Cells Flashcards

1
Q

5 kingdom classifications of life?

A
Plantae
Fungi
Animalia
Protista
Prokaryotae

Classification mainly based on morphology

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2
Q

3 domain classifications of life?

A

Bacteria
Archaea
Eukaryota

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3
Q

What are eukaryotic cells and what are prokaryote?

A
Eukaryote:
Plants
Animals 
Fungi
Protoctisa

Prokaryote:
Bacteria and Archaea (both are monera)

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4
Q

Organisation of a bacterium?

A
Pilli
Cell wall
Plasma membrane
Cytoplasm
Nucleoid (DNA) (so no nucleus)
Ribosomes
Flagellum
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5
Q

Organisation of a eukaryotic cells?

A
Plasma membrane
Golgi apparatus
Peoxisome
Mitochondrium
Lysosome
Enoplasmic reticulum
Nuclear membrane
Nucleus
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6
Q

Only cell that doesn’t have cell wall?

A

Animals

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7
Q

What extra do plants have?

A

Vacuole
Cell wall
Chloroplast

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8
Q

What extra do fungi have?

A

Cell wall

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9
Q

What is larger pro or eukaryote?

A

Eukaryote by far, also more complicated so theory that they developed after prokaryotes

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10
Q

A catalytic RNA molecule is called a?

A

Riboenzyme

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11
Q

Evidence RNA earlier than proteins?

A

RNA makes protein

RNA fundamental part of ribosome, whereas protein have just been added

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12
Q

How were the building blocks or RNA generated?

A

Random early earth conditions (eg lightening)

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13
Q

What could ribonucleotides bind together to form?

A

Replicase ribozymes which could make new replicases after polymerising on a clay surface

So can duplicate, due to temperature changes

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14
Q

How was a the lipid bi-layer in a cell made?

A

In Geysers, minerals catalyse the formation of fatty acids from hydrogen and carbon monoxide

Which have one end which hydrophilic (outside) and one is hydrophobic (inside) in a droplet known as micelles

Vesicle formation triggered by acidic pH or clay surfaces

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15
Q

What then occurs within the vesicle to from a protocell?

A

Flipping of fatty acids could bring in molecules, so they accumulate within the vesicle

The RNA replicase uses ribonucleotides to make a copy of another RNA replicase

Micelles fuse with the vesicle and enlarge it until it becomes unstable and divides

Random mistakes could lead to better replicases which could make protocol grow and divide faster

Protocell competes for resources driving evolution

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16
Q

What is the optical resolution limit and what does it rely on?

A

Minumum distance that allows recognition of object details

The optical resolution depends on the wave length of the light/beam used (smaller wave length = better resolution)

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17
Q

Features of light microscope?

A

Visible light ( wave length 390-700nm)

Glass lenses focus light

Resolution limit is 200 nm

Advantage is cells alive

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18
Q

Features of electron microscopy?

A

Electron beam ( wave length 0.0025 nm)

Electromagnetic lenses focus beam

Resolution limit 0.05 nm

Advantage is high resolution

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19
Q

Difference between scanning electron microscopy (SEM) and Transmission electron microscopy (TEM)?

A

SEM:
Electron beam scans over surface of sample
Can produce 3d images
Image shown on monitor

TEM:
Electron pass through THIN sample
Samples specially prepared
2D image shown on fluorescent screen

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20
Q

What is freeze fracture electron microscopy?

A

Freeze cell in resin, cut in half and analysis

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21
Q

What is averaging in microscopy?

A

Averaging many images together allowing reconstruction of the ultra-structure

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22
Q

What is fluorescence?

A

The emission of light by a substance that has absorbed light

The emission will be at a higher wavelength than excitation (the initial light), energy is lost before light is emitted

Allows visualisation of single molecules

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23
Q

What is GFP?

