Bio PPQs got wrong topic 4

Comment on the results of this investigation

• deficiency in both ions reduces flowering and fruit formation

• flower number reduced more by a deficiency in calcium than a deficiency in magnesium

• fruit production reduced more by a deficiency in magnesium than a deficiency in calcium

Explain the relationship between the structure and functions of a granum in photosynthesis

• granum is formed from many layers of thylakoid membranes to increase surface area (for absorbing light)

• thylakoid membranes contain chlorophyll to absorb light

• electron carrier molecules in thylakoid membrane involved in ATP production

What is calcium pectate?

A pectin fibre that is a crucial component of the middle lamella, it is formed when calcium ions bind to pectin

middle lamella

similarities

• both have glycosidic bonds

• description of every other monomer being inverted

Differences

• the monomers of chitin have eight carbon atoms whereas in cellulose there are 6 carbon atoms

• chitin has an additional side chin / contains nitrogen but cellulose does not

Compare and contrast the structure of cellulose and amylopectin

similarities

• both are polysaccharides / polymers of glucose

• both contain 1,4 glycosidic bonds

Differences

• cellulose contains beta glucose whereas amylopectin contains alpha glucose

• cellulose is not branched / does not contain 1-6 glycosidic bonds

• pieces of rope same length and diameter/width

• stored at a range of temperature above and below 18degreesC

• humidity at 60% / ropes stored for the same period of time

• masses / force / weights applied until rope breaks

• calculate change in tensile strength

(3)

• add 50g / 75g / 100g bamboo fibres to the same mass of resin

• tensile strength tested by adding masses / applying force until the fibre breaks

• calculate tensile strength by dividing fore by cross sectional area

• relevent variable controlled e.g. temp, humidity, length, age

the cellulose molecules form microfibrils. Name the bond between adjacent cellulose molecules in a cellulose mircrofibril

hydrogen bond

• B

• A

Explain why a seedling needs a supply of magnesium ions

• magnesium is needed to make chlorophyll

• because chlorophyll is required for photosynthesis

• because shoots need chlorophyll to carry out photosynthesis to grow

• effect of magnesium deficiency is shown earlier than the effect of calcium

• because the first leaf to die is leaf five in group B plants

• plants continue to grow in solution lacking magnesium

• plants stop growing in solution lacking calcium

• without calcium for the middle lamella new leaves cannot fully grow

• use of plants that are clones / same variety / same age

• a range of at least 5 different nitrate concentrations

• description of how an abiotic variable will be controlled - e.g. suitable method controlling temp or light described or pH of soil or presence of all other mineral ions in soil or volume of water provided e.g. height or mass

• grown for a set period of time

• relevant measure of growth

• repeats at each nitrate concentration to calculate mean values

A range of minerals is necessary for the formation of healthy plant tissue. 'The growth of seedlings is affected by the concentration of magnesium ions whereas germination of seeds is not.' Devise an investigation to obtain valid evidence to support this statement (5)

• range of magnesium ion concentrations

• measurement of germination rate

• use of seedlings germinated in solutions containing all mineral ions

• measurement of seedling growth

• environmental variables controlled temperature / humidity

Explain the role of the middle lamella when a plant cell completes mitosis

• produced between adjacent new cells in a cell plate

• because the middle lamella holds cell walls together

Explain the function of the plasodesmata

• cytoplasmic connection between cells

• which allows transport / communication between cells

Explain the effects of a shortage of magnesium ions on a plant

• limits the production of chlorophyll

• lack of glucose / carbohydrate / cellulose due to less photosynthesis

• therefore plant leaves may be yellow / plants may be small

Give 2 reasons why a sieve tube element does not require a RER and ribosomes

• there will be no transcription / mRNA therefore ribosomes are not required for translation

• no proteins will be synthesised to be processed in the endoplasmic reticulum

Plant-based products provide a sustainable alternative to oil-based plastics. A sustainable alternative is a plastic material that contains more than 30% plant-based polymers. Potato starch is a source of these polymers.

