paper 1 Flashcards
Describe and explain the effect of increasing carbon dioxide concentration on the dissociation of oxyhaemoglobin. (2)
- increases oxygen dissociation/unloading
2. by decreasing blood pH/increasing acidity of blood
Rate of movement
The student measured the time taken for water movement.
Give two other measurements he made to calculate the rate of water movement (2)
- initial and final mass of water
2. Number of xylem vessels
Give the reason for adding a layer of oil to the water in the beaker. (1)
To stop evaporation of water
Explain why coloured water moved up the stalks (3)
- water is transpired/ evaporates from leaves
- lower water potential which causes tension
- cohesion maintains a column of water
The student used a sharp scalpel to cut the celery. Describe how she should ensure she handled the scalpel safely during this procedure.
- cut away from the body
2. Against a hard surface
Explain how AV valve maintains a unidirectional flow of blood.
- pressure in left atrium is higher than in the ventricles which causes the valve to open
- pressure in left ventricle is higher than in atrium causing the valve to close.
Explain the role of the heart in the formation of tissue fluid. (2)
- contraction of ventricle produces high hydrostatic pressure.
- this forces water and some dissolved substances out of the capillary
Lymphoedema is a swelling in the legs which may be caused by a blockage in the lymphatic system.
Suggest how a blockage in the lymphatic system could cause lymphoedema. (1)
excess tissue fluid cannot be reabsorbed
Explain how changes in the shape of haemoglobin result in the S-shaped (sigmoid) oxyhaemoglobin dissociation curve for adult haemaglobin.
- oxygen binds to Hb causing a change in shape
2. this allows more O2 to bind easily
At birth 98% of the haemoglobin is HbF. By the age of 6 months, the HbF has usually completely disappeared from the baby’s blood and been replaced by HbA.
Use the graph above to explain why this change is an advantage for the baby.
- Adult haemaglobin has lower affinity for O2 at low partial pressures
- Easier unloading of O2 for aerobic respiration.
Suggest two reasons why water molecules and carbon dioxide molecules can both pass through aquaporins.
- both small/ similar size so can fit through channels
2. have a similar shape so can bind to channel
Outline a method by which you could find the area of a plant leaf
draw around the leaf on graph paper and count the squares.
Explain four ways in which the structure of the aorta is related to its function. (4)
- has elastic tissue allowing it to stretch/recoil/ maintain blood pressure
- tissue stretches when ventricles contract/ recoils when ventricle relaxes
- muscle for contraction
- Thick walls to withstand high pressure
- smooth endothelium, reduces friction
- semi lunar valve prevents backflow of blood
Species B is more active than species A. Use Figure 1 to explain how the haemoglobin of species B (more to the right) allows a greater level of activity.
- curve to the right so it has a lower O2 affinity
- Hb unloads more readily
- more O2 realeased to cells/ tissues/ muscles
- for more/faster respiration
One theory of translocation states that organic substances are pushed from a high
pressure in the leaves to a lower pressure in the roots.
Describe how a high pressure is produced in the leaves.
- water potential is lowered
- water enters phloem by osmosis
- increased volume of water causes increased pressure
During their experiment, the scientists ensured that the rate of photosynthesis of their plants remained constant.
Explain why this was important. translocation
- rate of photosynthesis is related to the rate of sucrose production
- rate of translocation is higher when sucrose concentration is higher.
Describe the role of iron ions, sodium ions and phosphate ions in cells (5)
iron:
1. present in Hb, Hb binds to/ transports oxygen
sodium ions:
- used in co transport of glucose
- becuase sodium ions are moved out by active transport by Na-K pump
- creates a concentration gradient
- affects osmosis/ water potential
Phosphate ions:
- affects osmosis/wp
- Joins nucleotides by forming sugar phosphate backbone in DNA/RNA
- Used to produce ATP
- Phosphorylates other compounds to make them more reactive
The movement of substances across cell membranes is affected by membrane structure.
