138 Molecular And Cell Biology Flashcards
(154 cards)
1
Q
Give features that are present only in an animal cell
A
Centriole - organises spindle fibres for mitosis
Microvilli
Glycosome - stores glucose
Lysosome
2
Q
Give features of plant cells that arent present in animal cells
A
Plasmodesmata
Large vacuole
Chloroplast
Cell wall
3
Q
What is a peroxisome?
A
Organelle involved in catabolism of long chain fatty acids, amino acids and polyamines.
It can also reduce reactive oxygen species e.g. Hydrogen peroxide
Contains catalyses and oxidases.
4
Q
Most significant differences between eukaryotes and prokaryotes
A
Membrane bound organelles
Nucleus
5
Q
How much of a cells volume is protein? What effect does this have on the inside of the cell?
A
20-30%
Very insoluble so a thick gel structure forms
6
Q
Describe the effect of the mycorrhizal arbuscules in plants
A
Small fungi that penetrate root cells, they supply the plant with nitrogen, phosphorus, and sulphur. In return the fungus receives metabolites e.g. Glucose. A symbiotic relationship
7
Q
What is meant by a coenocytic structure?
A
Very large cells that have more than one nucleus as well as an excess of other organelles.
8
Q
Give a use of compartmentation in the mitochondria during oxidative phosphorylation
A
Inner membrane is pH7 the matrix is pH 7.5 this enables a proton gradient to be maintained - protons will move through ATP synthase
9
Q
Give three general reasons for cell compartmentation
A
Enables sequestration of toxic compounds
Keeps enzymes and substrates separate
Keeps cell conditions optimum for the different activities within the cell
10
Q
Describe microtubules
A
Cylindrical tubes made from tubulin
20-25 nanometers wide
11
Q
Give three things that microtubules do
A
Determine cell shape
Form a trackway for organelles and vesicles to move along
Form spindle fibres for mitosis
12
Q
Describe microfilaments
A
Actin fibre - 3-6 nanometers involved in muscles contraction
13
Q
Describe intermediate filaments
A
8-12 nanometer and anchor the nucleus and give some flexibility
14
Q
What is the cytoskeleton
A
A mixture of protein filaments (microtubules, microfilaments) and motor proteins that form a 3-D mesh that works to hold the rigidity of the cell
15
Q
Which motor protein moves towards the positive side of the cell?
A
Kinesin
The positive side is away from the nucleus
16
Q
Dynein moves towards which side of the cell?
A
The negative end of the cell, i.e towards the nucleus
17
Q
What are melanosomes?
A
Vesicles containing melanocytes that can be moved through an organism. Enables it to change colour (melanocytes contain pigments)
18
Q
What is the use of cortical microtubules?
A
They reinforce the cell cortex, their direction determines the direction in which the cell elongates.
19
Q
What proportion of genes code for proteins that pass through the Golgi apparatus
A
1/3
20
Q
What is protein translocation?
A
Occurs in the endoplasmic reticulum
- where a protein enters
- protein has an N - terminal amino acid sequence
- this is removed when the protein enters the ER
21
Q
Give two modifications that may occur in the endoplasmic reticulum
A
Glycosylation
Disulphides bond formation
22
Q
What is the role of the Golgi apparatus?
A
Distribution, shipping and manufacturing of a cells chemical products
23
Q
Insulin is what type of hormone? Where is it released from?
A
Peptide hormones released from the pancreatic B cells (islets of langerhans)
24
Q
What type of protein is mucus?
A
Glycoprotein
25
Casein is found in what? From where is it released?
Milk
| Mammary gland
26
Describe the process of milk production
Smooth ER forms a lipid vesicle which it secretes into the cytoplasm
Rough ER synthesises casein
Casein packaged into vesicles and delivered via the Golgi
Lactose is synthesised from glucose within the golgi
27
What is the role of a protein body? Name one in plants
Store proteins to help aid rapid growth
| Vacuole
28
How do protein bodies prevent the castor bean plant poisoning itself?
Castor Beans contain Ricin (lethal does in humans is 22micrograms per kilogram) Its an anti herbivory meaning it inhibits protein synthesis by binding irreversibly to eukaryotic ribosomes.