A

A reporter to analyse proteins in the living cell

It fuses to the DNA which will make the protein - which are normally still functional

These proteins are transcribed

They are exposed to blue light and will appear green

Different colours discovered so can observe interactions between different proteins

Also quantitive information as brightness represents how many there are

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24
Q

Advanced use of fluorescent proteins

A

FRAP (fluorescent recovery after photobleaching):
High energy sent in, which photobleaches the gfp molecules so can’t reflect light, if molecules are moving they will move into it and it will light up again, if not then nothing is moving

FLIP Fluorescent loss in photobleaching:
Used to see if one protein moves to another, so photo bleach, and then see if this photo bleach area appears in the place we think it will move

Photoactivation (photo-activatble GFP):
400nmlaser light induces a chemical reaction

About 100 fold increase in fluorescence after photo-activation

So allows you to identify the proteins you want to, as they will give lots of light off as their gfp has been activated

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25
Features of plasma membranes?
Contains specific proteins, lipids and sugars Surrounds the cell Phospholipids are amphiphatic (hydrohphillic and hydrophobic) and assemble into bio-membranes in the presence of water Fatty acid tails are hydrophobic, phosphate groups are hydrophilic Cholesterol reduces membrane fluidity at moderate temperature and avoids solidification at low temperature (Temperature buffer) Cholesterol also serves as a hormone
26
What's a lipid raft protein?
Membrane regions that assemble specialised lipids and proteins to perform a certain task (Normally show reduced fluidity)
27
Types of protein in plasma membrane?
Transporters Enzymes Receptors Cell-cell recognition Intracellular joining Attachment to the extracellular matrix and intracellular cytoskeleton
28
What does bio-membranes being semipermeable lead to?
Uncharged and hydrophobic molecules can pass through the membrane However charged or polar cannot pass, so require a mechanism to get in and out Such as protein channels, which can be open or gated Also can go through via facilitated diffusion (protein changes shape not let molecule through, it can't go back and no ATP needed Pumps can pump molecules through requires ATP
29
4 types of gated channels?
Voltage Mechanically Temperature Ligand
30
What charge is in the inside of the membrane normally and how is it created?
-50 to -70mV SOPI pumps, and leakage channels
31
Example of non excitable and an excited cell?
Epithelial Muscle cells and neurones
32
What do cells in an epithelium establish?
Tight lateral and basal contact to withstand friction Tight junctions are formed hold membranes of the cells together, functions as a diffusion barrier, and consists of plasma membrane proteins that interact There are also here's junctions, consists of cadherin and catenin, cadherins bridge between the cells, catenins link to the actin cytoskeleton, they both control actin organisation Gap junctions allow diffusion from cytoplasm of one epithelial cell to another, made up of connexins There are desmosomes, contain specialised Catherine proteins that interact with each other and with intermediate filaments, they resist shear force in epithelia They are hemidesmosomes which contain man proteins that interact with the extracellular membrane, they anchor the epithelia cell to the basal lamina ( extracellular matrix underneath the epithelium, probably also used in signalling Extracellular matrix is fibres of secreted proteins, and they hold tissue together, provides strength and directing cell migration
33
Describe a simple intracellular signalling pathway?
Extracellular signal molecule Receptor protein, on plasma membrane of target cell Intracellular signalling molecules released, either will be via phosphorylation of proteins by protein kinases and phosphatases, or signalling by GTP-binding proteins Effector proteins: Metabolic enzymes - altered metabolism Gene regulatory protein - altered gene expression Cytoskeleton - altered cell shape or movement
34
Describe signalling via GTP-binding proteins?
G-proteins are molecular switches They are activated by a Guanine nucleotide exchange factor (GEF), and inactivated via a GTPase-activating protein(GAP) Small monomeric G-proteins receive signals from many receptors Large trimeric G-proteins interact with G-protein coupled receptors