Describe how. (5)
- allows diffusion of non-polar/lipid soluble substances.
- prevents movement of charged substances
- carrier proteins allow active transport
- channel/carrier proteins allow facilitated diffusion/co transport
- shape of channel/carrier determines which molecules can move across cell membrane
- Sa determines how much diffusion takes place
- Cholestrol affects fluidity/ rigidity/permeability
Suggest and explain one way the leaf growth of xerophytic plants would be different
- slower growth
- due to smaller number/area of stomata
OR - growth may continue at lower WP
2.due to adaptations in enzymes involved in photosynthesis.
Use your knowledge of gas exchange in leaves to explain why plants grown in soil with very little water grow only slowly.
- stomata close
2. less CO2 uptake for photosynthesis
Give two similarities in the movement of substances by diffusion and by osmosis.
- from high to low conc
2. passive/not active
Give three properties of water that are important in biology.
- is a metabolite
- is a solvent
- Has high heat capacity
- High latent heat of vaporisation
- cohesion/h-bonds between the molecules
Cells lining the ileum of mammals absorb the monosaccharide glucose by co transport with sodium ions. Explain how.
- sodium ions actively transported from ileum cell to blood
- maintains/forms diffusion gradient for sodium to enter cells from gut with glucose
- glucose enters by facillitated diffusion with sodium ions.
One theory of translocation states that organic substances are pushed from a high
pressure in the leaves to a lower pressure in the roots.
Describe how a high pressure is produced in the leaves.
- water potential lowers
- water enters phloem by osmosis
- increased volume of water causes high pressure.
Glucose is absorbed from the lumen of the small intestine into epithelial cells.
Explain how the transport of sodium ions is involved in the absorption of glucose by
epithelial cells.
- Na+ ions leave epithelial cells and enter blood
- By active transport
- so Na+ conc is lower than in the lumen
- Na+ ions enter by faciliated diffusion
- glucose is absorbed against its concentration gradient.
Explain why the diffusion of chloride ions involves a membrane protein and the diffusion of oxygen does not.
- chloride ions are charged/water soluble
- so cannot cross the lipid bylayer
- chloride ions have to be transported via facilitated diffusion.
- oxygen is not charged
- oxygen can diffuse across the bilyayer via simple diffusion.
Suggest and explain one advantage of asexual reproduction and one advantage of sexual reproduction
asexual:
1. quicker as theres fewer stages
2. only one parent involved so can colonise a new environment
3. produces clone so successful genopheno type is maintainted
sexual:
1. increases genetic diversity so has a greater chance of survival.
Other than hunting, suggest two reasons why populations might show very low levels of genetic diversity.
- might have been a small population
- inbreeding
- might have started with a small number of individuals
list the taxons
domain kingdom phylum class order family group species
what is genetic diversity?
The number of different alleles of the same gene
What is the name of a position of a gene on a chromosome?
locus
Suggest how a mutation can lead to the production of a protein that has one amino acid missing.
loss of 3 bases
Suggest how the production of a protein with one amino acid missing may lead to a genetic disorder
- Change in proteins tertiary structure
2. so a faulty/non-functional enzyme is produced
Use the information provided to explain how a very high diversity of bird species has
developed in the Amazonian forest. (5)
- no interbreeding
- mutations
- different selectional pressures
- adapted organisms survive and breed
- Change/increase in alelle frequency
What is speciation?
formation of a new species
Name an organelle found in both a chloroplast and a prokaryotic cell.
Ribosome
A biologist separated cell components to investigate organelle activity. She
prepared a suspension of the organelles in a solution that prevented damage to the organelles.
Describe three properties of this solution and explain how each property prevented
damage to the organelles.
- ice cold to prevent/reduce enzyme activity
- buffered to prevent denaturing of enzyme
- same water potential as cells (isotonic) to prevent bursting of organelle
Name the process by which prokaryotic cells divide.
