Exam Questions Flashcards
how do assimilates move from sieve tubes in leaves to sinks
mass flow
Sucrose decreases water potential
water enters sieve tubes down water potential gradient by osmosis
This causes an increase in hydrostatic pressure
Unloading of sucrose at the sink causes a decrease in hydrostatic pressure
Movements from source to sink is a gradient in hydrostatic pressure.
Advantage of plasmodesmata between cells in leaves
Increased diffusion of assimilates
Because more symplastic pathways.
How is the structure of the xylem vessel suited to its function
Transport of water and mineral ions
Elongated tubes for transport
No end wall so minimal resistance to flow of water
No organelle so more space for greater volume of flow
Cellulose walls allows adhesion of water molecules
Lignified walls prevent inward collapse and are waterproof so prevent loss of water
Pits allow lateral movement of water
Narrow diameter of lumen allows for adhesion
How is phloem transported from a stem to a fruit
Sucrose is loaded at source
Companion cells pump out H+ ions and sucrose moves in through co-transporter cells.
Water enters via osmosis
Hydrostatic pressure builds
Mass flow
Sucrose unloaded at sink gives a difference in hydrostatic pressure
Describe the process of gas exchange in healthy lungs and how is this impaired with someone who has emphysema (4)
In healthy lungs
1-Oxygen enters the blood from the alveolus and CO2 goes from blood to alveolus.
2- This is done by diffusion
3-Across the alveolar and capillary walls.
4- There is a higher rate of exchange with the healthy lung then the diseased lung
5- The healthy lung has a larger surface area for gas exchange
What type of plant is adapted to live in regions with low water supply (1)
Xerophytes
What part of the vascular tissue contains sucrose (1)
Phloem
Suggest why glucose is present in phloem sap (2)
1- Movement in sucrose from source to sink
2- The source is where the sucrose is synthesised, the sink is where it is stored
What is meant by hydrolysis of ATP (2)
Using water to break bond between phosphate group
What type of transport move K and Na ions (1)
Active transport
How do non competitive inhibitors affect the enzyme (4)
1- They reversible bind to a site other than the active site
2- Which changes the tertiary structure of the active site
3- The substrate can no longer fit into the active site
4- So less reactions can take place
Describe the sequence of events which occur in the left side of the heart during one normal cardiac cycle (4)
The left atrium fills with blood during relaxation of the left atrium and ventricle. Atrioventricular valve opens, the atria contracts increasing pressure and blood flows to the ventricle. The ventricles contract increasing the pressure in the ventricles. The bicuspid valve closes and semi-lunar valve opens. Blood flows into aorta
Suggest how the health of someone with heart failure could improve with drugs (3)
1- More powerful contractions of cardiac muscle.
2- Blood pumped at higher pressure.
3- More force required to overcome resistance in blood vessels.
4- More blood reaches lungs to obtain oxygen.
5- Less fatigue
Explain the importance of mitosis in the repair of damages tissue (2)
Devision produces new genetically identical daughter cells which retain function
Why are stem cells important in tissue repair (2)
Stem cells continuously divide. To produce cells that can differentiate. Can produce cells that can still function.
How are cells released in circulation to stimulate liver cells an example of cell signalling (3)
1- the chemicals released are cell signalling molecules
2- Liver cells are target cells
3- Binding of chemicals to receptors
4- The chemicals are complementary to receptors
Outline the key structures of viruses (3)
Protein coat made from capsomeres
Nucleic acid
DNA or RNA
Acellular
What is the global importance of HIV positive (but who do not have AIDs) pregnant and breast feeding women being on medication?
1- Because HIV can be passed from mother to child.
2- Reduces the number of HIV positive women becoming ill.
3- Reduced spread of HIV, the child may grow up without HIV and will not pass it on
4/5- Healthy women can contribute to workforce. Can be main carer if partner has died. Makes breastfeeding safer when there are no other options.