Explain why this plastic material is only partially sustainable. (2)

• because starch comes from plants that can be regrown

• however not 100% starch so some oil-based products are needed

Explain why starch must be broken down before it can be used by the cells of the growing plant (2)

• to produce glucose / maltose

• which is soluble / transported / enters cells easily / used in respiration

Describe the plasmodesmata

• the cell wall has only one layer / only primary cell wall present / a strand of cytoplasm

Describe the structure labelled Z that connects the cytoplasm of the companion cell to the sieve tube element. (2)

• the micrograph shows that the CC has many mitochondria whereas the ST has few / none

• the role of the ST is to provide a channel so cellular contents are kept to a minimum

• the ST has limited / no ability to carry out areobic respiration

• ATP / energy is supplied to the ST from the CC

Explain what is meant by tensile strength

• the pulling force the fibre can withstand before breaking

Plant-based products provide a sustainable alternative to oil-based plastics. The tensile strength of plant fibres can be tested using different methods. One method is to attach both ends of a fibre to clamps horizontally and hang increasing numbers of masses until the fibre breaks. A second method is to attach one end of a fibre to a clamp and the other to a forcemeter, pulling on the forcemeter until the fibre breaks. Explain which method will give more accurate results. (2)

• the second method will be more accurate because the exact value will be shown on the forcemeter

• the first method is less accurate because the true value will be between 2 masses

Describe how the tensile strength of plant fibres can be measured. (3)

• tensile strength can be calculated as a factor of force divided by cross sectional area of fibre

any 2 of the following

• addition of force / weight / mass to a fibre

• measurement of force / weight / mass required to break fibre

• calculation of cross - sectional area

• positive correlation between cell wall thickness and tensile strength

• due to presence of lignin

• no correlation between lumen diameter and tensile strength

• curaua fibres strongest as they had the thickest cell walls

Explain how the structure and properties of starch are related to its function as a storage molecule (3)

• contains glucose needed for respiration / energy

• insoluble so has no osmotic effect / remains in the cell

• amylose is coiled making starch compact so more can be stored

• amylopectin is branched / contains 1-6 glycosidic bonds so is rapidly hydrolysed

Tissues that contain lignin provide strength to plant fibres

Describe the positions in the stem of those tissues that contain lignin

• sclerenchyma fibres on the outer side of the vascular bundle / phloem

• xylem vessels on the inner side / inside of the vascular bundle

The fibres from different species of plants have different properties. Therefore, plant fibres can be used in the manufacture of a variety of materials. Describe the importance of magnesium ions in the production of plant fibres. (2)

• magnesium is essential to produce chlorophyll

• chlorophyll is necessary to produce glucose during photosynthesis

• glucose is needed to produce cellulose for the cell walls

Kapok (Ceiba pentandra) is a tree. Kapok produces seed pods containing waxy fibres made of cellulose covered in lignin. These fibres are used as fillings for cushions.

Devise a method to find the relationship between the actual diameter and the tensile strength of kapok fibres (6)

• extraction of individual fibres from seed pod / isolation of single fibre

• diameter of fibre measured (using capillipers / microscopy)

• control of relevant named variable

• clamping fibres and hanging masses from the fibre

• adding increased mass at regular intervals until fibre breaks

• repeat to find a mean at each diameter

• divide the force by the cross sectional area

Explain the relationship between the composition of the starch and the rate of hydrolysis by enzymes (4)

• as amylose content increases the % of starch hydrolysed decreases

• the less amylose present the greater the proportion of amyloopectin

• amylose is unbranched / amylopectin is branched

• amylopectin contains 1,4 and 1,6 glycosidic bonds

• branches / a greater number of terminal ends increases the rate of hydrolysis

Explain how the structures of amylopectin and glycogen make them suitable for storing energy (3)

• branched therefore can be rapidly hydrolysed to release glucose

• compact so more energy / glucose can be stored

• insoluble therefore does not affect osmosis

• molecules too large to diffuse across cell surface membrane

Describe 1 advantage and 1 disadvantage of using ropes made from plant fibres rather than ropes made from oil-based plastics (2)

