Cell Structure and Diversity Flashcards
1
Q
what is the limitation of cell size
A
the rate at which molecules can pass through the cell membrane in order to support the metabolic processes of the cell
2
Q
What are the three domains
A
bacteria, archaea, eukarya
3
Q
what are the kingdoms
A
animalia, plantae, fungi, and the protists
4
Q
what four things are needed for natural selection
A
time, genetic variation within the population, inheritance of genetic characteristics, and selection pressures
5
Q
what size are eukaryote cells?
A
10 - 100 microns
6
Q
what size are prokaryote cells?
A
0.1 - 5 microns
7
Q
what are the features of the light microscope?
A
- doesn’t need a stain
- can be used to view living cells
- colour images
- 1000 magnification in air
- 1400 magnification in oil
8
Q
why does oil immersion allow greater magnification than air in light microscopes?
A
because of the reduced diffraction of light
9
Q
resolution
A
the minimum distance which can separate two points and still have them visible as two separate points
10
Q
magnification
A
the ratio of image size to actual size
11
Q
what are the features of electron microscopes?
A
- stain needed
- can only view dead cells
- max magnification of x100,000
- black and white images
12
Q
how does a scanning electron microscope work?
A
electrons are fired over the surface of the cell, showing the 3D surface of the cell
13
Q
how does a transmission electron microscope work?
A
electrons are fired through a very thin sample of the cell, revealing the internal ultrastructure.
14
Q
what is spontaneous generation?
A
the idea that life can spontaneously arise from non-living matter in the correct environmental conditions
15
Q
what is germ theory?
A
the idea that microbes cause and spread diseases
16
Q
what did Pasteur’s experiment prove?
A
the germ theory because life only developed after the infusion was contaminated when the environmental conditions were kept the same
17
Q
What is sexual selection?
A
when a mate is chosen based on inheritable characteristics
18
Q
what does sexual selection select for?
A
extreme phenotypes
19
Q
what is sexual dimorphism?
A
sex based differences in size, colour, ornamentation, and behaviour
20
Q
what are Koch’s postulates?
A
- the suspected causative agent must be present in every case of the disease and generally not present in healthy organisms
- the microbe must be able to be isolated and grown in pure culture
- when a healthy host is infected with the microbe it must develop that specific disease
- the microbe must be able to be isolated from the deliberately infected host
21
Q
What are the most common atoms in the human body?
A
oxygen > carbon > hydrogen > nitrogen
22
Q
what is the monomer of polysaccharides?
A
monosaccharides
23
Q
what is a disaccharide?
A
a carbohydrate with two monosaccharide building blocks
24
Q
what is an oligosaccharide?
A
a carbohydrate with 3 - 9 monosaccharide building blocks
25
what is the monomer of DNA / RNA?
nucleotides
26
what is the monomer of protein?
amino acids
27
what is the monomer of lipids?
none - they are heterogenous
28
what is the function of hexose?
monomer for carbohydrates
29
what is the function of pentose?
used as part of larger molecules eg DNA
30
what is the functions of carbohydrates?
energy source and storage, structure, cell to cell recognition
31
which polysaccharides are composed of alpha glucose monomers? why?
glycogen and starch. this is because they are energy storage molecules, and alpha glucose bonds can be broken by enzymes. this means that the energy stored in the bonds can be released for use by the cell
32
which polysaccharides are composed of beta glucose monomers? why?
cellulose. this is because it is a structural molecule, and beta glucose bonds cant be broken down by enzymes, so the structural integrity of the cell is maintained
33
what is the difference between alpha and beta glucose molecules?
they are geometric isomers. alpha glucose is cis for the OH group on carbons 1 and 2, and beta glucose is trans.
34
what are the functions of lipids?
energy storage, regulatory, structural
35
describe the structure of a phospholipid
hydrophyllic head, hydrophobic tail.
| phosphate head, glycerol backbone, lipid tails.
36
describe the structure of a nucleotide
sugar with a phosphate bonded to carbon 5 and a nitrogenous base bonded to carbon 1
37
what are the differences between DNA and RNA?
- DNA = double stranded, RNA = single stranded
- DNA = deoxyribose sugar, RNA = ribose sugar
- DNA = thymine base, RNA = uracil base
38
what are the functional groups on amino acids?
amine group and carboxyl group
39
what are the eight protein functions?
```
structural
regulatory
contractile
toxic
storage
protective
catalytic
transport
```
40
what are the three prokaryote cell shapes?
