Bio MS Flashcards
how is chromosome number halved in meiosis
homologous chromosomes separate so one of each goes to each daughter cell
enzymes work in opposite directions to build DNA in DNA replication (4)
DNA has antiparallel strands
shape of nucleotide is aligned differently
enzymes have an active site with specific shape
only substrates with complementary shape can bind with active site of DNA polymerase
effect of hunting on genetic diversity (3)
few types of alleles left
inbreeding
few surviving populations
why populations might show low levels of genetic diversity (3)
population may have been small
population started with a small number of individuals (one pregnant female)
inbreeding
explain how tissue fluid is formed (2)
overall outward pressure
small molecules are forced out of the capillary
why is there a high hydrostatic pressure in the arteriole end than the venule end
water loss
how does high blood pressure lead to tissue fluid formation (3)
high blood pressure is high hydrostatic pressure
increases outward pressure from arteriole end of capillary
more tissue fluid formed than reabsorbed
water potential in blood plasma more negative at venule end than arteriole (3)
water moves out of capillary
proteins too large to leave capillary
higher concentration of blood proteins so lower water potential
advantage of high % cholesterol in red blood cells
not supported by other cells as it is free in the plasma so needs cholesterol to maintain shape
inactive (virus) definition
virus is not replicating
why push coverslip down and not sideways
spreads tissue
avoids rolling the cells together
describe appearance of chromosome
two sister chromatids held together by a centromere due to DNA replication
describe role of haemoglobin in supplying O2 to tissues of the body
associates with O2 at high ppO2 to form oxyhaemoglobin
dissociates with O2 at lower ppO2
how O2 in air reaches capillaries near alveoli (5)
trachea, bronchi, bronchioles down pressure gradient down diffusion gradient across alveolar epithelium across capillary epithelium
how does an asthma attack decrease the volume of air breathed out (4)
muscle walls of bronchi contract
walls of bronchi secrete more mucus
diameter of airway reduced
flow of air reduced
why are cats experimented on instead of humans other than ethical reasons (3)
small enough to keep in the lab
can use a large number
similar physiology to humans
why do mutations not spread to other species (4)
mutations are random
rate of mutations are only affected by environment
different species do not interbreed
alleles are not able to be passed from one species to another
why does it take time for appearance of species with mutation to appear
few individuals with favourable alleles
individuals with allele have more offspring
takes generations for alleles to be the most common allele
how is high pressure produced in leaves (3)
water potential is low as sugar enters phloem
water enters phloem by osmosis
increased volume of water increases pressure
difference between active and passive immunity (4)
active has memory cells, passive does not
active produces antibodies by plasma and memory cells so is long term
passive involves antibodies introduced into the body from outside source so is short term
active takes time to work/ passive is fast acting
mass flow theory (5)
sucrose enters into COMPANION CELLS by facilitated diffusion
sucrose enters PHLOEM BY ACTIVE TRANSPORT with H+
LOWERS WATER POTENTIAL of sieve cell so water enters phloem by osmosis
INCREASES PRESSURE causing mass flow from source to sink
SUGARS USED FOR RESPIRATION
why does the potometer not measure rate of transpiration (2)
water used for photosynthesis
water produced in respiration
advantage of lipid droplet and micelle formation (3)
droplets increases SA, so faster hydrolysis
micelles carry fatty acids through membrane of cell
properties of water which are important for biology (3)
metabolite
solvent
has cohesion/ H bonds between molecules
estimate the length of a cell using an optical microscope (2)
calibrate eye piece graticule with stage micrometer
measure length with eyepiece graticule
monoclonal antibody
a single type of antibody specific to one antigen only
how does an increase in temperature cause pigments to be released (3)
damage to membrane
membrane proteins denature
increases fluidity
why should control variable (2)
if control variable increases, affect on results
allows results to be comparable
cohesion tension theory (6)
water lost from leaves by evaporation lowers water potential in the leaf water is pulled up the xylem water molecules cohere by hydrogen bonds forms a water column adhesion of water to walls of the xylems
