past paper bio

• Describe what happens during fertilisation

  sperm and egg nuclei fuse/ gamete nuclei fuse
• What is formed in fertilisation

  diploid zygote
• what is meant by chromosome complement

  zygote has two sets of chromosome
• Most features of an individual phenotype are

  polygenic and show continuous variation
• Which term describes the type of variation in which a characteristic is controlled by more than one gene?

  continuous
• State the type of variation shown by tongue-rolling.

  discrete
• Explain what is meant by the term homozygous.

  (both) alleles are the same/identical
• State a feature of the cell membrane which allows the movement of only some substances into the cell.

  selectively permeable/ contains proteins
• Describe the effect of osmosis on a leaf cell if it was placed in pure water

  The cell would become turgid
• Describe the effect of osmosis on a red blood cell if it was placed in pure water.

  cell would burst
• What is the definition of diffusion

  movement of molecules from a higher concentration to a lowe concentration
• What is the definition of active transport

  Movement of moelcules/ions from a low to a high concentration against a concentration gradient
• Enzymes such as lactase are biological catalysts. Explain the role of enzymes in living cells.


  speed up chemical reactions
• name the substance of which enzymes are made.

  proteins/amino acids
• Explain why the fermenter must be sterilised using aseptic techniques before it is used.

  To ensure there are no other bacteria present
• The fermenter is controlled to provide optimum conditions. Name one factor which can be controlled.

  temperature/ pH
• Explain why muscle cells require many mitochondria

  requires a lot of energy for movement/ contraction
• name one substance produced by a cell carrying out aerobic respiration.


  carbon dioxide/ water/ (2) ATP
• A muscle cell will carry out fermentation when oxygen is not available. Describe the fermentation pathway in muscle cells. (3)

  • glucose converted into pyruvate
  • pyruvate converted to lactic acid
  • 2ATP produced
• function of cytoplasm

  site of chemical reactions
• the bases in a strand of DNA make up the code for the production of proteins. The DNA for every individual person varies.

  Describe how this code differs from person to person.

  sequence/order of bases
• what is a source of new alleles in a population

  mutations
• It is a biotic factor and causes a decrease in prey numbers. is what factor

  predation
• Function of sensory neuron


  carries/sends message/impulses/signal from sense organ relay neuron/CNS/spinal cord
• function of motor neuron


  carries/sends message/impulse/signal from CNS to muscle/effector
• function of relay neuron


  carries/sends message/impulse/signal from sensory to motor neuron/within CNS
• describe how information is passes along a neuron

  electrical impulse
• most features of an individuals phenotype are controlled by more than one gene

  polygenic
• describe the structures and processes involved as water moves through plants from soil to the air

  Water is absorbed by root hairs by osmosis/diffusion (1)

  (Water) travels upwards in the xylem (1)

  (water) travels to the stomata and diffuses out
• describe two features of these sturctures which improve the efficiency of gas exchange

  • large surface area
  • thin walls/ walls are one cell thick
  • rich blood supply/ dense capillary network
  • moist
• describe how mucus and cilia work together to prevent bacteria getting into the lungs

  Dirt/dust/ microrganisms are trapped in the mucus

  Cilia move these up and away from the lungs
• why is nitrates important to plants

  needed to make proteins
• name a site of mitosis in plants


  meristem/root tip
• when writing percentage change for increase you must include...

  +
• suggest why the eggs were blotted dry before reiweighed

  to remove excess water on the eggs so it wont alter mass
• describe one difference between passive and active transport

  passive transport moves down a concentration whereas active transport goes against a concentration gradient
• DNA contains genetic material which controls the synthesis of chemical made from amino acids. Name the chemical synthesised

  protein
• Give description of what mRNA is

  Messanger RNA is an order/sequence of bases (which determine base/sequence of amino acids)
• wheres is mRNA made

  nucelus
• name two products used in second stage of photosynthesis

  hydrogen and ATP