Explain why RNA can be described as a polymer and macromolecule (2)
Many monomers repeating, it is a large biological molecule
Outline the test and result for reducing sugars (2)
Add Benedict solution and boil. Precipitate changes to red
State the function of the Golgi body
Processing of proteins
State the function of centrioles (1)
Formation of spindle fibres
State the part of the haem group that binds to oxygen in each haemoglobin polypeptide (1)
Iron
State the compound formed when CO2 binds to haemoglobin (1)
Carbaminohaemoglobin
State the compound formed when hydrogen ions bind to haemoglobin (1)
Haemoglobinic acid
Function of vacuole (1)
Maintains turgor
Two structures in a cell which contain DNA
Nucleus, chloroplast
Why can you see the internal structures of cell organelle only with an electron microscope (3)
This is because a light microscope has a lower resolution then the electron microscope, with a resolution of 200nm and 0.5nm respectively. Resolution is the ability to see 2 point as different instead of just one point.
Describe the permeability of the cell wall and cell surface membrane (4)
The cell surface membrane is composed of a phospholipid bilayer. It has a hydrophobic interior meaning that polar and water soluble ions cannot pass through but lipid soluble molecules can. The cell wall has pores meaning that it is freely permeable to all molecules. The cell surface membrane has carrier and channel proteins meaning that water soluble molecules can pass through.
Osmosis
Large ion concentration lowers water potential, water moves from a high to low water potential down a water potential gradient.
Function of cell surface membrane
Controls the movement of substances in and out of the cell
Function of nucleolus
Production of ribosomes
Function of mitochondria
Aerobic respiration, synthesises ATP
Function of smooth endoplasmic reticulum
Synthesises lipids
Function of rough endoplasmic reticulum
Protein synthesis
Function of lysosomes
Contains digestive enzymes
Why is the cell surface membrane called a fluid mosaic model
Fluid= Molecules move about the membrane, ie phospholipid and protein molecules move about.
Mosaic = The protein molecules are scattered along the membrane, there are many different protein molecules
Explain why sodium ions cross the cell surface membrane by facilitated diffusion
Sodium ions are hydrophilic, they cannot pass through the hydrophobic interior. So they must pass through the hydrophilic transport proteins. Active transport is the only way to move sodium ions against the concentration gradient.
When does DNA replication occur
interphase
Explain the importance of mitosis in multicellular organisms
Mitosis can be used to replicate dead cells as the cells are genetically identical. It can be used in an immune response, for example cloning B and T lymphocytes. It can be used in growth as the production of genetically identical cells allows multicellular organisms to arise from zygotes.
Explain the difference in the thickness of the left and right ventricle of the heart
The left ventricle needs to generate more force as the blood is going a further distance all around the body. The right ventricle only needs to develop the pressure to take the blood to the lungs so can be thinner.
How are capillary’s adapted for their function
Their wall is one cell thick meaning that the oxygen does not have to diffuse a long distance. They are very small meaning they can get as close as possible to the respiring cells. Many gaps alow the substance to leave the blood
How does CO2 and hydrogen ions play a role in unloading oxygen from haemoglobin (5)
CO2 diffuses from the respiring tissue into the blood plasma and into the red blood cells. It reacts with H2O and is catalysed by the enzyme carbonic anhydrase to form carbonic acid, which dissociates into hydrogen carbonate ions and hydrogen ions. Haemoglobin has a higher affinity for hydrogen ions then oxygen so combines with the hydrogen ions, this changes the tertiary structure of the haemoglobin molecule causing it to release oxygen. The higher the partial pressure of CO2 the more oxygen will ne unloaded
How are cilia and goblet cells adapted to protect the trachea
Goblet cells produce mucus which is sticky and traps pathogens. The cilia moves the mucus and pathogens to the top of the larynx where it is swallowed and killed in the stomach acid. This gets rid of the pathogens so that they don’t harm the lungs and cause an infection
Function of SAN (2)
Initiates heart beat, send out wave of excitation which caused the atria to contract.
What are lifestyle diseases
Diseases caused by something you chose to do i.e. smoking
Suggest a reason why there is a rise in measles cases
A decrease in vaccination rates in the developed world
How do infectious disease differ from non-infectious diseases
Infectious disease are caused by a pathogen and are spread from infected person to non-infected person, or through a vector. Whereas non-infectious diseases are not caused by a pathogen and can be caused by a genetic disease or due to lifestyle choices.
How do macrophages protect the lungs (4)
The macrophage recognises the foreign antigen. The receptor on the macrophage binds to the antigen on the pathogen. The membrane infolds arounds the pathogen forming a phagocytic vacuole. The lysosome fuses with the vacuole and secretes digestive enzymes killing the pathogen.
