Biology - B2.1 - Cells, Tissues and Organs

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B2.1.1 - Animal and Plant Cells

  • Light microscopes - used in school, electron microscopes - magnify things thousands of times larger
  • Parts of a cell:
    • nucleus - control cell activities
    • cytoplasm - where many chemical reactions happen
    • cell membrane - controls movement in and out of cell
    • mitochondria - where energy is released during aerobic respiration
    • ribosomes - where protein synthesis happens
  • Parts of a cell only in plants and algal cells
    • rigid cell wall - made of cellulose, for support
    • chloroplasts - contain chlorophyll: photosynthesis - absorb light energy
    • permanent vacuole - contains cell sap
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B2.1.2 - Bacteria and Yeast

  • Bacteria - very small; can only be seen with a powerful microscope
  • Bacteria have a cell membrane and wall that surround a cytoplasm - they don't have a nucleus - the genetic material is in the cytoplasm
  • Bacteria multiply = colony - can be seen with naked eye
  • Yeast - single cell organism
  • Yeast has a nucleus, cytoplasm and membrane, surrounded by a cell wall
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B2.1.3 - Specialised Cells

  • Many different types of cells - as an organism matures, cells develop into particular types - structure is linked to function
  • Many mitochondria - lots of energy - sperm cell, muscle cell
  • Many ribosomes - lots of protein - gland cells: produce enzymes
  • Tails - able to move - sperm cells
  • Receptor cells structured to detect stimuli - cone cells in eye: light sensitive
  • Nuerons - specialised cells to carry impulses from receptors to CNS
  • Many chloroplasts - photosythesis - mesophyll cells of a leaf
  • Increased surface area - take up more water and ions - roots
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B2.1.4 - Diffusion

  • Liquid and gas molecules - move around quickly due to lots of energy
  • Diffusion - spreading out of gas particles or any substance in a solution
  • Net movement - depends on concentration of particles on each side
  • Particles move radomly - net movement from area of high concentration to low concentration
  • Concentration gradient - difference in concentration between two areas
  • Larger concentration difference = faster rate of diffusion
  • Examples of diffusion:
    • O2 into cells of the body from blood stream as cells respire and use oxygen
    • CO2 into actively photosynthesising plant
    • simple sugars and amino acids from gut
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B2.1.5 - Tissues and Organs - Tissues

  • When multicellular organisms develop, cells differentiate - different cell = different functions
  • Tissue - group of cells with similar structure and functions
  • Animal tissues include:
    • muscle tissue - contract to cause movement
    • glandular tissue - protect substances eg. enzymes or hormones
    • epithelial tissue - covers some parts of the body
  • Plant tissues include:
    • epidermal tissue - covers the plant
    • mesophyll - can photosythesise
    • xylem and phloem - transport substances around plant
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B2.1.5 - Tissues and Organs - Organs

  • Organs - made of tissues
  • Stomach - organ made of:
    • muscular tissue - churn stomach contents
    • glandular tissue - produce digestive juices
    • epithelial tissue - cover inside and outside of stomach
  • Leaf, stem and root - plant organs containing epidermal tissue, mesophyll, xylem and phloem
  • Groups of organs = organ systems - perform particular function
  • Digestive system - several organs, including small intestine
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B2.1.6 - Organ Systems

  • Food eaten - must be changed from insoluble -> soluble molecules - then can be absobed by blood - done by digestive system
  • Digestive system - muscular tube including
    • glands - eg. pancreas and salivary gland - produce digestive juices
    • stomach and small intestine - digestion occurs
    • liver - produces bile
    • small intestine - absorption of soluble food occurs
    • large intestine - water absorbed from undigestive food, producing faeces
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