35
What's a kinase?
An enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific substrates Process is known as phosphorylation
36
What are phosphatases?
An enzyme that removes a phosphate group from a protein, a process called dephosphorylation
37
What can occur to protein kinases for the signal to be amplified and spread to other pathways?
Get phosphorylated themselves Creates signalling cascade
38
Function of Cdk kinase?
Control of cell cycle progression
39
Function of Src-type kinase?
Control or regulate various biological functions
40
What do the particles and molecules undergo in cytoplasm?
Brownian motion - flickering movement due to collisions
41
What does diffusion in cytoplasm depend on?
Size of the molecule/organelle Smaller they are the more they move Diffusion is very limited to larger objects as it's too crowded
42
Features of ribosomes?
Consist of 2 subunits (small and large) made from ribosomal RNA and proteins Prokaryotes have 70 S (smaller) Eukaryotes have 80 S (larger) S (Svedbery value) stands for sedimentation rate of a particle - depends on mass density and shape Translate information from mRNA into proteins
43
Basic steps of protein translation?
Matching tRNA to mRNA codon Release of elongation factor Formation of peptide bond Elongation factor G triggers a forward movement of ribosome
44
What is a polysome?
Numerous ribosomes operating along a single mRNA molecule
45
What is the nucleus linked to?
The endoplasmic reticulum
46
Parts of the nucleus?
Euchromatin Heterochromatin Lamina Nuclear pore
47
Features of nuclear pores?
have 8 fold symmetry Made up of numerous proteins and control nuclear transport Made up of nuclearporins Gated, control what goes in and out
48
What goes in and out of the nucleus through the nuclear pores?
In (import): Proteins Out (export): Proteins RNAs Ribosomal subunits
49
What happens to the nucleus during mitosis?
It releases its content so has to re-import it's nuclear proteins Also the nuclear envelope and the nuclear lamina disassemble: Phosphorylation of lamins - breakdown Dephosphorylation of lamina Fusion of nuclear envelope fragments Fusion of enveloped chromosomes
50
What's the nuclear lamina and it's functions?
Forms a network at the inner nuclear membrane Consists of intermediate filaments (cytoskeleton) It organises chromosomes and supports transcription of genes Also anchors nuclear pores and prevents clustering
51
What does the nucleolus do?
Forms ribosomes Contains granular components which is the ribosome assembly site Contains fibrillar centres where rRNA transcription occurs Ribosomal proteins are imported into the nucleolus, the assembled ribosomes are then exported into the cytoplasm It's not membrane bound just a gathering of material
52
DNA associates with proteins into?
Chromatin
53
Features of DNA in the nucleus?
Heterochromatin: - Remains packed after mitosis - Transcriptionally less active - 8% of DNA - 2 types Consecutive Heterochromatin - Always packed, non-coding DNA near centromere and telomers) Faculative heterochromatin - Variable between cell type and development stages Then there is euchromatin which is 92% of DNA and transcriptionally active
54
When is all the DNA tightly packed?
Mitosis, makes it easier to transport
55
What does packing DNA require?
Being wrapped around positively charged proteins called histones Organised into nucleosomes - which loosen during transcription
56
What does RNA polymerase 1 form?
rRNA
57
What does RNA polymerase 11 form?
mRNA
58
What does RNA polymerase 111 form?
tRNA
59
What does RNA polymerase in plants form?
siRNAS required for heterochromatin formation
60
Basic Principle of transcription?
Numerous transcription factors bind to the TATA box in the promoter (upstream of the gene) RNA polymerase binds to the template strand and synthesises an exact copy of the coding strand (except thymines are replaced with uracil) RNA is released, further processed and the released from the nucleus bound to RNA binding proteins
61
Do prokaryotes have a nucleus, and how does this make them different to Eukaryotes?
NO, so transcription and translation occur in the compartment, and many genes on one mRNA Whereas in eukaryote transcription and translation are compartmentalised and, one mRNA per gene
62
What does the endomembrane system contain?
``` Nucleus Endoplasmic Reticulum Golgi apparatus Lysosome/vacoule Endosomal compartment Transport vesicles ``` All the compartments of the endomembrane system are connected by transport vesicles that serve material exchange
63
