paper 1 Flashcards
Describe the structure of glycogen (2) [2017]
- polymer of alpha glucose
- highly branched
Suggest and explain two ways the cell-surface membranes of the cells lining the uterus may be adapted to allow rapid transport of nutrients. (2) [2017]
- lots of folds and microvilli to increase surface area
- lots of protein channels for facilitated diffusion
(key word: cells!)
Sodium ions from salt (sodium chloride) are absorbed by cells lining the gut. Some
of these cells have membranes with a carrier protein called NHE3. NHE3 actively transports one sodium ion into the cell in exchange for one proton (hydrogen ion) out of the cell.
Use your knowledge of transport across cell membranes to suggest how NHE3
does this. (3) [2017]
- co-transport
- hydrolysis of ATP
- Na+ and H+ bind to the protein
- protein changes shape
High absorption of salt from the diet can result in a higher than normal concentration of salt in the blood plasma entering capillaries. This can lead to a build-up of tissue fluid.
Explain how. (2) [2017]
- higher salt levels means that there is a lower water potential in the tissue fluid
- less water returns to the capillary by osmosis at the venule end
- higher hydrostatic pressure
- more fluid forced out of capillary
Some proteases are secreted as extracellular enzymes by bacteria.
Suggest one advantage to a bacterium of secreting an extracellular protease in its natural environment. Explain your answer. (2) [2017]
- proteins are digested
- can absorb amino acids for growth
Mammals have some cells that produce extracellular proteases. They also have
cells with membrane-bound dipeptidases.
Describe the action of these membrane-bound dipeptidases and explain their
importance. (2) [2017]
- hydrolyse peptide bonds to release amino acids
- amino acids can cross cell membrane
The scientists suggested that people newly diagnosed with this bladder infection
should be treated with both the current antibiotic and the new antibiotic.
Explain why the scientists made this suggestion.
Use information from Figure 2 and your knowledge of evolution of antibiotic
resistance in bacteria in your answer. (3) [2017]
- new antibiotic doesn’t kill all bacteria
- resistance bacteria reproduces to produce more resistant bacteria
- one bacteria kills bacteria resistant to the other antibiotic
The damselfly larva is a carnivore that actively hunts prey. It has gills to obtain
oxygen from water. Some other species of insect have larvae that are a similar size and shape to damselfly larvae and also live in water. These larvae do not actively hunt prey and
do not have gills.
Explain how the presence of gills adapts the damselfly to its way of life (2) [2017]
- larvae has a much higher metabolic rate
- uses up more oxygen
Describe the structure and function of the nucleus (4) [2022]
- nuclear envelope and pores
- DNA with histones
- nucleolus
- holds genetic information for polypeptides
Suggest one reason why the scientists used biomass instead of the number of individuals of each plant species when collecting data to measure diversity (1) [2022]
- too time consuming
Clostridium difficile is a bacterial species that causes disease in humans.
Antibiotic-resistant strains of C. difficile have become a common cause of infection
acquired when in hospital.
Explain how the use of antibiotics has led to antibiotic-resistant strains of bacteria
becoming a common cause of infection acquired when in hospital. (3) [2022]
- some bacteria have alleles for resistance
- non resistant bacteria die / resistant bacteria survive
- high frequency of resistant allele in population
Describe how the scientists could use aseptic techniques to transfer
0.3 cm3 of C. difficile in liquid culture from a bottle onto an agar plate. (3) [2022]
- disinfect surfaces
- use sterile pipette to transfer bacteria
- remove bottle lid and flame bottle neck
- lift lid of agar plate at an angle
- work close to upward air movement
- use a sterile spreader
- place pipette into disinfectant after use
Give two features of all prokaryotic cells that are not features of eukaryotic cells. (1) [2022]
- DNA free in cytoplasm
- circular DNA
The higher rate of transpiration at high tide shows that the mangrove tree is absorbing
water from the sea water surrounding its roots.
Describe an experiment that you could do to investigate whether the mangrove root
cells have a lower water potential than sea water.
You are given:
* a piece of fresh mangrove root
* sea water
* access to laboratory equipment (4) [2022]
- record mass of root before and after
- place sea water for a certain time period
- method to remove surface water
- if mass of root increases, sea water has a higher water potential than the root, water moves into root by osmosis
Compare and contrast the structure of starch and the structure of cellulose (6) [2022]
- both are polymers of glucose
- both have glycosidic bonds
- both have carbon, hydrogen, oxygen
- starch has alpha glucose and cellulose has beta glucose
- starch is helical and cellulose is straight
- starch is branched and cellulose is unbranched
- cellulose has micro/macro fibrils and starch doesn’t
Lignin is a polymer found in the walls of xylem vessels in plants. Lignin keeps the
xylem vessel open as a continuous tube.
Explain the importance of the xylem being kept open as a continuous tube. (3) [2023]
- water column
- cohesion from H2 bonds between water molecules
- evaporation creates tension
The classification system used in the early 20th century grouped different species of
bacteria according to the position and shape of flagella on bacterial cells and by the
number of flagella per cell. These were observed using an optical microscope.
Each species of bacterium has a characteristic cell shape and arrangement of flagella.
These characteristics may be shared with other species within a genus.
Flagella are fragile, difficult to stain and may extend from the cell at any angle.
Consider the accuracy and limitations of the early classification of bacteria using the
arrangement of flagella. (3) [2023]
- can’t distinguish species
- optical microscope has a low resolution
- flagella broken or damaged
- flagella difficult to stain so aren’t visible
- flagella at an angle so not visible
- not all bacteria have flagella
Suggest why several bacterial species have been renamed in recent years. (1) [2023]
- DNA/ mRNA/ RNA base sequencing
Mutation can result in an increase in genetic variation within a species.
Describe and explain the other processes that result in increases in genetic variation
within a species. (4) [2023]
- independent segregation of homologus chromosomes
- crossing over between homologus chromosomes
- random fertilisation of gametes
- produces new combinations of alleles