Made of two pro ricin chains (A and B) these are modified in the ER and have their N terminal sequence removed, they are now active. The Golgi apparatus glycosaltes them and moves them to a protein body. Hence the active form is never present in the cytoplasm
29
Describe cystic fibrosis and how the endoplasmic reticulum causes cystic fibrosis
Cystic fibrosis is caused by a mutation in the chloride ABC (ATP binding cassette protein). This protein moves mucus from the lungs. Without it mucus accumulates = coughing and prevents enzymes from getting into the intestines.
Mutant chloride ABC usually has a mutation on the phenylalanine 508 protein, this doesn't effect function but the endoplasmic reticulum sees the mistake and degrades the protein.
30
How does the ER degrade mistaken proteins
Lysosomes and proteasome move in with degrading enzymes
31
What is the role of chaperones in the ER?
They try to prevent mutation of proteins, work to assist the intracellular folding of proteins
32
Give some roles of lysosomes
Recycle misfolded proteins
Storage of carbohydrates organic acids
Store toxic substances
33
Describe how cyanide doesnt kill the plants in which its made
You need a cyanogenjd glucoside (dhurrin) this is sequestered in a vacuole.
You also need glucosidases (enzymes that activate it)
The two need to mix, this only occurs where a vacuole is ruptured i.e. When bitten into.
34
Give evidence from: DNA, replication, ribosome size, size, porins and initiating amino acid for the endosymbiotic theory
Prokaryotes, mitochondria and chloroplast all have 1 single cicrular chromome eukaryotes hafe linear chromomes
" replicate by binary fission, eukaryotes by mitosis
" have 70s ribosomes, eukaryotes have 80s
" are 1-10ym whilst eukaryotes are 50-500ym
" have porins eukaryotes don't
" initiating amino acid is N-formymethionine, eukaryotes this is methionine
35
How has peptidoglycan helped provide evidence for endosymbiotic theory?
Make cell walls in cyanobacteria, genes for this still present in arabidopsis
36
How has cardiolipin provided evidence for endosymbiosis?
Constitutes 20% of mitochondrial inner membrane, but is only present elsewhere in bacteria
37
Describe a piece of living evidence for endosymbiosis involving sea slugs
Sea slugs eat seaweed and injest the chloroplasts which they can store on their backs. They can live without food for sometime after this, the chloroplasts are providing energy.
38
How many genes in arabidopsis have been transferred from cyanobacteria?
4500
39
mtDNA codes for what?
rRNA, tRNA and components for oxidative phosphorylation
40
Why is mtDNA inheritance very maternal?
1) egg cell far bigger: can contain up to 1 million mtDNA molecules, smaller sperm cell has at most 1000
2) then when fertilisation occurs the mitochondria within soerm are degraded anyway
3) some male mtDNA wont even reach the egg anyway
41
Describe the construction of rubisco
Has 8 large subunits made in the chloroplast on 70s ribosomes
And 8 small subunits made in the cytoplasm on 80s chromomes
The small unit has a signal sequence to enter the chloroplast which is removed on entry
Chaperones aid the assembly of the subunits pieces
42
Describe plastid diversity (i.e. Its "phylogeny")
Protoplastid - early in development
This develops into either a chloroplast or leucoplast (in dark conditions an etioplast)
Green cholorplast can change into a red chromoplast (green vs red peppers)
Leucoplast contain no pigment and store biological molecules wothin them: amyloplast store sugars; elaioplast store oils ; proteinoplast stores protein
43
Give an example of a plant without any plastid genes, why dpesnt it need them?
```
Rafflesia lagascae (the biggest plant - red)
Because it is parasitic it doesnt need photosynthesis
```
44
What are apicomplexia? Give an example and the disease it causes
Parasitic single celled eukartotic organisms that are derived from red algae. Their apicoplast ( a plastid) enables their parasitic nature.
E.g. Plasmodium that causes malaria
45
Why are the genomes of of individual organelles advantageous?
Having a genome is inexpensive (2% of cells energy budget)
Making proteins is very expensive (75% of cell budget)
Mitochondrial genes enable oxidative phosphorylation which increases the budget, hence creates a 200,000 fold rise in genome size in eukaryotes as opposed to prokaryotes
46
Give a brief timeline of DNA discovery
1874 - Friedrich misescher finds the chemical compositions of DNA through nuclein tissue extracts
1881 - Albert Kossel isolated the nucleotide bases
1953 - molecular structure of DNA resolved by x ray crystallography by Rosalind franklin
Watson and crick deduce helical structure and the spacing of the nucleotide bases
47
Which bases are the purines ?