- spirochaete = spiral shaped
- cocci = circular
- bacilli = rod shaped
41
what are the features of the cytosol?
- semifluid gel
- mainly water
- ions and proteins in it
- ~7pH
42
what size are ribosomes?
25nm
43
what are the three functions of capsules?
- resist dehydration
- resist phagocytosis
- increase adhesion to solid surface and other cells
44
what is a capsule?
a sticky protein or carbohydrate layer
45
what is the difference between a capsule and a slime layer?
a slime layer is less defined and less organised than a capsule
46
what is the function of the flagella?
motility via chemotaxis
47
what is the structure of the flagella?
flagellin protein arranged in alpha helix shape
48
describe the cell wall of Gram negative bacteria
- more complex
- two layers
- permeable
- less peptidoglycan
- contain lipopolysaccharides
- stains pink (crystal violet stain washes out)
49
describe the cell wall of Gram positive bacteria
- less complex
- one layer
- impermeable
- more peptidoglycan
- stains purple (crystal violet stain can't wash out)
50
what are the functions of the smooth ER?
- lipid synthesis
- calcium storage
- detoxification of drugs and poisons
- metabolism of carbohydrates
51
what are the functions of the rough ER?
- protein synthesis
- membrane factories
- glycolisation of secretory proteins in the lumen
- production of transport vesicles
52
what is the function of the fimbraie?
increased adhesion to solid surfaces
53
what is the function of the pili?
bacterial conjucation
54
describe the nucleoid
- region of genetic information
| - not membrane bound
55
what is an endospore?
- survival mechanism against starvation / adverse conditions
| - genetic material condensed into a spore which can survive adverse environmental conditions
56
what are the functions of the golgi body?
- modifies proteins
- glycolysation of cell surface proteins
- manufacture of macromolecules eg polysaccharides (pectin)
- direction of vesicles via vesicle markers
57
how are proteins processed through the golgi body?
- enter at cis face
- process through, being modified as they go
- exit at trans face
58
what is the function of the central vacuole?
- generate hydrostatic pressure
| - maintain cell structure / integrity
59
which organelles are in plant cells but not animal cells?
- chloroplast
- plasmodesmata
- cell wall
- central vacuole
60
which organelles are in animal cells but not in plant cells?
- centrosome with centromere
- lysosome
- flagella are more common
61
what size are viruses?
>20nm
62
what is a capsid?
a protein coat around the virus
63
describe the structure of the bacteriophage
- head where genetic information is stored
- tail
- sheath around tail
- tail fibres
- spikes
64
describe the lytic cycle
- genetic information is inserted into cell
- reverse transcription of RNA occurs using reverse transcriptase
- DNA replication of single stranded genomes occurs
- host cell genome is degraded
- virus takes over host cell mechanisms to produce reverse transcriptase and replicate the viral genome
- virus assembles within the cell
- viruses exit cell, lysing it
65
describe the lysogenic cycle
- genetic information is inserted into cell
- reverse transcription of RNA occurs using reverse transcriptase
- DNA replication of single stranded genomes occurs
- virus integrates itself with the host genome, creating a prophage
- virus exits genome when host cell replicates and forms a loop in the cytoplasm
- virus reinfects daughter cells
66
what is a viroid
a plant pathogen composed of naked circular RNA
67
how is a viroid different to viruses?
- much shorter - only a few hundred nucleotides
- only infects plants
- doesn't produce proteins
68
what is a prion?
a misfolded protein which converts other proteins to prions
69
what effects on the cell do prions have?
disrupt cell function, causing the cell to eventually die
70
describe the structure of the cell membrane
semipermeable phospholipid bilayer
71
how does the chemical structure of phospholipid tails affect the cell membrane structure?
saturated tails = densely packed phospholipids, less fluid membrane.
unsaturated tails = less densely packed phospholipids, more viscous membrane.
72
how does cholesterol affect the cell membrane?
cholesterol increases the fluidity of the membrane at low temperatures and decreases it at higher temperatures
73
what functions do plasma membranes have?
- separation of incompatible processes
- creates different environments for different processes
- allows concentration gradients to form
74
what are the functions of membrane proteins?
- active transport
- linking ECM and cytoskeleton
- signal transduction
- linking neighbouring cells
- cell identification
75
what is passive transport?
movement of lipid soluble / hydrophobic molecules through a plasma membrane down a concentration gradient without the use of ATP
76
what is facilitated diffusion?
movement of water soluble molecules through a plasma membrane down a concentration gradient without the use of ATP. requires membrane proteins or channels.