List two structures that are present in an animal cell but not a plant cell
Cillia, centriole, flagella, microvillus, lysosome
Outline the differences between the apoplastic and synplastic pathway after the water has left the xylem (4)
The apoplastic pathway is through the cell wall. The symplastic pathway is through the cytoplasm. In the symplastic pathway they move by osmosis across membrane such as the cell surface membrane, it moves through plasmodesmata and through vacuoles. The apoplastic pathway is the non-living pathway, more water moves this way and is helped along by hydrogen bonding to cell walls.
State two ways in which water is used in leaf cells (2)
Maintain turgor, reactant in photosynthesis, used in hydrolysis reactions
State one role of magnesium ions in the leaf (1)
Used in synthesis of chlorphyll molecules, used as enzyme
How are enzymes secreted by cells and packaged (4)
Vesicles are released from the Golgi body, vesicles move through cytoplasm to cell surface membrane, this is helped by the cytoskeleton. ATP is required in order for the vesicle to fuse with the membrane. Exocytosis occurs, this is possible due to the fluid nature of the phospholipid bilayer
What is the bond between glucose molecules in a polysaccahride
Gylcosidic bond
How does maltose and an enzyme with a similar shape affect the enzyme
The enzyme binds with the active site because it has a complimentary shape, so substrate molecules cannot bind to active site. It competes with substrate so is a competitive inhibitor. This slows the rate of the break down of maltose
Describe the secondary and tertiary structure of an enzyme
5
The secondary structure is the regular pattern due to hydrogen bonding between the CO of one amino acid and the NH of another. There is alpha helix and beta pleated sheet. The tertiary structure is due to regular folding and the interactions between R groups side chains. These could be hydrogen bonds or disulfide bonds. Hydrogen bonding is between polar groups. This gives the active site its precise shape. It is a globular protein
Why is it important for enzymes to have a tertiary structure (1)
Enables proteins to function as they have an active site.
Why is haemoglobin described as a globular protein with a quarternary structure (2)
Because it has a hydrophilic outside and is folded into a ball. It has 4 polypeptide chains
Why do people who lack iron in their diet feel tired (3)
Iron is needed for haem. So with less Iron less haemoglobin will be made, less oxygen will be transported to cells and the respiration rate will decrease.
Primary structure of haemoglobin
The order of amino acids
Secondary structure of haemoglobin
Alpha helix
Tertiary structure of haemoglobin
Folding of polypeptides, held in place by interactions between R groups
Quaternary structure of haemoglobin
The interactions between the 4 polypeptides
How does an environmental factor act as a stabilising factor in natural selection (3)
Unchanging environment (Blank) acts as a selective agent Organisms best adapted to these conditions survive Extreme phenotypes are selected against There is now a narrow range of genetic variation
Define species (2)
Similar morphological features
Reproduce to produce fertile offspring
Occupy same niche
Reproductively isolated
Explain how the process of speciation occurs when there is geographic isolation (5)
No breeding between populations Gene mutations occur Different selection pressures Different alleles are selected for Different chromosome numbers Genetic drift Cannot interbreed Allopatric speciation
Explain the process of natural selection (4)
Ideal characteristics selected by humans
(Give example)
Bred together
Offspring with ideal characteristics chosen to mate
Over many generations
Allele frequency for ideal characteristics increase
Directional selection
Why is maize produced by hybridisation
Hybrid vigour Increases heterozygosity Increases gene pool Reduces inbreeding depression Increases yield Is more nutritious
Suggest why photorespiration is more likely to take place in hot dry conditions
Stomata closed To reduce transpiration So CO2 cannot enter the leaf So CO2 concentration in leaf becomes low So RUBP is more likely to react with oxygen
What is the difference between the endocrine and nervous system
In the endocrine system, hormones are used as chemical messengers. They are released into the blood to target organs or cells. They interact with receptors on the cell surface membrane. One example of hormone would be adrenaline which initiates the fight or flight response. In the nervous system there are impulses which are relayed along the neurons. They diffuse across the synapse. The message goes from the receptor to the sensory neurone, then the motor neurone and effector. The endocrine system is much slower, has a longer lasting and more widespread effect.