Binary fission
Describe how you would use cell fractionation techniques to obtain a sample of chloroplasts from leaf tissue. Do not include in your answer information about any solutions.
- homogenise in isotonic solution and filter
- centrifuge
- at increasing speeds until chloroplast fraction is observed.
Give the function of a mitochondrion
- site of aerobic respiration
2. ATP is made
Contrast how an optical microscope and a transmission electron microscope work
and contrast the limitations of their use when studying cells
- TEMs use electrons and optical use light
- TEMs allow a greater resolution
- so smaller organelles can be observed
- TEM can only view dead specimens, light can view live specimens
- TEM doesnt show colour and optical can.
- TEM requires thinner specimens
- TEM requires more complex preperation
- TEm focuses using magnets and optical focuses using glass lens.
Describe how he should collect and process data from these seeds to investigate whether there is a difference in seed size between these two populations of trees.
- use random sample from each population
- large enough to be representative of the whole population
- indicate what size/mass was measured.
- calculate a mean and SD for each population
- use the studemts t-test
- Analyse if theres a significant difference
Name two structures present in plant cells that are not present in animal cells.
- cell wall (cellulose)
- chloroplast
- vacuole
- starch grains
Explain why the biologist used a blender and then filtered the mixture (ultracentrifugation)
- to break open the cell to release the organelles
2. remove larger debris
Name the organelle that made up most of the first pellet after centrifuging at a low speed (step 4)
nucleus
Give two ways in which the nucleotides in DNA are different from the nucleotides in RNA.
- DNA contains T. RNA contains U
2. DNA deoxyribose, RNA ribose
Name two structures in a eukaryotic cell that cannot be identified using an optical
microscope.
mitochondria / ribosome/ ER / lysosome/ cell membrane
Give one function of lysosomes.
break down cells/ toxins
What is a monomer?
A small repeating unit of which polymers are made
Describe two differences between the structure of a cellulose molecule and a glycogen molecule
- cellulose made of B glucose and glycogen is made of a glucose
- c straight chain and g is branced
- G coiled C straight
- G has 1,4 and 1,6 glycosidic bond, C only has 1,4
Describe and explain two features of starch that make it a good storage molecule.
- insoluble in water so doesnt affect wp
- branced/coiled so its compact/ store lots in one area
- polymer of a glucose so provides glucose for respiration
- branched, more ends for faster breakdown
- large molecule so can’t cross the cell membrane
test for starch
iodine/ potassium iodide
blue/black
Explain how cellulose molecules are adapted for their function in plant cells.
- long and straight chains
- linked by h-bonds to form fibrils
- provides strength to cell wall
Explain how digestion of starch in the gut (small intestine) leads to an increase in the concentration of glucose in the blood. Details of co-transport are not required.
- hydrolysed by enzymes
- produces glucose in the gut
- small enough to cross gut wall into blood
Explain why it is more useful to calculate an index of diversity than to record species
richness
- measures number of each species
2. useful because there might be many of one species than another
Give two ways the students would have ensured their index of diversity was representative of each habitat.
- random sample
2. large number of samples
Define species
a group of similar organisms that are able to produce fertile offspring
define species richness
the number of different species within a community
Outline a method the ecologists could have used to determine the plant species richness at one site
- select sample sites at random
- use a quadrant
- identify species in each quadrant
Species richness and an index of diversity can be used to measure biodiversity within a
community. What is the difference between these two measures of biodiversity?
- SR measures only number of different species
The forest was cleared to make more land available for agriculture.
After the forest was cleared the species diversity of insects in the area decreased. Explain why.
- decrease in variety of plants
- fewer habitats
- decrease in variety of foods
The scientists collected insects at sites chosen at random. Explain the importance of
the sites being chosen at random.
so its not bias
Explain the effect planting hedges could have on the index of diversity for animals.
