Tricky Multi-step Processes Flashcards
What is the process of clonal selection?
1) surface antigens on the pathogen enter the B-cell through endocytosis
2) B-cell digests the pathogen and presents the antigens on it’s surface, turning it into an antigen presenting cell
3) complementary activated helper T-cells bind to the presented antigens and release interleukins
4) These chemicals stimulate B-cells to divide rapidly by mitosis
5) B-cells either divide to become memory cells or plasma cells
What is the process of HIV infection of host cells?
1) HIV attaches to the surface of a T-cell
2) protein capsid fuses with the cell-surface membrane, releasing it’s RNA and enzymes into the cell
3) reverse transcriptase converts virus RNA to DNA
4) virus DNA gets inserted into nucleus of host cell, and remains dormant
5) virus DNA becomes active and creates mRNA using the host cells enzymes
6) uses host cells protein synthesis mechanisms to create new HIV viruses
7) new HIV cells are released from the cell, with a piece of the cell-surface membrane, forming their lipid envelope
What are the steps of an indirect ELISA test?
1) HIV antigens are bound to the base of a well, then washed to remove unattached antigens
2) Patients blood plasma added to the well, if positive, HIV antibodies will bind to the antigens
3) Well is washed to remove any unattached antibodies
4) Secondary antibody with specific enzyme attached binds to the primary antibody
5) Well is washed to remove any unattached antibodies
6) Solution is added to the well that contains a substrate that reacts with the enzyme on the secondary antibody
7) If reaction occurs, then colour change will be visible, showing presence of HIV antibodies
What are the steps of helper T-cell activation?
1) Pathogen invades body cells or are taken in by phagocytosis
2) Phagocyte presents antigens from the pathogen on it’s cell surface membrane
3) Receptors on a specific helper T-cell fit exactly onto these antigens
4) Attachment activates T-cell to divide rapidly by mitosis
5) Cloned T-cells can:
- develop into memory cells
- stimulate phagocytes to engulf pathogens by phagocytosis
- stimulate B-cells to divide into plasma cells
- activate cytotoxic T-cells
What is the process of the formation and reabsorption of tissue fluid?
1) At the start of capillary bed (arteriole end), the hydrostatic pressure inside the capillaries is greater than in the tissue fluid
2) This forces tissue fluid to move out of the blood plasma
3) As blood passes along the capillaries, the water is lost
4) This reduces the hydrostatic pressure and water potential inside the capillaries
5) Creates a water potential gradient, so water re-enters the capillaries from the tissue fluid at the end of the capillary bed (venule end)
What are the steps of transcription?
1) DNA helicase unwinds a small section of the DNA by breaking the hydrogen bonds between the bases
2) One strand acts as a template strand
3) Free mRNA nucleotides align opposite exposed complementary DNA bases on the template strand
4) RNA polymerase bonds the RNA nucleotides together to create RNA polymer chain