Adenine and guanine
48
Thymine, cytosine and uracil make up what group of DNA bases?
Pyrimidines
49
How many hydrogen bonds form between A and T
2
50
Which base pairs form 3 hydrogen bonds between them?
G and C
51
Nucleotides are added to which end of DNA backbone? Why?
3' end
Reaction occurs between one of three phosphates on nucleoside (nucloside has 3 phosphates which are removed to become a nucleotide) i.e. The nucleotide binds to the sugar
52
Is replication faster in prokaryotes or eukaryotes
Prokaryotes
53
Where does replication start? How many of these are there in a prokaryote?
At the origin of replication - determined by a sequence of bases
There is one in prokaryotes
54
Describe the replication of prokaryotic DNA (leave lagging strand synthesis)
1) unwinds - DNA helicase bind at start of the replication fork and untwist the helix. Isotopomerase deals with overwinding, breaks DNA and swivels it around and rejoins.
2) single stranded binding proteins bind to the DNA to stabilise it.
3) primase synthesises short RNA primers using parental DNA as a template (5-10 base pairs long)
4) new bases are added at the 3' end. DNA polymerase binds to the end of the primer with a sliding clamp protein attached anchoring the polymerase to the leading strand. Chain moves through the clamp polymerase complex whilst it itself is still adding bases on
55
Describe the process of synthesising the lagging strand of DNA
Periodic addition of DNA primers, to which polymerases attach
Polymerases synthesises between the primers
Polymerase 1 removes the primers and any gaps are filled in
Gaps formed are called Okazaki fragments, these are filled in by DNA ligase
The replication machinery REMAINS STATIONARY
56
Why do chromosomes get shorter through replication cycles? What can be done to reverse this
Nothing can be attached to the location of the first DNA primer, polymerase falls off at the other end before synthesising it all.
Telomeres counter this by being large sections of junk DNA, it has no effect if these are removed
Telomerase catalyses the replication of telomeres in germ cells
57
Describe how DNA is packed in prokaryotes
Supercoiled associated with small amounts of protein. Found in the nucleoid
58
Describe the packing of DNA in eukaryotes
Linear DNA associated with histones to make chromatin
Nucleosomes = first layer of packing
Nucleosomes interact with histone tails to form chromatin figres (30nm thick)
Fibre forms loop domains called domains attached to chromosomes to form a scaffold, fibre increased to 300 nm. Looped domains coil further until width is 700nm
59
Describe why transcription and translation are faster in prokaryotes
No nucleus therefore transcription and translation occur in the same place
Translation can therefore occur before transcription has finished
60
What is the main difference between prokaryotic and eukaryotic transcription?
In eukaryotes premRNA is formed which is spliced into mRNA (no premRNA in prokaryotes)
61
Describe the initiation step of transcription
RNA Polymerase binds to a promoter region (can be either side of the DNA)
Cannot do this directly - TATA boxes recognised by transcription factors, the factors bind
Facilitates binding of RNA polymerase
62
Describe the elongation process of transcription
RNA polymerase causes the helix to untwist
Nucleotides added to 3' end
Double helix winds back behind
63
Describe the termination step of transcription (prokaryotes and eukaryotes)
Prokaryotes: polymerase stops transcription at the end of specific RNA sequences - terminators
Eukaryotes: RNApol 2 transcribes the polyadenylation sequences (AAUAAA) 10-35 base pairs from here the transcript is cut off
64
Describe pre-mRNA processes
There are untranslated regions on the pre-mRNA
5' end receives a modified 5' "cap" which is an "attach here" signal for ribosomes
3' end receives a poly-A tail (long string of adenine) works to protect the mRNA from enzymatic activity in the cytoplasm and aids transcription in termination
Other sections are spliced out i.e. Non translating sections in the middle
65
Describe splicing
Occurs with a spliceosome - contains small nuclear ribonucleoproteins (snRNPs)
snRNPs pair with nucleotides at specific sites across the premRNA
Spliceosome cuts premRNA releasing introns for degradation, ehilst it splices exons back together
66
What is alternate splicing?