What do molecular motors do?
Transport vesicles and organelles within the cell, this is called membrane trafficking They are enzymes that use ATP to walk along the cytoskeleton
64
What happens at membrane with transport vesicles?
Exocytosis or endocytosis
65
What is secretory pathway?
Going out of cell
66
What is the endocytic pathway?
Outside to a vesicle inside
67
2 types of endoplasmic reticulum?
Smooth (no ribosomes) | Rough (studded with ribosomes)
68
Function of smooth ER?
Calcium storage for signalling Lipid synthesis Detoxification of poisons Metabolism of carbohydrates
69
What is the Golgi apparatus?
Disc shaped stack of membranes Has Cis end which receives transport vesicles from ER Trans end releases the secretory vesicles
70
What do oliogosacchardides do (sugar chains on membrane) and where are they processed?
Provide protection against pathogens Serves in cell-cell recognition and signalling Marks progression of protein Helps folding and interaction with other proteins Made in the golgi apparatus
71
2 ways oligosaccharides can be linked to proteins?
Asparagine (N-linked) Threonine (O-linked)
72
3 types of endosomes which are involved in processing endocytose material?
Early endosome Recycling endosome Late endoscope
73
Describe endocytosis?
Formation of a vesicle at the plasma membrane Fusion of vesicle with early endosome Decision - degradation or recycling If recycling - pH drop removes ligand, and the rest is taking out Or Maturation of early endoscope to late endosome - which can send material to Golgi Or Lare endosome could turn into a lysosome - this is degradation
74
Describe lysosomes ( can also be called vacuoles in certain circumstances)?
Serves as a disposal container pH far lower in lysosomes due to acid hydrolyses such as proteases, and lipases creating small building blocks pH is low due to H+ pumps, which requires ATP
75
3 pathways to degradation in lysosomes?
Bacterium taken up via phagocytosis, then broken down in the lysosome Pinocytosis and receptor mediated endocytosis, small particles go to lysosome and are broken down Autophagy, lysosomes break down own cytosol , eg if starved
76
What are peroxisomes?
Single membrane bound organelles that contain many enzymes Major site of oxygen utilisation Detoxification produces Hydrogen peroxide which is degraded by catalase Play important role in lipid metabolism
77
What are lipid droplets?
Fat storage droplets Vary in size and are enclosed by a monolayer Associated proteins regulate the metabolism of the fat droplets Created at the endoplasmic reticulum
78
What is a nucleomorph?
When algae have a DNA containing relict of an engulfed eukaryote
79
What does Fat-acid-binding protein (FABP) do?
Makes fatty acids water soluble
80
Features of transport vesicles?
Carry cargo 50 types of integral proteins Membrane speciality is provided by SNARE receptors Most common vesicle is v-SNARE
81
Steps of fusion of a vesicle with a target membrane?
Therthering: Rab-GTP on vesicle binds to Rab-binding tethering factor on membrane Docking: V-snare from vesicle forms complex with tT-snare on membrane Fusion: Cargo is unloaded into membrane
82
Features of vesicles having a coat?
Clathrin coat COP1 coat COP11 coat Different coats are specific for particular places in endocytic and exocytic pathways Coat concentrates specific proteins in patches
83
Features of extracellular vesicles?
Transport vesicles released from cells Found in body fluids Contain RNAs and proteins provided by the donor cell Deliver their contact to recipient cells
84
Features of micro vesicles?
500-1000nm diameter Formation at donors plasma membrane Transfer proteins mRNASs and miRNAs that control protein expression Uptake via fusion with plasma memrbrane
85
Features of exosomes?
40-100nm diameter Formed at early endosome, released from late endoscopes Transfer proteins, mRNAS and miRNAS that control protein expression Uptake via endocytosis or fusion with recipients plasma membrane
86
Functions of exosomes and micro vesicles?
In immunology In blood In CNS In bone Also can spread cancer
87
What provides tracks that link the regions of the cell?
Cytoskeleton
88
Definition of the cytoskeleton?
Consists of filamentous bio-polymers ( microtubules, F-actin and intermediate filaments) and of associated proteins that are modulating the activity, dynamics, or organisation of the cytoskeleton
89
Why is the cytoskeleton called this?
Connects all of parts of the cell Supports motility Helps spatial organisation
90
3 filaments that make up the cytoskeleton?
