A2 Flashcards
(191 cards)
1
Q
Homeostasis
A
maintaining of a consistent internal environment even if the external environment changes
2
Q
primordial soup
A
(hypothetical) water-based sea of simple monomers such as amino acids. This is thought to be the origin of living compounds
3
Q
Vesicle
A
Any small bubble of fluid surrounded by a phospholipid bilayer
4
Q
Compartmentalisation
A
Separation of functions into specific regions of the cells, allowing multiple distinct metabolic functions to occur at the same time
5
Q
Coalescence
A
Phospholipids naturally arranging themselves to come together and form a ring-like structure
6
Q
Three principles of cell theory
A
- All organisms are composed of one or more cells
- Cells are the smallest unit of life
- All cells come from pre-existing cells
7
Q
Organic vs inorganic compound
A
Organic: generally complex carbon based compound, made in living organisms
Inorganic: don’t have to contain carbon (most don’t), found inside and outside living organisms
8
Q
What did the Miller-Urey experiment demonstrate?
A
Inorganic gases can react to create organic compounds within conditions similar to early Earth.
9
Q
How does the structure of fatty acids contribute to vesicle formation?
A
Phospholipids in an aqueous solution form a barrier to create a vesicle. This may have happened in primordial soup and creates cell membranes of early cells.
10
Q
Requirements to be considered living
A
metabolism
growth
reproduction (independent)
response to stimuli
homeostasis
movement
nutrition
11
Q
What is a cell?
A
Smallest unit of life
12
Q
What is needed to create a living functional cell?
A
Catalysis: a catalyst that speeds up chemical reactions
Self-replication of molecules
Self-assembly of monomers into polymers (e.g. condensation reactions)
Compartmentalisation
- eukaryotes: organelles
- prokaryotes: ribosomes
13
Q
Examples of how cells fulfill criteria for being living
A
Homeostasis -> regulates H2O balance
Metabolism (ability to carry out chemical reactions using ATP) -> cellular respiration happens in each cell
Reproduction/self-replication -> cell replication/mitosis
14
Q
Examples of how viruses fail to meet the criteria for living
A
Homeostasis -/> no internal environment
Metabolism -/> does not use ATP
Reproduction/self-replication -/> needs a host
15
Q
Conditions of the Miller Urey experiment
A
Inorganic gases: methane, ammonia, hydrogen
Vert hot ocean with water (due to high temperatures and lots of UV penetration)
Electrical activity (through an electrode)
= mimics conditions of Early Earth
16
Q
Process of Miller Urey experiment
A
A lower chamber (the ocean) is heated, to mimic the hihg temperatures of Early Earth.
This produces water vapour that travels into the upper chamber. This upper chamber is filled with inorganic gases (methane, ammonia, hydrogen), which mixes with the H2O vapour. An electrode hits this upper chamber, to mimic lightning.
This goes through a condenser.
17
Q
Proucts of the Miller Urey experiment.
A
Amino acids + carbon hydrogen chains, as well as water vapour. This combination is dubbed primordial soup. This contributed to evidence that biomolecules could spontaneously form under Early Earth’s conditions.
18
Q
What does spontaneous vesicle formation provide evidence for?
A
Explains how all membranes arrived.
19
Q
What is the process of spontaneous vesicle formation?
A
Amphipathic phospholipids spontaneously form a vesicle due to hydrophobic interactions
20
Q
Ribozymes
A
Special type of RNA that can act as a catalyst. Has a role in protein synthesis
21
Q
Protocell
A
General term for any unit contained by a membrane that is completing a cellular reaction
22
Q
Radioactive isotope
A
Unstable form of an element that emits radiation
23
Q
Half life
A
Length of time it takes for half of a radioactive isotope to change into another stable element
24
Q
Index fossils
A
Distinctive, widespread and abundant fossils that is limited to a specific geological time
25
Hydrothermal vents
Places where hot water emanates from beneath the ocena floor. Formed when cracks of the crust of the seabed expose seawater to rocks below
26
Unique properties of RNA that suggest it could be an ideal first genetic material
Can spontaneously form from monomers as it is a simpler structure than DNA
Self-replicating properties
Can catalyse chemical reactions
27
Sequence of major stages in the evolution of life
Abiotic chemical compounds e.g. methane
Small organic compounds e.g. primordial soup
Polymers (aids by RNA catalysis)
Membranes (due to amphipathic nature)
Protocell
True cell with organelles
28
Last Universal Common Ancestor
Common ancestor to all currently living things. i.e. from before all prokaryotes and eukaryotes branched off
29
Relative dating of fossils
Whether the fossil is comparatively older or younger than nearby fossils absed on their placement in the rock
30
Absolute dating of fossils
Determining a specific age of a fossil in years, using carbon dating and knowledge of half lives
31
What is the RNA World Hypothesis?