77
what types of channels are used to enable facilitated diffusion?
- voltage gated = ion fluxes
| - ligand gated = open with extracellular signal
78
what is active transport
movement of molecules up their concentration gradient through a membrane with the use of ATP
79
how does cotransport work? use H+ / sucrose cotransporter as example
- H+ ions pumped onto one side of membrane, creating a high concentration of H+ on one side
- low concentration of sucrose on the same side
- H+ ions flow through cotransporter, dragging sucrose along with them
- sucrose is added to side with high concentration
80
what is the function of the endomembrane system?
manufacture and transport of material within the cell
81
what are the functions of lysosomes?
- break down endocytosed material
- break down unwanted cellular structures
- autophagy (preprogrammed whole cell death)
82
what is endocytosis and how does it occur?
when materials are taken into the cell from the environment
works by having the cell fold around and form a vesicle with solutes enclosed in it
83
what is phagocytosis?
uptake of food particles
84
what is pinocytosis?
non-selective uptake of solutes
85
what is receptor mediated endocytosis?
selective uptake of solutes, mediated by receptors on the cell membrane which bind with certain solutes
86
what is exocytosis?
expulsion of materials from the cell
87
what is the constitutive pathway?
exocytosis of materials needed for the ECM
88
what is non-secretory exocytosis?
when materials are taken to the cell surface but are not excreted out of the cell
89
what is regulated exocytosis?
when hormones and neurotransmitters are exocytosed, allowing for a rapid response
90
what is the ECM made up of?
collagen embedded in a network of proteoglycans
91
what do fibronectins do?
link the ECM to the cell
92
what do integrins do?
- form a communications link between the ECM and the cell
| - links the ECM and cytoskeleton
93
what is an important property of collagen?
it absorbs water, allowing the ECM to resist compression and retain its shape
94
what is a tight junction?
a seal between neighbouring cells which prevents fluid from moving across the cell layer
95
what is a desmosome?
a junction which anchors sheets of cells together
96
what is a gap junction?
a point of cytoplasmic contact between cells which ions and molecules can move through, allowing for rapid intercellular communication
97
what are two functions of the cytoskeleton?
- maintaining cell shape
| - positioning organelles
98
what are the cytoskeleton components?
microfilaments, intermediate filaments, microtubules
99
what is the diameter of microfilaments?
around 7nm
100
what is the diameter of intermediate filaments?
8 - 12 nm
101
what is the diameter of microtubules?
25nm
102
what is the structure of microfilaments?
double chain of actin subunits
103
what are the six functions of microfilaments?
- cytoplasmic streaming in plants
- resisting tension
- maintaining cell shape
- organelle movement
- whole cell movement
- change in cell shape
- animal cell division
104
what is the structure of microtubules?
tubulin subunits arranged into a hollow tube
105
what are the functions of microtubules?
- resisting compression
- whole cell movement (controls cilia and flagella)
- organelle movement (walk along microtubules using ATP)
106
what are the structures of intermediate filaments?
cables of varying subunits. made of proteins such as keratin. supercoiled into coils.
107
what are the functions of intermediate filaments?
- very stable but not dynamic
- therefore used to maintain cell shape
- anchor organelles
- neural processes
108
reasons why cells need energy
- active transport
- organelle motility
- whole cell motility
- production of macromolecules
- growth
- repair
- reproduction
109
what is the size of the mitochondria?
1 - 10 microns long
110
what is the structure of the mitochondria?
- phospholipid membrane with embedded proteins
- inner membrane is highly folded cristae
- semiautonomous (mtDNA and ribosomes)
- mitochondrial matrix is the fluid within the cristae
111
what is glycolysis?
- cytoplasm
- glucose split into two pyruvate molecules
- ATP produced
- NADH produced
112
what is pyruvate oxidation?
pyruvate is oxidised to acetyl co-enzyme A
113
what is Citric Acid cycle?
- matrix
- processes acetyl co-enzyme A on sequence of enzymes
- requires high concentration
- produces ATP
- NADH and FADH2 produced
114
what are the two stages in oxidative phosphorylisation?
- electron transport chain
| - chemiosmosis
115
what happens in the electron transport chain in cellular respiration?
- cristae
- e- passed along sequence of enzymes
- energy released
- used to pump H+ ions into matrix
- creates high concentration of H+ ions in matrix
116
what happens during chemiosmosis in cellular respiration?
