Biology

• Compare the phloem and xylem structure 


  structure-Xylem is made of dead cells, hollow, do not contain pores in the end walls,lignin,tubular,made from cells

  Phloem- made of living cells, pores- end walls,contains cytoplasm,no lignin,tubular,made of cells
• Compare the function of phloem and a xylem tissue


  Xylem transports minerals ions, water involved in transpiration

  Phloem transports dissolved sugars involved in translocation

  Both transports liquids through stem,leaves,roots,plants
• Advantages of using an electron microscope instead of a light microscope

  higher magnification

  higher resolution
• Compare the structure of an artery with the structure of a vein(3 marks)


  Arteries have a thicker layer of muscle than veins

  Arteries have a narrow lumen than veins

  Veins have valves-Arteries does not

  Arteries have thicker elastic tissue
• TMV can cause plants to produce less chlorophyll-Explain why(4marks)


  -Less photosynthesis because of the lack of chlorophyll therefore less glucose is made

  -Less energy released for growth because glucose is needed for respiration

  -Less amino acids which weakens the growth of cellulose
• Explain why having more red blood cells per cm of blood is an advantage to an athlete


  -More red blood cells means more haemoglobin present

  -Therefore more oxygen can be transported

  -more oxygen allows for more aerobic respiration of muscle cells(gives more energy)
• Urea is transported in the blood plasma

  Name 2 other substances transported in the blood plasma (2 marks)

  -Carbon dioxide

  -Water
• Give two ways a person with a mild infection of salmonella can help prevent the spread of bacteria to other people.(2 marks)


  -wash hands after being sick

  -isolate infected person(isolation)

  -Avoid preparing food
• A person has a tumour blocking the tube leading from the gall bladder to the small intestine.Explain why this person would have difficulty digesting fat.(5 marks)


  -less bile reaches the small intestine

  -less emulsification of fat

  -smaller surface are for lipase to break down fat

  -pH of small intestine is not neutralised/is alkaline

  -Lipase is not at its optimum pH to break down fats
• Explain how amylase breaks down starch.[LOCK AND KEY](3 marks)


  -starch substrate binds to active site of enzyme

  -shape of enzymes active site and substrate are complementary

  -A chemical reaction occurs to produce smaller molecules

  -bonds between starch molecules are broken to produce smaller molecules
• Name 3 parts of the human digestive system that produce amylase(2 marks)


  -Salivary glands

  -pancreas

  -small intestine
• Energy is released in respiration.Give two uses of the energy released in respiration.(2 marks)


  -movement/muscle contraction

  -keeping warm

  -active transport

  -building larger molecules
• Name one type of cell in a potato plant that does not contain chloroplasts.(1 mark)


  -root hair
• Before mitosis occurs,the cell grows.The genetic material in the cell doubles when the DNA replicates.After the chromosomes have been pulled to each end of the cell,the cytoplasm divides.
• Aspirin made from willow

  Digitalis made from Foxglove
• Salmonella food poisoning is caused by bacteria in food. Give one symptom of salmonella food poisoning.

  • fever

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

  -only a few bacteria killed so live bacteria continued to reproduce

  -time delay before antibiotic reached bacteria

  -time delay before antibiotics could kill bacteria
• Suggest why doctors do not give antibiotics to patients with minor infections.

  to reduce / prevent resistant strains / bacteria developing or to reduce / prevent antibiotic resistance (in bacteria)
• Smallest to largest

  Gene-Chromosomes-Nucleus-Cell
• Give one way that cell division by mitosis is important in fully grown animals.

  repair of tissues

  replacement of cells
• Explain how the structure of enzyme molecules is related to the effect of pH on the activity of amylase.


  • enzymes are protein molecules

  • lock and key theory

  • have an active site which has a specific shape

  • shape of active site will only match shape of substrate

  • starch is substrate for amylase

  • at pH values above or below the optimum the shape of active site is changed (in some molecules) so substrate can no longer fit the active site

  • at extreme pH values enzyme is denatured so shape of active site is changed so amylase can no longer digest starch so rate of digestion decreases
• A student investigated the effect of different colours of light on the rate of photosynthesis at room temperature. The student used pondweed in water. A piece of pondweed was placed in red light, then in blue light and then in green light. Each colour of light was the same intensity. Describe how the student should make accurate measurements to obtain valid results for the rate of photosynthesis.


  allow the pondweed to equilibrate in the light

  use a gas syringe or

  use a (measuring) cylinder to measure / stopwatch / stopclock

  repeat the measurements and calculate the mean
• Benign tumours and malignant tumourspt1


  • Similarities:
  • Result from changes in the cell / DNA / genes
  • Uncontrolled cell growth / division
  • Can form a lump of cells
  • Made up of abnormal cells
• DIFFERENCES:pt2

  • MALIGNANT TUMOURS
  • Made of cancer cells, benign tumours are not or benign tumours are made up of cells that are more similar to normal cells
  • Grow faster than benign tumours
  • Invade neighbouring tissues, but benign tumours do not
  • Can spread (to other parts of the body) but benign tumours stay in one place or cells
  • can travel in the blood, but benign tumours do not
  • Can form secondary tumours, benign tumours do not
• There are no new cases of skin cancer diagnosed in people younger than 15 years of age. Explain why

  little exposure to ionising radiation

  or little exposure to carcinogens

  (so) less cell / DNA / gene damage
• Why is the heart described as an organ?

  it is made up of (different) tissues that perform specific functions
• Explain the effects on a person if the valve labelled in Figure 11 developed a leak. [4 marks]

  • some blood would flow back into the ventricle
  • heart (so) less oxygenated blood would be pumped to the body cells require oxygen for respiration
  • less aerobic respiration (so) person would become out of breath
  • (so) less energy transferred
  • (so) person would be tired