Advantage

• being sustainable / can decompose / is biodegradable

Disadvantage

• less strong / can decompose / is biodegradable

• some seeds that have been kept for long periods will not be useful / no longer grow

• different types of seed lose viability at different rates

• therefore regular testing is needed to ensure seeds are still viable

• seeds from the seed bank can be grown to produce fresh seeds to replace the old seeds

State aseptic techniques that should be used when working with bacteria safely

• boiliing culture medium before use

• flaming / disinfecting of the instuments

• keeping lids off for the min time

• working in updraught of a flame / a flow hood

• disinfecting bench before or after working

• autoclaving used plates

Explain why some bacteria can grow rapidly in skin wounds (3)

• the temp is warm increasing rate of reactions in bacteria

• availability of energy source from tissue / blood

• availability of water for bacterial cell functions

• considerations of the role of oxygen EITHER oxygen availability is good allowing aerobic respiration OR oxygen supply is limited, but some bacteria are able to respire anaerobically

S. aureus can cause infections which are difficult to treat in humans. Describe how scientists, after testing the salve on mice, could test whether the salve is an appropriate treatment for humans with wounds infected with S. aureus. (4)

• salve must be applied to healthy humans

• treat one group of patients with the salve and another group with an existing treatment

• neither the doctors nor the patients involved in the trial should know which treatment is being used

• participants must be monitored fore side effects / adverse reactions associated with the salve

• compare the outcomes of patients treated with the salve and the control group

Explain how breeding programs in zoos maintain the genetic diversity of captive populations (3)

• animals are selected to prevent breeding between closely related individuals / inbreeding depression

• a studbook is used to select individuals for mating / keep a record of all breeding events

• exchange of animals / gametes between zoos

Comment on the antimicrobial properties of these four plant extracts. (3)

• extract P is the least effective

• all extracts inhibit / prevent growth of bacteria

• no significant differences between extracts Q, R and S due to overlap of ranges

Plant biodiversity in the Boyacá region of Colombia is amongst the highest in the world. Many of these plants have potential medical uses. Natural vegetation is being cleared to enable the rearing of cattle. The Royal Botanic Gardens at Kew has begun a project to conserve plant species from Boyacá, Colombia. Seed banks preserve seeds by drying them. Predictions from initial research suggest that seeds from 80% of flora in Boyacá will survive the drying process.

Explain the advantages of drying seeds before storage. (2)

• extends storage time of the seeds

• because drying prevents germination / decomposition of seeds

Plant biodiversity in the Boyacá region of Colombia is amongst the highest in the world. Many of these plants have potential medical uses. Natural vegetation is being cleared to enable the rearing of cattle. The Royal Botanic Gardens at Kew has begun a project to conserve plant species from Boyacá, Colombia. Seed banks preserve seeds by drying them. Predictions from initial research suggest that seeds from 80% of flora in Boyacá will survive the drying process.

Justify the benefits of conserving seeds from Boyacá (3)

• prevent species from becoming extinct

• conserving species with potential medicinal properties

• safeguarding genes that may prove useful in the future

• allow for reintroduction of species (in the future)

Medicinal drugs undergo clinical trials before they are licensed to be used. In January 2016, a clinical trial of a different drug involved 128 healthy volunteers aged 18 to 55. In this trial, different doses of the drug were given to 90 of these volunteers and the others were given a placebo. Six people, who were given the drug, became ill and had to be treated in hospital. (i) Explain why healthy volunteers were given different doses of the drug or a placebo. (2)

• check for side effects

• different doses to determine safe dose

• placebo to make sure that any side effects described were due to the drug

Medicinal drugs undergo clinical trials before they are licensed to be used. In January 2016, a clinical trial of a different drug involved 128 healthy volunteers aged 18 to 55. In this trial, different doses of the drug were given to 90 of these volunteers and the others were given a placebo. Six people, who were given the drug, became ill and had to be treated in hospital

Compare and contrast this drug testing protocol with that used by William Withering when he tested digitalis soup. (3)

• Both trials used different doses (to determine safe dose)

• William Withering did not use healthy volunteers and this drug trial did

• William Withering did not use a placebo while this trial did

Ebola virus disease (EVD) is a rare and deadly disease most commonly found in Africa. Following a severe outbreak in 2014, in which 11 000 people died, work has been underway to develop a vaccine. The vaccine is still undergoing clinical trials, but was given approval for use in recent Ebola outbreaks.

