Practice Questions Flashcards
Compare the structure of a red blood cell with the structure of a plant cell
- Red blood cells do not have a nucleus, but plant cells do
- Red blood cells have a bi-concave shape, but plant cells do not
- Plant cells have a cell wall, but red blood cells do not
- Both red blood cells and plant cells have cell membranes and cytoplasm
- Red blood cells have haemoglobin, but plant cells do not
- Plant cells have chlorophyll, but red blood cells do not
Placed into a beaker of water, explain why a red blood cell bursts but a plant cell does not
Water enters the cell by osmosis but the plant cell has a cell wall which prevents it from bursting
Describe how root hair cells are adapted to increase the absorption of substances from the soil
- Root hairs increase surface area
- Thin walls for short diffusion rates
Compare the structure and function of xylem tissue and phloem tissue
- Xylem tissue is made of dead cells and phloem is made of living cells
- Xylem is hollow and does not contain cytoplasm but phloem contains cytoplasm
- Xylem contains lignin but phloem does not
- Xylem transports water and mineral ions but phloem transports dissolved sugars
- Xylem is involved in transpiration and phloem is involved in translocation
- Both are made of cells and both transport substances throughout the stem
Describe how glucose from the small intestine is moved to a muscle cell
- Glucose diffuses into the bloodstream
- The glucose is transported by the blood to the muscle cell by the capillaries
Compare anaerobic respiration in a yeast cell with anaerobic respiration in a muscle cell
- Yeast produces ethanol and carbon dioxide, whereas muscles produce lactic acid
- Both release small amounts of energy
Complete the equation for aerobic respiration
glucose + oxygen –> carbon dioxide + water
Explain how oxygen passes from the blood to the mitochondria
- Oxygen from the blood diffuses into the cell
- From a high to low concentration
- Through cell membrane
Describe how the ribosomes and mitochondria help the cell to make enzymes
- Ribosomes make enzymes
- From amino acids
- Mitochondria provide the energy needed for this process
Describe how information passes from the relay neurone to the motor neurone
- Release of neurotransmitters by the relay neurone
- Neurotransmitters diffuse across the synapse
- These chemicals stimulate an impulse in the motor neurone
What is a hypertonic solution?
More concentrated than the cell
What word is used to describe plant cells placed in a hypertonic and a hypotonic solution?
Hypertonic solution = plasmolysed
Hypotonic solution = turgid
Explain how oxygen moves into the blood
- By diffusion
- From a high concentration to a low concentration
- Because there is a higher concentration of oxygen in the air
Explain one way in which the gills are adapted for rapid absorption of oxygen
- Many gill filaments give a larger surface area
- Thin so short diffusion pathway
- Good blood supply to maintain the concentration gradient
- Continually ventilated to maintain the concentration gradient
Why did the scientists use groups of 10 lugworms and not just 1 lugworm at each concentration?
- One worm is too light to measure change
- More representative
- To be able to calculate a mean
What process do plants use to move mineral ions into root hair cells?
Active transport
Describe how water moves from roots to leaves
- By transpiration stream
- In xylem
Name two substances transported by xylem tissue
- Water
- Mineral ions
Explain why translocation is important to plants
- Sugars are made in the leaves
- So they need to be moved to other parts of the plant for respiration
What is translocation?
Movement of dissolved sugar
Explain why active transport is necessary in root hair cells
- For movement of minerals
- Against their concentration gradient
Give the reason why the algal cell does not burst
Cell wall prevents it from bursting
Complete the word equation for photosynthesis
carbon dioxide + water –> glucose + oxygen
Explain why single-celled organisms, like algae, do not need complex structures for gas exchange
- Cell has larger surface area to volume ratio
- Short diffusion distance
- Diffusion via cell membrane is sufficient
Suggest how the highly folded cell surface helps the epithelial cell to absorb soluble food
Increases surface area for diffusion
Name one food molecule absorbed into epithelial cells by active transport
Sugar/glucose
Suggest why epithelial cells have many mitochondria
- Releases energy from respiration
- Required for active transport
How does oxygen move into and out of cells? (1 mark)
Diffusion
How does water move into and out of cells? (1 mark)
Osmosis
What is diffusion?
The movement of particles from high to low concentration
Name one advantage and disadvantage of using a light microscope
Advantage: relatively cheap, can be used almost anywhere, can magnify live specimens
Disadvantage: limited resolution and magnification
Name one advantage and disadvantage of using an electron microscope
Advantage: high magnification and resolution, can give 3D images
Disadvantage: can only magnify dead specimens, expensive, can only be used in temperature, pressure and humidity-controlled rooms
Evaluate the use of an electron microscope and a light microscope, giving one example where each type of microscope might be used
- Electron microscope: magnify up around x 2,000,000, have a resolving power of of about 10nm (scanning electron microscope) or 0.2nm (transmission electron microscope), may be used to examine sub-cellular structures
- Light microscope: magnify up around x 2,000, have a resolving power of around 200nm, may be used to look at cells dividing
What is resolution?