Benefits in maintaining biodiversity (4)
Aestetic pleasure, moral reason = we have no right to destroy the planet. We can use the species for medication. Lots of peoples livelihood relies on it. When a crop fails we can breed it with its wild relatives in order to bring out desired characteristics. Leisure activities
Why is it useful if a zoo is near the species natural habitat (2)
The species bred through captive breeding may be able to be reintroduced to the wild. The species wont die in an area which is drastically different from their natural one.
Why are the seeds in a seed bank checked every couple of years (2)
To check that they are viable, if a lot of the seeds do not germinate then they will collect more seeds
Why might a plant become an endangered specie (3)
Habitat loss due to deforestation, people picking the flower, people killing it if it is a weed or has a bad smell
Biodiversity (1)
The richness and abundance of a species in an environment
Ecosystem (2)
The interaction between the organism and their envionment
How can humans damage coral reefs (3)
The release of CO2 in industrial processes causes the acidification of sea water. Coral bleaching. Trawling and litter
Why is ATP needed at the start of glycolysis
Provides activation energy
Role of NAD in glycolyses
Acts as a coenzyme
What happens to the hydrogen released in the link reaction
It combines with NAD to form reduced NAD which is transported to the electron transport chain to be used in oxidative phosphorylation
Why is ATP regarded as the universal energy currency (5)
It only releases small amounts of energy. It carries energy between energy releasing and energy requiring cells. It is readily hydrolysed to release energy. It is a reversible reaction. High turnover. Used in active transport. Water soluble so can move around the cell
How does a second infection differ from the first (3)
The secondary response is faster because of the production of memory cells in the primary response. There is a faster production of B lymphocytes, a greater concentration of antibodies in the blood. The pathogen is removed faster
How are the lungs adapted to protect against bacteria
Cilia beats the mucus away from the lungs. The mucus is barrier for bacteria to enter epithelial cells, mucus traps pathogens. Capillaries bring phagocytes to the lungs
Describe the role of carbonic anhydrous in the blood (4)
It catalyses the reaction between carbon dioxide and water to for carbonic acid, this is a very fast reaction which happens in the cytoplasm of the red blood cell. The carbonic acid dissociates into hydrogen ions and hydrogencarbonate ions. The hydrogen ions cause the dissociation of oxyhaemoglobin. Increasing the supply of oxygen to respiring tissue. Carbon dioxide is transported as hydrogencarbonate ions.
How can DNA sequencing be used to measure genetic variation (4)
DNA is denatured and a primer is added. Copies of pieces of DNA with different lengths are produced. PCR is used to increase the number of strands. Fluorescent dyes are added and electrophoresis is used. The DNA sequence is then read and they can be compared.
What is the aim of gene therapy (2)
You insert a normal allele of a gene in order to obtain a functioning polypeptide in order to reduce the symptoms of the disorder. This will increase quality of life
Why is isolating mRNA easier then isolating the DNA which codes for insulin
The mRNA is only from the gene coding for insulin and there is a large number of this mRNA. Whereas the DNA contains all the genes, so it is difficult to isolate the gene as a restriction enzyme would be needed
Use of restriction enzyme
They cut plasmid DNA at specific sites which form sticky ends
Describe electrophoresis (9)
A section of DNA containing VNTR is used, the quantity of this DNA is increased by PCR. The DNA is then fragmented by a restriction enzyme. This DNA is then placed in wells cut into agarose get at the cathode. A buffer is also added and a direct current is applied. As the phosphate groups on the DNA has a negative charge, the DNA is attracted to the anode. The short pieces of DNA will move further. The pieces are transferred to absorbant paper. Probes are added and under UV light a pattern of stripes appear
How can bacteria be genetically modified and then identified using antibiotic resistant genes (7)
Th recombinant plasmids are mixed with the bacteria, some of these bacteria will take up the plasmid when they are subjected to heat shock. To identify the bacteria containing the plasmids, they should be grown on gar jelly containing antibiotics. The bacteria which contain the plasmid with the antibiotic resistant genes will survive. In order to identify the recombinant bacteria a replica plate is used which has on it the agar jelly containing the second antibiotic. The resistance genes are inactivated by the insertion of the new genes do the colonies which contain recombinant bacteria will not grow on the second plate.