Evolutionary theory that RNA was the initial genetic material, and evolved into DNA and proteins. This is contrasted by the Central dogma, which states DNA -> RNA -> proteins
32
Specific hypothesised details of RNA World Hypothesis
Within primordial soup, RNA easily self assembled. This is because of its simple structure. The RNA can then act as a catalyst for DNA replication (which requires many enzymes) and protein synthesis (ribozymes in RNA still do this).
33
Evidence for shared ancestry/Last Universal Common Ancestor
Universal genetic code
Same biomolecules
Same metabolic processes
Tracked ~300 shared genes
34
Why is it hypothesised that LUCA is in hydrothermal vents?
The ~300 shared genes were for anaerobic processes (occuring in the absence of O2). Therefore, LUCA may be found in a low oxygen environment. This low O2 environment, and other favourable conditions and many fossils, fits with Hydrothermal Vents
35
Most common substance for absolute dating of fossils
Carbon-14
5730 years half life
36
Cytology
Specific branch of biology focused on the study of the cell and all aspects related to cellular structure and function
37
Micrograph
Photo taken through a microscope
38
Micrometre compared to one centimetre
1 micrometre = 10^-4 cm = 10^-3 mm
39
Coarse v.s. fine focus on a microscope
Coarse makes larger adjustments to bring objects into focus
Fine makes small adjustments to add sharpness and clarity.
40
Contribution of cryogenic electron microscopy
Provides a resolution at 0.12 nanometres, allowing for the atoms within a protein to be visualised
41
Magnification
How many times larger the viewed image is than the actual image size
42
Resolution
How well you can differentiate two objects as separate (i.e. clarity and sharpness)
43
With a light microscope, what occurs when magnification increases?
Resolution decreases. Therefore, ideal magnification of a light microscope is 400-1000x, although some light microscopes can reach 2000x
44
What is the difference between electron and light microscopes in terms of resolution/magnification?
Electron microscopes can preserve resolution even at high magnifications. However, light microscopes decrease in resolution as magnification increases, usually working from 400-1000x
45
Formula for magnification
Magnification = image size/actual size
46
How to calculate magnification using a scale bar
Magnification = measured scale bar with ruler / given size on bar
47
What can light microscopes observe?
Living organisms. Both surface and internal (if thin).
Creates 2D images
48
What magnification do light microscopes work well with?
400-1000x. Some can go up to 2000x
49
What type of images do light microscopes create?
2D
50
Advantages of light microscopes
Can observe living organisms (see processes in action)
Can be in colour
Affordable (increases access)
51
Disadvantages of light microscopes
Poor resolution limits magnification
52
What is a scanning electron microscope (SEM)?
Electron microscope that uses a beam of electrons to scan outer surfaces of dead matter, creating detailed images of the exterior
53
What is a transmission electron microscope (TEM)?
Electron microscope that uses a beam of electrons through a very thin section of specimen that allows for internal structures to be viewed.
54
What can scanning electron microscopes observe?
Dead matter, detailed 3D images of surface.
55
Magnification of scanning electron microscopes
Up to 1,000,000x with great resolution
56
Advantages of scanning electron microscope
Higher magnification, 3D images
57
Disadvantages of scanning electron microscopes
Only black and white
Only non-living matter
Expensive
58
Type of images created by scanning electron microscopes
3D
59
What can transmission electron microscopes observe?