(i) Describe how clinical trials of a vaccine would be conducted. (3)

• small group of healthy volunteers given the vaccine to test for side effects

• healthy volunteers tested for presence of antibodies to the virus (following vaccination)

• a group of people at risk of contracting the disease is given the vaccine

• the number of people who develop the viral disease (following the vaccination) are monitored

Ebola virus disease (EVD) is a rare and deadly disease most commonly found in Africa. Following a severe outbreak in 2014, in which 11 000 people died, work has been underway to develop a vaccine. The vaccine is still undergoing clinical trials, but was given approval for use in recent Ebola outbreaks.

The Ebola vaccine was given to health workers and immediate family of those with the disease. Justify the use of this vaccine, even though the clinical trials had not been completed. (4)

• large numbers of people died from the disease

• health workers are in close contact with people suffering from the disease

• the side effects of the vaccine will not be worse than contracting ebola

• vaccinating immediate family will help to reduce the spread of disease

• if health workers were vaccinated they could care for more people

Svalbard Global Seed Vault (SGSV) is a seed bank. It keeps seeds from almost 4000 species of plants, focussing on food crops such as wheat, rice and maize. State suitable conditions for keeping seeds in a seed bank. (2)

Cold and dry

IGNORE COOL

(ii)

The purpose of the placebo is to (1)

A increase the accuracy of the measurements

B increase the reproducibility of the data

C show that exercise has an effect

D show that testosterone has an effect

• increase in cross sectional area with testosterone (and not with placebo)

• greatest increase with testosterone

• significant difference for testosterone plus excercise / group D as the SDs (for start and after 10 weeks) do not overlap

(ii) D

*(ii) Land use has changed over time in Borneo, with areas of forest being removed due to logging. The land may then be used for planting oil palms, which are not a suitable habitat for orangutans. The following comments refer to other issues concerning the conservation of orangutans in Borneo.

• Over the past 100 years, 80% of suitable habitat for orangutans has been lost.

• Only 2% of the remaining forest suitable as orangutan habitat is protected.

• From 1999 to 2015, the orangutan population decreased by 50%.

• Captive-bred orangutans may spread human diseases into wild populations.

• When captive-bred orangutans are released, their offspring often die young because the females have not learnt parenting behaviour from older individuals.

• Large numbers of orangutans are hunted in Borneo, even though they are a protected animal. It has been stated that habitat protection is more important than captive breeding programmes for the conservation of orangutans in Borneo.

Evaluate this statement. (6)

Basic information

• captive breeding will increase population size

• deforestation is reducing the habitat

• captive animals will be protected from hunters

Evidence of linkages

• orangutan numbers are declining and captive breeding will increase population size

• as loss of habitat is a major reason for the decline, animals should be released into areas of forest in protected areas

• more of the forest needs to be protected to reduce the rate at which habitat is being lost

• captive bred animals show behaviour that may make them unable to compete in the wild

• loss of habitat would lead to increased competition due to reduced food availability

Evidence of sustained scientific reasoning

• it is important to restrict passage of disease from humans to the wild population by minimising contact and releasing anials away from wild populations

• if deforestation is not reduced or protected areas are increased there will not be enough habitat left in which to release captive bred orangutans

• judgement on relative importance of captive breeding and habitat protection taking into account rate of deforestation and loss of suitable habitat

• releasing animals if there is insufficient habitat could lead to an increased vulnerability to predation and poaching

