What is the enzyme that catalyses the reversible reaction that converts Glucose-6-Phosphate to Fructose-6-Phosphate?
Phosphofructokinase
Phosphoglucose isomerase
Aldolase
Glyceraldehyde-3-phosphate
What is the function of exonuclease?
Removal of RNA primers
Removal of DNA primers
Stitching together of Okazaki fragments
Joining adjacent nucleotides together
What direction does the coding strand run in?
5' to 3'
3' to 5'
What direction does the template strand run in?
What is the function of Gyrase?
Prevent DNA supercoiling
Add DNA sequence repeats to the 3' end of DNA strands at the end of chromosomes
Unwind the DNA strand
Remove RNA primers
RNA contains the bases Adenine, Thymine, Cytosine and Guanine.
snRNA forms part of a complex with proteins (snRNPs) which aid in the formation of the spliceosome that is involved in pre-mRNA splicing.
What post-transcriptional modifications are added to mRNA?
5' methyl-guanosine cap
3' poly A tail
5' methyl-adenosine tail
3' mono A tail
What codon signals the start of translation of a protein?
AUG
ATG
TAC
UAA
Why is the triplet code known as degenerate?
More than one codon codes for one amino acid
Codons can become mutated
Codons are read three bases at a time
Where does DNA replication, transcription and splicing occur?
Cytoplasm
Nucleus
Mitochondria
Extracellular Matrix
An open reading frame is a section of RNA with a small number of codons that results in a truncated, non-functional protein.
What is the enzyme responsible for charging tRNA with amino acids?
Amino-acyl tRNA synthetase
Peptidyl Transferase
Signal Peptidase
Phosphotransferase
Most mutations are only detrimental to a protein if they occur in the exons; the coding regions of DNA.
Phospholipids are amphipathic molecules, what does this mean?
They possess two properties in a single structure
They can form bilayer sheets
They are highly hydrophobic molecules
They can form micelle structures
Phase transition occurs at a lower temperature in plasma membranes that have shorter, more unsaturated fatty acid tails.
Where does phospholipid synthesis occur?
Outer cytosolic leaflet of the endoplasmic reticulum
Outer cytosolic leaflet of the golgi apparatus
Inner cytosolic leaflet of the golgi apparatus
Inner cytosolic leaflet of the endoplasmic reticulum
What is the function of scramblase in the formation of new plasma membrane?
Catalysing the 'flip-flop' mechanism that distributes phospholipids between the outer cytosolic and inner cytosolic portions of the plasma membrane
Catalysing the fusion of the newly synthesised portion of the plasma membrane to the existing plasma membrane
Catalysing vesicle release from the endoplasmic reticulum after the newly synthesised portion of the plasma membrane is produced
What are the three subtypes of phospholipid?
Phosphotidylcholine
Phosphotidylethanolamine
Phosphotidylserine
Phosphotidylvaline
Phosphotidylethylamine
Phosphotidyladenosine
The function of the enzyme Flippase is to aid fusion of the newly synthesised plasma membrane with the current plasma membrane.
Glycosylation is the process by which a triglyceride side chain is added to a protein, such as when glycoproteins are made in the endoplasmic reticulum.
Transmembrane proteins contain which of the following components that enable them to become embedded in membranes?
Signal sequence
Stop-transfer sequence
Embed sequence
Translocate sequence
Recognition of the stop-transfer sequence in a transmembrane protein causes what to happen?
The transmembrane protein to travel across the membrane
The transmembrane protein to become embedded in the membrane
The transmembrane protein to be removed by enzymatic digestion
Steroid and Thyroid hormones can travel across the plasma membrane and the nuclear membrane due to what property?
Lipophilic
Hydrophilic
Lipophilic hormones such as Testosterone (steroid hormone) can only exhibit its function if :
A special transporter protein that enables testosterone transport across the membrane is present
The receptor that testosterone binds to in order to act as a transcriptional factor is not faulty
The enzyme that catalyses testosterone transport is not denatured
Due to adrenaline's lipophobic nature, how can it cause intracellular effects?