The ability to distinguish between two separate points
Name the main structures you would expect to find in a human cell
- Nucleus
- Cytoplasm
- Ribosomes
- Cell membrane
- Mitochondria
Name the three extra features that may be found in plant cells and not animal cells
- Chloroplasts
- Permanent vacuole
- Cell wall
Describe the main functions of the extra three features found in a plant cell
- Chloroplasts: contain chlorophyll which absorbs sunlight for photosynthesis
- Permanent vacuole: contains cell sap, keeps cells rigid to support the plant
- Cell wall: strengthens cell and provides support
Suggest why the nucleus and mitochondria are so important in all cells
- The nucleus contains the instructions for making new cells or new organisms and controls all cell activities
- The mitochondria is the site of aerobic respiration and releases energy for the cell
Suggest two types of plant cells that are unlikely to have chloroplasts and in each case explain why they have none
- Root hair cells, they have no exposure to light
- Cells in the centre of a tree trunk, no exposure to light
- Cells in flowers of plants, their function is not to photosynthesise
Describe the difference between the genetic material in a prokaryotic cell and the genetic material in a eukaryotic cell
Eukaryotic cell, genetic material enclosed in a nucleus
Prokaryotic cell, genetic material not enclosed in a nucleus and may contain extra rings of DNA (plasmids) separate from the main genetic material
Describe what flagella are
Long protein strand on some types of bacterium that lashes about
explain why an axolotl may die in water with a low concentration of oxygen
- the concentration gradient of oxygen is shallower
- therefore less oxygen diffuses into the blood
- less aerobic respiration occurs so less energy is released
- so less metabolism
give two uses of the energy released in respiration
- muscle contraction
- active transport
- keeping warm
- building larger molecules e.g. cellulose
describe two differences between aerobic and anaerobic respiration in humans
- aerobic produces carbon dioxide and anaerobic does not
- aerobic produces water and anaerobic does not
- anaerobic produces lactic acid and aerobic does not
- aerobic releases more energy than anaerobic
- aerobic occurs mainly in the mitochondria and anaerobic does not
what are the two products of anaerobic respiration in plants?
ethanol and carbon dioxide
name the three parts of the digestive system that produce amylase
- salivary gland
- pancreas
- small intestine
explain how amylase breaks down starch (answer in terms of the lock and key theory) (3 marks)
- starch binds to the active site of the enzyme
- because the shape of the substrate and active site are complementary in shape
- bonds between the starch molecules are broken to produce smaller molecules
describe what happens to cells when a tumour forms
cells divide uncontrollably
Suggest one way we could reduce the rate of development of antibiotic resistant strains
- not prescribe antibiotics for viral infections/non-serious infections
- patients should take the complete course of antibiotics
Suggest one way we could reduce the rate of development of antibiotic resistant strains
- not prescribe antibiotics for viral infections/non-serious infections
- patients should take the complete course of antibiotics
explain the process of therapeutic cloning
- involves using cells from an adult to produce a cloned early embryo of themselves, would provide a source of perfectly matched embryonic stem cells
- could be used for medical treatments such as growing new organs for the original donor
- new organs would not be rejected by the body as it is made from the body’s own cells and has the same genes
how are stem cells currently used in medicine to treat conditions?
- transplantation of blood stem cells to treat disease and conditions of the blood and immune system e.g. leukaemia
- skin stem cells are used to treat extensive burns
- test new drugs for safety and effectiveness
what is a pathogen?
a disease-causing microorganism
how do bacteria cause disease?
they reproduce rapidly inside the body by binary fission and release harmful toxins that kill cells
how do viruses cause disease?
they invade and reproduce inside living cells, causing cell damage
give three ways in which pathogens can be spread
- physical contact
- air
- water
give four ways in which the spread of pathogens can be reduced
- personal hygiene: washing hands, sneezing into a tissue, disinfectants
- reducing contact with infected individuals, quarantine
- removing vectors: using pesticides and insecticides, removal of habitats
- vaccination
why is it especially important to prevent the spread of viral diseases?
- viral disease can not be treated with antibiotics
- scientists have not yet developed many cures for viral diseases
describe how energy for the photosynthesis reaction is gained by plants
- uses the sun’s light energy
- which is absorbed by the chlorophyll in chloroplasts
which two products are formed when lipids are broken down?
fatty acids and glycerol
suggest reasons why viruses are not classed as cells
- they have no nucleus
- they have no cytoplasm
- they do not have mitochondria
- they do not have ribosomes
which part of a plant shows discolouration caused by TMV?
the leaf
explain why a high level of TMV infection reduces growth in a plant
- less chlorophyll
- so less glucose made for growth
explain how increased phagocytosis of the Candida albicans pathogen will help the patient
- more pathogens engulfed by phagocytes
- so less damage to cells
Describe how the clinical trials should be carried out (6 marks)
- drug given first to healthy volunteers at a very low dose to test for toxicity
- then to some patients with the disease to test for efficacy in a double blind trial
- drug is then tested on a large scale, testing on a large number of people with or without the disease to test for dosage
suggest one reason why these new mAbs have been more successful in treating diseases in humans than mAbs made using mice
the human body does not reject these new mAbs
describe how injecting a monoclonal antibody for RSV helps to treat a patient suffering with the disease
- monoclonal antibody binds to the antigen on the surface of the virus
- white blood cells kill the virus
why were some patients given a placebo?
- to act as a control
- to compare the effects of the treatment vs no treatment
explain how the pregnancy test strip works to show a positive result (6 marks)
- as urine passes though the reaction zone
- HCG hormone binds to the mobile HCG antibody in the reaction zone
- HCG hormone binds to the immobilised HCG antibodies in the results zone
- other antibodies do not attach to HCG
- bind to the antibodies in the control zone
- blue dye appears in both the control and results zones
explain how vaccination makes a person immune to a disease (4 marks)
- a vaccine contains dead or weakened forms of a pathogen
- stimulates white blood cells
- to produce antibodies which kill the pathogen
- in the case of second infection, the immune system can produce the correct antibodies rapidly
explain fully why antibiotics cannot be used to cure viral diseases
- viruses live inside body cells
- viruses are inaccessible to antibiotics
There has been a large increase in the populations of many antibiotic-resistant strains of bacteria in recent years. Explain why.
- non-resistant strain of bacteria are killed by the overuse of antibiotics
- so less competition for nutrients and oxygen
describe two ways to control the spread of malaria
- use insect nets to prevent mosquito bites
- stop mosquitoes from breeding
