topic 2 ppqs Flashcards
explain why it is not possible to determine the identity of the structures labelled X using an optical microscope [2]
- resolution is too low
- because wavelength of light it too long
describe the role of one named organelle in digesting (these) bacteria [3]
- lysosomes
- fuse with vesicle
- to release hydrolytic enzymes
describe how a sample of chloroplasts could be isolated from leaves [4]
- break open cells and filter
- in ice cold isotonic buffer solution
- centrifuge to remove nuclei
- centrifuge at higher speed so nuclei settle out
outline the role of organelles in the production, transport and release of proteins from eukaryotic cells [4]
- DNA in the nucleus is code for protein
- ribosomes / rough endoplasmic reticulum produce protein
- mitochondria produce ATP for protein synthesis
- golgi apparatus packages and modifies
- vesicles transport
- vesicles fuse with cell-surface membrane
explain how the body responds to a cold and suggest why you can get a cold again [5]
- you will complete the primary immune response after first exposure to cold virus
- producing specific memory T/B lymphocytes
- secondary immune response is only possible if re-exposed to same strain with same virus
- there are multiple strains of cold virus
- these strains all have different antigens
- more likely to encounter strain with different antigen, requiring new primary immune response
2 changes to the structure of the cell-surface membrane that would increase the rate at which glucose is transported into the cell
- increase SA with microvilli
- more proteins with pores that span the PLB
explain why glucose does not easily pass through the PLB [2]
- only lipid-soluble substances diffuse across the PLB easily
- water-soluble substances (like glucose) diffuse only very slowly
explain why reabsorption of glucose into the blood in the kidneys occurs by active transport rather than by diffusion [2]
- diffusion, at best, can only reabsorb 50% of the glucose lost from the blood
> the other 50% will be lost from the body - active transport can absorb all of the glucose, leaving none to be lost from the body
how can rate of movement across membranes be increased? [3]
- increase SA
- increase concentration gradient
- increase density of protein channels
why does the body’s immune system take a number of days to control the pathogen after it has entered? [1]
lymphocytes that will finally control the pathogen need to build up their numbers and this takes time
why would it be inaccurate to say that the body takes days to ‘respond’ to the pathogen? [1]
the body ‘responds’ to the pathogen immediately; the delay is in building up the numbers of lymphocytes and therefore controlling the pathogen
suggest why lysozymes are also found in tears [3]
- the protective covering of the eye, especially the tear ducts, are potential entry points for pathogens
- the eyes are vulnerable to infection because the coverings are thin to allow light through
- lysozymes will break down the cell walls of any bacterial pathogens and so destroy them before they can cause harm
suggest why antibodies made of proteins, rather than carbohydrates or fats, are more likely to be effective against a wider range of diseases [2]
- there must be a massive variety of antibodies as each responds to a different antigen, of which there are millions
- only proteins have the diversity of molecular structure to produce millions of different types
describe the role of a ribosome in the production of a polypeptide [3]
- mRNA binds to ribosome
- idea of two binding sites
- allows tRNA with anticodons to bind
- catalyses formation of peptide bonds between amino acids, which are held by tRNA molecules
- moves along mRNA to the next codon
use your knowledge of transport across cell membranes to suggest how — (a carrier protein) actively transports one sodium ion into the cell in exchange for one proton out of the cell [3]
- co-transport
- uses hydrolysis of ATP
- sodium ion and proton bind to the protein
- protein changes shape to move sodium ion and proton across the membrane