- H+ ions move through ATP synthase to area of lower concentration
- go from matrix to intermembrane space
- go down half channel
- ATP synthase turns, smashing together ADP and P to produce ATP
- H+ goes down other half channel and into intermembrane space
117
what is the direction of proton flow in cellular respiration?
matrix to intermembrane space
118
what is a endergonic process?
a process which absorbs energy
119
what is an exergonic process?
a process which releases energy
120
how does energy coupling work?
ATP transfers energy from exergonic processes to endergonic processes
121
Describe the structure of ATP
sugar linked to a nitrogenous base and three phosphate groups
122
what is ATP hydrolysis?
- an exergonic process which breaks the phosphate-phosphate bond
- couples to endergonic processes by transferring the phosphate
123
what are the functions of vacuoles?
storage of primary and secondary metabolites
124
what are primary metabolites?
growth related molecules eg ions, amino acids, lipids, and proteins
125
what are secondary metabolites?
non-growth related molecules eg tannins, pigments, alkaloids
126
what are proplastids?
undifferentiated plastids
127
what is the function of chromatids?
production and storage of pigments
128
what is the function of leucoplasts?
storage
129
what is the function of chloroplasts?
photosynthesis
130
how do plastids divide?
- binary fission
| - budding off
131
what triggers the development of chromoplasts?
hormones
132
what triggers the development of chloroplasts?
light
133
what three molecules do chloroplasts use to capture light?
- chlorophyll A
- chlorophyll B
- cartenoids
134
what light colours does chloroplasts absorb
- red
| - blue violet
135
describe the structure of the chloroplast
- ctDNA
- outer, inner, and thylakoid membranes
- thylakoids stacked into grana
- lumen = matrix within thylakoid membrane
- stroma = matrix between thylakoid and inner membranes
136
where do dark reactions occur?
stroma
137
where do light reactions occur?
thylakoid membranes
138
where are leucoplasts located?
- roots
| - parts of the plant which dont do photosynthesis
139
Describe what happens in photosystem 2
- photon hits Mg ion in head of chlorophyll
- e- gets excited
- e- jumps around chlorophyll molecules
- e- goes to primary electron acceptor
- water split to produce e- to replace e- (also produces O2 and H+ which go into lumen)
140
describe what happens on the first electron transport chain of photosynthesis
- e- falls down chain to photosystem 1
- goes through cytochrome complex
- energy used to generate ATP
- puts more H+ into lumen
141
describe what happens in photosystem 1
- photon strikes a Mg atom and excites an electron
- electron from Photosystem 2 replaces it
- e- bounces around chlorophyll molecules
- e- goes into primary electron receptor
142
describe what happens in the second electron transport chain of photosynthesis
- electron goes through NADP+ reductase
| - produces NADPH
143
describe what happens in carbon fixation
rubsico fixes carbon dioxide into an organic molecule
144
what happens during reduction?
electrons from NADPH are added to the organic molecule, reducing it to form a sugar
145
how is the carbon dioxide acceptor regenerated in photosynthesis?
- carbon dioxide accepter is rubisco
- 6 sugars are made but only one leaves the chloroplast
- the other five are used to regenerate rubisco
146
what are the stages of the Calvin Cycle?
- carbon fixation
- reduction
- regeneration
147
how do anaerobic organisms carry out photosynthesis?
they use nitrogen fixation and repress photosystem 2 so that no oxygen is produced
148
What is the composition of the cell wall?
- 25-30% cellulose
- 15-20% hemicellulose
- 35% pectin
- 5-10% protein
149
what are the two phases in the cell wall?
- crystalline microfibre phase
| - non-crystalline matrix
150
what is the structure of the crystalline microfibre phase?
strong cable-like structures composed of cellulose microfibres
151
what is the structure of the non-crystilline matrix?
- hemicellulose linkes cellulose cables together
| - pectin links neighbouring cell walls together
152
what is the function of hemicellulose in the cell wall?
limits cell wall extensibility, so regulates cell enlargement
153
what is the function of pectin in the cell wall?
traps water, increasing the elasticity. this is needed for cell wall expansion
154
how much of the cell wall is water?
~6.5%
155
which cell wall is secreted first?
primary, so it is on the outside of the cell
156
where is the matrix of the primary cell wall formed?
Golgi body
157
where is the extensin of the primary cell wall formed?
its a protein, so rough ER
158
where is the cellulose in the primary cell wall formed?
rosettes on the cell wall
159
what is the function of the middle lamella?
sticking adjacent primary cell walls together
160
what is the function of the secondary cell wall?
strengthening the cell wall
161
what is the structure of the secondary cell wall?
multiple lamaniated layers of microfibrils which are oriented in different directions
162
how is the composition of the secondary cell wall different to the primary cell wall?
