Paper 1

• centi

  x 10^-2
• milli

  x10^-3
• giga

  x10^9
• mega

  x10^6
• kilo

  x10^3
• micro

  10^-6
• nano

  10^-9
• tera

  10^12
• pico

  10^-12
• Animal cell:

  Cell membrane: controls what enters and leaves the cell

  Nucleus: contains genes and controls the activities of the cell

  Cytoplasm: where chemical reactions take place

  Mitochondria: releases energy through respiration

  Ribosomes: where proteins are made (proteinsynthesis occurs)
• Plant cell

  Cell membrane: controls what enters and leaves the cell

  Nucleus: contains genes and controls the activities of the cell

  Cytoplasm: where chemical reactions take place

  Mitochondria: releases energy through respiration

  Ribosomes: where proteins are made

  Chloroplasts: contains chlorophyll which absorbs light energy

  Cell Wall: protects and supports the cell

  Vacuole: stores water
• Bacteria cell:

  Cell membrane:controls what enters and leaves the cell

  Cytoplasm: where chemical reactions take place

  Ribosomes: make proteins

  Loop of chromosomal DNA: contains genes

  Plasmid DNA: extra DNA

  Cell Wall: Protection

  Flagellum: helps them move
• Enzymes

  biological catalysts that speed up reactions in the body. Each enzyme is specific to its substrate. Activity of enzymes is affected by temperature, substrate concentration, and pH
• Effect of temperature on enzymes:

  • At the optimum temperature, the enzyme is working at its fastest rate
  • At lower temperatures, molecules move more slowly, so substrate molecules take longer to fit into and react in the active site
  • Higher temperatures cause the active site to change shape so it can't hold the substrate as tightly and the reaction goes more slowly.
  • At very high temperatures, the active site breaks up and the enzyme is denatured
• Effect of substrate concentration on enzymes:

  • When substrate concentration is low, not every active site of each enzyme is busy so the rate of reaction is low
  • Adding more substrate increases the rate of reaction because more active sites are busy
  • Adding more substrate after a certain point will have little effect because the active site of every enzyme molecule is busy
• pH and enzymes practical:

  • add amylase to buffered stash solution in a test tube
  • place the tube in a water bath heated by a bunsen burner for a constant temperature
  • take samples of mixture at regular intervals and mix with iodine on a dimple tile
  • repeat until done stops changing colour when mixture is added
  • record time taken for this to happen
  • repeat procedure at different pH values
• Carbohydrates turn into sugars during digestion. Sugars turn into carbohydrates during synthesis. The enzyme for carbohydrates is amylase.
• Lipids turn into fatty acids and glycerol during digestion. Fatty acids and glycerol turn into lipids during synthesis. The enzyme for lipids is lipase.
• Proteins turn into amino acids during digestion. Amino acids turn into proteins during synthesis. The enzyme for proteins is protease.
• Digestion: The process of breaking down large molecules into smaller molecules. Happens in the gut when large food molecules are broken down so they can be absorbed into the blood.
• Synthesis: The process of making large molecules from smaller molecules. Important in the cells for supporting life processes and growth.
• Diffusion: The net movement of particles from an area of high concentration to an area of low concentration through a partially permeable membrane.
• Active transport: The movement of molecules from an area of low concentration to an area of high concentration against a concentration gradient using energy from respiration.
• Osmosis: The movement of water molecules from a region of high water concentration to a region of low water concentration.
• Mitosis:

  Interphase: DNA is duplicated, extra sub cellular parts created

  Prophase: nuclear membrane begins to disappear, spindle fibres start to form

  Metaphase: chromosomes line up in the middle of the cell, spindle fibres attach to the centre of the chromosomes

  Anaphase: spindle fibres pull apart chromatids to each end of the cell

  Telophase: Chromosomes reach each end, nuclear membrane starts to form

  Cytokinesis: Cytoplasm separates, nuclear membrane divides cell into 2 genetically identical diploid daughter cells
• Meiosis:

  • cell making gametes has a full set of chromosomes
  • these chromosomes copy themselves and stay attached to each other
  • The cell splits into two, with each new cell getting half the chromosomes
  • Each cell divides into two again and splits the pairs of chromosomes in half
  • Four non-identical haploid daughter cells are produced
• Image size= Actual size x magnification
• Advantages of stem cells:

  • can be used to replace damaged or diseased cells
  • testing new drugs before they are tested on people
  • can be studied to show how cells become damaged to develop new treatments
• Embryonic stem cells:

  • are pluripotent - they can develop into any type of cell
  • they are easy to extract from an embryo
  • the embryo is destroyed when cells are removed- some people may think the embryo has a right to life
  • Replace faulty cells with healthy cell so the person is well again
  • may not stop dividing, causing cancer
  • Could be rejected from the patients body if the donor is external
• Adult stem cells:

  • are multipotent - have a limited number of different cells they can be developed into (Bone, blood, skin)
  • found in bone marrow
  • Not an ethical issue as no embryo is being destroyed
  • if taken from the patient, there is no risk of rejection
• Plants have meristems as their stem cell. These are found in rapidly growing parts of the plant such as root tips and shoots
• Relay Neurones:

  Carry impulses from one part of the CNS to another.
• Synapse: the gap between neurones that allows the transmission of nerve impulses.

  Neurotransmitters: carry the impulse across the gap

  1. electrical nerve impulse reaches the end of the axon
  2. electrical impulse causes chemical neurotransmitter to be released
  3. neurotransmitter diffuses across the gap and fits into receptors causing a new electrical impulse in next neurone
• The reflex arc: sensory neurone, relay neurone, spinal chord, motor neurone
• Human Evolution:

  1. Ardi: smallest skull volume, tree climber, could probably walk upright
  2. Lucy: smaller but has larger skull volume, walked upright, ape-like face
  3. Homo Habilis: <1.3m, larger skull volume flay face, used simple stone tools
  4. Homo erectus: Larger skull volume, height of around 175cm, long distance walker, strong build
  5. Homosapiens- modern man: wide variety of height but generally tallest. Largest skull volume, user of complex tools
• Classification: organises living things into groups based on similarities

  Three domain system: eukarya (Plants, animals, fungi), bacteria, archaea

  Five kingdom system: plants, animals, fungi, protists, prokaryotes

  Three domains is better as it was found they have more similar genes
• Cancer: A change in the cell's DNA which causes uncontrollable cell growth and division.
• HIV enters the body and reproduces inside white blood cells, destroying them.

  This leads to the immune system eventually being unable to work, causing the onset of AIDS