Genes can code more than one polypeptide dependant on how they are spliced
67
How do tRNA molecules correctly match to an amino acid
Aminoacyl tRNA synthase
- 20 different synthase each with a specific active site for a particular tRNA - amino acid combo
Catalyses a covalent bond between them via ATP hydrolysis
Aminoacyl tRNA is formed
68
What is wobble? (Referring to translation)
The fact that the pairing between the third base of the codon and the anticodon is flexible
69
Of the large subunit of the ribosome what are the E, P and A sites?
E - Exit site, where discharged tRNAs leave the ribosomes
P - peptidyl - tRNA binding site, this holds the growing polypeptide
A - holds the next amino acid to be added to the chain
70
What is the role of the small subunit in the ribosome?
Location of the mRNA binding site
71
Describe the initiation stage of translation
Small ribosomal subunits bind with mRNA at the 5' cap and a special initiator tRNA (carries methionine) then binds to large subunit. (Uses a molecule of GTP)
Moves along the mRNA until it reaches AUG start codon
72
Describe the elongation phase of translation
tRNA pairs with complementary anticodon at the A site
Moves through
Amino acid in P site bonds with that of the A site
Empty tRNA moves to E site and is released
73
Describe the termination step of translation
UAG, UAA, UGA (stop codons) cause a release factor to bind to the codon.
Hydrolysis occurs between amino acid in the P site and the polypeptide
Polypeptide released
Large subunit detaches
74
How is translation of the same mRNA sped up?
Polysomes - many ribosomes all on the same mRNA molecule
75
Whats the difference between ribosomes bound to a membrane and free ribosomes?
Bound ribosomes make proteins that are secreted from the cell
76
How do proteins to be synthesised by bound ribosomes, bind the ribosome to the membrane?
These peptides have a signal recognition peptide, this binds the ribosome to the membrane system. Signal cleaving enzyme removes the signal recognition peptide
Translation commences directly into the ER Lumen
77
What was the cost of and how long did the human genome project take? Compare the cost to Jan 2017
13 years costing 2.7 billion dollars
| Just 1000 dollars in january 2017
78
How many genomes have been sequenced? How much of this is eukaryotic?
24,000
| 10% eukaryotic
79
Give an example to show how there is no relationship between kingdom/domain and genome size
Fritllaria assyriaca (flower) has a genome 40 times larger than that of humans
80
Why is the number of genes not associated with genome size?
Some genomes have far larger sections of noncoding DNA than others
81
What is an ortholog?
A gene that has evolved from a common ancestral gene
82
What is an operon?
functional genes and there promoter region
83
What can the promoter region of a gene be split up into to?
Operator sequence - determines the expression
| RNA polymerase binding site
84
What does the lac operon enable E.coli to do?
Digest lactose
85
Describe now the lac operon maintains metabolic homeostasis
A suppressor blocks the lac gene
Lactose binds to the Lac 1 suppressor and makes it inactive
Suppressor cannot bind to the operator so RNA polymerase transcribes the DNA
Produces beta galaxtosidase which hydrolyses lactose, hence the concentration of lactose is reduced
The suppresors become active again and expression of the lac operon is stopped.
86
Describe the negative feedback loop created by the Trp Operon
Operon contains five genes codes for the tryptophan synthesis protein complex which builds tryptophan
Operon has an inactive repressor
Tryptophan binds to the repressor and activates it
87
Why is the lac operon negative feedback system useful?
Very energetically expensive to maintain the translation and production of beta galactoaidase
88
What is quorum sensing ?
signalling between bacteria to coordinate group population density dependant behaviour
89
Describe how quorum sensing works in the context of bioluminescence
LuxCDABEG operon controls luminescence
6 coding genes form an enzyme that catalyses D - luciferin into oxyluciferin, this reaction produces light
Regulatory sequence (Lux box) controlled by two genes:
1) Lux R - codes for inactive activator for lux
2) Lux L - gene coding for N-acyl homoseriene lactones - these activate the Activators
Homoserienes are secreted at a constant rate, where there is a lot of bacteria the concentration rises to the point that the homoseriene moves by diffusion back into the bacteria
Hence binds to the Lux activator and activates it
LuxCDABEG
90
How many base pairs will there be in one nucleosome, how many histones are associated with this?
4 histones make one nucleosome that has 146 base pairs of DNA
91
What is densely packed chromatin called ?
