topic 2

Question 2

why are viruses known as cellular and non living

Answer 2

acellular not made of cells no cell membrane
non living no metabolism

Question 3

general virus particle structure

Answer 3

nucleic acid surrounded by capsid
attachment proteins to attach to host cells
some have lipid envelope

Question 4

optical microscope

Answer 4

light focused using glass lens passes through specimen
Dif structures absorb Dif wavelengths generating a 2D image

Question 5

tem

Answer 5

electrons focused using electromagnets
pass through specimen and denser parts absorb more electrons and appear darker

Question 6

SEM

Answer 6

electrons focused using electromagnets and detect of surface

Question 7

viewing the size of an object using an optical microscope

Answer 7

Line up eyepiece graticule with stage micrometre
Calibrate eyepiece graticule - use stage micrometre to calculate size of divisions on eyepiece graticule
3. Take micrometre away and use graticule to measure how many divisions make up the object
4. Calculate size of object by multiplying number of divisions by size of division
5. Recalibrate eyepiece graticule at different magnifications

Question 8

cell fractionation and ultracentrifuge

Answer 8

homogenise tissue using a blender to disrupt cells membrane and break them open
place in cold (reduces enzyme activity)
buffered (prevents ph changes)
isotonic (no water enters or leaves by osmosis)
filter the homogenate to remove large debris
centrifuge homogenate at high speed removing pellet of heaviest organelles reskin at higher speed until all organelles are separated out

Question 9

interphase

Answer 9

dna replicates semi conservatively
2 sister chromatids joined by centromere
volume of cytoplasm increases

Question 10

cancer treatment on cell division

Answer 10

Some disrupt spindle fibre activity So chromosomes can’t attach to spindle by their centromere
So chromatids can’t be separated to opposite poles
○ So prevents / slows mitosis
● Some prevent DNA replication during interphase
○ So can’t make 2 copies of each chromosome

Question 11

binary fission

Answer 11

plasmids and circular dna replicate
division cytoplasm to two daughter cells
one copy of circular dna and a variable number of plasmids

Question 12

viral replication

Answer 12

AP attach to complementary receptors host cells
inject their nucleic acid into host cell so infected parts of host cell replicate

Question 13

movement across membranes simple diffusion

Answer 13

lipid soluble and small molecules move from an area of high conc to low conc down a conc gradient across a phospholipid bilayer

Question 14

carrier and channel protiens role in facilitated diffusion

Answer 14

shape and charge of proteins determines which protiens move
channel protiens facility diffusion of water soluble molecules
carrier protiens facility diffusion of slight larger substances Complementary substance attaches to binding site
Protein changes shape to transport substance

Question 15

importance of hydrolysis of ATP

Answer 15

atp hyrolysed to ADP AND PI through Complementary substance binds to specific carrier protein and ATP binds
Carrier protein changes shape, releasing substance on side
of higher concentration
Pi released → protein returns to original shape

Question 16

antigens

Answer 16

foreign molecules that stimulate an immune response leading to the production of an antibody

Question 17

how are cells identified by the immune system

Answer 17

cells have specific molecules on their surface often proteins with a specific tertiary structure

Question 18

phagocytosis

Answer 18

phagocyte attracted to chemicals on pathogens
phagocyte engulfs pathogen surrounding it in its cell surface membrane and contains the pathogen in its vesicle
lysosome fuses with phagosome which releases lysozymes which hydrolyse the pathogen

Question 19

b lymphocytes response to foreign antigen

Answer 19

clonal selection
specific b lymphocyte with complementary receptors on it’d cell surface membrane bind to antigen
this is stimulated by helper t cells
divide rapidly by mitosis to form clones
some differentiate into b plasma cells so secrete antiboides
some differentiate into b memory cells which remain in the blood for secondary immune response

Question 20

antibodies

Answer 20

quaternary strutter protiens
secreted by B Lymphocytes
bind specifically to antigens to form an antigen antibody complex

Question 21

how do antibodies lead to destruction off pathogens

Answer 21

antigens bind to antibodies on pathogen forming an antigen antibody complex
specific tertiary structure so binding site complimentary to antigen
each antigen binds to two pathogens at a time cusing angulation of pathogens
antibodies attract pathogens
phagocyte bind. to antigens and phagocytose many pathogens at once

Question 22

primary response

Answer 22

Primary - first exposure to antigen
○ Antibodies produced slowly & at a lower conc.
○ Takes time for specific B plasma cells to be
stimulated to produce specific antibodies
○ Memory cells produced

Question 23

secondary

Answer 23

Secondary - second exposure to antigen
○ Antibodies produced faster & at a higher conc.
○ B memory cells rapidly undergo mitosis to
produce many plasma cells which produce
specific antibodies

Question 24

how do vaccines protect against disease

Answer 24

specific b lymphocyte with complimentary receptor bind to antigen
specific t helper cell bind to antigen presenting cell and stimulate B cell
B lymphocytes divide by mitosis to form clones
some differentiate into b plasma cells which release antibodies and some into b memory cells
on 2nd exposure to antigen b memory cells rapidly divide by mitosis to produce b plasma cells relating antibodies faster at a higher conc

Question 25

antigen variability effects on disease

Answer 25

antigen on pathogen change shape or tertiary structure due to gene mutation
so no longer immune
b memory cells receptors cant recognise antigen on second exposure
so specific antigen no longer complemntary

Question 26

replication of HIV in t helper cells

Answer 26

hiv attachement protiens attach to receptors on t helper cell
lipid envelope fuses with cell surface membrane releasing capsid into cell
capsid uncoats relaxing RNA and reverse T
RT conv RNA TO DNA
viral dna incur into T cell dna
viral protein produced
DNA transcribed into HIV mRNA
HIV mRNA translated into new HIV proteins
7. Virus particles assembled and released from cell

Question 27

HIV causing symptoms of AIDS

Answer 27

hiv infect and kill t helper cells as they divide rapidly
so t helper cells cant stimulate cytotoxic T cells B cells and phagocytes
no plasma cells to release antibodies for angulation and destroying pathogens
more susceptible to disease and pathogens reproduce releasing toxins

Question 28

why are antibiotics ineffective against virus

Answer 28

virus aren’t metabolic
virus don’t have meiurn cell wall and bacterial enzymes

Question 29

monoclonal antibody

Answer 29

antibody produced from genetically identical plasma cells
same tertiary structure

Question 30

monoclonal antibodies in medical treatment

Answer 30

they have a specific tertiary structure
comp to receptor
Therapeutic drug attached to antibody
Antibody binds to specific cell, forming antigen-antibody complex, delivering drug

Question 31

antibodies in elisa

Answer 31

attach sample with potential antigens to well
add comp monoclonal antibodies with enzyme attached
which bind to antigens if present
ash well to remove unbound antibodies
add substrate emzyme creates products that cause a colour change

Question 32

ethical issues with monoclonal antibodies and vaccines

Answer 32

pre clinical testing. on animals
clinical trials on humans can create harmful effects