F-Actin - Short range transport, cell migration, 7-9nm Microtubuli - Long-range transport, Chromosome inheritance (mitosis and meiosis), 25nm Intermediate filaments - mechanical strength, 10nm
91
Types of actin?
``` Filamentous actin (F-actin) Actin bundles (stress fibres) Actin monomers (G=Actin pool) ```
92
Where do you find Microtubules?
Coming from the centrosome - microtubule organising centre, near the nucleus
93
Where do you find F-actin?
Gathered on One side of the cell
94
Where do you find intermediate filaments?
Everywhere in cell
95
Describe the structure of F-actin?
G-actin Protein subunits that forms 2 Protofilaments wrapped around each other
96
Structure of microtubules?
Have dimers which are made of Beta tubulin and alpha tubulin, which forms protofilaments which form microtubulus
97
Describe polymerisation of a microtubule?
GTP-bound tubulin dimers get added to the positively charged end (polymerisation) A cap of GTP tubulin stabilises the growing microtubule
98
Describe pausing of a microtubule and what can occur after?
Stops growing as GTP-Tubulin cap has all been hydrolysed by tubulin behind forming GDP-tubulin + phosphate Then a rapid depolymerisation will occur: The microtubule becomes unstable, this moment is known as a catastrophe However then polymerisation can occur again, GTP-tubulin can bind creating a new cap, this is known as a rescue attempt The switch between growth and shrinking is known as dynamic instability
99
Why is dynamic instability useful?
Allows the microtubule to reorganise
100
How has speckle microscopy proven dynamic instability?
If label some tubulin with GFP then will appear in patches on microtubule
101
What do plus-end binding proteins do?
Control the dynamics of microtubules and participate in intracellular motility
102
What do animal centrosomes contain, and what do they do?
They contain centrioles and the PCM Centrioles consist mainly of microtubule Become the basal body of flagella and cilia They organise the pericentriolar material (PCM) and ensure it's inheritance Fungi and plants do not have centrioles
103
Do centrioles replicate during the cell cycle?
Yes
104
What does PCM contain?
Gamma tubulin which nucleates (making) the microtubules
105
General function of intermediate filaments?
Providing mechanical strength and in organising cytoplasmic architecture Interact with microtubules and F-actin
106
Structure of intermediate filaments?
Made up of protein subunits which form a coiled coil made up of alpha helices alpha helices are often amphipathic (charged at one side) which serves protein interaction
107
Extra facts on intermediate filaments?
Only found in animal cells Do not require ATP or GTP for assembly, but rather self assemble into an apolar filament (2 bind to each other due to being amphipathic They can disassemble into subunits to allow cell movement Have different types of sun units
108
What forms the nuclear lamina and what does it do?
Intermediate filaments Lamina provides stability and organises the nucleus
109
Example of an intermediate filament?
Keratin - makes nails Some intermediate filaments also determine the optical properties of the eye lens
110
What drives cell motility and examples?
Molecular motors which are mechanical enzymes (protein complexes that utilise ATP to walk along the cytoskeleton) Microtubule associated: Kinesin Dynein Actin associated: Myosin
111
How do molecular motors move across cytoskeleton?
They walk
112
Antony van Leeuwenhoek is famous for?
the discovery of microbes using a simple microscope
113
According to the "RNA World Hypothesis, the protocell had the following features?
It was surrounded by a lipid-bilayer (a bio-membrane) It contained ribozymes and RNA
114
Which of the following structures confer resistance against shear forces and thereby ”strengthen” epithelial tissues?
Desmosomes Hemidesmosomes Tight junctions
115
What does the nucleus contain?
Heterochromatin Euchromatin A nucleolus
116
Organelles of the endomembrane system communicate with each other by?
Transporting vesicles
117
What does the endosomal compartment consist of?
early endosomes recycling endosomes late endosomes
118
Lipid droplets are fat storage compartments that are generated at the?
Smooth ER
119
Fusion of transport vesicles with a target membrane involves?
tethering of the vesicle to factors in the target membrane docking of the vesicle to the target membrane
120
What do motors take through the cell?
Vesicles and organelles
121
Principle how a motor works?
Weak binding Tight binding due to ATP-binding Hydrolysis and power stroke Release of ADP and Pi