Sterile nutrient agar is a medium used for growing microbes. Describe how aseptic techniques are used when handling bacterial cultures. (3)

• working near a bunsen burner to provide convection current

• sterilising work surfaces

• sterilising equipment with heat

• limiting time containers are open

William Withering tested his digitalis 'soup' by an early form of drug testing. Withering reported that his first patient found that the digitalis "made him very sick, the sickness recurring at intervals for several days." Modern drug testing protocols include four stages. Modern drug testing protocols must ensure that new drugs are effective at treating patients. Explain the role that a placebo and a double blind trial have in producing valid conclusions. (4)

Placebo

Double blind trial

Placebo

• because is provides a control group for comparison

• therefore ensuring that the active ingredient / drug is causing the effect

Double blind trial

• because neither doctors nor patients know who has been given the actual drug

• therefore ensures that bias is removed from the trial

• the drug did not show a significant improvement when compared with the placebo

• because the ranges overlapped

• because some people in the trial had an increased blood pressure

The effects of these plant extracts were tested on pathogenic bacteria. It was found that each extract had an effect on its own, but the effect was greater when used together. Devise a procedure that scientists may have used to measure the effects of these extracts on pathogenic bacteria. (4)

• description of production of agar plates with bacteria

• description of method used to add plant extract to plates (e.g. on filter paper discs or in wells)

• extracts used separately and in combination

• incubate for appropriate period of time at 37degreesC (time from 24-72hrs)

• measure and compare the sizes of zones of inhibition

) Describe the effect of storage time on the germination of seeds for these two varieties of wheat. (3)

• % germination decreases as length of time stored increases (for both varieties)

• correct calculation for both varieties (e.g. from 0-120hrs 40% decrease for P and 36% decrease for Q)

• little change / 1 or 2 % in percentage germination when stored for up to 48hrs for both varities

• greatest decrease in percentage germination occurred later for P than Q / 72 hours for P and from 48 hours for Q

Explain how the results for the control were useful in this investigation (2)

• allowed a comparison between the 2 varieties / stored seeds and seeds that had not been stored

• to see the effect of seeds being stored at 80% humidity / 42degreesC

• data showed that the % germination success was high / not 100% in the control seeds

Explain why the agar plate was incubated at 25 °C

• colonies present with a different shape / size / colour

• therefore belonging to different species / contaminants

(ii)

• to allow bacteria to multiply

• without encouraging pathongenic organisms

Sepsis is a bacterial infection in the bloodstream. Sepsis can cause tissue death in limbs. This may require parts of a limb to be removed (amputation). Open wounds can become infected by bacteria, leading to sepsis. Explain why bacteria are able to multiply in the bloodstream when they enter the body. (3)

• warm conditions / water / glucose / amino acids /ideal pH available

Plus any 2 of the following

• suitable temperature for bacterial enzymes

• glucose used for respiration

• amino acids used for growth

• available to future generations

• because bamboo is a renewable resource

• because more bamboo plants can be grown

It was concluded from this investigation that spruce caused bacterial growth to decrease at a constant rate after the first day. Criticise this conclusion. (2)

• conclusion is not valid

• time is not show as a continuous scale

• no data between 4 and 8 days

Explain how this investigation could be improved to provide additional data to determine whether pine or larch have greater antimicrobial properties.

• shorter time intervals / hourly measurements

• between 0 and 1 day / within 1st 24 hours

• because no bacterial growth in either after 1 day

• test with different bacterial cultures

• because antimicrobial properties may vary

Svalbard Global Seed Vault (SGSV) is a seed bank. It keeps seeds from almost 4000 species of plants, focussing on food crops such as wheat, rice and maize. SGSV keeps seeds from more than 865 000 varieties of plant, including 200 000 varieties of wheat and rice. Some of these varieties are rare or extinct in the wild. Since 2004, more than 410 million dollars have been spent on SGSV and other seed banks around the world. However, it is estimated that 75% of global crop diversity is not stored in international seed banks. Critics argue that many crop varieties stored in SGSV are not actually used for food, and that the money would be better spent supporting farmers who are growing food crops. Justify the continued funding of SGSV (3)