Dead matter, 2D images of internal structures
60
Magnification of transmission electron microscopes
Up to 1,000,000x with great resolution
61
Advantages of transmission electron microscopes
Higher magnification, has revealed organelle structure
62
Disadvantages of transmission electron microscopes
Must be very thin specimen (techniques required)
Non-living
Black and white only
Expensive
63
Advances to micrography
Freeze fracturing
Cryogenic electron microscopy
Use of fluorescent stain
64
Freeze fracturing
Technique that aids in viewing internal structures with an electron microscope.
Specimen is frozen and then broken at plane (i.e. fracture plane). Then, an etching of the plane is created and observed under an electron microscope
65
What scientific developments are a result of freeze fracturing?
Understanding the bilayer
66
Cryogenic electron microscopy
Protein structure is frozen on grid. The grid is placed under an electron microscope. Pattern of electron transmission reveals the structure of protein down to atoms. Software is used ot create a 3D image
67
What scientific developments are a result of cryogenic electron microscopy?
Detailed understanding of protein structure
68
Fluroescent stain
Fluroescent stain binds to a cellular component (only binds with specific ones). This is observed with a fluroescent light via microscopes with UV lights.
69
What scientific developments are a result of fluroescent stain?
Bright images of cellular structures
70
Immunofluoresence
Technique that uses antibodies with flurosence added. Antibodies are matched to bind to certain target molecules and give them a viral glow once bound
71
What scientific developments are a result of immunoflourescence?
Visualisation of specific proteins (i.e. whether present or not)
72
Prokaryotic cell
Simple and small cells that lack complex organelles
73
Eukaryotic cell
More complex cells that have membrane-bound organelles carrying out unique functions & all DNA is enclosed in a nucleus
74
Peptidoglycan
Carbohydrate and protein polymer that usually makes up the cell wall of prokaryotes
75
Features common to all cells
Cell membrane
DNA
Ribosomes
Cytoplasm
76
Gram positive bacteria
Has thick layer of peptidoglycan as cell wall
77
Gram negative bacteria
Has additional thin layer of membrane surrounding the thick layer of peptidoglycan
78
Examples of eukaryotic organelles
Nucleus
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Golgi apparatus
Mitochondria
79
Difference between ribosomes of prokaryotes and eukaryotes
In eukaryotes, ribosomes are 80s and are larger and denser than the 70s ribosomes of prokaryotes.
80
Similarities between ribosomes of prokaryotes and eukaryotes
Both are made of two separate subunits that clamp together in translation
81
Functions that a unicellular organism must carry out to be classified as living
Metabolism
growth
reproduction
reponse to stimuli
homeostasis
nutrition
excretion
movement
82
Size difference between prokaryotes and eukaryotes
Eukaryotes are much larger
83
Features of all prokaryotic cells
Cell membrane
cell wall
DNA/nucleoid region
ribosomes
cytoplasm
84
Features of some prokaryotic cells
Plasmids
Flagellum
Capsule
Pili
85
Cytoplasms
Interior of the cell, containing the fluid cytosol. Provides internal space for chemical reactions (metabolic processes). Other cellular structures can exist within them
86
Ribosomes
Sites of translation where polypeptides are formed. No exterior membrane and made up of mRNA/protein
87
Pili
Small hair structures on the outside of a cell wall. Can be used for adhesion/attachment to other prokaryotic cells or to
facilitate DNA exchange (as a part of sexual reproduction)
88
Nucleoid region (prokaryotic cell)
One circular region where the DNA of a prokaryotic cell is found.
This DNA is free in the cytoplasm with no nucleus, providing instructions
89
Cell wall
Rigid external layer that is specifically designed to provide structural support and rigidity
90
Different cell wall materials across cell types
Bacteria (almost all have) = peptidoglycan
Plant = cellulose
Fungi (many have) = chitin
91
Do all prokaryotes have a cell wall?
Almost all esp. bacteria
92
Cell membrane
Phospholipid bilayer that allows transport in + out of the cell.
Therefore, it has a role in homeostasis, transport and cell communication
93
What organelle has a role in homeostasis?