122
Which molecular motors walk towards the plus end, and which walk towards the minus end?
Plus: Kinesin Myosin Minus: Dynein
123
How are motors recycled?
For example Kinesin and dynein would bind to the same cargo on either side of it Then Kinesin would take it to plus end, when it reaches there will flip over to other side and dynein can take it back
124
How are collisions between Kinesin and Dynein avoided?
Dynein can move to avoid the Kinesin, as can move to another protofilament on the track Kinesin just moves forward
125
What is the motility in neurones known as?
Axonal transport - Dynein and Kinesin working together
126
What does skeletal muscle mainly consist of?
Myosin, and F-actin in sarcomers
127
What do thick filaments consist of?
Myosin 11
128
What do thin filament consist of?
F-actin (sandwich the thick filaments)
129
How is muscle contraction controlled?
Stimulus from neutron spreads over the plasma membrane of the muscle cell Depolarisation of membrane releases calcium from the sarcoplasmic reticulum into the cytoplasm Binding of calcium to the troponin complex releases the bloke of the myosin binding site on actin Myosin binds actin and walks towards the Z-disk Calcium is removed by calcium pumps and myosin releases the actin filament = relaxation of muscle
130
Features of cardiac muscle?
Spontaneous contractions Same principle of skeletal just less ordered
131
Difference between flagella and cilia?
Flagella come in smaller numbers and move the cell, propellar like motion Cillia are in larger numbers and have function in fluid and particle transport, back and forth movement
132
Describe the structure of a cilliim/flagella?
Axoneme - The core, made from microtubules Basal body anchors them to the cell - formed from centrioles
133
What support the formation and function of the cilium?
Intraflagellar transport along the axoneme: Kinesin-2 moves building material up Dynein bring moves material back down
134
Ultrastructure of cilium and flagellum?
9 pairs of microtubules around edge but on is half attached 1 microtubule pair in the middle Dynein (slides microtubules against each other- they have protein bridges so results in bending): Radial spokes (like a bike) Outer arm dynein Inner arm dynein
135
What leads motility in cells?
Actin in treadmilling, so led by the actin side Steps: Extension of plasma membrane pushing it forward due to actin polymerisation Adhesion so doesn't spread out Translocation of the body forward De-adhesion Process that heals wounds
136
What occurs in prophase?
Chromosomes condense Nuclear envelope disrupts Spindle is formed
137
What occurs in metaphase?
Microtubules make contact with chromosomes Chromatids are positioned in one plane
138
What occurs in anaphase?
Microtubules and motifs pull on chromosomes Chromatids move to the poles Rapid elongation of the spindle Formation of a contractile ring
139
What occurs in telophase?
Cell middle contracts and separates (cytokinesis) The chromosomes decondense The nuclear envelope is formed
140
3 types of microtubules in the organisation of the mitotic spindle?
Astral microtubules Polar microtubules Kinetochor microtubules
141
How can you test that microtubules are required for mitosis?
Use Nocodazole which is anti microtubule, and see that mitosis can no longer occur
142
2 mechanisms that microtubules provide the force for chromosome segregation by creating a polar ejection force?
1- de/polymerization of microtubules Exerts force on attached chromosome 2- Molecular motors that act on the microtubules
143
What's checked at different checkpoints?
G2 (entering M) - is all DNA replicated, is environment favourable Metaphase (end of M) - Are all chromosomes attached to the spindle G1 (entering S) - is environment favourable
144
How does cytokinesis occur?
A contractile ring localises the area of constriction, near the cortex at the end of anaphase composed of actin, myosin 11, regulators and actin binding proteins
145
Main features of mitochondria?
Have a double membrane with inner membrane folds (Cristae) and their own mitochondrial genome Use sugars fats and oxygen to produce ATP (power house of the cell)
146
Steps of energy generation in mitochondria?
Uptake of food molecules from the cytosol into the mitchondrial matrix Oxidation of Acetyl-CoA into carbon dioxide (Citric acid cycle = Krebs cycle); Production of the electron shuttle molecule NADH NADH transfers the electrons to the respiration chain at the inner membrane; electron flux is used to build up a proton gradient Back-flow of protons drives ATP synthesis
