Cells Flashcards
How many cell types in the body?
1) 100
2) 200
3) 300
4) 400
200 different cell types. 100 trillion total
What is the size of a cell?
10-20 micrometers in diameter
What is the size of a virus?
10 nanometers
What occurs in the Golgi apparatus?
Proteins and lipids from the endoplasmic reticulum are modified and sorted for transportation
Where is ribosomal RNA transcribed?
The nucleolus
What feature of the nucleus can adenovirus take advantage of?
Nuclear pores
What is the name of a short cylindrical array of microtubules found at the base of cilia and flagella?
Centriole
What three types of filament make up the cytoskeleton?
Actin filaments
Intermediate filaments
Microtubules
What are the artificially prepared vesicles made from the lipid bilayer called?
Liposomes
Where are most lipids secreted and membrane-bound proteins made?
Endoplasmic Reticulum
What type of endoplasmic reticulum is involved in lipid synthesis?
Smooth endoplasmic reticulum
What type of endoplasmic reticulum is involved in protein synthesis?
Rough endoplasmic reticulum
What is the sarcoplasmic reticulum?
Specialist form of smooth endoplasmic reticulum found in smooth and striated muscle
What is a eukaryotic cell?
A cell with membrane bound organelles
What type of cell has flagella or pili?
Prokaryotes
Pili for adhesion
What do prokaryotic cell walls contain?
Peptidoglycan
What type of cell can be cocci, bacilli, spirillae or spirochetes?
Prokaryotes
What type of cell has a cytoskeleton?
Eukaryotes
What is endosymbiosis?
The theory of incorporation of prokaryotes to form eukaryotes with mitochondria
What is the average blood volume for men and women?
Men: 5L
Women: 3.5L
What are the types of white blood cell and their concentrations?
Neutrophils: 40-80% Lymphocytes: 20-40% Monocytes: 2-10% Eosinophils: 1-6% Basophils:
What molecule does haemoglobin form when it transports oxygen?
Oxyhaemoglobin
What reaction allows erythrocytes to transport carbon dioxide?
Carbonic anhydrase-> bicarbonate
How big are erythrocytes?
7.5 micrometers
What organ stimulates the release of erythropoietin?
The kidney
What hormone stimulates erythropoietin release?
Testosterone
What hormone stimulates erythropoiesis?
Erythropoietin
What are immature erythrocytes called?
Reticulocytes: they contain ribosomes
What are high circulating reticulocytes diagnostic of?
Anaemia or chemotherapy
How are reticulocytes removed from the circulation?
Reticulo-endothelial system: phagocytic macrophages in the spleen
What is the lifespan of an erythrocyte?
120 days
What is a haemoglobin molecule made up of?
4 polypeptides with a haem group and a ferrous iron
What are immature erythrocytes called?
Reticulocytes: they contain ribosomes
What are high circulating reticulocytes diagnostic of?
Anaemia or chemotherapy
Where does the oxygen bind to haemoglobin?
It binds to the ferrous iron
What is the oxidised form of haemoglobin?
Methaemoglobin
What form of haemoglobin is found in the foetus?
HbF which has a higher affinity for oxygen
What are the normal haemoglobin levels?
Per 100ml of blood:
Male: 15.8g
Female: 13.7g
What is a normal red cell count?
Male: 5.4x10^12
Female: 4.8x10^12
What is a normal haematocrit?
Male: 0.40-0.54
Female: 0.35-0.47
What is a normal mean cell volume, mean cell haemoglobin and mean cell haemoglobin concentration?
MCV: 82-99fl
MCH: 27-33pg
MCHC: 320-340g/l
What is microcytic anaemia and what causes it?
A failure of haemoglobin synthesis. Caused by a continuous leaching of blood (menstruation, GIT lesions or cancers, parasitic infection- continuous leaching of blood)
What is normocytic anaemia and what causes it?
Fewer erythrocytes than normal caused by a sudden and acute loss of blood.
What is macrocytic anaemia and what causes it?
Failure of cell division. Caused by folic acid or B12 deficiency.
What cells are polymorphonuclear granulocytes and what are their characteristic features?
Neutrophils, eosinophils and basophils
Segmented nucleus, full of cytoplasmic granules, engulf, kill and digest microorganisms, release inflammatory mediators and adhere to blood vessels and migrate to tissues
What type of immunity do B cells provide?
Humoral immunity
What are the five types of antibody?
IgM, IgG, IgA, IgD and IgE
Which type of immune response is quicker, primary or secondary?
Secondary response
What type of immunity do T cells provide?
Cellular immunity
What do monocytes secrete and what does this stimulate?
Inflammatory mediators and they stimulate angiogenesis
What is the size of platelets?
2-3 micrometers
What is a normal platelet count?
25x10^4 per micro litre
What is the life span of platelets?
8-10 days
What do platelets adhere to?
Exposed collagen
What do platelets produce from cycloxygenase enzyme?
Thromboxane A2
What does aspirin inhibit?
Cycloxygenase
What does the vascular endothelium produce to inhibit platelet activation?
Prostacyclin and nitric oxide
What is the function of plasma proteins?
Exert osmotic pressure to maintain blood volume
What proteins are found in the blood plasma?
Albumins
Globulins
Fibrinogen
What is the function of albumins and globulins?