Most important is the cell membrane
94
Capsule
Additional thick layer outside the cell wall, made up of polysaccharides.
Allows adhesion + protection
Some bacteria have
95
Do all prokaryotic cells have a capsule?
No, just some bacteria
96
Flagellum
Whip-like tail for movement/locomotion
97
Plasmids
Single circular rings of DNA that are not connected to the main chromosome. Not essential but helpful. Often contain additional adaptive DNA e.g. antibiotic resistance
98
Organelles specific to animal cells
Centrosomes and lysosomes
99
Organelles specific to plant cells (not animal cells)
Chloroplasts
Cell wall
Large central vacuole
Amyloplast
100
Organelles of animal cells
Golgi apparatus
Rough endoplasmic reticulum
Ribosomes
Plasma membrane
Nucleus
Smooth endoplasmic reticulum
Lysosomes
Centrosome
Cytoskeleton
Small vacuole
Cytoplasm
Mitochondria
101
Rough endoplasmic reticulum
Interconnected network of tubules extending from the nucleus throughout the cell with ribosomes on the surface. Transports polypeptides in cell
102
Two types of eukaryotic ribosome
Free or attached
103
Nucleus
Organelle in which DNA resides. Has a porous double membrane (nuclear envelope) that mRNA exits from.
Contains linear DNA wrapped around histones.
Contains a spherical structure that produces and assembles ribosomal subunits -> nucleolus
104
Smooth endoplasmic reticulum
Interconnected network of tubules that extend from the nucleus without ribosomes. Makes and transports lipids e.g. phospholipids, steroids
105
Lysosome
Single membrane vesicle full of hydrolytic enzymes to break down biomolecules
106
What type of cells are cytoskeletons found in?
All eukaryotic cells
107
Cytoskeleton
Network of filaments and microtubules that maintain cell shape, anchor organelles, aid in cell and organelle movement, etc.
108
Small vacuole
(Found in animal cells) Storage organelle formed by the Golgi Apparatus that stores H2O, food, wastes, etc.
109
Mitochondria
Rod-shaped organelle that performs aerobic cellular respiration.
Has its own DNA and ribosomes, as well as highly folded innner membrane
110
Centrosome (two centrioles)
Structure of animal cell that aids in cell division
111
Golgi apparatus
Set of flattened saccs (cisternae) that collect/packages/modifies/distributes cellular products
112
Organelles of plant cell
Chloroplast
Golgi apparatus
Rough ER
RIbosomes
Cell membrane
Mitochondria
Cell wall
Smooth ER
Nucleus
large central vacuole
113
Purpose of cell wall in plants
Protection and structure of cell
114
Purpose of large central vacuole
Storage organelle that stores water and other materials.
115
What happens if the large central vacuole is full in plant cells?
Gives turgidity/shape to the cell
116
Plant organelle that not all have
Amyloplast
117
Amyloplast
Plant organelle (not all have) that stores starch granules inside cell
118
Chloroplast
Organelle that has flattened membrane discs (thylakoids) to absorb sunlight for photosynthesis to make glucose.
Has inner and outermembrane, as well as own DNA and ribosomes
119
Specialised cells
Cells that change structure to carry out a specific function within a multicellular organism
120
Cell differentiation
Process by which a stem cell turns off unneeded genes and expresses only ones relevant to its function in order to become specialised
121
Characteristics of animal cells that make them unique from other eukaryotes
No cell wall, centrioles that form the centrosome, store carbohydrates in specialised cells, small and numerous vacuoles, may have flagella
122
Characteristics of plant cells that make them unique from other eukaryotes
Fixed cell wall shape, chloroplasts for photosynthesis, large central vacuole for storage, no flagella/cili, no centrioles
123
Characteristics of funal cells that make them unique from other eukaryotes
Protective and flexible cell wall, no chloroplasts, store carfbohydrates, no centrioles, occasionally have cilia
124
What allows for cells to differentiate in multicellular organisms?
Only some genes are expressed/used
125
Do animal cells have plastids?
No
126
Do animal cells have a cell wall?
