Eukaryotes Flashcards
What are peroxisomes?
Site of oxidative metabolism
Why are topologically equivalent pathways good?
As molecules can move between compartments without crossing a membrane
What is the significance of the cristae and thylakoids?
extensive internal invaginations for max SA and capacity for energy metabolism
Name for ETC supercomplex on cristae membrane
Respirasome
How are cristae insulated?
Narrow junctions at neck = diffusion limitation
Densely packed with ETC complexes
Name fro type of plastid from which many diff types are derived?
PROPLASTID
What do gerontoplast plastids do?
senescing chloroplasts
What do TOC and TIC stand fro in terms of chloroplasts?
TOC- translocase of outerchoroplast membrqne
TIC- translocase of innerchoroplast membrqne
4 pathways fro thylakoid import
1- Sec pathway
2- SRP-like pathway
3-TAT
4- spontaneous insertion
How are number of mitochondria and chloroplasts controlled?
Fission (Dynamin) and fusion (GTPase)
Where does glycosylation occur and what happens?
In ER- ADDITION OF n-LINKED GLYCANS TO PROTEINS
Name of flattened membrane sacks in golgi
Cisternae
Primary function of golgi?
polysaccharide factory (processing of N-linked glycans on glycoproteins adn synthesis of glycolipids
What are functional compartments of golgi?
Cis- Medial- Trans- cisternae
function of endocytic pathway
transport macromolecules from external environemnt to lysosomes/vacuole for digestion
What does cell wall affect in endocytic pathway?
precluded phagocytosis (but not endocytosis)
2 layers of COPII transport vesicle coat
Adaptor proteins (interact with membrane) cage proteins (assembled in lattice)- deforms membrane
what is characterisitc of ER resident proteins?
primary structure of short aa sequences
effect of KDEL signals in ER residency
Necessary for residency of protein AND sufficient for causing residency of secreted protien if transplanted
how do KDEL signals maintain ER proteins in the ER?
continuous retrieval from golgi
How is cholesterol stransported?
As LDL (low density lipoprotein )particles
`What are the 2 protein layers of CCV’s ?
clathrin complex adn Adaptin complex
4 fates of proteins going to golgi
1- to PM/ secreted (default)
2- to CCV
3- return to ER
4- retention in golgi
SNARES are present on which proteins?
ALL
What happens when v-SNARE matches t-SNARE?
compatible
forms complex
pulls closer to membrane
What is the acrosomal vesicle?
membranous organelle located over the anterior part of the sperm nucleus that is highly conserved throughout evolution. This acidic vacuole contains a number of hydrolytic enzymes that, when secreted, help the sperm penetrate the egg’s coats.
In mammilian fertilisation what does the sperm first bind to?
Zona Pellucida
What event occurs after fertilisation of 1st sperm to prevent any more fertilising the egg? (mammals)
Membrane depolarisation
What triggers mulitple waves of calcium?
applications of a calcium ionophores
What is the consequence of positive feedback of calcium during mammalian fertilisation?
Calcium induced calcium release
What is released from corticol granules under PM to toughen up zygote in harsh condition?
polysaccharides- after fertilisation
3 functions of calcium wave following fertilisation?
1- depolymerise membrane potential = block polyspermy
2- harden zona pellucida
3- stimulate centrosome duplication and anaphase promoting factor
What are mendels 2 laws of assortment?
1- alleles separate in equal proportion
2- alleles at diff. loci assort independantly
(2nd law should state UNLINKED characters assort independently)
What are dimorphic chromosomes?
diff. length e.g. Sex chromosomes-
What is result of linked alleles not assorting independantly?
Parental characters remain together in progeny
What does hemizygous mean?
posseses a single allele at a locus
What are polytene chromosomes?
large chromosomes which have thousands of DNA strands e.g. in Drosophila
Difference between coupled and repulsed alleles?
Coupled- WT on 1 chromosome and mutant on the other
Repulsed- each chromosome carries 1 of each
What is recombination?
exchange of genetic material between the maternal and paternal chromosomes
When does recombination happen?
meiosis prophase 1
What is a holliday junction?
4 strands containing branched intermediate
What can suppress recombination?
Chromosomal inversions
What is a nucleosome?
DNA wrapped twice around histone protein
What are the 5 elements of a protein coding gene (RNA)?
cap, 5’ UTR, coding sequence, 3’ UTR, poly-A tail
Whats the modal length of an exon?
111bl (37 codons)
What are centromeres mostly composed of?
alpha-satellites
How do spindle fibres attach to centromere during mitosis?
Using kinetochore
What is the repeated sequence in telomeres and how long are they?
TTAGGG- 10,000 bp long
What to retrotransposons exist to do?
Reproduce themselves
What happens to density of genes on chromosomes near centromeres and telomeres?
centromere = low/none telomere = high
How many exons in the average gene?
4
What is average length of exons with respect to histones?
Approx same length as DNA wrapping round histones
What is satallite DNA?
Repetitive elements only simple sequence repeats (1-6bp long)
What does CDK stand for?
cyclin dependent kinases
What is MPF and what does it do?
maturation promoting factor- stimulates mitotic and meiotic phases
why is fission yeast good for studying the cell cycle
can tell where it is in the cell cycle by its size
What are the 2 subunits of MPF?
CDK and cyclin B
What does cdk actually do?
its a kinase so adds a phosphate onto a serine or threonine group
What are the 2 approaches to genetic studies?
