AS revision WRONG questiopns Flashcards
name the type of cell that carries out phagocytosis and where is it carried out?
Phagocytes in the blood
Describe how HIV works?
HIV binds to protein CD4 on helper T cells. The capsid fuses with the cell-surface membrane and the RNA and enzymes enter the cell. The reverse transcriptase enzymes convert viral RNA to DNA which is inserted into the cell’s DNA. This creates mRNA that codes for viral proteins and HIV particles which combine with part of the cell-surface membrane, forming a new virus.
Why can a person be HIV-positive and not develop AIDS?
The virus can lie dormant for years before becoming active and
causing AIDS.
Describe the process of ELISA testing.
Antigens are applied to a surface and surplus washed off. Specific antibodies are applied and left to bind before washing surplus antibodies off. A second antibody attached to an enzyme binds to the first antibody, then a colourless substrate is added, which becomes coloured after enzyme action. The intensity of the colour reflects the amount of antigen.
how do closed guard cells become open?
- transport potasium in through active transport
- causes water potential to drop so water enters through osmosis
-increasing pressure causes the thin outer-facing membrane bends more than the thick inner-facing membrane, so the cells become distorted in shape, opening the stoma.
Explain the role of bile salts in separating fatty acids into micelles.
Bile salts emulsify fats into small droplets. Bile salts have lipophilic heads which are attracted to fatty acids, and lipophobic tails which repel lipids and stick out into the watery solution of the small intestine. This holds the lipids together in small droplets, while preventing them from combining into larger, indigestible units.
How does glucose move across the epithelial membrane?
Through carrier proteins with Na+