Carrier molecules
What is serum?
Plasma with the proteins removed due to clotting
How thick is a membrane
5-7 nanometers
What does amphiphilic mean?
Contains both hydrophobic and hydrophilic group
Eg phospholipids
What creates diversity in membranes?
Unsaturated and saturated fatty acid tails in phospholipids
What are membranes permeable to?
Small, neutral and fat soluble molecules and water
What are membranes impermeable to?
Large macromolecules like proteins and RNA
Hydrophilic molecules like glucose
Charged molecules including cations and anions (but some can leak through down the concentration gradient
What is osmosis?
Diffusion of water across a permeable membrane from an area of low to high concentration
What is active transport?
Diffusion against the concentration gradient using the hydrolysis of ATP to provide energy and using a carrier protein
What is facilitated diffusion?
The movement of a hydrophilic (charged) molecule down their concentration gradient through protein pores to pass the hydrophobic core
What is protein mediated permeability?
The use of pores to provide a route for substances to move down the concentration gradient
What is a symporter?
Allow the movement of sugars and amino acids into a cell with the movement of Na as it moves down the concentration gradient
What are antiporters?
Allow the movement of molecules in opposite direction to Na to exchange
What is the lipid to protein ratio in myelin sheath, plasma membrane and mitochondrial inner membrane?
Myelin sheath: Lipid- 80%: Protein- 20%
Plasma membrane: Lipid- 50%: Protein- 50%
Mitochondrial inner membrane: Lipid- 25%: Protein- 75%
What type of cell signal molecule can cross the cell membrane?
Lipid soluble molecules: eg steroid hormones, prostaglandins and nitric oxide
What do impermeable signals rely on for cell signalling?
Trans-membrane receptors
Chemical gradient moves particles where?
Down the concentration gradient, spontaneously
Electrostatic gradient moves particles according to what?
Charge
Chloride ions move where (with regard to the concentration gradient) and how?
Inward, down the concentration gradient through chloride channels
Excess negative charge in a cell caused by non-diffusible proteins and lipids does what to chloride ions?
Pushes them out of the cell
What prevents the dissipation of ionic gradients in a cell?
Na+K+ pumps
The alpha chain of Na+K+ pumps spans the membrane how many times?
10 times
What is the role of the beta chain in Na+K+ pumps?
It is the controller
How is glucose transported into the cell?
Using facilitated diffusion through a symporter to move down the concentration gradient, co-transported with Na
What polypeptide chains make up a Na+K+ pump?
Two: one alpha and one beta chain
What is the ionic gradient in a cell? Inside is there more or less Na and K?
Less Na and more K
Where is there more of a negative potential? Inside or outside?
Inside
What is a membrane potential?
A difference in electric charge on the two sides of a membrane
What channels does K use to travel in and out of a cell?
Na+K+ pumps and K+ leak channels
What is the membrane potential of a cell?
-70mV
In what cells do action potentials occur?
Elongated cells (nerves and muscles)
What is an action potential?
A brief disruption in the membrane potential caused by a current pulse which causes the voltage gated Na+ channels to open
Explain the process of an action potential?
A stimulus causes voltage gated Na+ channels to open and Na flows into the cell causing depolarisation from -70mV to +50mV.
This voltage reversal causes inactivation of the channels preventing further entry of Na.
Voltage gated K+ channels then open resulting in K effluc which helps to restore the resting membrane potential
The process propagates down the nerve/muscle
What channel does the scorpion toxin target?
The K channel: mimicing water that the K channel is usually surrounded by
Which ions have specific pumps and use ATP hydrolysis tp provide the energy?
Na+, Ca+ and H+
Which pump in mitochondria moves H+ and can work in reverse to generate ATP from the ion gradient?
F1-ATPase
What is pinocytosis?
Engulfment by the membrane of extracellular solute and small molecules enclosing the contents in small intracellular membrane-bound vesicles
How do bacteria replicate?
Binary fission
Systemic fungi infections are common among what group of people?
Immunocompromised
Malaria and leishmania spp are examples of what type of infection?
Protozoan
Tapeworms, flukes and roundworms are examples of what type of infection?
Helminths
What are the main differences between prokaryotes and eukaryotes
Size, peptidoglycans, organelles and nuclei
Are prokaryotes haploid or diploid
Haploid
Give examples of the agents below and the disease they cause:
Bacteria, virus, fungi, protozoa and helminth
Bacteria: Shigella, Neisseria
Virus: HIV
Fungi: Candida
Protozoa: Plasmodium spp (malaria) and Leishmania
Helminth: Schistosomiasis, Tania saginata (tapeworm), roundworms
How does HIV replicate in it’s host?
Is uses reverse transciptase enzyme to convert its own RNA genome into DNA template, which it integrates into the host genome. This makes the host cell manufacture the proteins it needs to replicate.
Explain the pathogenesis of Shigella including the infectious dose?
Shigella is transmitted via the faecal oral route and has an infectious dose of 10-100 bacteria. It enters a cell via a vacuole and replicated intracellularly. Using the host’s actin it spreads from cell to cell.
How do protozoa replicate?
Replicate in the host via binary fission or formation of trophozoites inside a cell. They have a complicated life cycle involving two hosts- infection occurs through ingestion or through a vector (eg malaria)