- 15-35% ligin (adds strength)
- more cellulose
- more fibrin
163
what is the plasmodesmata?
a channel between cell walls which makes the cytoplasm, ER, and plasma membrane of neighbouring cells continuous
164
what is the function of the plasmodesmata?
hormones and other small molecules can pass through, allowing for rapid intercellular communication
165
how do viruses pass through the plasmodesmata?
proteins on the plasmodesmata thread the viral genome through
166
what is the panspermia theory?
the theory that the molecules of life had extraterrestrial origins
167
what proof for the panspermia theory does the Mars meteorite offer?
contains water, carbon, and mangenite.
| carbon and mangenite can only be produced by living organisms and water is essential for life
168
what proof for the panspermia theory does the Murchison meteorite offer?
contained lipids, amino acids, nucleotides, and simple sugars. these molecules are unique to life
169
what proof against the panspermia theory is there?
- unlikely biological molecules could survive space
- or descent to earth
- contamination from earth
170
what is the chemical evolution theory?
the idea that life arose by a series of chemical reactions
171
what were the four steps in the chemical evolution theory?
1. abiotic reactions formed amino acids and nitrogenous bases
2. spontaneous abiotic production of macromolecules occurred
3. a protocell formed after a membrane formed around macromolecules. this occurred by lipids being added to water
4. self-replicating molecules developed
172
what was the first self replicating molecule?
ribozymes, which were a combination of RNA and enzymes
173
what environmental conditions were needed for the chemical evolution theory to occur?
- reducing atmosphere
- lightning / UV to act as a catalyst
- certain types of clay
- hydrothermal vents
174
what evidence for the chemical evolution theory is there?
the Miller and Urey experiment which derived organic molecules from a simulation of early earth's environment
175
what is serial endosymbiosis?
the theory that eukaryotic cells arose due to failed phagocytosis of prokaryotes
176
how were inner cell membranes developed?
the cell membrane folded inwards, forming the nuclear envelope and endoplasmic reticulum
177
how did mitochondria arise?
a heterotrophic prokaryote was phagocytosed by a larger prokaryote but did not go to the endolysosome pathway
178
how did chloroplasts arise?
a phototrophic prokaryote was phagocytosed by a larger prokaryote but did not go to the endolysosome pathway
179
did chloroplasts or mitochondria arise first? why?
mitochondria bc all cells have them and only some cells have chloroplasts
180
what evidence for the serial endosymbiosis theory is there?
- inner plasma membranes of eukaryotes are very similar to cell membrane
- mitochondria and chloroplasts are semiautonomous
- mitochondria and chloroplasts are vunerable to some prokaryote antibiotics
- the inner membrane of mitochondria and chloroplasts are like prokaryote membranes and the outer ones are like eukaryote cell membranes
181
how would serial endosymbiosis be mutually beneficial?
eukaryote cell = new energy source
| mitochondria and chloroplast = protection and constant environment
182
what size is the nucleus diameter?
5 - 10 microns
183
what cells do not have one nucleus? why?
- red blood cells so they can carry more oxygen
| - muscle cells because they are made up of multiple cells fused together
184
what is the structure of the nuclear envelope?
double phospholipid bilayer
185
what is the function of the nuclear envelope?
-protect the genetic material
186
where is the nuclear lamina?
on the inside of the nuclear envelope
187
what is the structure of the nuclear lamina?
made of intermediate filaments
188
what is the function of the nuclear lamina?
- provides support and shape for nucleus
| - organises packing of DNA
189
what is a nuclear pore?
a highly regulated channel on the outside of the nuclear envelope
190
what does the nuclear pore allow to exit the nucleus?
- mRNA
- tRNA
- rRNA
191
what does the nuclear pore allow to enter the nucleus?
- energy
- materials
- hormones
192
what is the diameter of DNA?
-2nm diameter
193
which proteins are used for DNA packing?
histones
194
what is the first stage of DNA packing?
- DNA combines with histones to form chromatin fibres
- nucleosome beads
- 10nm diameter
195
what is the second stage of DNA packing?
histones twist the 10nm chromatin fibres to form a 30nm fibre
196
what is the third stage of DNA packing?
30nm fibres supercoil around histone proteins to form 300nm fibres which then coil to form metaphase proteins
197
what is euchromatin?
less dense areas of interphase DNA which is used more often
198
what is heterochromatin?
more dense areas of interphase DNA which is used less often.
