Biology 1

• Animal Cell: (multi-cellular)

  • cell membrane: control which substances pass in and out of the cell
  • ribosomes: site of protein synthesis
  • mitochondria: provide cells with energy to function
  • nucleus: contains genetic material/DNA
  • cytoplasm: where chemical reactions take place
• Plant Cell: (multi-cellular)

  • cell membrane: control which substances pass in and out of the cell
  • nucleus: contains genetic material/DNA
  • cytoplasm: where chemical reactions takes place
  • mitochondria: provide cells with energy to function
  • ribosomes: site of protein synthesis
  • permanent vacuole: contains cell sap( sugars, salts,water)
  • chloroplasts: contains chlorophyll for photosynthesis
  • rigid cell wall: contains cellulose to support, structure
• Bacterial Cells: (uni-cellular)

  • cell wall
  • cell membrane: control which substances pass in and out of cell
  • plasmids: extra genes e.g. antibiotic resistance
  • circular strand of DNA: genes they need to survive and reproduce
  • ribosomes: site of protein synthesis
  • cytoplasm: where chemical reactions take place
  • flagella: propel the bacteria
• Light Microscope:

  • eyepiece lens: fixed magnification
  • course focusing knob
  • fine focusing knob
  • arm
  • base
  • light source: mirror
  • stage
  • microscope slide
  • objective lenses: different magnification
  • body tube
• Object:

  The real object or sample that your looking at
• How Light Microscope Works:

  1. Light from the room is reflected upwards through the object
  2. Light passes through the objective lens, then through the eyepiece lens, then into out eye (lenses spread out light rays so the image we see is far larger than the object)
• Resolution

  The shortest distance between two points on an object that can still be distinguished as two separate entities(how detailed an image is)
• Pathway Of Light Through Microscope:

  1. Light source
  2. Stage
  3. Microscope slide
  4. Object
  5. Objective lens
  6. Body tube
  7. Eyepiece lens
  8. Eye
• Light Microscope Advantages:

  • small
  • easy to use
  • rely on light
• Light Microscope Disadvantages:

  • resolution is limited
  • any details less than 0.2ųm is blurry
  • not good enough for sub cellular structures
• Electron Microscope Advantages:

  • much higher resolution
  • max resolution is 0.1ųm
• Electron Microscope:

  • very expensive
  • hard to use
  • use electrons
• Stages of Mitosis:

  1. Cell grows in size and number of sub cellular structures increases
  2. DNA is duplicated and 2 new cells each a full set of DNA
  3. Duplicates each of the 46 chromosomes
  4. Chromosomes line up in the centre of the cell, fibres from each side of the cell connect to the chromosomes
  5. Cell fibres pull chromosomes to each pole of the cell( now genetic material has been divided)
  6. Cytokinesis: cell membrane and cytoplasm pull apart forming 2 daughter cells
• Stem Cells Can…

  • divide by mitosis to form more cells
  • able to differentiate into specialised cells
• Embryonic Stem Cells:

  Can differentiate into any type of cell
• Adult Stem Cells:


  Cannot differentiate into all cells and found in the bone marrow (they replace damaged cells, do not form new tissues)
• Plant Stem Cells:

  • found in plant tissues called meristems
  • Palisade Cells: photosynthesis
  • Phloem + Xylem cells: transport sugars and water
  • Root hair cells: absorb water and minerals
• Embryonic Cell stages:

  1. When sperm cell fertilises an egg cell they form a single cell called a zygote
  2. This cell then divides by mitosis to form a ball of cells which we call an embryo
  3. The cells in this embryo are known as embryonic stem cells and can differentiate into any type of cell
• Sperm cell:


  The role is to deliver genetic material to an egg cell in order to fertilise it
• Adaptations Of A Sperm Cell:

  • nucleus has half as much genetic material
  • flagellum allows sperm to swim to reach egg
  • Streamlined shape to help swim
  • lots of mitochondria to provide energy for swimming
  • loads of digestive enzymes to break a hole in the egg cell
• 2 types of stem cells:

  • embryonic stem cells (differentiate into anything)
  • adult stem cells (found in bone marrow)
• Conditions caused by faulty cells:

  • Type 1 diabetes: damage to pancreas cells that normally produce insulin
  • Paralysis: caused by damaged nerve cells
  • Sickle Cell anaemia: caused by misshapen red blood cells
• Stem cells can replace faulty cells:

  1. Extract embryonic stem cells from early embyros
  2. grow them in a laboratory
  3. stimulate them to differentiate into any specialised cell
  4. Give back to patient to replace faulty cells
• Alternatives to using stem cells:

  • use adult stem cells instead (more supply and will not reject)
  • but only can differentiate into blood cells
• Risks of stem cells in medicine:

  • virus transmission
  • tumour development
• Diffusion:

  The net movement of particles from an area of higher concentration to an area of lower concentration
• High concentration:


  particles are closer together
• Low concentration:


  particles are spread apart
• 3 factors that affect rate of diffusion:

  • concentration gradient: difference in concentration between 2 places (the bigger the concentration gradient, the quicker particles will diffuse)
  • temperature: higher temperature means the particles will have more kinetic energy so will move around faster and diffuse more quicker
  • surface area: a larger surface area means a higher rate of diffusion
• Osmosis:


  The net movement of water molecules across a partially permeable membrane, from a region of higher water concentration, to a region of lower water concentration
• Water concentration:


  The amount of water, as compared to other molecules, like sugars or salts (solutes), that are dissolved in the water
• Active Transport: 


  The movement of molecules against their concentration gradient

  • lower to higher
• Does active transport require energy?

  Yes
• Where does active transport get its energy from?

  Cellular respiration (in the mitochondria when they break down glucose to release energy)
• Root hair cell adaptations:

  • lots of mitochondria (energy for cellular respiration)
  • long hair-like protrusions (large surface area for absorptio)
• Surface area of a cube

  Area of single face x 6
• Volume of a cube

  length x width x height
• Bacteria have…

  • high surface area : volume ratio
  • can rely on diffusion across their surface to exchange everything they need
• Humans have…

  • low surface area : volume ratio
  • cant rely on diffusion
  • specialised exchange surfaces e.g. Lungs and intestines (increase our surface area)
• Diffusion distances:


  As organisms get larger, distance molecules have to diffuse increases