Lecture 1: Cells and organelles 1) Demonstrate the following on a suitable transmission electron micrograph: nucleus; nucleolus; nuclear envelope; mitochondrion; rough endoplasmic reticulum; smooth endoplasmic reticulum; ribosomes; Golgi apparatus; secretory granules; plasma membrane; cytoskeletal components.
2) Identify the essential characteristics of prokaryotic and eukaryotic cells. Prokaryotes Eukaryotes Include all bacteria Include protest, fungus, animal and plant cells Surrounded by plasma membrane Surrounded by plasma membrane Contain no organelle Contain many orange Contain 70s ribosomes Contain 80s ribosomes Cell wall made of murein (peptidoglycan or Cell wall made of cellulose / chitin mucapeptide) Have clear nucleus and plasmid (associated with Have no clear nucleus but have a nuclear region antibiotic resistance) Contain flagellum for propulsion Much larger than prokaryotes and are bout 40-100 μm Have a capsule for protection/attachment Have invaginations in the cell membrane where mesosomes are and where respiration occurs 3) Explain the relationship of individual cells to the organisation of the whole body. • Cells in a multicellular organism, though they contain the same DNA, can be very different. They use different parts of their genetic information selectively, according to cues accumulated from their environment. Cells with the same function form tissues, which in turn form organs, which form organ systems.
Lecture 2: Infectious agents 1) Name the main types of infectious agent causing disease in humans. • Viruses, bacteria, fungi, protozoan parasites, helminth parasites. 2) Give examples of each type of infectious agent and the disease it causes. • Virus – HIV causes AIDS. • Bacteria – Mycoplasma (M. pneumoniae) causes pneumonia, often described as atypical. • Protozoa – Plasmodium species causes malaria. • Fungi (yeast-like) – Pneumocystis carinii causes pneumonia in immunosuppressed hosts. • Helminth parasites – Enterobius vermicularis causes intestinal infestation by threadworms. 3) List the key differences between prokaryotes and eukaryotes. Prokaryotes Eukaryotes Include all bacteria Include protest, fungus, animal and plant cells Surrounded by plasma membrane Surrounded by plasma membrane Contain no organelle Contain many orange Contain 70s ribosomes Contain 80s ribosomes Cell wall made of murein (peptidoglycan or Cell wall made of cellulose / chitin mucapeptide) Have clear nucleus and plasmid (associated with Have no clear nucleus but have a nuclear region antibiotic resistance) Contain flagellum for propulsion Much larger than prokaryotes and are bout 40-100 μm Have a capsule for protection/attachment Have invaginations in the cell membrane where mesosomes are and where respiration occurs
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4) Name the distinguishing features of the different types of infectious agent and explain how they replicate. • • • • •
Viruses – not cells in their own right. Make use of a host cell nuclear synthetic machinery to replicate. Can have either single or double-stranded DNA or RNA. Bacteria – prokaryotic. Contain a chromosome of DNA but no nucleus. Divide by binary fission. Fungi – eukaryotic. Occurs as yeasts, filaments or both. Filaments form hypahe. Yeasts bud or divide. Protozoa – Unicellular eukaryotes. Replicate in the host by binary fission or formation of trophozoites inside a cell. May have a complicated life cycle involving two hosts. Helminth parasites – Visible to the naked eye. Have life cycles outside the human host and most cannot multiply in humans. Complexity of the life cycle varies from simple embryonation to alternation of generations in the different hosts.
Lecture 3: Cell membranes 1) Explain the formation of phospholipid bilayers in an aqueous environment. • Since the environment is aqueous, and lipids are hydrophobic and phospholipids are cylindrical, bilayers form very easily with the hydrophilic phosphate groups facing the outside and inside of the cell, and the hydrophobic lipid tails facing within the membrane, therefore the hydrophobic layer are protected from the aqueous solution and the hydrophilic layers are in contact with the water 2) Draw the structure of phosphatidylcholine and identify the component parts.
Fatty acid chains
Glycerol Headgroup containing phosphate
3) Describe the permeability properties of a phospholipid bilayer with respect to macromolecules, ions, water and organic compounds (including drugs). • They are permeable to small neutral or lipid-soluble molecules, and impermeable to large, hydrophilic or charged molecules. 4) Distinguish simple diffusion, facilitated diffusion and active transport of ions and molecules across cell membranes. • Simple diffusion can only occur if the molecule is small neutral or lipid-soluble, meaning it can pass through the membrane directly • facilitated diffusion is the passive transport of larger, charged or hydrophilic molecules via carrier proteins (which undergo conformational changes to transport their solute) or channel proteins (which span the membrane and allow diffusion – which is faster) • active transport is needed to pump molecules in the direction against their respective electrochemical gradients, which uses ATP hydrolysis or an ion gradient. 5) Categorise the functions of membrane proteins. • Channel proteins, carrier proteins, pump proteins, receptor proteins. 6) Explain the movement of Na+ and K+ ions across the cell membrane against a concentration gradient and the consequences of failure of such a movement. • Sodium is in higher concentration outside of the cell, but is needed in cotransport to bring some molecules e.g. glucose into the cell and to regulate cell volume through osmosis, so it is pumped out using the sodium/potassium pump, an ATP-powered antiporter that brings in potassium to maintain the charge symmetry, but potassium also moves out again down its concentration gradient, making the interior of the cell slightly negative (basis of the resting potential); failure to do so would mean the inability of the sodium dependant cotransporters. 7) Explain how the entry of glucose and amino acids into the cell against a concentration gradient is coupled to ATP dependent Na+ transport. • A glucose- Na+ symport (carrier protein coupled transporter that moves both solutes in the same direction across the membrane); the downhill movement of Na+ down its gradient provides the energy to move glucose and amino acids up their concentration gradient and into the cytosol.
