Other Flashcards
Most common medical imaging file format
DICOM
Imaging resolution
Number of pixels across each axix
intensity/ grey scale
Number for a pixel (identity)
Intensity/ grey scale resolution
range of possible intensity values
Spacial resolution
measure of smallest discernable detail in an image
Aspect ratio
ration of its width to its height
Dynamic range
range of intensity values to display the image
Difference between low intensity and low spatial resolution
Low intensity: not able to discen objects that look similar Spatial resolution: not able to see small object/ structures
Visualisation in slice vs volume mode
slice: slices of a 3d image Volume: 3D visualisation progamme.
How x ray works
electrons fired at a target, x rays are reflected back and they have different penetrances in the body.
From black to white state order of following tissues water, fat, air, bone, metal, soft tissue
air, fat, soft tissue, water, bone, metal
What is a CT scan
x rays at many different angles, giving depth to the image
Difference between alpha and beta decay
Alpha decay: alpha particle (H2+) ejected Beta decay: positron (beta plus) or electron (beta minus) is released
Gamma emission
particles decay and give off gamma rays
Most penetrating ionising radiation: beta, gamma or alpha
Gamma, then beta then alpha
PET scans
Emits gamma rays, creating 3D image
MRIs
Emits magnetic waves which detect hydrogen concentration. Very good for soft tissue differentiation
US (ultrasound imaging)
emits ultrasound pulse and see what is reflected
Match body compartment with amount of fluid in l it has Interstitial space, plasma space, Intra cellular space 3.5, 28, 10.5
Intracellular : 28 Interstitial : 10.5 Plasma: 3.5
Plasma and intracellular concentrations of: NA, K, Ca
Crystalloid vs oncotic pressure
Crystalloid: pressure excerted by small diffusible particles (usually equal on both sides of membrane)
Oncotic: pressure created by non diffusible larger particles like proteins (usually slightly higher on one side of membrane)
Normal RBC and WBC Count
Red blood cell: 5*10ˆ12
White blood cells: 4-11 *10ˆ9
Series vs parallel
check
Darcy’s law
Flow proportional to pressure difference (P1 -P2 ) and inversely proportional to the resistance to flow
Poisseuille’s law
resistance to flow is 4 times to the power of the radius of the tube
Axial streaming in blood vessels
Particles in blood tend to move to area with fastest moving fluid - the center. Reduces viscocity
Normal blood pH and living range pH
Normal blood: 7.35-7.45
Living range: 7.0 - 7.8
What is pH, and what is the equation of pH
pH: concentration of free hydrogen ions
pH = -log [H+]
What is pKa, what a high or low pKa means
pKa: the log of the pH at which an acid is half dissociated.
The lower the pKa, the stronger the acid is.
The pH at which a certain buffer will work best is…
at the pKa of the acid in the buffer
Which amino acid is a buffer in the body? Why?
Histidine: it’s pKa is around physiological pH
It is part of haemoglobin and it’s pKa changes depending on oxygenation:
Oxyhaemoglobin: pKa of 6.8
Deoxyhaemoglobin: pKa of 7.8
What is the concept of cooperativity thinking about haemoglobin
Haemoglobin displays cooperativity because it’s affinity for it’s ligand changes with the amount of ligand already bound (oxygen)
Will bind oxygen better if it already has oxygen bound to it
What action does BPG have on O2 binding?
What is the difference in it’s effect in fetal and adult haemoglobin?
BPG lowers Hb’s affinity for oxygen by binding to the center of the tetramere in it’s t-state and stabilising the structure. It is produced by all metabolic tissues.
BPG is less effective in fetal haemoglobin, which means that fetal haemoglobin will have a higher affinity for O2 compared to HbA.
Location of the heme group within the globin molecule (and the letter name of alpha helices it is bound to).
Role of E7 his residue
Bound between E and F helices.
E7 histidine group stabalizes the bond of O2 with Fe and destabilizes the bond of CO2 with Fe.
Difference between tense and relaxed conformations of haemoglobin
Tense occurs at tissues in presence of low pH and other, causes low affinity for oxygen
Relaxed occurs at lungs where higher pH, low BPG, causes higher affinity for oxygen.
Classify the following types of protein as being targeted by a) signal peptide or b) other peptide signal
Secretes protein
Membrane Protein
Mitochondrial proteins
Lysosomal proteins
Perixosomal Proteins
Nuclear Proteins
Describe the pathway of protein synthesis and its binding to the membrane using Signal Recognition Particle
Translation begins, and signal sequence is the first to be synthesised. It binds to a SRP, which itself binds to a SRP receptor on the ER. This binds the ribosome to the ER, and the rest of the protein synthesised gets guided through a translocon into the ER membrane. Signal Peptidase cleaves this signal sequence, and SRP is recycles
Fate of membrane proteins
Membrane proteins remain in the ER membrane. The translocon goes away when stop sequence is reached , leaving the matured protein.
Protein processing in the golgi and 4 different pathways they follow after that
Proteins enter cis-golgi where they more through its cisterna via vescicles and get packaged and sorted. They become:
Membrane proteins
Stimulated secretory pathway (insulin)
Continuous secretory pathwy (matrix proteins)
Lysosomes
Pathway for mitochondrial proteins
Get translated and released in an unfolded form into the cytoplasm (still has signal sequence). They bind to chaperones which brings them to specific receptors on the mitochondria. They translocate through the membranes and are cleaved of their signal sequence and fold once iside.
Pathway for nuclear proteins
Nuclear proteins have a specific signal called a nuclear localisation signal (PKKKRKV). They are not folded either before entering nucleus. The NLS binds to an importin protein which transports it through nuclear pores. The complex then dissociates and protein folds.
Pathway of lysosomal proteins
Lysosomal proteins are tagged with mannose-6-phosphate in the golgi. This directs the protein within the golgi to transport vescicles.
In inclusion-cell disease, the proteins are not tagged and get secreted instead.