It acts on a receptor on the external cell surface, causing the alpha sub-unit of the heterotrimeric complex to activate and go on to activate adenylyl cyclase. This enzyme produces cAMP that participates in further cascade reactions in order to produce adrenalines required effect - glucose release.
A special accomodating channel protein (AACT) allows adrenaline and other catecholamines to be transported across lipophilic membranes and produce their effects intracellularly, without altering osmolarity.
Wnt is another lipophobic hormone. It activates the destruction complex which destroys beta-catenin and then allows activation of transcriptional factors to promote transcription.
How many layers does pseudostratified epithelium contain?
1
2
3
What is the appearance of stratified columnar epithelium?
One layer thick
Multiple layers thick
Equally wide and long, cuboidal in shape
Long, thin, column arrangement in shape
What is the barrier and fence function?
The prevention of paracellular movement of molecules due to tight junctions between cells
The prevent of diffusion of molecules across the plasma membrane, without a facilitating channel protein
The way in which lateral surface modules (such as desmosomes) anchor adjacent cells together
Adherens junctions contain actin filaments.
Desomosomes contain tubulin microtubules.
Collagen formation occurs in what order?
Protocollagen -> Tropocollagen -> Collagen fibre assembly
Tropocollagen -> Protocollagen -> Collagen fibre assembly
Collagen fibre assembly -> Tropocollagen -> Protocollagen
Collagen fibre assembly -> Protocollagen -> Tropocollagen
Intermediate filaments are cell specific.
What are the layers of the epidermis in descending order?
Stratum Corneum -> Granular layer -> Spinus layer -> Basal layer
Granular layer -> Spinus layer -> Basal layer -> Stratum Corneum
Spinus layer -> Basal layer -> Granular layer -> Stratum Corneum
Granular layer -> Stratum Corneum -> Basal layer -> Spinus layer
Where is more K5/K14 found?
Apical layer
Basal layer
Where is more K1/K10 found?
Keratin genes are differentially expressed in the different epidermal layers, producing dominant subtypes in different epidermal layers
What are the components of a desmosome?
Desmogleins
Desmocollins
Plakoglobin
Plakophilin
Plakotrypsin
Desmoglobulin
Desmochitin
What is a hemidesmosome?
A basal cell-cell adhesion module that can interact with the ECM of the basement membrane
A lateral cell-cell adhesion module that permits electrical communication between cells
A lateral cell-cell adhesion module that anchors adjacent cells together
Pemphigus Foliaceus affects what epidermal layer?
Upper
Lower
Epidermolysis bullosa affects what cell-cell adhesion module?
Desmosomes
Hemi-desmosomes
Tight junctions
Adherens junctions
What are types of epidermolysis bullosa?
EB Simplex
EB Junctional
EB Dystrophic
EB Vulgaris
EB Foliaceus
EB Desmosomal
Why is Tubulin known as "dynamically unstable"?
It is continually assembled and disassembled at its plus end
It cannot be stored in cells as it is unstable
Tubulin is composed of more than one sub-units
Actin's structure shows a twisting pattern due to the + and - charges on G-actin during polymerisation
Mutations in intermediate filaments are more detrimental to cells than mutations in actin filaments or tubulin microtubules
What is meant by actin cycling?
The disassembly of actin filaments, diffusion and subsequent reassembly close to a stimulus site
The way actin polymerises into F-actin
Which of the following protein translocations into organelles are unidirectional?
Nucleus translocation
Mitochondria translocation
Peroxisomal translocation
Mutations in peroxisomes are not always fatal because peroxisomes are cell specific.
Which of the following are ER modifications of proteins?
N-linked glycosylation
Completion of translation
Folding of proteins
Formation of disulphide bonds
Modification of N-linked oligosaccharide side chains
Oxygen-linked glycosylation
Mannose-6-phosphate modification
Sorting to final destinations
Which of the following are Golgi modifications of proteins?
Nitrogen-linked glycosylation
What is direct sorting in the golgi network?
Vesicles travelling straight to the membrane from the golgi apparatus
Vesicles travelling from the golgi to the wrong domain and then being retrieved by early endosomes and being sent to the correct domain such as the membrane
What is indirect sorting in the golgi network?