147
Do mitochondria and chloroplasts have their own genome?
Yes
148
What is apoptosis?
Programmed cell death Occurs in multi cellular organisms Blocks are recycled after death It's triggered by cell damage, apoptotic proteins cause damage to the mitochondria, which release factors that activate the apoptotic enzymes
149
Features of viruses?
DNA or RNA that is protected by a protein coat (capsid) 1000 x smaller than a human cell Extracellular form known as a vision Intracellular form = replication of DNA/RNA to assemble virus Infecting fungi = mycophaves Infect bacteria = bacteriophage They are not alive They self assemble
150
What's a naked virus?
Protein coat (capsid) Nucleic acid (RNA or DNA) Enzymes (not always)
151
What's an enveloped virus?
Protein coat (capsid) Nucleic acid (RNA or DNA) Enzymes (not always) Biomembrane (lipids from host cell) Enveloped proteins (from the virus)
152
What's a complex virus?
Protein coat (capsid) Nucleic acid (RNA or DNA) Enzymes (not always) Complex protein tail
153
3 distinct ways viruses enter the host cell?
Endocytosis - enters as a Trojan horse Membrane fusion Injection - inject genetic information and leave rest of virus particle behind
154
Lifecycle of a complex virus?
Virus attaches to surface receptors The tail contracts, enzymes break the cell wall, and the core needle pinches the cell The content of the head (proteins, DNA/RNA) is released into the cell The bacterial metabolism is disrupted and the genomic DNA degraded Viral DNA is transcribed into mRNA Viral DNA is replicated mRNA is translated into viral proteins Complex virus particle self assembles (50-100) Cell lysis and release
155
Lifecycle of an enveloped virus
Entry into the host cell by endocytosis or membrane fusion Release of DNA into cytoplasm, motors (dynein) can also bind directly to the viral capsid so virus is making use of the intracellular transport machinery DNA made and translation of proteins occurs, new viruses made Budding occurs, virus leaves cell taking membrane to form it's envelope
156
What are magnetotatics?
Bacteria that navigate along magnetic fields by detecting it They contain crystals of an iron material called magnetosomes, they use them for magnetotaxis (a compass) Gram negative
157
Main actin like proteins in prokaryotes?
MreB - cell shape ParM - DNA partitioning MamK- forms filaments
158
Modes of motility of bacteria and archaea and how they move ?
Swimming Swarming - on surfaces Gliding Twitching Flagella rotating due to protons generating ATP Have directly motility for food Pili retract and grow to allow twitching (creates colonies) or slow gliding
159
How do bacteria enter mammalian cells?
They force the host cell to take them up A protein ring assembles into a needle The needle injects proteins into the human cost cell to manipulate the actin cytoskeleton, thereby forcing uptake Type 3 or type 6 secretion systems inject the proteins
160
2 major growth forms of fungi?
Yeast: Uniceullar and often rounded Grow by budding Hyphal: Usually multi-cellular and elongated Extend by polarized growth
161
What does fungal growth rely on?
Delivery of vesicles to the growth region (bud or hyphal tip) via the cytoskeleton and the fungal motors on them Dynein to negative end, kinesis to positive end
162
What's the spitzenkorper?
The apical body involved in hyphal growth It's a vesicle cluster at the tip, it serves as a vesicle supply centre Contains secretory and recycling vesicles Hyphal growth relies on this structure
163
Describe hyphal growth?
Transport along the cytoskeleton Storage of vesicles in the spitzenkorper Release and fusion with plasma membrane
164
Function of Woronin bodies?
Prevent if one cell dies in fungal chain the cytoplasm leaking out of all of them Blocks the gaps between the cell bodies by plugging They are specialised peroxisomes Contain hexagonal crystals of the protein Hex1
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Why do mushrooms release spores?
For reproduction
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What actually is a mushroom?
The organisation of basidiomycete fruiting body
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Mechanism of spore discharge in basidiomycetes?
Two water drop are formed Due to secretion of secretion of mannitol and other hygroscopic sugars on the surface of the spore The Adaxial drop and the Buller's drop Buller's drop increases in size due to recruitment of atmospheric water Sudden change of centre of gravity by fusion of both drops create a propulsive force