Heterochromatin
92
What is the name of lightly packed chromatin?
Euchromatin
93
Why does DNA bind effectively to histone proteins?
DNA is negatively charged, histones have tails with residues made form arginine and lysine making it negatively charged
94
What two chemicals can be added to the histone tails to neutralise the positive charge. What enzymes undertake this role? What about the enzymes for the other direction?
Methyl and actyl groups
Added by histone methyl/acetyl transferases
Removed by histone deacetylases / demethylases
95
To get euchromatin where will methyl and acetyl groups bind?
Acetylation occurs at H3K9 histone 3, lysine 9
| Triple methylation occurs at lysine 4 on the third histone (H3K4)
96
How can chromatin modification be passed on through cell division?
Through cytosine modification
Methylated DNA recruits histone deacetylases and demethylases to gain more tightly packed DNA
Unmethylated DNA is associated with lightly packed chromatin where histone tails are methylated and acetylated
97
Describe the stalled state of RNA polymerase and how it is modified to become active
RNA bound to the TATA box with some transcription factors in place - phosphorylation on fifth serine
To activate phosphorylation of the second serine activates the polymerase
98
Describe how miRNA can degrade mRNA (or block its translation)
Identical to their target - double stranded
Associate with dicers (enzymes)
Form an miRNA protein complex
If the miRNA is 80-90% complementary translation will be blocked
The mRNA Will be degraded if its 100% complementary
99
How do siRNAs work in expression control
siRNAs induce DNA methylation at complementary gene sequences - silences the DNA
100
Describe the role of ubiquitin in protein degrdation
Non functional proteins are labeled with ubiquitin, if a protein has three ubiquitin molecules it will be degraded.
Moved to a proteasome, in which it is unwound and cut into smaller peptides
101
What is the basic process of biotechnology
```
Obtain the starting material (gene)
Amplify the gene - PCR
Get into the useful form - ligations,restriction enzymes and cloning factors
Transformation- put into a bacterium
Selection - check it has worked
```
102
How can you extract genes from microbes?
Heat to break the membrane
Or
Alkaline lysis by adding a base
103
Give some sophisticated methods of DNA extraction in higher organisms
Bind to silica membranes - wash to remove excess
Remove proteins with phenol and chloroform
CsCl gradient to purify DNA (old method)
104
Describe the process of PCR
Denature the DNA at 94-98 degrees to make single stranded
Anneal specific primers - 55 degrees
Taq DNA polymerase extension- 72 degrees
105
What goes into PCR?
```
Template DNA
Primers
dNTPS (deoxyribose nucleotides)
Buffers
Taq DNA polymerase
```
106
What is a common error in PCR? How can this be rectified?
Taq Polymerase isn't perfect, some mutations will occur. Taq often falls off around 2Kb
Find different more accurate polymerases
107
Describe how you can get DNA into a useful form for biotechnology
Restriction endonuclease are enzymes with a specific nucleotide sequence they cleave DNA around their recognition site
Use the same enzyme on a vector (the ends will be the same)
Use DNA ligase to join the DNA fragment into the vector
108
Describe how antibiotics can be used to select bacteria that have had a gene successfully inserted
Along with the wanted gene add an antibiotic resistant gene
Grow the bacteria in a solution with antibiotic
Only those with the gene will survive
109
Describe the process of transformation of genes into bacteria
Add ligation mixture into competent cells
Heat shock the sample at 42 degrees - destabilised they can now accept the DNA
(Can be done instead via electroporation - applying an electric current)
110
Describe the process and results of Blue white screening
Plasmid used has a LacZ gene - produces part of a Beta galactosidase enzyme
Combines with another part of the bacterial chromosomes to create an active enzyme
Active enzyme turns X-GAL blue
IPTG is added to the growth medium - induces expression of LacZ
This is done in partnership with antibiotic screening
Three potential scenarios
1) no plasmid present - colony dies, no antibiotic resistance
2) X-GAL goes blue - gene not inserted successfully, beta galactosidase is formed
3) gene inserted succsessfully - LacZ gene disrupted, no beta galactosidase is produced - colony remains white
111
What is a protoplast?
Plant cells without cell walls
112
How is a helical structure formed in proteins?
