Complete set of notes for this element in the Bristol A100 Pre-clinical course. This is everything you need to know to achieve 90% marks. It is presented in a simple question, simple answer layout. If you have any questions or if anything doesn’t make sense, email me at mh14782@my.bristol.ac.uk....
Table of Contents
ELEMENT 3 – PHYSIOLOGY ................................................................................................ 1
3.1 – 3.3: Chemistry of the Cell and Cell Membrane .................................................................... 1
3.4 & 3.5: Cell and its Organelles ................................................................................................ 3
3.6: Cell Division ......................................................................................................................... 4
3.9 & 3.10: Resting Membrane Potential and Action Potentials .................................................. 6
3.11: Neuromuscular Junction .................................................................................................... 7
3.12: Structure of Muscle ........................................................................................................... 8
3.13: Molecular Mechanism of Muscle Contraction .................................................................. 10
3.14: Regulation of Muscle Contraction .................................................................................... 12
3.15: Muscle Mechanics ........................................................................................................... 14
3.16: Autonomic Nervous System ............................................................................................. 17
3.17: Endocrine System ............................................................................................................ 18
3.18 & 3.19: Homeostasis ......................................................................................................... 19
ELEMENT 3 – PHYSIOLOGY
3.1 – 3.3: Chemistry of the Cell and Cell Membrane
• What are the four major cell types? Muscle, nerve, epithelial and connective
• What is a tissue? An association of similar cells that perform a similar function
• What is an organ? An association of tissues which combine to perform specific functions
• Roughly how many organ systems are there? 10
• What is the integumentary system? It is comprised of the skin and any appendages it may have
(including sweat glands or feathers etc.) and is responsible for protection against various damages
including abrasions, UV light and water loss.
• What are the percentages of fluid in the body?
• In terms of energy, why doesn’t oil dissolve in water? To minimise the systems potential energy
• What are the major sources of energy for the brain? Only glusoce
• Does the brain store glycogen? Yes, but only in cells called astrocytes
• What is the general structure of steroid molecules? Three 6C rings, one 5C ring.
• What are the subunits of the DNA polymer called? Nucleotides
• What are the relative concentrations of the main ions in and outside the cell?
Ion Where is there more of it?
+
K Inside cell
Na+ Outside cell
, Mg2+ (really low concs) About the same
2+
Ca (really low concs) Outside cell
-
Cl Outside cell
HCO3- Outside cell
Inorganic Phosphate Inside cell
Amino acids (really low concs) Inside cell
Glucose (really low concs) Outside cell
ATP (really low concs) Inside cell
Protein (really low concs) Outside cell
• What is the electro-chemical driving force? The sum of the force generated by chemical and
electrical gradients
• What is the equilibrium/reversal potential? The membrane potential at which there is no net flux of
charged particles (as chemical force = electrical force)
• How can you calculate it?
Using the Nernst
equation, where z equals the
valence of the ion (always
given)
• How is the Goldman equation different to the Nernst equation in terms of when you’d use it? The
Goldman equation is for when you want to work out the membrane potential given the
concentration of all the various ions involved.
• Where does the 61.5 come from and is it always the
same? It’s a constant derived from R=8.31, and varies
with temperature.
• What does the p(ion) represent in the Goldman equation? The relative permeability constant of the
cell to that particular ion.
• What factors affect the rate of simple diffusion, leading to Fick’s law?
1. Magnitude of the driving force
2. Surface area Net Flux = P * A * ΔC
3. Permeability of the membrane
• What factors affect the rate of facilitated diffusion, once saturation of the transporters has
occurred?
1. Number of carriers on the membrane
2. Transport rate of the individual carriers
• In what ways can ion channels be selective? They can be selective towards charge due to the
specific amino acid side chain orientation within the cells, or towards size (including hydration
weights)
• What factors affect the rate of diffusion through ion channels?
1. Magnitude of electrochemical driving force
2. Number of available channels
3. Conductance = transport rate for ion channels
4. State of channels (i.e. open or closed)
• What are the intracellular and extracellular concentrations of sodium and potassium?
Intracellular (mmol) Extracellular (mmol)
+
K 140 4
+
Na 15 145
, 3.4 & 3.5: Cell and its Organelles
• What’s the difference between cytoplasm and cytosol? Cytoplasm = cytosol + organelles
• The nucleus
o Why do eukaryotic cells need nuclei but prokaryotic cells do not? Because the genome is much
larger and the handling of the genome is much more complex
o What is chromatin and where is it found? Its loose strings of DNA found floating around in the
nucleus
o Why does DNA need to be loosely coiled as chromatin between divisions? To allow access to
proteins and enzymes which need to work on the genome
o What are nuclear pores? They are small specialised micro-channels in the nuclear envelope that
allow selective movement of molecules in and out of the membrane
• Endoplasmic reticulum, Golgi and ribosomes
o What are the two types and what are their structural differences? Rough (has ribosomes
associated to it so is indirectly involved with protein synthesis) and smooth (no ribosomes)
o What is the general structure of a ribosome? Large and small protein subunits with associated
ribosomal RNA
o What confers the ribosomes catalytic activity during translation? The rRNA, which is termed a
ribozyme.