- greater variety of plants
2. Another habitat/food source
Explain two advantages for a farmer of removing hedgerows
- source of pests so no more pests
- weeds no longer taking up nutrients of crops
- can grow more crops in them areas
Apart from providing a habitat for predators of crop pests, give two biological benefits of replanting hedgerows.
- increases biodiversity
- increases food source for animals
- habitat for animals
Describe the gross structure of the human gas exchange system and how we breathe in and out. (6)
- trachea branches off into bronchi which branches off into bronchioles that have alveoli sacs on the end of them.
- breathing in- diaphragm contracts and external intercoastal muscles relax
- causes an increase in volume and decrease in pressure allowing air to move in
- breathing out- diapragm relaxes and external intercoastal muscles contract
- causes a decrease of volume and an increase of pressure in the thoracic cavity
Compare and contrast the structure and properties of triglycerides and phospholipids.
- both contain ester bonds
- contain glycerol
- fatty acids on both maybe saturated/unsaturated
- insoluble in water
- Both contain C,H,O but phospholipids also contain P
- tri has 3 fatty acids, phospho has 2
- phospho form bilayer
- tri are hydrophobic, phospho have a hydrophobic and hydrophillic region
Describe how lactose is formed and where in the cell it would be attached to a polypeptide to form a glycoprotein
- glucose and galactose
- condensation reaction
- glycosidic bond
- added to polypeptide in the golgi apparatus
Explain three ways in which an insect’s tracheal system is adapted for efficient gas
exchange.
- Tracheoles have thin walls so short diffusion distance to cells
- Highly branched / large number of tracheoles so short diffusion distance to cells;
- Highly branched / large number of tracheoles so large surface area (for gas exchange);
- Tracheae provide tubes full of air so fast diffusion (into insect tissues);
- Fluid in the end of the tracheoles that moves out (into tissues) during exercise so faster diffusion through the air to the gas exchange surface;
OR
Fluid in the end of the tracheoles that moves out (into tissues) during
exercise so larger surface area (for gas exchange); - Body can be moved (by muscles) to move air so maintains diffusion / concentration gradient for oxygen / carbon dioxide;
Suggest two ways the student could improve the quality of her scientific drawing
- no shading
- only use single lines
- ad labels/ annotations
- add magnification
- dont cross label lines
Explain two ways in which the structure of fish gills is adapted for efficient gas exchange.
- Many lamellae / filaments so large surface area;
2. Thin (surface) so short diffusion pathway;
Explain how the counter current mechanism in fish gills ensures the maximum amount of the oxygen passes into the blood flowing through the gills. (3)
- Water and blood flow in opposite directions;
- Blood always passing water with a higher oxygen concentration;
- Diffusion gradient maintained throughout length (of gill)
Suggest an explanation for the effect of temperature on the rate of carbon dioxide release.
. Enzymes / metabolism faster;
2. Higher rate of respiration and carbon dioxide production / release;
3. Spiracles open more often / remain open to excrete / get rid of carbon dioxide /
get more oxygen;
Describe two adaptations of the structure of alveoli for efficient gas exchange
- thin walls (short diffusion pathway)
2. large surface area
Abdominal pumping increases the efficiency of gas exchange between the tracheoles and muscle tissue of the insect. Explain why.
- More air / oxygen enters / air / oxygen enters quickly / quicker;
- (So) maintains / greater diffusion or concentration gradient;
Describe and explain how the structure of the mammalian breathing system enables efficient uptake of oxygen into the blood.
- alveoli provide a large surface area; 6 max
- walls of alveoli thin to provide a short diffusion pathway;
- walls of capillary thin / close to alveoli provides a short diffusion pathway;
- walls (of capillaries / alveoli) have flattened cells;
- cell membrane permeable to gases;
- many blood capillaries provide a large surface area;
- intercostal / chest muscles / diaphragm muscles / to ventilate lungs /
maintain a diffusion / concentration gradient; - wide trachea / branching of bronchi / bronchioles for efficient flow of air;
- cartilage rings keep airways open;