8) Explain how external chemical signals can be sensed at the interior of a cell. • Steroid hormones are lipidsoluble and so can diffuse through the membrane and act on steroid receptors in the
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nucleus; hydrophilic signalling molecules must bind to receptor proteins on the exterior, which cause conformational changes within the cell.
Lecture 4: Blood and blood cells 1) List the main functions of the blood. • Respiratory function, ie transport of O2 and CO2 • pH buffering, ie stabilisation of acidity/alkalinity status • Nutritional, ie transport of glucose, fats etc. • Excretory, ie transport of waste products eg urea • Hormone transport • Haemostasis ie clotting to stop blood loss • Defence against infection • Temperature control • Maintenance of fluid balance 2) List the major components of the blood. • Plasma and the formed elements: erythrocytes (RBCs), leukocytes (WBCs), thrombocytes (platelets) • There is approximately 5-6l of blood in males and 4-5l of blood in females 3) Explain the difference between plasma and serum. • When plasma is allowed to clot and the clot removed, the liquid that remains is called serum. Serum is plasma minus fibrinogen. 4) Describe the essential features of the erythrocyte and list its major functions. • Constitute almost half the volume of blood. Anucleate, biconcave discs – diameter 8.5μm, thickness 2.4μm filled with a concentrated haemoglobin solution surrounded by a membrane. Functions are O2 transport in combination with haemoglobin; CO2 transport – greatly facilitated by carbonic anhydrase which speeds up CO2 + H2O H2CO3 5) Explain the erythrocytic difference between men and women. • Females have a lower haematocrit (H) (% of blood which is the RBC), whole blood Hb (Hb) (conc. of Hb) and red cell count (n). This is because increased testosterone boost the bone marrow into producing more erythrocytes. Females lose RBCs in menstruation. • Also women tend to be small on the whole, and therefore carry less blood and therefore fewer red blood cells. • Red Blood cell parameters:
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N (or RBC) = number of red blood cells (about 5.1x1012 in males and 4.5x1012 in females) H (or Hct) = haematocrit – this is the percentage of the volume of a sample of blood occupied by the red blood cells (46% in males and 41% in females) Hb = concentration of haemoglobin in the blood (15.5g/dl in males and 13.7g/dl in females)
MCV = mean cell volume = Hct/(RBC x 100) (normally around 90fl) • MCH = mean cellular haemoglobin (Hb x 10)/RBC (around 30pg) • MCHC = mean cell haemoglobin concentration (Hb x 100)/Hct (around 34g/dl) • Note that the final three do not depend on gender 6) Define anaemia and list the major causes. • Anaemia is a condition in which the Hb falls below the normal range for the subject. • Disturbed production (Fe, B12 or folic acid deficiencies and kidney disease). • Increased destruction eg sickle cell disease. • Haemorrhage – loss of red cells and iron. 7) List the major erythrocyctic differences between iron deficiency and vitamin B12 deficiency anaemias. • Iron deficiency anaemia – low values for haematocrit, whole blood Hb, red cell count, mean cell volume, mean cell Hb, mean cell Hb concentration ie all parameters. Essential for haemoglobin production – it occurs due to the lack of intake but more likely due to excessive loss (microcytic- small cells) • Vitamin B12 anaemia – low values of haematocrit, whole blood Hb and red cell count but high values for mean cell volume and mean cell Hb. This is essential for normal DNA synthesis during maturation of primitive erythroid cells (macrocytic-large cells anaemia) 8) List the major differences between the leukocyte and platelet populations of normal blood and the erythrocyte population. • Leukocytes have a nucleus and are fewer in number than the RBCs but of a similar or slightly larger size. Platelets are anucleate and very much smaller than the RBCs. • RBC : WBC = 500 : 1; RBC : Platelet = 12 : 1 9) Explain simply the major functions of the leukocytes and platelets. • Leukocytes defend against infection; platelets are important in haemostasis, stemming the loss of blood after a haemorrhage ie clotting. 10) Explain simply the meaning of phagocytosis, immune reaction, chemotaxis, diapedesis. • Phagocytosis – ingestion of foreign material by engulfing into the cytoplasm. • Immune reaction – the role of lymphocytes. Antibodies bind specifically to the antigen that induced its formation. • Chemotaxis – movement of cells up a concentration gradient towards the site of infection where the infected agent releases a chemical that is detected by the cells. • Diapedesis – migration of cells through the walls of blood capillaries into the tissue spaces. 11) Describe the major requirements, nutritional and otherwise, of normal erythropoiesis. • Iron is essential for haemoglobin production.
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Vitamin B12 and folic acid are essential for normal DNA synthesis during the maturation of prmitive erythroid cells. Erythropoiesis = takes place in red marrow (skull, ribs, sternum), there is a close balance between production and destruction, which keeps RBC count within a small range in health. RBC production is under the control of erythropoietin (EPO)- which is produced in the kidney and production is increased when renal tissue becomes hypoxic.
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