• SGSV conserves genetic diversity of crops

• crop varieties kept in SGSV are protected from natural disasters / drought / mismanagement / economic factors / effects of climate change which can threaten varieties grown by farmers

• crop varieties in SGSV may have traits that are useful in the future such as frought resistance / pest resistance / disease resistance / tolerance of changing environmental conditions

• SGSV helps to ensure future food security if crop varieties currently grown were to fail

Wildlife conservation can involve keeping animals in zoos as well as protecting habitats. Describe the roles that zoos play in animal conservation. (3)

• description of role in protection - e.g. protection from poachers, hunting, vet care, administrating medicines

• description of role in repopulation e.g. increase numbers, breeding programs, release back into wild

• description of role in education e.g. conservation

• description of role in research e.g improving health, discovering better nutrition, breeding cycles, developing a genetic database

A three-phase protocol will be used when developing the phospholipase inhibitor as a new drug. Explain the purpose of each phase of this protocol for a phospholipase inhibitor. (3)

• for phase 1 - to make sure the phospholipase inhibitor is not harmful

• for phase 2 - to see if it is effective in treating the condition / preventing allergic reactions to wasp venom

• for phase 3 gather much data / data for statistical tests to look for rare side effects

• to test for side effects in phase 1 / phase 2

Plant-based products provide a sustainable alternative to oil-based plastics. In a single year, over 7600 million single-use plastic bags were given to customers by supermarkets in England. The mean mass of each bag was 5.5 g. Calculate the total mass in kilograms of plastic bags given out to customers. Give your answer in standard form. (2)

Evaluate the statement that Pumba Game Reserve has a more successful reintroduction programme than the one at Schotia Game Reserve. (4)

• more variety / higher number of species of carnivores in Pumba

• Pumba has no wild dog population

• schotia has a higher number of carnivores per hectare

• only shows data for carnivores

• isolate Scottish wildcats from domestic cats

• use studbooks / selection of mates

• increase the number of Scottish wildcats

• prepared for reintroduction to native habitat

A number of seed banks have been set up around the world. When a seed bank receives new seeds, it processes them in several ways. The processes can include the following stages: • washing the seeds with disinfectant • allowing the seeds to dry. Explain the advantages of these two stages. (3)

• washing with disinfectant will kill any microorganims

• drying to reduce chance of germination / decrease enzyme action

• therefore preventing decay / infection / damage to the seeds ALLOW: for long term storage

The stems of plants contain tissues involved in transport and in support. Fibres can be extracted from the stems of nettle plants and used to make clothing. Explain why the production of fibres from nettles is more sustainable than fibres produced from crude oil. (3)

• nettle plants can be grown so they are renewable

• crude oil is non-renewable and will run out

• use of fibres from nettles will be available to future generations

• clothing made of nettle fibres is biodegradable

Why is something described as endemic?

It is found in only 1 location

Use the Hardy-Weinberg equation to show that more than 50% of the forest elephant population are homozygous for the GBA gene. (3)

The electron micrograph shows a difference in the number of mitochondria in the sieve tube element and in the companion cell. Explain the difference in the number of mitochondria. (3)

• the micrograph hows that CC has many mitochondria whereas ST has few/none

• the role of the ST is to provide a channel so cellular contents are kept to a minimum

• the ST has limited / no ability to carry out (areobic) respiration

• ATP / energy is supplies to the ST from the CC

• smaller surface area of alveoli (with emphysema)

• therefore need a larger concentration gradiet

• to maintain rate of diffusion

Explain why water is a good solvent

• description of water as a polar / dipole / dipolar

• water surrounds polar molecules allowing them to dissolve

• hydrogen bonds form

Explain how the structure of an artery wall is adapted to withstand and to maintain high blood pressure (3)

• collagen in the walls provides strength

• contraction of muscles allows constriction of lumen / artery

• elastic fibres allow stretch and recoil / lumen to return to original size