Hydrogen bonds WITHIN the protein chain
113
How is a beta pleated sheet formed in proteins?
Hydrogen Bonds BETWEEN different chains
114
Why is it that disulphide bond formation can occur in the endoplasmic reticulum?
ER lumen provides an oxidising environment so favours disulphide bond formation
115
Why do disulphide bonds get broken in the cytosol?
Cytosol is a reducing environment that favours the breaking of disulphide bonds
116
Glutathione has two forms, the switching between these two forms causes what in proteins? What are the two forms?
Glutathione exists as GSH its reduced form, It can reduce disulphide bonds (break them) and in turn it becomes GSSG (the oxidised form)
117
25% of amino acids in keratin are what? Why?
Cysteine
| It enables the formation or many disulphide bonds to add strength
118
Keratin is used in beaks and claws as well as hairs and horns, the protein structure is different in each, which fit into which group?
Keratin in Hair,horns and hooves form alpha heleix
| Beaks and claws from beta pleated sheets
119
What is the most abundant protein in animals?
Collagen
120
What is collagen used for?
Extracellular structural protein, helps tissues withstand stretching.
121
Why does a lack of vitamin C cause scurvy?
Collagen protein has large amounts of proline, can be modified in the ER to hydroxyproline. This enables the twisting of the chain.
Forming hydroxyproline needs vitamin C.
Hence without vitamin C your tissues become very fragile
122
Why is it that fiborin has a rigid structure?
Made of antiparallel beta pleated sheets - rich in non polar side chains (due to high glycine and alanine levels)
123
How does fibroin (silk) excreted from the spider)?
Stored as an emulsion. Its C-terminus makes it soluable whilst the core is hydrophobic
Water and Na+ leave the lumen, K+ surfactants and lubricants enter causes pH to change from 7.6 to 5.7
Causes unfolding thread leaves the spinneret through the spigot
Residual water stripped off
Molecules strech out and link together to form long strands
124
Why is abscorbic acid added to wheat in bread making?
Ascorbic acid is vitamin C acts as an oxidising agent that breaks the disulphide bridges
Stretches out the polypeptide chains enables bubbles of CO2 form between them
Gives the bread structure
125
What is the genetic basis of the sickle cell anemia disease?
GAG -GTG
Glu6 to Val6
Valine is uncharged whilst glycine is polar and hydrophillic
126
Describe why sickle cell anaemia is dangerous
Deoxygenation causes hydrophobic residues to associate, generates rigid fibres of haemoglobin.
Oxygenation causes the fibres to melt, normal shape reemerges.
Cells sickle and return to normal over and over
Damages the cells cytoskeleton
127
19,000 genes can be turned to how many different proteins due to post translation modification?
Over 1 million
128
What are moonlighting proteins?
| Give two examples
Proteins with more than one job, their job is dependant on the conditions
E.g. Crystallins - structural proteins in the eye as well as metabolic proteins
E.g. aconitase - iron homeostasis as well as the krebs cycle
129
What are the three hormones involved in controlling glycogen metabolism? What is each hormone involved in?
Insulin - glycogen synthesis
Glucagon - glycogen breakdown, comes from pancreas
Epinephrine- adrenaline - glycogen breakdown, comes from adrenal glands
130
Describe the action of insulin on glycogen metabolism
Binds to cell surface receptors
Activates protein phosphatase 1
This de phosphorylates glycogen synthase a to b turning it on, glycogen synthesis occurs.
phosphorylase kinase inactivated
Inactivates glycogen phosphorylase which stops glycogen degradation
131
Describe the action of glucagon on glycogen metabolism
Activates adenylyl cyclase pathway = cAMP
cAMP is a messneger that activates kinase A
Glycogen synthase A is active, phosphorylated by kinase A to become inactive
Kinase A phosphorylates phosphorylase kinase (activates it)
This phosphorylates glycogen B phosphorylase B (activates it)
This enzyme can break down glycogen
132
How many people have diabetes, whats the increase expected by 2025
380 million, 50% increase expected by 2025
133
Give reasons why transport in eukaryotic cells is necessary
Metabolism needs fuel and produces waste products
Cytosol to organelles
Proteins secreted by the secreatory system
Signalling between cells
134
How does transport occur between animal cells, what is the exclusion limit for these transporters? How many in human genome?