No, which makes them flexible and round
127
Do animal cells have vacuoles?
Yes. Small and many - can have different functions
128
DO animal cells have centrioles?
Yes. They grow microtubules for mitosis
129
Cilia
Small, hair-like structures present on the surface of some animal cells. Used for trapped dust, pathogens and food
130
Do animal cells have cilia?
Lots do
131
Do animal cells have flagella?
Some have a flagella
132
Do plant cells have plastids?
Yes (chloroplasts and amyloplasts)
133
Do plant cells have a cell wall?
Yes, made of cellulose, which creates a fixed and angular shape
134
Do plant cells have vacuoles?
Yes, one large central vacuoles that stores all components
135
Do plant cells have centrioles?
No. They do have a centrosome region that grows microtubules
136
Do plant cells have cilia/flagella?
Rarely have either, as they make their own food source
137
Do fungal cells have plastids
No
138
Do fungal cells have a cell wall?
Yes made of chitin, which makes the fungal cells protective anf flexible
139
Do fungal cells have vacuoles?
Depends on fungal species, but either like animal (small and many) or plant (one central)
140
Do fungal cells have centrioles?
No, but they do have a centrosome region that grows microtubules
141
Do fungal cells have cilia/pili?
Rarely have either
142
Examples of atypical cells that break the 'one nucleus per cell' rule
Fungal hyphae
Phloem sieve tube element
Skeletal muscle cells
Red blood cells
143
SIgn that a cell is specialised
Lack certain crucial organelles
144
Fungal hyphae (atypical cell example)
Long one-cell-wide filaments with many nuclei, due to a loss of membrane between cells.
Produced by fungi, usually expand underground and play a role in cell absorption
145
Phloem sieve tube elements (atypical cell example)
Cells that form thin tubes to transport sugars in plants.
Lost all organelles, so have companion cells with a nucleus and mitochondria. These companion cells meet the needs of the sieve cells as well as their own
146
Skeletal muscle cells (atypical cell example)
Long tubular cells that can contract and relax with multiple nuclei. Have internal and external mitochondria / additional mitochondria
Fibres of long thin cells = best for contractions
147
How are skeletal muscle cells adapted for contraction?
Fibres of long thin cells = best for contractions
148
Red blood cells (atypical cell example)
No nucleus in order to reduce volume and thus, increase SA:V to allow more haemoglobin to be at the surface to carry more O2.
This is also seen with the biconcave shape
149
Are red blood cells considered to be cells?
No, as they lack the criteria
150
Endosymbiotic theory
Theory that an early eukaryotic ancestor engulfed a prokaryotic cell, which remained functional due to no enzymes to digest. The prokaryote functions inside the eukaryote, producing energy for the eukaryote to use. This makes this particular eukaryote the fittest of all cells. Overtime, due to natural selection, eukaryotes with this adaptation became the norm. The prokaryote became mitochondria first, and then later some cells gained a chlorplast through a similar process
151
Evidence for endosymbiotic theory
Both mitochondria and chloroplasts have:
Own 70s (prokaryote size) ribosomes -> not from parent cell
Double membrane -> outer one from host (gained when entering cell)
Own DNA. Circular like that of prokaryotes
Same size as prokaryotes
Self-replicate separate to cell
i.e. behave like a prokaryote
152
How do multicellular organisms develop specialised cells?
Gene expression (i.e. turning genes on)
153
Virus
Non-living particle that infects cells and reproduces inside of them
154
Capsid
Simple protein that contains the genetic material of a virus.
155
Prophage
The combined nucleic acid of the viral DNA and host DNA
156
Outbreak v.s. epidemic v.s. pandemic
Outbreak = spread of infection isolated to a small geographic area
Epidemic = moves more quickly than expected and to more areas
Pandemic: epidemic crosses countries
157
In what forms can genetic material of viruses exist?
DNA
RNA
RNA transcribed to mRNA
RNA reversed transcribed to DNA
158
Features common to all viruses
Protein spikes
Nucleic acid
Protein capsid
159
Are viruses living?