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How do ascomycetes release spores?
Turgur pressure built up within the ascus and a sudden burst
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What are chloroplasts?
Use light, carbon dioxide, and water to produce glucose and oxygen = photosynthesis Surrounded by a double membrane Have inner membrane system Have their own genome
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What's the thylakoid?
membrane compartment; the thylakoid membrane surrounds the thylakoid lumen
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What's a granum?
A stack of thylakoids Contains light capturing system and ATP synthase
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What's the storm?
Matrix of the chloroplast Contains fixation enzymes, chloroplast DNA, Ribosomes
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Why are plants green?
Doesn't absorb green light So they don't use the visible spectrum very efficiently But if they did (say there were black) too much heat would be generated Mainly absorbs blue and red light.
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Why do leaves turn from green to yellow to red in autumn?
Sense of reduced photosynthesis Degradation and recycling of cellular components is induced Chloroplasts turn into gerontoplasts Breakdown products get stored in the plant vacuole Formation of anthocyanin that protect against too much light and oxidative stress (turns them red) Finally the cells get killed and the recycled cellular components released from the vacuole and delivered to the plant
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Are chloroplasts motile? Why?
yes To avoid photo damage from light 3 steps: Photoperception - Plant blue - light photoreceptors perceive the light Signal transduction - Calcium signalling Chloroplast movement - Motor dependent
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What is cytoplasmic streaming?
Occurs independently of chloroplast movement Depends on energy and requires F-actin There is a nonmoving cytoplasm (Exoplasm) and a streaming cytoplasm around the vacuole (endoplasm) it's moving due to sliding theory (so basically just motors moving everything which drags the cytoplasm)
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Features of plant cell wall?
Primary wall is flexible and unorganised, The secondary wall is formed in fully developed cells far more rigid. Contains Lignin (wood) Both contain cellulose Cellulose synthase complex forms a rosette in the plant plasma membrane in which a nascent 36 gluten chains are extruded into the wall. These organise the walls
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What control expansion of the cell?
Plant vacuole Generates outward pressure (turgor) that is counter balanced by the cell wall Variation in cell wall rigidity due to orientation of the cellulose fibres directs cell expansion
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What is plasmolysis?
The reversible shrinkage of the plant cell, due to reduced turgor pressure in the vacuole Reveals cell-cell contacts
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What connects plant cells?
Cytoplasmic bridges called plasmodesmata They allow free passage of small molecules Can be plugged by formation of callose if one cell is infected
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How do plant cells divide?
Microtubules form a plant-specific array called the phragmoplast in the middle Vesicles then transported to here to form the cell plate by fusing Endoplasmic reticulum crosses the cell plate (helps form plasmodesmata) Cell wall in interior fuses with plasma membrane
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What is cellular endosymbiosis?
Is when a single cell organism lives in a host cell
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What is endosymbiosis theory?
Three fundamental organelles, mitochondria, chloroplasts and basal bodies of flagella were once themselves free-living cells With the mechanisms of: Phagocytosis of a prokaryote Host cell and endosymbiont reproduce Development of an interdependence
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Arguments for endosymbiosis theory?
Mitochondria and Chloroplasts have their own circular genomes Mitochondria and Chloroplasts have 70S ribosomes which is the same as prokaryotes Chloroplasts and cyanobacteria (prokaryote) ave thylakoid membranes Chloroplasts and mitochondria both have a double membrane - derived from incomplete phagocytosis