a polar, hydrophilic head and a non-polar, hydrophobic tail, forming stable circular bilayers in water.
21
Q
What is a significant fault of DNA compared to RNA?
A
DNA needs enzymes for replication, while RNA is self-replicating and can store the same information.
22
Q
Why is RNA considered to have come before DNA?
A
RNA is self-replicating and can store the same information as DNA without needing enzymes.
23
Q
How does the accuracy of RNA polymerase compare to DNA polymerase?
A
RNA polymerase is much less accurate, leading to a higher mutation rate
24
Q
Why is a higher mutation rate beneficial for viruses but harmful for multicellular organisms?
A
It allows viruses to invade the host’s immune system faster but disrupts the gene stability needed by multicellular organisms.
25
What role does RNA play in living cells?
RNA catalyzes certain reactions, including the synthesis of polypeptides in ribosomes.
26
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.
27
What is the oldest undisputed evidence of life?
Structures resembling fossilized stromatolites from Western Australia, dating back 3.2 billion years.
28
Why are there no rocks older than 4 billion years?
Rocks undergo subduction over long periods, preventing older rocks from remaining intact.
29
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.
30
What did Robert Hooke and other biologists conclude about living organisms?
Living organisms consist of cells.
31
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.
32
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.
33
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.
34
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.
35
Where is DNA located in prokaryotic and eukaryotic cells?
In the cytoplasm of prokaryotic cells and the nucleus of eukaryotic cells.
36
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.
37
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.
38
What are the advantages of multicellularity?
Longer lifespans, larger size, and complexity through cell differentiation.
39
What is endosymbiosis?
A relationship where an endosymbiont lives inside the host, entering via endocytosis.
40
How did mitochondria originate?
Mitochondria were prokaryotes that developed anaerobic respiration and were ingested by larger prokaryotes, becoming endosymbionts.
41
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.
42
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.
43
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.
44
What is a syncytium in skeletal muscle?
A large multinucleate structure formed by the fusion of cells.
45
What is aseptate fungal hyphae?
Hyphae without walls (septa), forming a large multinucleate structure called a coenocyte.
46
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.
47
Why are viruses not considered living?
They cannot carry out vital functions independently and rely on host cells for reproduction.
48
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.
49
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.
50
What is the composition of phospholipid molecules in cell membranes?
Phospholipid molecules have a phosphate "head" and two hydrocarbon tails.
51
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.
52
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.
53
What influences the permeability of molecules through the membrane?
The size of the molecules influences permeability; larger molecules have lower permeability.
54
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.
55
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.
56
What kind of molecules can easily diffuse through the cell membrane?
Nonpolar molecules like oxygen can diffuse easily through the cell membrane.
57
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.
58
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.
59
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.
60
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%.
61
Define osmosis
Osmosis is the net movement of water molecules across a cell membrane due to differences in solute concentration on either side
62
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).
63
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.
64
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.
65
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.
66
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.
67
What are glycolipids and their function?
Glycolipids are molecules with carbohydrates linked to lipids, found in plasma membranes, and involved in cell recognition, helping distinguish between self and non-self-cells.
68
Define compartmentalization in eukaryotic cells and its advantages.
Compartmentalization involves membrane-bound organelles dividing the cytoplasm, allowing for efficient reactions, containment of harmful substances, maintenance of ideal conditions, and organizational mobility.
69
How do mitochondria produce ATP?
Mitochondria produce ATP through aerobic respiration, with the inner membrane hosting oxidative phosphorylation and the matrix containing enzymes and substrates for the Krebs cycle.
70
Describe the structure and function of chloroplasts.
Chloroplasts have an outer envelope, thylakoids for light absorption, and stroma for the Calvin cycle, facilitating efficient photosynthesis and ATP production.
71
Explain the phospholipid bilayer principles.
The hydrophobic core of the phospholipid bilayer never gets exposed to water, with the membrane adopting shapes to avoid exposure, and integral proteins forming pores for molecule passage.
72
What are nuclear pores and their function?
Nuclear pores are large channels in the nuclear membrane that allow proteins, RNA, and ribosomes to move between the nucleus and cytoplasm, regulated by protein-lined rims.