No
160
Role of protein spikes in viruses
These protein spikes are a form of ID recognised by the host, allowing the virus to invade the host cell
161
What is a common feature of viruses (many not all)?
An envelope that surrounds the protein capsid. This envelope is a phospholipid bilayer and is the host cell's membrane
162
Types of nucleic acid within viruses
DNA: either double or single stranded
RNA: either double or singl estranded
163
Host cell of bacteriophage lambda
E. Coli bacteria
164
Nucleic acid of bacteriophage lambda
Double stranded DNA
165
Structure of bacteriophage lambda
Has capsid and DNA, tail sheath, base plate with protein spikes and tail fibres
166
Life cycle of bacteriophage lambda
Can follow either lytic or lysogenic life cycle
167
Host cells of Coronavirus
Human respiratory cells
168
Nucleic acid of coronavirus
Single stranded RNA
169
Structure of coronavirus
Spherical shape, single stranded RNA as genetic material, envelope and capsid attached closely to RNA, spike proteins on the envelope.
170
What is Coronavirus an example of?
Zoonosis (transferred between species)
171
Host cell of Human Immunodeficiency Virus (HIV)
Human Helper T Cells (WBCs)
172
Nucleic acid of Human Immunodeficiency Virus
Two identical RNA strands that convert into DNAS
173
Structure of HIV
Two identical strands of RNA (that are copied into DNA) and the reverse transcripase enzyme within a capsid coat; outer envelope; glycoprotein spikes
174
Extra information about Human Immunodeficiency Virus
Is a retrovirus. If untreated, causes AIDS (acquired immunodeficiency syndrome)
175
Lytic cycle steps
Step one: attachment (virus attaches to host cell)
Step two: DNA penetration (virus inserts DNA into host cell)
Step three: DNA replication
Step four: transcription (DNA is transcribed to become mRNA)
Step five: translation of viral parts
Step six: assembly and lysis (viral parts assemble into viruses, placing pressure on the cell, which forces it to lyse and release virus)
176
How quickly will symptoms occur if a virus works in the lytic cycle?
Quickly
177
How is the lysogenic crycle different to the lytic cycle?
Involves integration of viral DNA into the host DNA without being used to make viral parts. Slowly spreads as the cell reproduces. If viral DNA is released from the prophage, the lytic cycle is initiated
178
Steps of lysogenic life cycle
Step one: attachment (virus attaches to host cell)
Step two: DNA penetration (virus releases DNA into the host cell)
Step three: integration (viral DNA combines with the hsot DNA to become a prophage)
Step four: cell division (mitosis or binary fission)
*Could leave the prophage and enter the lytic cycle*
Step five: DNA replication
Step six: transcription
Step seven: translation of viral parts
Step eight: assembly and lysis
179
Why might viruses be an example of convergent evolution?
Wide variety in viral structure so are likely to have evolved separately and lack a common ancestor. This is seen through the diversity in genetic material
All similarities are a result of convergent evolution (e.g. spikes for attachment)
180
Theories about where viruses come from
Viruses first hypothesis
Regressive hypothesis
Progress hypothesis
181
Virus first hypothesis
Viruses existed before cells. Cells evolved from them
182
Why is the virus first hypothesis weak?
Viruses have genetic diversity + primordial soup was the origin of cells
183
Regressive hypothesis
Viruses were once cells that lost structure and function, becoming reliant on a host
184
Progressive hypothesis
Cellular components escaped, evolving into a virus by gaining function
185
Antigenic shift
Two or more different viruses invade the same cell and recombine genetic material, leading to dramatic changes in a short amount of time.
186
Example of antigenic shift
Influenza
187
What is the result of antigenic shift?
Rapid new virus formation, with new spikes that are not recognised by memory cells
188
Antigenic Drift
Once a virus invades a host, mutations occur to the viral DNA within a host cell. These smaller genetic changes accumulate overtime, leading to a new virus that is no longer recognised.
189
Example of antigenic drift
HIV
190
Why did the influenza virus evolve so rapidly?
Antigenic shift
191
What contributes to the rapid evolution rate of HIV?
Antigenic drift