Connexins in vertebrates or inexins in invertebrates
Exlusion limit of 1kDa
Around 20 in human genome
135
What are plasmodesmata? What runs through them?
Channels in plants that run through the cell wall
1kDa exclusion limit that can be 20kDa when dilated
Endoplasmic reticulum runs through them called the symplasm
136
Describe the gorter and grundel experiment of 1925
Extract Lipids from red blood cells using a solvent
Suspend a droplet on water
Langmuir trough used to measure area of the lipid
All of the lipids merged into one droplet
The total lipid area is twice the area of the red blood cell hence the lipids are in a bilayer
137
What are aqua porins?
Pores in membranes that conduct water and small uncharged molecules
10 genes in man 30 in arabidopsis
138
Give three types of active transport
ATP pump
Couple molecules e.g. Na/K pump
Light driven pumps - halo bacteria
139
Give 4 types of ATP pumps
ATPase - transport ions
PPases -similar to ATPase
ABC transporters - ATP binding casssette proteins
Rotary ATPases - proton pumps with role in energy conversion
140
How many genes for ion channels in man?
100
141
Parietal cells are used for what?
Parietal cells are the epitherial cells that secrete hydrochloric acid and HCl
142
Describe the role of transporters in HCl secretion of the gastric parietal cells
Pump protons against a concentration gradient into the stomach
This is done by an ATPase that drives H+ into the stomach and K+ out
K+ accumulates outside the stomach and moves back in via diffusion through ion channels
The protons come from carbonic acid within the parietal cells, CO2 reacts to form carbonate ions and protons
An anion antiporter transports bicarbonate out into the blood for Cl- into the parietal cells
Cl- accumulates in the parietal cells and diffuses through ion channels into the stomach
143
How is sucrose transported against the concentration gradient in plants?
Sucrose and protons move through a H+ symporter
| A proton gradient is maintained by a proton pump
144
Give three names of methods used for visualising gene expression
Gus reporters
Fluorescent proteins
Luciferase
145
Describe the methodology behind Gus reporters as a method of visualising gene expression . (In context of pathogen resistance)
Gus A gene = beta glucuronidase
When expressed the enzyme changes the colour of the X-Gluc (5-bromo-4-chloro-3-indolylbeta - D - glucaronide) from colurless to blue.
Salycilc acid will turn on the PR1 promoter which has had GUS attached, hence GUS enzyme converts X-Gluc blue
146
Describe how fluroescent proteins can be used to visualise gene expression
Promoter region fused to a gene coding for a fluorescent protein (flurophore). Flurophore can absorb particular wavelength, it emits light of a different wavelength
147
What is meant by quenching when referring to Fluorescent proteins as a means of visualising gene expression
The sample loses its fluorescence over time
148
A promoter can be fused to luciferase to help visualise gene expression, what reaction does this undergo? Give two advantages of this method of expression visualisation
D-Luciferin is degraded by luciferase enzyme to oxyluciferin which outputs light.
V sensitive so good for low level transcription,
Very short half life therefore it will degrade where its no longer working so you can see movement
149
What is the key gene we look at in the arabidopsis practical?
PR1 - Pathogen related 1
150
Give four important plant stress hormones and the stresses they work on
Salycilic acid - biotrophic pathogens
Jasmanic acid - necrotrophs
Ethylene - insects, necrotrophs and biotrophs
Absisic acid - drought stress
151
Describe the mechanism for salicylic acid dependant immunity
Pathogen recognition receptors detect microbe associtaed molecular proteins (MAMPS). This releases transcription factors, that cause salycilic acid to be formed. SA reaches a threshold point at which it effects the redox charge of the cell.
The NPR1 gene usually exists in conglomerate form, varied redox state effects this and it becomes monomeric and moves into the nucleus activating its defence genes
152
What is the name of the gene that is always turned on in the arabidopsis practical?
p35S:GUS
153
Why is P.Cucumerina hemibiotrophic?
To avoid the SA initiated immune response
154
Describe the basic results for each question in the arabidopsis practical
SA vs Aspirin
- asprin induces the PR1 gene to a similar extent to SA, to much SA causes death
Salt stress
- no affect on expression of SA induced pPR1:GUS
Gus isn't quantitative or abiotic stress doesn't effect biotic stress
P.Cucmerina
- increases the SA response, halo around necrotic patch
