Biology gsce paper 1

• One advantage of using an electron microscope to observe plant cells


  A higher resolution/ higher magnification

  So more detail can be seen
• One difference in the sub-cellular structures in a cell in the potato and those in a cell in the leaf of the potato plant are...

  No chloroplasts in potato cells

  Potato cells do not photosynthesise
• So many unique enzymes can exist in nature because...

  Enzymes are made from proteins

  Protein molecules can have a large range of structures and shapes
• If a substrate with a shape that is not complementary to the enzyme tries to enter the active site...

  The substrate is not able to bind efficiently to the active site

  No reaction is catalysed
• They used the root tip because...

  Contains meristem

  For growth
• We can use the microscope to produce a clear image as follows...

  Start with lowest objective lens

  Use focusing wheel to obtain a clearer image
• Benefits of stem cells

  Can differentiate to become any type of cell

  Replace cells
• Risks of stem cells

  Stem cells continue to divide

  Rejecting cells
• Gregor Mendel was able to show

  The principles of inheritance

  That inherited characteristics can be dominant or recessive
• Phenotype

  Visible characteristics
• Genotype

  Combination of alleles for a particular characteristic
• New stone tools

  More sophisticated
• Why protease is added to DNA

  Breaks down proteins

  In the cell membrane
• Controls for DNA practical

  Mass of fruit

  Volume of ethanol

  Temperature
• Alleles

  Different versions of the same gene
• Benefits of Genome Project

  Identify useful genes

  Understand diseases

  Discover new medicine
• Why an allele may be different

  Different base sequence
• Repeating experiment

  To calculate an average
• When the eye changes from focusing on a distant object next to focusing on a near object

  The lens gets thicker to bend the light rays more
• Exercise causing weight loss

  Burning calories

  Losing fat
• How gastric band helps you to lose weight

  Reduces volume of the stomach

  Reduces food intake
• Osmosis- larger SA =

  More water absorbed
• Process occurring when cells develop into root cells

  Differentiation
• Why the agar growth medium is autoclaved

  To kill unwanted microorganisms

  Sterilises agar growth medium
• Why calorimeter has a lid

  More accurate results

  Reduces heat loss
• Why it is important to stir the water in a calorimeter

  So all the water is at the same temperature
• Sequence for developing new medicine

  Testing using cultured cells

  Testing using healthy volunteers

  Double blind trials on patients
• How an adult develops immunity

  Exposure to pathogen

  Stimulates immune response

  Production of B lymphocytes

  Production of memory lymphocytes
• Benefits of adult stem cells (3)

  No need to kill embryos

  No rejection of cells

  Can produce any cell type
• Pentadactyl limb as evidence for evolution

  Same bone structure

  Common ancestor also has pentadactyl limb
• Why we use control variables

  So results can be compared
• Benefits and risks of GM

  Increased yield

  Cheaper

  May not be effective
• DNA sequences

  DNA has different bases

  Changes in the DNA are mutations

  Results in different alleles for these genes

  Produces variation
• Outcome of DNA sequencing


  Identify genetic diseases

  Identify risk of developing diseases
• HGP: Impact on medical treatment

  Take preventative medicine

  Better understanding of some diseases
• To see how effective antibiotics are


  Measure the zone of inhibition
• When antibiotic stop bacteria binding to RNA polymerase


  Kills bacteria

  Doesn't affect human cells

  Prevents production of mRNA

  During transcription

  Prevents proteins being produced
• Lytic lifecycle

  Virus cannot replicate outside a host

  Virus binds to host cell

  Inserts genetic material into host cell

  Uses cells machinery to produce vital proteins and nuclei c acids

  Components assemble into new viral particles

  Viruses exit the cell through the host cell membrane

  Causes lysis of host cell

  Allows production of many virus particles
• how viruses are spread from lytic cycle

  Virus particles leave the host

  Released into body fluids

  Spread through airborne droplets
• Why ror decreases when concentration of enzyme increases

  All active sites are occupied