73
What is the role of ribosomes in protein synthesis?
Ribosomes, composed of rRNA and proteins, synthesize polypeptides, with free ribosomes releasing them into the cytoplasm and bound ribosomes transporting them into the rough ER.
74
Describe the function of the Golgi apparatus.
The Golgi apparatus processes, modifies, and transports proteins from the rough ER, directing them to lysosomes, vacuoles, or the plasma membrane for secretion.
75
What are vesicles and their functions in cells?
Vesicles are membrane-bound sacs that transport materials within cells, increase plasma membrane area during cell growth, and assist in processes like endocytosis and exocytosis.
76
What is fertilization?
Fusion of male and female gametes to form a single cell.
77
What happens during embryo development?
Cell division creates genetically identical cells.
78
What role does mitosis play in embryo development?
Ensures genetic uniformity among cells in the embryo.
79
What are the characteristics of early embryo cells?
Early embryo cells are unspecialized (undifferentiated).
80
What is cell differentiation?
Cells develop along different pathways, becoming specialized.
81
Why is cell differentiation important?
Enhances efficiency by focusing on specific functions.
82
How do cells optimize for their functions during differentiation?
Cells optimize structures and enzymes for specific functions.
83
How many distinct cell types develop through differentiation in humans?
220 distinct cell types.
84
What happens when a gene is activated?
Active genes produce proteins or gene products.
85
What is selective expression?
Specific genes are activated in different cell types.
86
How does gene regulation determine cell type and function?
Via gene expression patterns.
87
How do positional cues influence differentiation?
Cell position in embryo determines differentiation pathway.
88
What role do signalling chemicals play in differentiation?
Gradients of chemicals signal cell position and function.
89
Give an example of a signaling chemical influencing development.
Retinoic acid gradients guide forelimb, pancreas, lung, and kidney development.
90
What is the origin and significance of stem cells?
Coined in the 19th century for zygote and early embryo cells. All adult tissues originate from stem cells.
91
What is a key property of stem cells?
Can divide indefinitely.
92
Give an example of stem cells in continuous use.
Skin stem cells replace lost skin cells continuously.
93
What are totipotent stem cells?
Cells in early-stage embryos capable of differentiating into any cell type.
94
What are pluripotent stem cells?
Cells capable of differentiating into many, but not all, cell types.
95
What are multipotent stem cells?
Stem cells in adult tissues capable of differentiating into a limited range of cell types.
96
What happens during embryonic development in terms of differentiation?
Cells commit to specific differentiation paths.
97
What is the transition in stem cell potency during maturation?
Transition from totipotent to pluripotent and eventually multipotent in adult stem cells.
98
What is cell metabolism?
Chemical reactions occurring in the cytoplasm of cells collectively known as metabolism.
99
Why is surface area-to-volume ratio important for cells?
Determines efficiency of substance exchange and heat regulation in cells.
100
What is cell specialization?
Cells adapted to perform specific functions such as substance transport.
101
How are red blood cells adapted for their function?
Biconcave disc shape, small size, and large surface area-to-volume ratio for rapid oxygen exchange.
102
What is the function of Type I pneumocytes in the alveoli?
Adapted for diffusion of oxygen and carbon dioxide.
103
What is the role of Type II pneumocytes?
Produce surfactant and facilitate alveolar maintenance.
104
What is the microscopic structure of skeletal muscle tissue?
Appears striped or striated under a light microscope due to alternating light and dark bands.
105
What is the function of cardiac muscle tissue?
Allows synchronized contraction of heart muscle cells, leading to efficient pumping of blood.
106
What are the structural features of egg cells?
Largest cell in the human body, contains a haploid nucleus, zona pellucida, cortical granules, yolk, mitochondria, and centrioles.
107
What are the structural features of sperm cells?
Tail (flagellum), midpiece with mitochondria, head with nucleus, acrosome, and receptors for ZP3 glycoproteins on the zona pellucida.
108
How do egg and sperm cells differ in their roles in fertilization?