Why doe polar ions have to move by facilitated diffusion through the phospholipid bilayor
The sodium ions are charged / hydrophilic and cannot pass through the hydrophobic, core / interior, (of phospholipid bilayer). So it must pass through, transport proteins. Active transport is the only way to move sodium ions against their concentration gradient
How is hydrogen bonding involved in the movement of water through the xylem
Cohesion and adhesion help form the transpiration stream. There is cohesion between the water molecules, there is adhesion to the cellulose in the xylem walls as cellulose is hydrophilic. This helps maintain a column of water.
The induced fit model (4)
The substrate shape is not (exactly) complementary to the shape of the active site. The active site changes shape slightly when the substrate enters. So the active site and substrate molecule are now complementary. Which allows the formation of the enzyme substrate complex. The interaction of R groups lowers the activation energy
Describe what causes oxygen to be released from the oxyhaemoglobin as blood flows through respiring tissues (4)
Oxygen is used up in (aerobic) respiration, this results in a lower partial pressure of oxygen. A small decrease in partial pressure leads to a large dissociation of oxygen. This is because there is a decrease in haemoglobins affinity for oxygen. There is a higher partial pressure for CO2. The CO2 combines with water using the enzyme carbonic anhydrouse to form carbonic acid which dissociates to form hydogen ions. The hydrogen ions combine with haemoglobin. As haemoglobin has a high affinity for hydrogen
Describe the role of the accessory pigments (2)
They pass on light energy to the primary pigment, beta carotene absorbs blue light and xarathyl absorbs green light
Why does the concentration of CO2 not effect photosynthesis in C4 plants (2)
The concentration of CO2 in bundle sheath cells is always high, something else is the limiting factor
Describe the arrangement of chloroplast pigment and their effect on the absorbtion spectra (8)
Chlorphyll a is a primary pigment, chloropyll b is an accessory pigment. They are arranged in light harvesting clusters on the grana. The primary pigment is in the reaction centre and the accessory pigments surround the primary pigment. Light energy is absorbed by the accessory pigments and passed onto the primary pigments. Chlorophyll a and b absorb red and blue light. Carotenoids absorb light in blue/violet region. These peaks will be shown on the absorbtion spectra
How is NADP used in the light dependent and light independent stage (7)
In the light dependent stage of photosynthesis, there is the photolyses of water which release H+ by the secondary pigment. Electrons are released by the primary pigment, both combine with NADP. This reduced NADP reduced GP to TP, ATP is used and the NADP is regenerated.
Describe the structure of a chloroplast (9)
Th stroma is used in the light independent stage of photosynthesis and contains the enzymes needed as well as sugars and DNA. The light dependent reaction takes place with the thylakoid membrane. The grana are stacks of thylakoid and the grana holds the photosynthetic pigment. The grana has a large surface area for maximum light absorbtion. The pigments are arranged in light harvesting clusters. The primary pigment is surrounded by the accessory pigments, the primary pigment passes energy to the accessory pigments. Different photosystems absorb different wavelengths of light.
Describe how you would separate chloroplast pigments in chromatography (6)
You grind the leaf with the solvent (propanone), the leaf extract contains mixture of pigments. The pencil line is drawn on some chromatograpy paper and the extract is placed on the paper, there is repetitive spotting and drying between spots in order to make it more concentrated. Paper is placed vertically in a jar of a different solvent. The solvent rises up the paper and the pigments separate as they ascend. Distance moved by pigment is unique. Calculate Rf value
How does the biochemistry of C4 plants differ from C3 plants
The first product of photosynthesis is the four carbon malate, the first CO2 acceptor is PEP. Malate releases the CO2 to enter carbon cycle
What is the role of rubisco in the calvin cycle
It fixates CO2. It catalyses the reaction RUBP and CO2 to give two molecules of GP via an unstable intermediate compound
What is the role of a primer in PCR
You add it close to a specific section of DNA, the primer binds to the DNA by complimentary base pairing. Primer reduce re-annealing of separated strands
What steps might be taken to increase the number of a species in the wild (4)
Education programmes. Ban on hunting. Population monitering. International agreement, CITES may make the trade of that organism illegal. National parks may be set up. Captive breeding and reintroduction could be implemented.
Role of oxygen in aerobic respiration (3)
It is used in, oxidative phosphorylation as the final electron acceptor. It also accepts protons to form water and allows the electron transport chain to continue.
