Biology paper 1

• What happens as a cell differentiates?

  It acquires different sub-cellular structures to enable it to carry out a certain function. It has become a specialised cell
• What happens during mitosis?

  1. One set of chromosomes is pulled to each end of the cell and the nucleus divides

  (2. The cytoplasm and cell membrane divide to form 2 identical cells)
• Give 2 advantages of using an electron microscope instead of a light microscope (2)

  . higher magnification

  . higher resolution
• Why would a student dry the surface of each potato with a paper towel after experiment

  to remove excess water
• Which chemical could be used to test if the burgers contain protein?

  biuret reagent
• Why is using iodine solution risky? How do you minimise the risk?

  . can cause allergic reaction or skin rash

  . wash skin immediately
• how is using a sharp knife in the microscopy practical risky? How would you minimise the risk?

  . may cut your skin

  . cut on a chopping board
• Why should a thin layer of onion epidermis be used in the microscopy practical

  to help see individual cells
• Why should iodine solution be added to the onion epidermis in the micrscopy practical

  to stain and see parts of the cell
• why is the cover slip lowered to the onion epidermis at an angle in the microscopy practical

  to prevent air bubbles
• how do you convert mm into μm

  x 1000
• how do you convert μm into nm

  x 1000
• Give 2 ways a student could improve a cell drawing

  . include the magnification

  . do not draw overlapping cells
• Give two ways onion cells would look different when seen using an electron microscope.

  . would look more magnified

  . sub-cellular structures would be seen in detail
• Describe how mitosis produces 2 genetically identical cells (4)

  . DNA is replicated

  . The replicated chromosomes are pulled to each end of the cell

  . Cytoplasm divides to form 2 cells

  . the set of chromosmes are identical to one another
• What is meant by the term diffusion (2)


  . spreading out of particles

  . from an area of higher concentration to an area of lower concentration
• TMV can cause plants to produce less chlorophyll this causes leaf discoloration explain why plants with TMV have stunted growth (4)


  . less photosynthesis because of the lack of chlorophyll

  . therefore less glucose is made so less energy is released for growth

  . because glucose is needed for respiratin

  . therefore less amino acids for growth because glucose is needed in making amino acids
• Give 3 symptoms of salmonella food poisoning

  . fever

  . stomach cramps

  . vomiting
• The concentration of live bacteria in the body continued to increase after starting the course of antibiotics. Suggest one reason why

  . it takes time for the antibiotic to work

  . bacteria was reproducing when the course started
• Explain how the structure of enzyme molecules is related to the effect of pH on the activity of amylase. (6)

  . enzymes are protein molecules so have a 3d structure

  . in the lock and key theory, they have an active site

  . which has a specific shape of active site which will only bind to the shape of its substrate

  . starch is the substrate for amylase

  . If the ph values are above or below the opitimum the shape of the active site will change

  . so the substrate will no longer fit the active site

  . so the rate of digestion decreases
• A student investigated the different colours of light (red, blue and green) on the rate of photosynthesis using pondweed. Describie how the students would take measurements to obtain results for the rate of photosynthesis (4)


  . allow the pondweed to equlibriate in the light

  . use a gas syringe to measure the volume of oxygen produced from the pondweed

  . measure how long it takes for the oxygen to be collected using a stopwatch

  . repeat the measurements AND calculate a mean
• Describe the similarities and differences between benign tumours and malignant tumours (4)

  . They are both similar because they are made out of abnormal cells

  . they are both similar because they are a form of uncontrolled cell division

  . malignant is different from benign because they usually grow faster then benign tumours

  . malignant spreads to other parts of the body but benign stays in one place

  . malignant can cause secondary tumours but benign does not
• Explain the effects on a person if the valve had a leak (4)


  . some blood will flow back into the heart

  . so less oxygenated blood will be pumped to the body

  . less aerobic respiration in cells

  . so the person is out of breath as well as less energy transferred
• Explain why it is important that the pondweed remains at a constant temperature. (2)

  . temperature affects the rate of photosynthesis

  . because photosynthesis is controlled by enzymes
• Vaccinating a large proportion of the population reduces the spread of the measles virus. Explain why (2)


  . Most people are immune so they do not become ill

  . There's a less chance of unvaccinated people being exposed to the virus
• Describe what happens in each of the three stages in the cell cycle (5)

  . cell grows and the organells increase in number

  . DNA replicates

  . one set of chromosomes move to each end of the cell

  . the nucleus divides

  . the cytoplasm and cell membrane divide to form 2 genetically identical cells
• Give two advantages and two disadvantages of therapeutic cloning in medical treatments. (4)


  Advantages

  . may be used to treat diseases

  . cells produced could be used for research

  . cells of any type could be produces

  Disadvantages

  . potential life is killed

  . may transfer viral infection

  . shortage of donors
• Explain how increasing the temperature would affect the results of a photosynthesis investigation (2)


  . bubbles of gas would be produced faster

  . because enzymes work faster
• Describe how to test a sample of food for protein, starch and sugar. Give the colors that would be seen if the food sample contained protein, starch, and sugar. (6)

  . for protein grind up food then add biuertt reagant

  . it will turn purple/lilac if protein Is present

  . for starch add iodine solution

  . it will turn blue-black if starch is present

  . for sugar, grind p food then add benedicts solution, heat it in a water bath

  . it will turn brick red
• Explain why plants infected with tobacco mosaic virus grow slowly (3)


  . discolouration in leaves

  . reduced photosynthesis

  . so less amino acids are made
• Give 2 uses of sugar in the body (2)

  . respiration

  . to make amino acids/ proteins
• Explain how the villi are adapted for efficient absorption of sugar molecules (4)

  . has many microvilli to increase the surface area

  . walls of the villi are thin so short diffusion pathway

  . cells have many mitochondria where respiration takes place

  . good blood supply to maintain a concentration gradient
• Give 4 diseases related to being overweight (4)

  . (type 2 diabetes)

  . CHD

  . high blood pressure

  . cancer
• People are encouraged to control their body mass with diet and exercise. Describe how the balance between the mass of food eaten and the amount of exercise a person does controls body mass. (3)

  . if more food is eaten the energy intake increases

  . more exercise more energy is transferred

  . if more energy is taken in than it is transferred than the body masses increases
• During long periods of vigorous exercise, the body respires anaerobically. Explain the changes that happen in the body during and after vigorous exercise. (6)


  . increased breathing rate

  . to take in more oxygen for aerobic respiration

  . and exhale more carbon dioxide

  . increased heart rate

  . so increased blood flow to the muscles

  . so transports glucose to respiring cells faster

  . insufficient oxygen is supplied during vigorous exercise

  . so lactic acid is formed

  . and oxygen dept is created causing muscles to become fatigued

  . increased body temperature and sweating happens
• Describe how a vaccine would work to prevent a disease. (4)

  . dead or weakened pathogens is injected

  . white blood cells are stimulated to produce antibodies

  . memory cells are produced

  . in re-exposure to the disease it will be produced in larger quantities

  . bacteria is killed and do not produce a larger enough population to cause the disease
• Give one way that the spread of salmonella food poisoning from one human to another is controlled


  . wash hands before preparing the food
• How can oxygen production be used to show the rate of photosynthesis?


  . measure the volume of gas produced in a given time
• What happens to the rate of photosynthesis when there's no light (3)

  . when there is no light their is no photosynthesis

  . so no oxygen is produced

  . but respiration happens all the time and oxygen is used
• suggest one reason why low doses of the drug are used in phase 1 clinical trials

  . to look for side effects, test toxicity of the drug