Forward and reverse genetics
What are 3 methods of identifying mutant genes?
1) insertion mutagenesis
2) linkage mapping and map based cloning
3) whole genome sequencing
What does insertion mutagenesis rely on?
transposons
What is the hypothesis of linkage gene mapping?
Recombination frequency of a gene pair is related to the distance between them on a chromosome
What is the equation fro recombination frequency?
total number of recombination events/ total no. of gametes tested X100
how are linkage maps generated?
combination of recombination frequencies of different genes
What does it mean that genetic and linkage maps are COLINEAR?
same order
What are 2 types of molecular markers?
INDELS (insertion/deletion)
SNP’s (single nucleotide polymorphism)
what is cosegregation?
transmission, together, of 2 or more genes on the same chromosome, as a result of their being in very close physical proximity to one another
What does map based cloning eliminate?
Estimation
What are steroid hormones used for?
long, slow pathways, activating gene regulatory proteins
What are the 3 types of cell surface receptors?
enzyme-linked, G-protein coupled and ion channel
What are enzyme linked surface receptors capable of?
MASSIVE AMPLIFICATION
What type of surface receptors are used as major drug targets?
G-protein coupled receptors
How can GABA ion channel recreptors be used as muscle relaxants?
as they inhibit action potential by maintaining membrane hyperpolarisation
What does adrenaline use to trigger specific tissue responses?
cAMP
What is a method of visualising ion channels using a specific probe?
transgenic chameleon probes = colour change detected by ratiometric sensors
What can be used to measure ion channels?
Patch clamp
What is ion selectivity determined by?
ionic radius and hydration energy
What are the 2 types of post synaptic potentials?
excitatory e.g. glutamate channels and inhibitory e.g. GABA
What are the 3 types of synapse?
neuromuscular, neurone-neurone, neuroglandular
How are voltage gated channels associated with movement of charges within a protein?
helices move with change i membrane potential as contain charged residues
How many proteins per cell?
1,000,000,000
What are the 3 distinct regulation stages of transcription?
Initiation, Elongation. Termination
What is the function of transcription factors?
recruit/ block recruitment of other proteins + recruits initiation complex
What is the function of the capping enzyme during transcription?
Cps first nucleotide to exit polymerase which protects RNA from degradation
What is the rate of transcription (nucleotides per second)?
72
What is the average time taken to transcribe a gene?
4.5 mins
What happens to nucleosomes during transciption?
dissociate and associate
How many protein coding genes in human genome?
20,000
what brings polymerisation to a halt during transcription
cleavage and poly adenylation complex
what does the pre-initiaion complex recruit during transcription?
polymerase
What do miRNA’s do?
can degrade /inhibit mRNA
Why is miRNA ability to degrade/inhibit mRNA useful in genome?
defence against retrotransposons and viral infection
What is an oocyte?
cell in an ovary which may undergo meiotic division to form an ovum.
What type of cleavage is it when the whole cell divides?
holoblastic cleavage
What does the first division after fertilisation determine in many bilaterians?
radial symmetry
What is teloblastic cleavage?
only part of fertilised egg divides (as seen in teleost fish)
What organ systems does the ectoderm go on to make?
nervous system + epidermis
What organ systems does the endoderm go on to make?
gut +associated digestive and respiratory organs
What organ systems does the mesoderm go on to make?
muscle, skeleton, excretory system and gonad
What is myogenesis?
formation of muscle tissue from myoblast precursors
What is a syncytium?
a single cell or cytoplasmic mass containing several nuclei
What is the difference between symmetric and asymmetric stem cell division?
symmetric= either 2 x commited or 2 x stem cell- asymmetric = 1 of each
what can a totipotent stem cell differentiate into?
everthing inc. extra-embryoninc tissue
what can a pluripotent stem cell differentiate into?
all cells in embryo and adult
what can a multipotent stem cell differentiate into?
all cell types in a tissue or organ
what can a oligopotent stem cell differentiate into?
several related cell types
what can a unipotent stem cell differentiate into?
one 1 type of cell
What regulate stem cells and maintain in stable undifferentiated state?
TF, Epigenetics, microRNA
What does in vitro mean?
it happens outside of a living organism
What does in vivo mean?
with or within an entire, living organism.
What type of stem cell produce red blood cells?
Haematopoietic (very productive)
Overexpression of what can reprogram differentiated cells to a pluripotent state?
Yamanake /OSKM transcription factors
What generates the polar ejection force during mitosis?
plus end motors of the microtubules
what synchronises spindle formation, chromosome condensation, NEB and motor protein localisation to initiate mitosis?
CDK
What is the name for the stable attachment of microtubules to the kinetochore?
amphitellic
What acts as chromosome glue between sister chromatids?
cohesins and condensins (SMC proteins)
What is the name of ring the structure stabilsing siser chromatids make of SMC proteins?
Solenoid
What is transdifferentiation?
with or within an entire, living organism.
What is a neoblast?
non-differentiated cells found in flatworms called planarians
What are 2 methods of cells changing fate during regenration?
transdifferentiation and undifferentiation to a pluripotent state
What happens during methylation?
charge left intact - methyl groups recruit diff diff/ set of proteins which interact with DNA in a diff. way-generally tightening
What happens during acetylation?
K and R basic residues are affected- their chatge is removed and the interaction between histone tails and DNA loosens = ready for transcription
Are epigenetics inherited?
YES- methylation points inherited therfore have same genetic profile as parent cell or organism