o Where are ribosomes manufactured? The nucleolus
o Why don’t all ribosomes associate with endoplasmic reticulum? Because proteins that need to
remain in the cytoplasm don’t need to be packaged by RER and the Golgi body. Proteins made by
the ribosomes on RER are needed either for the RER itself or needed to secrete out of the cell.
o What does RER do for the cell? Its involved with protein trafficking, directing proteins that need
to be secreted out of the cell to the Golgi body.
o How does RER alter these proteins?
1. Folding of the protein into the physiologically active shape
2. Glycosylation (adding sugar residues)
o What does the Golgi body do? Further modification and packaging into vesicles as the protein
passes through its layers
o What does SER do?
1. Production of lipids
2. Stores and releases calcium (biggest Ca2+ store in cell)
• Mitochondria
o What is its structure? Double membrane, the inner most is folded into cristae.
o What is its function? ATP formation
o What are mitochondria originally thought to have been from? From bacteria that learnt to
permanently live in our cells – symbiotic relationship.
• What two ways can cells ingest molecule or particles from outside?
1. Pinocytosis – vesicle endocytosed contains mainly fluid
2. Phagocytosis – vesicle contains large particles (e.g. bacteria or debris)
• What are endosomes? The vesicular product of endocytosis. They’re the intracellular sorting
machines that ‘decide’ whether to recycle or breakdown the vesicle contents.
• What does clathrin do? It’s a protein in the cell membrane that acts as a scaffold, which is needed to
create the invagination necessary for endocytosis (as membrane wants to be flat)
• What type of molecule will be ‘recycled’? Useful membrane proteins or membrane fragments (e.g.
clathrin)
• What happens in the degradation pathway? The early endosomes become late endosomes and
fuse with lysosomes, which digest the contents.
• What’s the difference between early and late endosomes? Early endosomes become more and
more acidic to become late endosomes and eventually fise with lysosomes.
, • What do lysosomes do? They contain hydrolytic enzymes that digest molecules to be broken down.
• Why are they so acidic? Because they use ATP to pump protons in.
• What types of enzymes are in lysosomes? Acid hydrolases
• What conditions do they like and how is this a useful feature? A very low pH, which makes them
more aggressive towards pathogens and also makes them inactive should the lysosome break and
the contents spill out into the non-acidic cytosol.
• What are Tay-Sachs and Gaucher’s disease examples of? Lysosomal storage diseases
• What do peroxisomes do?
1. Contains enzymes that use oxygen to oxidise harmful substances
2. Contains catalase, to degrade the H2O2 produced (as its toxic and is non polar so can diffuse
throughout the cell
3. Metabolism of long-chain fatty acids (for heat and cholesterol NOT ATP)
• What are the three components of the cytoskeleton?
1. Microfilaments
2. Intermediate filaments
3. Microtubules
• What is actin an example of and what two types of this are there? Actin, g-actin (globular) and f-
actin (fibrous)
• How does an actin microfilament grow? From the polymerisation of actin monomers. One end
always grows faster (called the plus end)
• What does filamin do? Cross links actin microfilaments
• What does cadherin do? Extracellular connectors of cell
• What does catenin do? Membrane spanning anchor
• What is Duchenne’s muscular dystrophy caused by? Poor anchoring of muscle bundles.
• How do microtubules grow? Polymerisation of tubulin monomers, at equal rates each end.
• What is their function? Long distance rails for transporting substances
• What feature allows them to do this? The fact that tubulin has a positive and negative end (i.e. are
polar), meaning microtubules have +ve and –ve poles.
• What structure carries molecular cargos along these rails? Molecular motors, of which there are
two types, that “walk” along the microtubule:
1. Kinesin – towards +ve pole
2. Dynein – towards –ve pole
• What do intermediate filaments do? Provide mechanical support, acting as ropes attached to
anchors in the extracellular matrix. Made of fibrous monomers.
• A protrusion of cell membrane that has no active movement (e.g. microvilli) is likely to be
supported by what molecule? Actin
• An actively moving/beating protrusion of the cell membrane (e.g. flagella or sperm tails) are likely
to be supported by what molecule? Microtubule
• How is this movement achieved? Cross links of dynein-like proteins in the microtubules
• What are the diameters of the three components of cytoskeleton?
Component Diameter
Microfilament 7nm
Intermediate filament 10nm
Microtubule 25nm
3.6: Cell Division
• What are the different stages of the cell cycle?
1. G0 phase – no division or growth (cell can be made to enter or exit this stage by growth factors)
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