depth in bio 2022 Flashcards
suggest further improvements that could be made to the beetroot investigation and give a reason as to why [4]
I same number/size/mass/volume
R to control/same surface area
I pieces from the same beetroot
R to control pigment conc.
I rinse/wash/wipe/dry pieces
R to remove pigment released by cutting/cell damage
I use one/new flask/tube per temperature/repeat
R to test effect of/ get absorbance for one/single temp.
explain the results around 20oC including knowledge of the structure and properties of phospholipid molecules [3]
Low temp (20oc)
- membrane is impermeable/least permeable
- pigment escapes through gaps between moving phospholipids
- as temperature increases, kinetic energy increases, meaning more phospholipid movement
- membrane becomes more permeable
- more pigment loss, higher absorbance figure –> graph curves upwards
explain the results around 70oC including knowledge of the structure and properties of phospholipid molecules [3]
High temp (70oC)
- membrane is disrupted
- phospholipid bilayer breaks down making the membrane very permeable
- large increase in pigment loss, increase in absorbance figure –> graph curves up more steeply
explain the structure and properties of phospholipid molecules [4]
structure
- phosphate and glycerol head
- 2 fatty acid hydrocarbon tails
properties
- heads are hydrophilic
- tails are hydrophobic
- phospholipid bilayer is formed
- form barrier to water/water-soluble molecules
state processes that take places during stage G2 [5]
size of cell increases
protein synthesis occurs
organelle replication
energy stores increase
DNA checked for errors
DNA repair
outline the importance of differential staining when observing cells undergoing mitosis [1]
the chromosomes are more visible when stained
similarities between prophase in mitosis and prophase in meiosis [2]
- chromosomes consist of 2 sister chromatids
- chromosomes condense
- nuclear envelope breaks down
- centrioles move to opposite poles
- spindle fibers form
differences between prophase in mitosis and prophase in meiosis [2]
- meiosis has prophase 1+2 whereas…
- homologous chromosomes pair in prophase I whereas…
- crossing over occurs in meiosis whereas
- chromatids are genetically different in prophase 2 whereas…
describe how the structure of a polyunsaturated triglyceride molecule would differ from a saturated triglyceride [1]
more than one C=C (double bond between carbons)
more than one kink/bend
fewer H atoms
outline the role of B memory cells in the secondary immune response [2]
B memory cells divide to form plasma cells
plasma cells release antibodies
antibodies bind to and destroy antigens
outline the roles of phagosomes and lysosomes in phagocytosis [3]
phagocytes engulf the pathogen to form a phagosome
lysosomes bind with the phagosome to form a phagolysosome
this then breaks down the pathogen by secreting hydrolytic enzymes
explain how haemoglobin acts as a buffer [2]
CO2+H20 forms carbonic acid
carbonic acid dissociates giving H+
H+ binds to haemoglobin
so CO2 can be carried as HCO-3
explain why the Bohr effect is important during exercise [2]
more CO2 during exercise so curve shifts to the right
at same pO2 Hb has a lower % saturation of oxygen
so oxygen dissociates from Hb more readily
more oxygen needed for muscles and aerobic respiration
describe how the apparatus can be used to model the changes that take place during inspiration in mammals [6]
pull down elastic sheet to make balloons expand
this models the diaphragm contracting
volume in bell jar increases
this models thorax volume increasing
pressure in bell jar decreases
this models thorax pressure decreasing
air pressure outside is higher than in the bell jar
represents higher pressure outside lungs
air pushed into balloons / balloons fill
this models inflating lungs
explain how the process of natural selection has resulted in this distribution of the two forms of peppered moth [4]
colour difference due to genetic variation
pale are more likely to be eaten
dark are more likely to survive
dark will reproduce and pass on its advantageous allele
frequency of allele increases for dark moths and decreases for pale moths