Egg cell is passive in movement, contains food reserves, and initiates fertilization by receiving sperm. Sperm cell is actively motile, adapted for competitive swimming to fertilize the egg, and equipped with enzymes to penetrate the zona pellucida.
109
What is cell division?
Cell division is the process where one cell (mother cell) divides to produce two daughter cells.
110
What is the purpose of cell division?
The purpose of cell division is essential for growth, maintenance, and reproduction in all organisms
111
How does cell division support the theory of new cell formation?
Cell division strongly supports the theory that all new cells originate from the division of pre-existing cells.
112
What are the implications of cell division in human biology?
Trillions of cells in the human body are derived from the division of pre-existing cells, and each cell traces back to the original zygote formed by the fusion of sperm and egg.
113
How are sperm and egg cells formed in humans?
Sperm and egg cells are formed through cell division in parents.
114
How does cell lineage show ancestral continuity?
All cells in parents trace back to a zygote and continue through generations of human ancestors.
115
How does cell lineage trace back in evolutionary history?
If humans evolved from ancestral species, cell origins trace back millions of years to the earliest life forms.
116
How do new cells form?
New cells form only through the division of pre-existing cells, maintaining genetic continuity.
117
What is cytokinesis?
Cytokinesis is the process where the cytoplasm of a cell divides into two daughter cells following nuclear division.
118
How does cytokinesis occur in animal cells?
In animal cells, cytokinesis involves the formation of a cleavage furrow, where contractile proteins form a ring that contracts, pulling the plasma membrane inward to divide the cell.
119
How does cytokinesis occur in plant cells?
In plant cells, cytokinesis involves the formation of a cell plate, where vesicles produced by the Golgi apparatus fuse at the equator of the cell, forming a new cell wall.
120
What are the differences between cytokinesis in animal and plant cells?
Animal cells form a cleavage furrow using actin and myosin, while plant cells form a cell plate through the sequential deposition of vesicles and wall materials.
121
What is the difference between equal and unequal cytokinesis?
Equal cytokinesis divides the cytoplasm equally between daughter cells, while unequal cytokinesis divides it unequally, producing cells with varying sizes and resources.
122
How do cells divide during root tip growth?
During root tip growth, cells divide equally to maintain the growth and structure of the root.
123
What is necessary for the survival of small daughter cells?
Small daughter cells must receive a nucleus and essential organelles, like mitochondria, for viability.
124
How does unequal cytokinesis occur during oogenesis in humans?
During oogenesis, unequal cytokinesis produces a large oocyte and a small polar body, ensuring one viable egg with ample cytoplasm and nutrients.
124
What happens if nuclear division does not precede cell division?
Without nuclear division preceding cell division, one daughter cell would lack a nucleus, making it unable to synthesize polypeptides and limiting its growth and maintenance.
125
What are the key differences between mitosis and meiosis?
Mitosis produces two genetically identical daughter cells for growth and repair, while meiosis produces four haploid gametes for sexual reproduction, ensuring genetic diversity.
126
What happens to DNA before mitosis or meiosis?
DNA undergoes replication to ensure each daughter cell receives a complete set of genes, resulting in pairs of identical DNA molecules held together by cohesin proteins.
127
How do chromosomes change during cell division?
Chromosomes condense and become visible under a microscope during mitosis or meiosis, starting as elongated and uncondensed structures in the early stages and becoming tightly packed later.
128
How do chromosomes move to opposite poles during cell division?
Chromosomes move to opposite poles through the action of microtubules forming a spindle-shaped array, with kinetochores on chromatids shortening the microtubules to pull the chromosomes.
129
What initiates chromosome condensation?
Chromosome condensation begins with DNA wrapping around histone proteins to form nucleosomes, with further stages actively researched.
130
What role do kinetochores play in chromosome segregation?
Kinetochores, assembled on the centromere of each chromatid, act as microtubule motors that shorten microtubules and create tension, moving chromatids to opposite poles.
131
What are the stages of mitosis?
The stages of mitosis are Interphase, Prophase, Metaphase, Anaphase, and Telophase, each involving specific chromosomal activities.
132
What is the function of microtubules in cell division?
Microtubules form spindles that attach to kinetochores on chromatids, facilitating their movement to opposite poles for segregation into separate nuclei.
133
What is the role of the microtubule organizing center (MTOC) in cell division?
The MTOC assembles microtubules, forming a spindle-shaped array that links the poles of the cell, crucial for chromosome movement during cell division.
134
How does cohesin contribute to chromosome segregation?
Cohesin holds sister chromatids together until anaphase, ensuring orderly chromosome segregation when cleaved.
135
What is the size range of viruses?
20-300nm in size.
136
Do viruses grow in size outside of their host cell?
No, they have a fixed size and do not grow outside of their host cell.
137
What is the genetic material of viruses used for?
Virus proteins are synthesized through nucleic acid-to-polypeptide translations inside the host cell, following the universal genetic code.
138
What is a capsid made of in most viruses?
Protein, with repeating protein sub-units enclosing the genetic material.
139
Do viruses have cytoplasm or many enzymes?
No, they lack cytoplasm and have few enzymes, relying on the host cell's metabolic functions.
140
Is there a gene that occurs in all viruses?
No, viruses are very diverse and unique with no gene common to all.
141
What types of genetic material can viruses contain?
Either RNA or DNA.
142
How can the genetic material of viruses be arranged?
It can be arranged in a circular loop or a linear strand.
143
How do positive-sense RNA viruses use their genes?
They use their genes as direct messengers for the RNA.
144
How do negative-sense RNA viruses use their genes?
They transcribe their genes to make messenger RNA.
145
How do retroviruses replicate their genetic material?
They make double-strand DNA copies of their RNA and then transcribe the negative-sense strand of DNA to produce mRNA.
146
What are enveloped viruses?
Viruses that become enveloped by a layer of phospholipid derived from the host cell and glycoproteins from the virus.
147
What are non-enveloped viruses?
Viruses that do not become enveloped, mostly infecting plant or bacteria cells.
148
What is the lysogenic cycle?
The viral DNA becomes integrated into the host cell, new virus particles are not produced, and the host survives.
149
What does "temperate" mean in the context of viruses?
It refers to viruses that do not kill their host and cause minimal harm.
150
What is the lytic cycle?
The virus reproduces and bursts out of the host cell, killing it.
151
What type of virus is Bacteriophage lambda?
It is a DNA virus that uses either a bacterium or an archaeon as its host.
152
What type of virus is COVID-19?
It is an RNA virus with a crown-like shape that uses an animal cell as its host.
153
What type of virus is HIV?
It is a retrovirus that converts its RNA genome to DNA after infecting a host.
154
Is Bacteriophage lambda enveloped or non-enveloped?
Non-enveloped.
155
Is COVID-19 enveloped or non-enveloped?
Enveloped.
156
Is HIV enveloped or non-enveloped?
Enveloped.
157
What is the genetic material of Bacteriophage lambda?
One double-stranded DNA molecule with positive and negative sense strands and 48,502 base pairs.
158
What is the genetic material of COVID-19?
One single-stranded positive-sense RNA molecule with 29,903 bases.
159
What is the genetic material of HIV?
Two copies of a single-stranded positive-sense RNA molecule of 9,749 bases.
160
What is the progressive hypothesis about the origin of viruses?
It suggests that viruses evolved from genetic material that gained the ability to move from cell to cell.
161
What is the regressive hypothesis about the origin of viruses?
It suggests that viruses evolved from fully-functional cells, such as intra-parasitic bacteria.
162
Why can viruses show extremely rapid rates of evolution?
Because of their short generation time, high mutation rates, and intense natural selection pressure.
163
How does the influenza virus replicate its genetic material?
It uses RNA replicase, which does not proofread or correct errors, leading to high mutation rates.
164
What proteins act as antigens in the influenza virus?
Haemagglutinin and neuraminidase.
165
What enzyme does HIV use to convert its RNA genome to DNA?
Reverse transcriptase.
166
What causes the high mutation rate in HIV?
The lack of proofreading by reverse transcriptase and the action of the host enzyme cytidine deaminase.
